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My Chemical-Free House

A Guide to Creating a Healthy Home

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mold prevention

Hempcrete for Mold-Safe, Healthy Homes

November 3, 2021 by Corinne 1 Comment

Hemp can be used in building homes in many ways but building with hemp is very different than building with conventional construction methods.

Hempcrete can be tamped into board-formed walls, used as premade bricks, sprayed into cavities, or formed into precast panels.

It acts as insulation and as an interior and/or exterior surface, though it is not load-bearing – you still need a wood frame.

This article will review all the ways that hemp can be used to build a healthy home and is an investigation into whether it’s mold-prone.

Beautiful hempcrete salon, Hemp House Hair Salon, in British Columbia, Canada.

Before we look at the building methods closer, letโ€™s look at what goes into hempcrete. 

What is Hempcrete Made of

1. Hemp hurd

The first ingredient of hempcrete is the aggregate, called the โ€˜hurdโ€™. Hurd is the woody core of the hemp plant that remains after the plant has been stripped and the fiber sold for rope or textiles. 

The hurd is like the inside of a twig, after the bark has been stripped off, just less dense and with a hollow core. The woody core is dried and then chopped up; it looks a lot like wood mulch. 

Hemp is an organic material โ€“ meaning, it is carbon-based, just like wood (and can be mold food, just like wood). In fact, it contains more cellulose than wood does (hemp has 65-70% cellulose and wood has 40%). 

Quality is not consistent from supplier to supplier, so make sure you are buying good quality hurd before committing to a large purchase.

A good place to buy hemp hurd in the US is through Hempitecture in Idaho. 

2. Lime Binder

The lime binder contains calcium carbonate (lime) and compounds which allow it to harden โ€“ either soluble silica, alumina oxide or ferric oxide. When a lime binder can harden with the addition of water, this is called hydraulic lime. 

Hydraulic lime is readily available in the UK and France but is difficult to find in North America and often has to be imported. 

There are some binders that are produced in the US. One place to buy lime binder in the US is also through Hempitecture.

Do your research on binders before choosing one. There are binders out there that have caused mold problems where there shouldnโ€™t have been any due to added ingredients in the binder. 

3. Water

When water is added to the hydraulic lime binder, it causes a chemical reaction (hot!) which makes it possible for it to harden once dried. 

4. Air

It feels funny to list air as an ingredient, but itโ€™s one of the most important parts of hempcrete! 

When dried, there are many air pockets in hempcrete โ€“ both between the pieces of hemp and inside each piece of hemp. 

Air is what makes hemp a good insulator (air is the most important part of any insulation) and humidity regulator.

Water, lime, and hemp hurd. Photo courtesy of Homeland Hempcrete in North Dakota.

Put them together! 

When hemp hurd is mixed with the lime binder and water, it dries into a hard solid mass. 

Before it dries, you sprinkle it into framed molds that surround the buildingโ€™s wood framing. It is then tamped down to compress it a bit, and left to dry. 

The drying time is important (between 4-8 weeks). If you donโ€™t allow it to dry enough before removing the form work and plastering, there could be big problems (mold, staining, crumbling).

Mixing hemp and lime together: https://www.instagram.com/p/Bsn2G21hMxn/?utm_source=ig_embed&utm_campaign=loading

Building with Hempcrete: How it is Used

Hempcrete can take the place of insulation, drywall, and siding in a new wall. 

It is not a 1 to 1 replacement, though; Hempcrete canโ€™t just be substituted for fiberglass insulation (or cellulose, etc.). Using hempcrete requires a different plan and approach compared to conventional building. 

Besides being a totally different type of material and insulation, hempcrete has a different insulation value than fiberglass or cellulose, and so it will require thicker walls.

As Insulation

This is a cross-section of a hempcrete wall – the hempcrete encapsulates the wood framing.

Hempcreteโ€™s most important function is as insulation. The amount of insulation you require will determine how thick your wall will have to be. 

The insulation requirement (R-value requirement) depends on your local codes. The colder the climate, the thicker the wall will have to be.

Hempcrete’s R-Value is usually listed as ranging from 2-3 per inch. But some companies have claimed it can be as high as 4.8 per inch.

Photo courtesy of Hempitecture. 

As Siding (Exterior Skin)

This is the exterior wall of a hempcrete tiny house before plastering.

The outside of hempcrete can be plastered, similar to the interior. This can create more moisture risks if not done precisely or maintained properly. 

This might not be advisable in certain climates. Please find a professional to discuss what the best exterior options are for your climate.

Photo courtesy of Hempitecture.

As Interior Wall Face (Interior Skin)

This is an interior hempcrete lime-plastered wall.

Drywall is not needed when building with hempcrete. The typical interior finish is a lime render (plaster) that is applied directly to the dried hempcrete. This allows the wall to stay vapor permeable.

Anything that you add to the wall must be vapor permeable, inside and out. 

Photo courtesy of Hempitecture.

Note! 

Hempcrete is not concrete. Unlike what the name suggests, hempcrete is not made from concrete and it does not contain concrete. Even though hempcrete dries and hardens, hempcrete is not structural or load-bearing โ€“ it canโ€™t hold up the weight of the roof. It must always be used in combination with a wood frame (or other framing material). 

Reasons to consider hempcrete

  • Hemp has a unique cellular structure that allows it to absorb and adsorb water better than other plant-based fibers. This gives it an edge in moisture management over other plant-based materials.
  • The use of a lime binder makes glues and other high VOC materials unnecessary for the wall components. 
  • It can help with maintaining healthy indoor air quality.
  • It is a fast-growing crop, so multiple harvests can be grown in one year (it is a weed, after all).
  • Hempcrete generally has very good (but not excellent) insulation value. 
  • It is very fire-resistant.
  • We know all of the ingredients in it.
  • It is vapor permeable, i.e. โ€œbreathableโ€- if moisture gets in, it can get out.
  • It is carbon dioxide sequestering.

Building with Hempcrete, Various Forms

1. Poured, or Formed Hempcrete

With formed (or poured) hempcrete walls, the finished walls are hardened hempcrete usually plastered with a lime render.

How it works

Forms holding hempcrete to make hempcrete walls. Photo courtesy of UK Hempcrete. Copyright UK Hempcrete

The hemp, lime binder, and water are mixed together on-site. 

Temporary wood framing aka form work (similar to when concrete is poured) is placed surrounding the structural wood frame. 

The hempcrete mix is then โ€œpouredโ€ into place inside the wood forms and then tamped down to create a thick wall. The wood forms are left there for several weeks until the hempcrete is dried. 

Hempcrete creates a solid wall. There is no need for an interior wallboard, like drywall, just a nice lime plaster. 

The thickness of the wall will depend on how much insulation is required by code in your location, or how much insulation you want. 

Depending on location, the exterior can also just be plastered, but this should be discussed with a building science-literate professional who is familiar with your climate zone. 

Photo of hemp in exterior forms: https://www.instagram.com/p/Bsa_xkVjMMi/?utm_source=ig_embed&utm_campaign=loading

Benefits of a solid hempcrete wall

  • A good amount of thermal mass (heavy, thick walls) makes temperatures and humidity more even.
  • Using a single material means no seams and gaps like in traditional, wood-framed houses.
  • A homogeneous material makes moisture and temp management more consistent.
  • A heavyweight, formable material means less need for taping or specific air-sealing layers.
  • Building with a homogeneous material means thereโ€™s no abrupt shift in temperatures (i.e. at the sheathing), minimizing the chance of condensation.
  • Consistent vapor openness due to single material (hempcrete) makes it easier for the wall to โ€œbreatheโ€ and dry.
  • Hempcrete works with moisture, humidity, and temperature like an experienced dance partner; conventional construction relies on keeping them away by using increasingly complex layers of barriers, insulation, boards, and tapes.

Drawbacks of a solid hempcrete wall

  • It could give you false reassurance โ€“ it still requires extensive planning and precision to avoid mold.
  • If not planned, mixed, and detailed correctly, it can become moldyย .
  • The lime dust can be hazardous to breathe in and for the skin.
  • Using a framing material (i.e. wood) is still necessary.ย 
  • There are many unknowns about how it will perform in US climates.
  • Contractors and laborers may be inexperienced with hempcrete.
  • You will be an โ€œearly adopterโ€.

2. Pre-Cast Hempcrete Blocks

Precast hempcrete block. Photo courtesy of UK Hempcrete. Copyright UK Hempcrete

In order to make hempcrete thick to have enough insulation value, you can use precast hempcrete blocks on one side of the exterior wall.

The opposite side will be framed with temporary forms and be poured with hempcrete to fill the cavities and encapsulate the wood framing.

Hempcrete blocks are not load-bearing, so they will still need to be used with a wood frame. 

There is one company in Canada that is making a load-bearing block. They have not responded to my request for more information about the block. Their block is not approved for load-bearing use in the US. 

Components

Most hempcrete blocks have the same ingredients as poured walls โ€“ hemp hurd, lime binder, and water.

However, there are some that have different binders, or use a finer ground hemp, and these can cause problems. 

Always make sure you know what is in the block before committing to anything. 

Like in the picture below, the hempcrete blocks will be placed on one side of the wood-framed wall. 

A build with hemp blocks in progress: https://www.instagram.com/p/B3WirPkntVr/?utm_source=ig_embed&utm_campaign=loading

Benefits of using hempcrete block

Same as benefits for poured hempcrete, plus:

  • They are pre-dried, so you can begin applying interior plaster weeks earlier than with poured hempcrete. 
  • Faster install time.

Drawbacks of hempcrete blocks

Same as poured hempcrete, plus:

  • The cost is higher due to the labor required to cast and dry the blocks off-site.

A layer of hemp blocks complete: https://www.instagram.com/p/B3pkZnKn8uy/?utm_source=ig_embed&utm_campaign=loading

3. Sprayed-In Hempcrete

This type of hempcrete is mixed on-site, like poured hempcrete, but applied by spraying rather pouring into a form. It’s a similar process to wet-applied dense-packed cellulose or spray foam.

There must be a surface to spray against, like a hempcrete block layer or plywood.

This is a video of the whole preparation and spraying process. 

Components

Same as in poured hempcrete: hemp hurd, lime binder, water.

How it works

Mixed on-site, like poured hempcrete, but applied by spraying vertically rather than pouring into a form. 

According to Alex Sparrow, who owns UK Hempcrete and is the author of The Hempcrete Book, in the UK it is common to use sprayed hempcrete when renovating old stone houses. The stones have uneven surfaces and spraying allows the hempcrete to fill in the gaps and valleys. 

Spraying in hempcrete: https://www.instagram.com/p/Bz_LQRRBYW7/?utm_source=ig_embed&utm_campaign=loading

Benefits of sprayed-in hempcrete

Same as poured-in hempcrete.

Drawbacks of using sprayed-in hempcrete

Same as poured concrete, plus the possible compression of the hempcrete, resulting in lower insulation values.

4. Hempcrete Prefab Panels

Some companies are beginning to produce prefab wood frame hempcrete panels. These panels combine structural wood framing with hempcrete.

Components

The ingredients in prefab panels are usually the same as hempcrete. But, like blocks, it could vary from company to company, so make sure to find out what the binder is before committing to anything. 

How it works

The panels are framed with wood. They are sometimes referred to as โ€œcassettesโ€. When using prefab panels, the wood framing is not encapsulated with hempcrete. 

Panels will require more care for air sealing, etc. due to the wood joints. There is also more potential for thermal bridging and condensation. 

Uses for prefab hempcrete panels would be similar to any prefab panel. Wall sections are made off-site and transported to the lot for installation. They could be used in place of hempcrete blocks, with poured or sprayed hempcrete on the opposite site.

A video showing hemp precast panels: https://www.instagram.com/p/Bz8amlcBfr-/?utm_source=ig_embed&utm_campaign=loading

Benefits of using prefab hempcrete panels

  • Possible faster install time.
  • Faster dry time.
  • Less on-site prep.

Drawbacks of using prefab panels

  • More detailing, similar to a traditional construction wall, because wood frame is not encapsulated in hempcrete.
  • More expensive.
  • Less oversight for how the wall is being made.
  • More potential for problems with the wood.
  • It makes interior finishes more tricky (lime plaster over studs?).

Precast panels: https://www.instagram.com/p/ttjdPmhKt4/?utm_source=ig_embed&utm_campaign=loading

5. Hemp Insulation Batts

Hemp insulation is not hempcrete but I thought I would briefly mention it here. It is not mixed with a lime binder that encapsulates the hemp hurd and hardens it.

It is hemp fibers, usually with some synthetic fibers mixed in, made into batts and used in walls just like fiberglass, mineral wool, and other batt insulation types.

My post on insulation mentions this in more detail.

Is Hempcrete Mold Resistant?

Photo courtesy of UK Hempcrete

Plain hemp can grow mold in the right conditions, but hempcrete is a little different.

Hempโ€“lime mixes can go moldy if it 1) it absorbs water for prolonged periods of time in moist conditions, 2) does not have adequeate ventilation inside or 3) wrong choice of protective coating.

Hemp is made of cellulose (it has even more than wood!) and mold likes cellulose. If you put plain wet hemp in a plastic bag and seal it, it will get moldy. 

Hempcrete has less risk for mold. This is because the hemp in hempcrete is mixed with a lime binder that makes it possible for the hempcrete to harden. 

Lime is what gives hempcrete its mold-resistant property. Lime is alkaline (high pH). Mold, in general, doesnโ€™t like alkaline environments. When the lime binder is mixed in and coats the hemp pieces, it essentially creates an inorganic, alkaline buffer that mold cannot survive in.

However, one study I read found that mold was still able to grow, even in the presence of lime binder, when the hempcrete wall was exposed to heavy rain. 

A lot depends on using the right binder, mixing it correctly, making sure anything put on the walls is vapor-permeable, and avoiding bulk water (rain, roof-run off, etc.)

When a hempcrete house is properly planned and correctly built, the chances of mold growing are likely less with hempcrete than with traditional building materials. 

Do your research on binders before choosing one. There are binders out there that have caused mold problems.

If you want to avoid mold in your future healthy house, proper planning for moisture management (weather and vapor) are essential. 

Please find a qualified architect or building science professional to create a plan for your new healthy home.

What climates are safe for building with hempcrete?

This study found the most microbial growth in a simulated tropical environment. The Mediterranean climate simulation induced the growth of six species of bacteria and four species of fungi, with moderate diversity. In the arid climate simulation only four species of bacteria and two species of fungi appeared. Hempcrete certainly faired the best in the arid desert climate simulation.

There are many hempcrete houses in the rainy UK, as well as institutional buildings and multi-family complexes.ย In North America, there are hempcrete buildings in coastal North Carolina to snowy Idaho and cold, wet Canada.ย If you intend to build in a wet climate you should go visit some of these homes when possible.

Since hempcrete is an insulation, it should be just as safe as something like blown-in cellulose. The details will change depending on the climate, however โ€“ humid, dry, rainy, cold, warm, etc. 

It might be necessary to protect the exterior wall with large overhanging eaves, or sheathing combined with a rain screen (gap) and siding. 

This is where an experienced architect can help you determine the details that are necessary for your location to avoid mold and rot.

Is Hempcrete Cost Effective?

  • The cost appears to be 10-30% more than typical wood construction.
    • Much of it has to be imported (and it can be difficult to source, depending on where you live).
    • It takes a long time to dry which can slow down the build.
  • The cost depends on the method you use.
    • A double stud wall is more expensive (double cost).
  • There are very few experienced architects or builders.
  • Blocks and precast panels tend to be more expensive because they need to be cast individually unlike a whole wall that can be cast as one.

Related post: on more natural building wall systems to consider.

Where to Learn More About Hempcrete

Helpful books:

  • The Hempcrete Book: Designing and building with hemp-lime by William Stanwix and Alex Sparrow
  • Essential Hempcrete Construction: The complete step-by-step guide by Chris Magwood

Helpful videos:

  • Alex Sparrow speaking at Hempfest
  • Introduction to Natural Hempcrete Construction Options

Trainings:

  • US Hemp Building Summit โ€“ annual 
  • Endeavor Centre โ€“ Canada
  • UK Hempcrete

Products:

  • Hempitecture โ€“ hempcrete samples, hemp hurd, blocks, hempwool, binder, and tools/machinery
  • Hemp Eco Systems
  • Tradical Hemcrete
  • Tradical Hembuild โ€“ Pre-cast wall panels
  • Sativa Building Systems โ€“ insulated panels
  • CannaGrove HempBoard
  • Just BioFiber โ€“ blocks 
  • NaturHemp insulation panel
  • AcoustiHemp semi-rigid acoustic panel
  • NaturFelt Hemp Wool floor underlayment

Design / Build

USA

  • Hempitecture โ€“ Idaho
  • Homeland Hempcrete โ€“ North Dakota
  • New Frameworks โ€“ Vermont

Europe

  • UK Hempcrete

Corinne Seguraย is a Building Biologist Practitioner with 7 years of experience helping others create healthy homes.

Buy Me a Coffee at ko-fi.com

Did you find this post helpful? If so you canย buy me a coffeeย to support the research behind this blog. Thank you!

Filed Under: Healthy Building Tagged With: Healthy building, mold prevention

Non-Toxic Decking Material Options

August 15, 2021 by Corinne 8 Comments

This is a complete guide to non-toxic decking – types, materials, additives, and brands.

For most people, the main choice is between composite decking and solid wood decking. For the chemically sensitive you will have to get samples yourself of the decking materials as well as the stains needed for real wood – as this choice is very individual.

The long-term benefits of not having to do any maintenance on composite decking can outweigh the initial concerns.

There are also some more unusual options to choose from like aluminum decking.

Composite Decks

A close up of composite decking

Material Make Up

Composite decking material is generally made from a mix of wood fibers and plastic. The plastic is polypropylene (PP) or polyethylene (PE), mixed together with wood dust, pigments, UV inhibitors, and usually borate. This plastic is usually recycled, like from plastic grocery bags.

If you do well with polyethylene or polypropylene that should be OK for you, but ask to see a sample of the ones available near you and see if you can get a sample of one that is as newly manufactured as the one you would buy. These plastics do have a little bit of odor.

Most of them now are capped in an outer layer of plastic. The type of plastic is not always specified, but you should ask, especially if you are avoiding PVC vinyl.

Additional Chemicals During Install

Glue is not used to install composite decks, but you are meant to seal the rough edges of some brands with a lumber wax – be sure to tests out the product that the company recommends if you are super sensitive.

Trex does not recommend using a lumber wax, sealant, or any other glue or sealant in the installation.

The only maintenance needed for most brands is soap and water.

Mold Prone?

Many have reported their composite decking becoming prone to growing mold. Some experts have recommended only going with brands that are capped with plastic on all sides to help prevent this issue. Brands with bamboo fibers might also be less prone to mold since the fibers do not clump as much.

Brands

Capped composites like Trex Transcend or TimberTech Earthwood Evolutions use a traditional composite decking core with an added plastic polymer cap.

Trex is the most well-known brand of composite decking made with recycled bags (PE), and it is capped with an unspecified type of plastic, which they said is not PVC.

Dura-Life brand is a blend of polypropylene (about 20 percent), recycled wood and plastic (about 25 percent), and hardwood flour (about 55 percent). Dura-Life planks have a polypropylene cap outer shell covering the extruded composite core. 

I have heard from really chemically sensitive folks who did well with Dura-Life. I sampled this one and I would describe the odor as a fairly mild glue odor when sniffed directly.

A non-wood composite, Lumberock Premium Decking, offers a line of decking materials made from a combination of plastics and mineral materials instead of wood fibers. You might want to check that one out if you are sensitive to the natural odorants of wood.

Wood-based composites do still retain some wood odor. For example, a cedar composite that I tested definitely smelled like cedar. The ones I tested (Trex, Dura-Life) also have an odor that I would describe as a light glue odor.

Cost

A Trex deck typically runs from $9 to $16 per square foot.

Maintenance

Non-toxic cleaning products that won’t damage composite decks are here.

PVC Decking

A PVC deck

Material Make Up

Some PVC decking is 100% plastic and some is a composite decking made of PVC and wood fibers.

Many chemically sensitive folks like to avoid PVC since it tends to be higher in offgassing, odors, and added chemicals, however, the odor here of the wood-PVC composites is fairly mild and in my experience was milder than the composites above.

These are some brands that make PVC decking which generally look the same from the atop view as the non-PVC composites.

Additional Chemicals During Install

With solid PVC boards you would not need to seal the edges.

Mold Prone?

Mold growth would only be superficial on solid PVC boards since it cannot grow in the material. With composite products, if they have real wood in them they likely are prone to mold to some degree, especially if not capped on all sides.

Brands

AZEK and TimberTech AZEK products are made from a solid PVC which they claim is highly resistant to stains, scratches, splits, mold, and mildew.

Despite being PVC, I found that the TimberTech AZEK only had a slight odor when new (when sniffing it up close) – less than the odor of TREX and Dura-LIfe composites, in my opinion.

TimberTech Pro and TimberTech Edge are composites – a mix of wood fibers and plastic PVC, capped with PVC. (Not capped in PE as some websites say).

Envision Composite Lumber with no natural wood fibers and PVC. Some lines are capped (in PVC) and some are not.

EverNew by CertainTeed line includes decking materials that are either solid vinyl or a blend of PVC vinyl and wood flour.

Fortress Apex PVC Decking’s “foam core” is cellular PVC reinforced with bamboo. The boards are encapsulated in an acrylic polymer.

Fiberon company makes surface decking, railing components, and fencing products that are made from a solid PVC “Permatek” outer shell bonded to a wood composite core.

Cost

Azek is 2-3 times the cost of Trex composite.

Maintenence

Non-toxic products that won’t damage vinyl decks are outlined in this post on deck cleaners.

Real Wood Decks

Pressure Treated Decks

Pressure-treated wood for decking is usually pine, treated with copper and quaternary ammonia. The ammonia will offgas from the pine, but for those who are extremely sensitive, they can have challenges with this when it is fresh.

I have also seen pressure-treated wood treated with flame retardants, though this is not the norm – examples: wood from Hoover and FRX.

One other challenge with pressure-treated wood is that it can not be sealed or stained for about 6 months when it is new unless it’s already been dried out.

Cedar Decks

A cedar deck being installed

Cedar is the most common natural wood option and it’s good for those avoiding toxins since it doesn’t need pressure-treating (with copper-quats) like pine does.

Cedar does have a rather strong natural odor which bothers some people with extreme chemical sensitivity. My post on the odorants of wood looks more at this issue.

Although it doesn’t require pressure treating you should stain it every few years, so you will have to find a sealer you can tolerate. My post on deck sealers goes through the options.

Usually the base structure of decks is made from pressure-treated wood.

Redwood is another naturally rot-resistant wood used for decking in North America. Like Cedar, it is not pressure treated and does require a sealant.

Cedar and Redwood are pricier than pressure-treated pine.

Ipe Decks

All natural Ipe wood decking being installed

Ipe is a wood species for decks that could be ideal for those avoiding toxins.

Though it’s quite pricey, pricier than Cedar and Redwood, it does not require sealing (or pressure-treating). Though adding a sealer can help preserve it. You can choose between natural oil options and a very low VOC oil/water hybrid detailed here.

Other Rot-Resistant Woods Used in Decking

Massaranduba, Cumaru, Tigerwood, Garapa, Mahogany, and Teak are a few other naturally rot-resistant tropical woods that can hold up as outdoor decking.

Out of the woods used for decking, Cedar is the highest odor wood and Garapa is the lowest. If you find yourself sensitive to the natural odorants of wood, get a few samples of different species and see how you do.

Samples of low odor rot resistant woods that can be used for decking

Non-Toxic Modified Woods

Thermally Modified Wood

Thermally modified wood for decking is treated with heat. This makes it more durable and gives it protection against rot and termites. No chemicals are used in the treatment. It has the smell of smoked wood.  

Thermory is a heat-treated wood brand, they say it lasts as long as a tropical hardwood like Ipe.

There is a wax to seal the edges of Thermory. Other than those edges it comes finished and you donโ€™t have to refinish this again if you don’t want to.

Acetylated Wood

Accoya wood is Radiata Pine and Alder species treated with acetic anhydride. The treatment leaves the wood harder, more dimensionally stable, and immune to insects. Some acetic acid is left in the wood and that does leave it smelling a little bit like vinegar.

You can add a finish or leave it unfinished.

Furfurylated Wood

Kebony is another modified wood. Furfuryl alcohol is impregnated into the wood and is polymerized. Iโ€™m a little more hesitant to recommend this type of wood due to more unknowns with this chemistry.

Aluminum Decking

Aluminum decking
Photo via www.nexaninc.com

Aluminum decking by Nexum, pictured above, is made from powdered coated aluminum. A chemically inert product and certainly the safest one on this list for the extremely chemically sensitive.

The above type is gapless which can help to provide usable area under the deck.

Related:

Non-Toxic Deck Stains & Sealers

Non-Toxic Deck Cleaners

Corinne Seguraย is a Building Biologist Practitioner with 7 years of experience helping others create healthy homes.

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Filed Under: Healthy Building Tagged With: Healthy building, healthy exterior/gardens, mold prevention

Review of Boxabl, Home of Elon Musk

July 12, 2021 by Corinne 16 Comments

Review of Boxabl SIPS Prefab House

The company Boxabl has created a metal SIPs (structurally integrated panel) house that has caught a lot of folksโ€™ attention.

The main reason it has gone so viral is that it promises it all โ€“ fast, easy, cheap, resilient, and healthy.

My job as a Building Biologist is to review homes for durability, indoor air quality and resilience to mold.

It may be cheap and fast, but is this home a durable and healthy home?

First, is it “eco-friendy”

The basic structure of this house is a steel and styrofoam structural panel. This is very safe even for those with chemical sensitivities. That part has practically no offgassing and I am a big fan of SIPS.

They also use MgO (magnesium oxide) board on the interior surfaces which is generally safe option as it has extremely low or no offgassing in my experience.

Itโ€™s not clear how that is attached to the walls in this case, itโ€™s likely glued on, which could be a problem for offgassing. (More on in the inherent risks of MgO against steel below).

The flooring appears to be glue down vinyl, though they have described it in different ways. The countertops and tabletop are laminate (which is a melamine plastic glued onto a substrate which is almost always MDF). And the interior cabinetry is conventional (which is typically particle board and laminate).

These three elements will contribute to offgassing – VOCs, plasticizers and glue from the vinyl floor; glues and formaldehyde from particle board based cabinets; and glues and formaldehyde from MDF based laminate countertops.

While this is not high in offgassing per se, according to conventional wisdom, it absolutely could be too high for those who are sensitive to formaldehyde.

At this time the interior cannot be customized and it includes all the interior finishes other than the bed and sofa.

Even though it would be quite easy to choose your own healthy floor and cabinets in theory, it would likely be difficult to remove the already glued down vinyl.

With just a little more effort this company, they could have reduced offgassing significantly by choosing better cabinets, countertops and floors. (Though keep in mind we do not know the exact materials or brands used so I am making some best guesses based on what is most typical right now).

Is it a durable design?

In general, metal SIPS are very resistant to mold because as long as the wall remains laminated they are immune to condensation problems. Moisture cannot get into any wall cavity to find a cold spot to condensate.

If they are well connected and well sealed then they could also be durable against leaks. The waterproofing will depend on how well the seams are connected. I owned a metal SIPS trailer (Camplite) that was very leaky!

There are a number of concerns I have with this house:

  • There is a clear negative lapย at the bottom of the first piece. Itโ€™s not just an exterior trim detail, itโ€™s integral to the design. I donโ€™t see how you would not always be battling water pooling up and soaking the wall.
  • Itโ€™s nice that it unpacks quickly into a full livable house butย how are all those seams waterproofed?ย I do not think we have enough information on that right now.
  • Because itโ€™s done almost entirely in a factoryย we would need to see a detailed factory tourย to see if this is a good design (the company does not yet have a full-sized factory and is still raising money at the time of writing). There are so many details I would want to see including how the windows and all seams are waterproofed.
  • The house, like all prefabs,ย needs to be seen in person, especially during installation to see if there are any areas vulnerable to water. Because this company does not have a show house and is not in full production yet, itโ€™s highly unlikely you will be able to see one any time soon. Myย prefab postย goes over the due diligence needed here, and with this house, we donโ€™t have enough information to even do the due diligence.
  • MgO and steel have not gone well togetherย in the past.ย In Denmark, massive problems (and lawsuits) resulted when salts naturally leached out of MgO board and corroded the metal in the buildings.
  • The website says that Boxabl โ€œdoesnโ€™t use lumber or sheetrockโ€ and in an email they said โ€œwe do not use wood or materials that can rot or moldโ€. But inย multiple videos,ย wood appears to be the framingย of the edges of the SIPs. Hidden wood in a metal-based house is a problem in my books.

Is this a reliable company?

Still in development

Well, I donโ€™t think we know if this is a reliable company yet. As I discuss in my general prefab post I never go with the prototype of a prefab. They commonly have problems.

There could be situations in which we know a lot about a company, the construction details, and the testing of the prototype, but I donโ€™t see enough information here to be confident.

The company needs to raise 10 million dollars to be in full production, and at the time of writing they are still raising money. They are not yet at production stages.

Inconsistencies

On the fundraising page it says โ€œearly investors get a discountโ€. When someone asked what the discount is they responded โ€œIt is possible there will be a discount. We havenโ€™t announced it yet.โ€

In one of the videos, the rep states that you could install this without a foundation or permit. That sounds ill-advised.

It does not seem like the reps actually know what the floors are made of.

Elon Musk Involvement

It definitely adds legitimacy that Elon Musk is living in one. But it’s unclear whether he is backing the company or not. His area of expertise is not in construction but it would be great if he did lend his mind to making this a better built home than what it looks like. It has great potential to solve the problem of lack of affordable and healthy housing around the world. But in my view this house has not proven itself yet.

Filed Under: Healthy Building Tagged With: Healthy building, mold avoidance paradigm, mold prevention

Non-Toxic Insulation: A Complete Guide

April 5, 2021 by Corinne 156 Comments

There are so many excellent choices for non-toxic, healthy, green insulation, there should be one to fit everyone’s needs.

Look out for Greenwashing

There are many new options that claim to be “green” “soy-based” or are formaldehyde-free – this does not mean that they are VOC-free or safe. Look very closely at what’s in it. Also, flame retardants and mildewcides are not counted as VOCs.

Green Certified?

On top of that, certifications are not that useful: almost every insulation now qualifies as GreenGuard Gold, which for sensitive folks is not enough information.

The post includes the best of green non-toxic insulation and includes a cost comparison as of 2021.

What is the Safest Insulation?

Well, that depends. Technically, the options with no offgassing and no additives are the purest. But the natural odors in the organic options might not agree with everyone. Neither will the cost or availability.

Mineral wool is my top pick for most people, in most cases, because it’s simple in its composition and comes to a complete cure, leaving a zero-VOC product.

The types are outlined below organized by where they are used in the home, and in the order in which I would consider them.

I recommend all of the products here, some products have affiliate programs and some do not. Upon purchase, I earn a small commission through affiliate links at no extra cost to you.

Options Used in Wood Framed Houses

1. Fiberglass Insulation

Fiberglass batts in a attic ceiling

Fiberglass is the most common insulation used in standard stick-framed houses in Canada and the US. For this reason, I am starting here. It’s not actually my top pick in the batts category.

You can use it between wooden studs of a house, between floor joists, and in the attic. It is used in many trailers, but I don’t recommend that.

This option has improved dramatically in recent years, and the following brands are now extremely low in VOCs.

Formaldehyde-Free Fiberglass Brands:

1. Knauf EcoBatt is recommended by many extremely sensitive folks who could not tolerate polystyrene, cotton, or wool. They are formaldehyde-free and their declare label lists all ingredients down to 100 ppm.

2. Owens Corning Ecotouch fiberglass insulation has GreenGuard GreenGuard Gold certification. The binder is formaldehyde-free and “made from widely available plant materials”, according to the company. All ingredients except the pink dye are listed. The patent can be found here.

3. Certainteed Fiberglass insulation is also made with a plant-based binder.

4. Johns Manville Fiberglass insulation is GreenGuard Gold and uses a formaldehyde-free acrylic binder. A patent by the company that is likely related to this product can be found here.

What are BioBinders in Fiberglass Insulation?

We don’t know much about what bio binders actually are, but by looking at this patent you can tell that they look mostly safe. However, it’s hard to zero in on what it is.

There are some preservatives in there, and when they use a biobased binder it looks like they are adding a biocide. (According to patents the acrylic binders might also use biocides, but which type is unknown).

Are there Flame Retardants in Fiberglass?

Fiberglass insulation is made with boron but I don’t see any other flame retardant added, especially in the batts that do not have paper backing, and in the spray in type.

Neither Declare labels nor the companies’ patents suggest flame retardants. Pharos also does not list flame retardants as a component.

Blown-In Fiberglass

Blown-in fiberglass that I have looked at recently contains borates, soda ash, lime, siloxanes/silicates/silane, mineral oil, and an unknown anti-static additive.

Owens Corning unbonded loose-fill and Knauf Jetstream Ultra look similar. A client reported a “strong smell” from JM Climate Pro Fiberglass blown-in, but I don’t see the ingredients for that one, so I cannot compare it to the other two.

Fiberglass Insulation Around Pipes

The fiberglass insulation for around pipes that I have seen is also formaldehdye-free.

  • R-Value
    • 3.5 inches is R-11-R-15.
  • Cost USD (2020)
    • Knaff Ecobatt is 0.49/sq ft and you can buy it at Home Depot or through your contractor.

2. Mineral Wool Insulation

mineral wool batt insulation in a wall

Mineral wool is my top choice for batt insulation. It is in widespread use by builders who build green or high-quality homes and it is the most obvious alternative to fiberglass. It is also easy to source.

  • The batts can be used between wood studs anywhere in the house.
  • It’s very good at staying in place with compression fitting, so it fits well between framing.
  • It fits and holds up well in ceiling joists.
  • It can be used in an attic if detailed really well and if you don’t do well with any of the blown-in options.
  • It can be used on basements walls.

Non-Toxic Mineral Wool Brands

1. Rockwool (formerly Roxul) is the most common and accessible mineral wool insulation.

They have a newer version, called AFB evo, that does not contain formaldehyde. The binder is an undisclosed polymer (a plastic, likely acrylic). It also contains mineral oil. It’s much harder to source than their standard batts.

The standard Rockwool ComfortBatt does contain phenol-formaldehyde which will cure completely and quite quickly if it’s not already cured by the time it gets to you.

Rockwool ComfortBatt is the type for perimeter exterior walls, Safe N Sound, their soundproofing version is for interior walls, and ComfortBoard is exterior insulation (outside of the sheathing).

All three contain the same binders/additives: <3% phenol-formaldehyde, <1% starch, and <0.2% mineral oil source.

You could try both options (the regular and AFB evo), but there are few situations in which the regular Rockwool does not work for someone after airing it out for a short time.

2. Thermafiber by Owens Corning is a brand that has a regular phenol-formaldehyde line and a formaldehyde-free line (you will see the letters FF), the latter usually has to be special ordered through a store. They also have a blown-in option as well.

3. American Rockwool is a brand that is harder to source (in 2020 they stalled production). The company claims no chemical additives or binders, and that would be a bonus for the extremely sensitive. They also have a blown-in option.

Other Info

An easy way to cut through mineral wool is with an electric carving knife.

This insulation has good soundproofing qualities. The Safe N Sound version can be used on interior walls for soundproofing between rooms.

The fibers can cause a contact allergy if you are not using gloves, but the insulation itself is hypoallergenic for most people.

  • R-Value
    • 3.5 inches is R-15.
  • Cost USD (2020)ย 
    • $0.95/ sq ft forย Rockwoolย (Comfortbatt, 3.5 inch)
  • Where to Buy
    • ย Rockwoolย and Thermafiberย at hardware stores across the US and Canada, or through your contractor.

3. Wool Batt (and Blow-In) Insulation

Real wool insulation being placed between studs in a wall
Havelock Wool Insulation via www.havelockwool.com

Wool batting might be the next insulation type to consider if you want a non-fiberglass option and you have ruled out mineral wool.

It can be used between wood-framed walls and in the attic floor. It’s more expensive than fiberglass and mineral wool above.

Top Brands of Wool Insulation

1. Havelock Wool has no synthetic fibers and no binders. It’s only wool and boric acid. They provide a Declare Label for all of their ingredients. This is the purest of the wool options (and really the most natural insulation all around).

It’s definitely a favorite in the environmentally sensitive community. You can buy it online which makes it the most accessible wool brand.

2. Oregon Shepard adds boric acid, sodium pentaborate dehydrate, and a proprietary component that includes a natural protein, last I checked with them.

3. Black Mountain NatuWool which is 95% wool and 5% polyester binder and is treated with borax.

Blown-in Wool Insulation

The purest option here will be the blow-in wool insulation.

Some extremely sensitive folks have done well with Oregon Shepard blow-in and another extremely sensitive person did well with Havelock loose-fill. I tested Havelock and found that it did have a noticeable wooly smell, though others have barely noticed it.

The natural oils of the wool have an odor that may not work for some sensitive people, although it is not an additive or chemical smell.

While none of them claim organic certification, wool is one of the purest options.

As for borax/boric acid, I’m mostly concerned about inhalation, ingestion, and absorption through touching eyes and mouth. I’m not very concerned about it once it’s behind the wall.

  • R-Value
    • Wool in batts has R-13.7 in 3.5 inches
      Blow in dense-pack R-value: can be 15.3 in 3.5 inches
  • Cost USD (2020)
    • Havelock Loose Fill is $1.97/sq ft
      Havelock Batts is $1.62/sq ft
  • Where to Buy
    • Buy through local green building supply shops or buy Havelock online.

4. Recycled Cotton Batt

a close up of recycled cotton batt insulation in a wood framed wall

Ultratouch Insulation is what my builder used in my chemical-free tiny home. If you rule out fiberglass, mineral wool, and real wool, this would be something else to consider.

It used to be made from new denim scraps, but they have moved to recycled denim now. It does contain boric and ammonium sulfate and an olefin binding fiber (similar to rayon).

You have to test it for your own sensitivities. I became more sensitive to fabric treatments after I moved into my house (and I had the type made from new scraps).

I would not use this insulation again due to its poor ability to hold itself tight in the walls, the potential for mold if it gets wet, and the slight odor I picked up.

It can be used between wood-framed walls though it does not hold itself up well in ceilings/between floor joists, especially compared to mineral wool. I personally would not use it in a basement.

  • Other Info
    • Wear an N95 mask while cutting and installing as it does get extremely dusty when working with it.
  • R-Value 
    • For the 3.5” thickness, you get an R-Value of 13
  • Cost USD (2020) 
    • $0.79/sq ft
  • Where to Buy
    • This had to be special ordered when I built my house. Now, you can buy it at Lowes and Home Depot.

5. Hemp Insulation

A person cutting hemp insulation with scissors

Hemp insulation is the newest alternative insulation in the North American market. It’s been used for much longer in Europe.

I think it is very promising. It’s harder to source and more expensive than some of the other options in this category, but it could be really great for someone who wants something natural and who hasn’t done well with the other options above.

Brands

1. Thermo-Hemp out of Europe was one of the first brands.

2. NatuHemp Semi-Rigid panels are available in the UK and Canada. Canadian NatuHemp, which can be shipped throughout Canada and the US, is made of 88% hemp fiber and 12% polyester fiber, with no chemical binders and no off-gassing (they claim).

3. HempWool is 92% wool and 8% polyester. It’s available through their website and ships within the US (not to Canada).

4. MEM in Canada.

Companies have been coming and going out of business rapidly in the hemp insulation industry.

Ask them what they add to it, apart from hemp: alternate fibers, binders, flame retardants, and if it’s organic. And always test a sample first!

  • R-Value
    • It is R-13 for 3.5 inches
  • Cost USD (2020)
    • NatuHemp is $1.80/sq ft
      Sunstrand batt is $1/sq ft
  • Where to Buy
    • Contact the companies on where to source it.

Blown-In Insulation

1. Cellulose

Blown in cellulose insulation in the floor of an attic

Recycled cellulose is an option often slated for those with chemical sensitivity. It is a blown-in insulation made with recycled newspaper that contains a fire repellent like boric acid.

Newspapers are made with “soy-based” inks but they still contain many other chemicals in the inks apart from soy, and there are additional additives in the insulation, usually mineral oil.

Dense-packed cellulose is often used in Passive House design, which has great attention to details around moisture management and green healthy materials.

It is used in both walls and attics.

Safe Brands of Cellulose Insulation

1. Greenfiber brand from Lowes and Home Depot is 85% recycled newspaper. It contains boric acid, sodium poly borate, sodium tetraborate pentahydrate, amylopectin, and mineral oil.

2. Ecocell makes batts that are a mix of cellulose and cotton. It also contains PET plastic, very small amounts of boric acid, as well as sodium poly borate, and ammonium sulfate. You can find this insulation without ammonium sulfate – that may be special order. This used to be sold at Home Depot but now it’s not clear where to source it.

3. Weathershield brand by Rona in Canada.

  • R-Value 
    • 13.3 for 3.5 inches
  • Cost USD (2020)
    • $0.32/sq ft

2. AirKrete Cementitious Insulation

AirKrete is a cementitious blown-in insulation that claims to be VOC-free. It has passed the “sleep next to it test” of many chemically sensitive people.

The company, however, has declined to participate in the industry-standard VOC test as well as the proper R-value test, so there is some doubt around this product’s claims.

We don’t know what the undisclosed 2% of this product’s ingredients are, but many with severe chemical sensitivities have chosen to go with this option and have done well with it.

Because it is a foam, it will get into all the cracks and crevices and therefore give you a higher “real life” R-Value than the batts.

Some people have reported shrinking, crumbling, and trouble drying. Here is the source for the concerns.

Paula Baker-Laport continues to recommend this insulation, so I’m assuming that many are still doing well with it.

It can be used in walls and roofs. (Consult with an architect when designing an unvented roof).

Non-organic options like AirKrete are more likely to be hypoallergenic.

  • R-Value
    • R-13 for 3.5 inches
  • Cost USD
    • Around $2.25/sq ft including installation costs
  • Where to Source
    • You would have to check to see if you have a certified installer in your area before proceeding.

3. Real Wool, Mineral Wool, and Fiberglass Blown-In

A close up of blown in fiberglass insulation in a attic floor with a man measuring the depth of it

These three insulation types can be blown in as well. Fiberglass (pictured) is the most common blown-in insulation, followed by cellulose.

Mineral wool and real wool blown-in are less common but are healthier choices.

Brand names can be found in those respective sections above.

Exterior Insulation for Houses 

1. Styrofoam/Rigid Foam

i. Polyisocyanurate “Polyiso” Foam Board Insulation

A man installing thick polyiso insulation between wood studs

Polyiso is one of the insulation types that is used on the exterior side of sheathing.

Typical current blowing agents for polyiso are CO2 and pentane. There is some “thermal drift”, meaning the blowing agents offgas over time. The offgassing is extremely minimal.

This is going to become a very common exterior insulation as building codes move towards requiring exterior insulation.

It can be used in trailers and metal structures as well. It’s not to be used under slabs.

Flame retardants are a bigger concern than trace pentane. The most common flame retardant is TCPP. It’s best to look for brands that don’t use a halogenated flame retardant like TCPP. Newer and safer flame retardants are non-halogenated phosphorus-based.

Though the foil does block the FR, the edges are unsealed and it will never be perfect.

Healthy Brands of Polyiso Foam Insulation

1. Johns Manville Foil Faced Polyiso has been the most popular brand among those who are sensitive, but they have discontinued Energy 3E, which was the one made without TCPP (all they have said is that it is phosphorus-based and is non-halogenated).

2. GAF polyiso EnergyGuard-NH uses a halogen-free flame retardant (which is phosphorus-based, like the Energy 3E FR was). “Unlike TCPP, the flame retardant becomes part of the polymer backbone of the insulationโ€”so there is no free flame retardant that can leach out”, according to GAFโ€™s director of sustainability Martin Grohman. “TCPP, by contrast, is not chemically bonded to the polyiso polymer, so it can more readily escape.” Source

3. ZIP System R-Sheathing is the Huber Zip OSB sheathing, polyiso, and weather-resistant barrier all in one. Though you can use the above two brands as exterior insulation on the outside of the plywood or OSB, “ZIP-R”, as this type is normally called, is integrated with the sheathing, with the polyiso on the interior side.

  • R-Value 
    • Technically it’s R-6/ inch but it’s really about R-5.6/inch over its lifespan because it loses R-Value over time. It also loses R-value the colder it gets.
  • Cost by R-Value (R6)
    • R-6 is $0.60 / sq ft

ii. Extruded Polystyrene (XPS)

A close up of pink XPS foam board insulation on concrete

XPS (extruded polystyrene) is another common exterior insulation outbound of the sheathing. It is also used on exterior concrete basement walls, underneath the slab, and in trailers.

XPS, like polyiso, has some “thermal drift” i.e. some very slow offgassing of the blowing agents over time.

“Over a long period of time (50 to 75 years), the blowing agent slowly diffuses through the thickness of the foam” (source).

Typical blowing agents for XPS are CFC-12, HCFC-142b, and HFC-134a, but they change their formulas over time.

HFCs contribute to global warming. Changes started January 1st, 2021. Eleven states have banned foams blown with HFC-134a and other high-GWP blowing agents, including HFC-245fa as of January 1st 2022. A ban on high-GWP blowing agents also went into effect in Canada on Jan. 1, 2021. Canada did not ban HFC-134a but created maximum GWP for foam blowing agents.

XPS insulation was treated with the flame retardant hexabromocyclododecane (HBCD) until recently. The two main brands, Dow Styrofoam (Lowes) and Owens Corning Foamular (Home Depot) no longer contain HBCD.

Most are now using a butadiene styrene brominated copolymer as the flame retardant (Source). DOW lists a brominated flame retardant (FR122P) in some of their XPS.

How Concerning are These Flame Retardants in Rigid Foam?

Flame retardants are sometimes considered non-volatile and sometimes semi-volatile. They leach out in dust form as opposed to gas. If they become dust borne in the house, the main route of exposure is hand to mouth, though you can also inhale them.

My post on Flame Retardants goes into more detail.

  • R-Value
    • R-5/inch
  • Cost by R-Value
    • R-5 is 0.60/ sq ft

2. Mineral Wool Board 

A man placing a board of mineral insulation on the exterior of OSB sheathing

The other common and easy-to-source exterior insulation used in the US and Canada is Rockwool, in board form.

The Rockwool Comfortboards will be used more and more as many codes across the US shift to requiring exterior insulation.

Foam and Rockwool will be the two main exterior insulation types to consider since they will be familiar to builders and easy to source.

The boards can also be used on interior basement walls. They are also being used under the slab, as the only alternative to foam insulation there.

  • R-Value 
    • R-4/inch
  • Cost by R-Value (R6)
    • R-6 is $1. 24 sq ft

3. Cork

The exterior corner of a building that is covered completely in cork insulation

Thermacork insulation, unlike cork flooring, does not contain adhesives. It is held together by compressing it with heat which releases a natural binder in the cork.

The cork does give off a smoky smell that dissipates with time, as well as the natural odor of cork.

This is a newer product in North America and is more expensive than the more conventional options.

If you can afford it, it is my top pick for non-toxic exterior insulation due to a lack of additives and flame retardants.

It can be used as exterior insulation or even the facade of a house which serves the purpose of siding, insulation, and noise reduction.

See this post as an example or cork used as the facade.

  • R-Value
    • R-4/inch
  • Cost by R-Value (R8)
    • R-8 (doesn’t come in R-6) it’s $4.93/sq ft for the insulation type (rougher than the facade)
      R-8 in the facade grade, which covers your exterior insulation and your siding in one, is 10.77/sq ft
  • Where to Buy
    • You can buy this through green building supply stores.

4. Wood Fiberboard Insulation

Wood fiber insulation boards stacked up side by side

Wood fiberboard is often used in High Performance/Passive House designs as exterior insulation. It can be used closer to the interior as well.

One popular brand in North America is Gutex. It is 95% wood (spruce/fir, post-industrial, recycled and new wood), 4% polyurethane, and about 1% paraffin. The total VOC level is 187 ฮผg/m3.

  • R-Value
    • R-3.7/inch
  • Cost
    • R 5.8 is $1.81/sq ft
  • Where to Source
    • You can buy this through 475.

Insulation Typically Used in Trailers, RVs, and Vans

1. Rigid Foam

EPS (Expanded Polystyrene aka Styrofoam)

EPS insulation being installed on the exterior of a commercial building by a guy being held up by a harness

EPS (expanded polystyrene) is often used in trailers and can be referred to as “block foam” by the companies.

It can also be used as exterior insulation, insulation over concrete basement walls on the interior, and under the slab. Though you are far more likely to see the XPS type of styrofoam under a slab.

Blowing Agents

EPS usually is made with pentane as a blowing agent, the final product has trace amounts of pentane which dissipates rather quickly and completely. Some butane can also be used as a blowing agent.

Sometimes the only blowing agent is carbon dioxide (based on DOW xnergy Declare label).

Zero-VOC

EPS, despite the name (polystyrene), does not offgas styrene under normal conditions.

It is considered 0-VOC (and pentane and styrene are not exempt from the VOC testing).

What about Styrene?

The concerns over polystyrene (styrofoam) and styrene comes from the following a) chemicals released during the manufacturing of the product b) the product is very toxic if you burn it and c) the styrene can leach if you drink beverages especially hot or acidic beverages out of styrofoam cups.

This is a very old product with a long track record. Here are a couple of links to back up the claims.

In the form of insulation, I would consider this product to be non-toxic, zero-VOC, odorless, and stable, with the only risk being the flame retardants.

Flame Retardants

EPS used to be treated with hexabromocyclododecane (HBCD), but luckily it no longer is. Polymeric FR (a copolymer of polystyrene and brominated polybutadiene) is now the most common FR.

The foil faces on these insulations block the flame retardants. However, the foil and plastic-backed versions can have some offgassing odor. Some EPS is not backed with anything.

EPS used in packaging and cups does not contain a flame retardant and people have sometimes been able to source this type of foam for small structures.

If using EPS in a living space I would recommend borate treated foam to prevent ants from tunneling in.

R-14 for 3.4 inches EPS.

2. Reflectix and Prodex Insulation

A roll of reflextix insulation

Reflectix is a bubble foil made of aluminum over polyethylene bubble wrap. It is flexible, very thin, and claims to have a very high R-value. The thicker version claims R-21 (which is higher than 5 inches of wool).

These claims are disputed by Green Building Advisor and the Government of Canada. The former states that the 3/8th-inch foil has an R-value of only 1 (the same as a single pane of glass).

This would hardly be useful anywhere unless it is in a curved trailer, RV, or vehicle where all other options have been ruled out. Sometimes it’s just used to insulate windows, which can be a great help.

Prodex is another similar material – foil and polyethylene-based – that also has a disputed R-value.

Many similar brands can be found easily on Amazon or Home Depot.

3. Aerogel Insulation

A small sheet of aerogel insulation

Aerogel is a fairly new product – unusual, extremely expensive, and harder to source.

The term itself can refer to a variety of materials from the original silica translucent product to polymer-based products that may include the addition of fibers.

The original Aerogel insulation was developed by NASA.

Aspen Aerogel collaborated with NASA to make their polymer enhanced aerogel combined with fibers.

Some companies are selling insulation online that they claim is Aerogel. I would look closely at what’s really in it. Look for proper studies on the R-Value of it.

They claim an extremely high R-value of R-10 to R-30 per inch.

This may be ideal for small, round, and difficult to insulate places, if you can source it.

4. Thinsulate Insulation

A small folded sheet of thinsulate insulation

3M Thinsulate (SM600) is an insulation used in vans, other vehicles, and RVs.

It is made of polyethylene terephthalate (a type of polyester) and polypropylene fibers which will be tolerable for most people. The backing is polypropylene.

One percent or less of the additives are proprietary and therefore unlisted. The health rating is 0 which is good.

What I don’t love about using this product in vehicles is that the insulation itself is vapor permeable and it is attached to the walls with 3M 90 Spray (GreenGuard certified, not GreenGuard Gold, not reported to be very tolerable by many chemically sensitive people).

You may find this insulation tolerable and it may be a good product for a tiny house or structure.

You can buy it on Amazon and Ebay.

R-value

5.2 for the 1.65 inch

NB. I have seen similar but more unusual insulation made from polyethylene and polyester for homes in batts. (It is more popular in some countries outside of North America.) It may be tolerable depending on what is added to it.

5. Vacuum Insulation Panels 

Vacuum Insulation Panels have the highest insulation value of any of the insulation materials.

These Panasonic panels have an R-Value of R-60 per inch. They were used in the latest Leaf House design (tiny house). This could allow you to build a tiny house for almost any climate. Though this introduces a tricky metallic vapor barrier which needs to be carefully thought out.

The foil vacuum pack will block any VOCs from migrating through, but your moisture management system would have to be planned carefully here.

These won’t work in most houses. You might consider them in some trailers or metal framed homes.

They are very pricey and harder to source than almost all of the other options.

6. Non-Toxic Spray Foam Insulation

A person in full PPE spraying in 2 part polyurethane insulation

Spray foam that is used to fill cavities of walls is two-part polyurethane. Some of it may have soy added, but it’s still mostly polyurethane foam.

This insulation has to be mixed perfectly, under the right conditions (there are many), and applied correctly. When looking for a good spray foam you are looking for an excellent installer (the best one you can find) and not a specific brand.

The companies have claimed that it is no-VOC, or close to that once cured, but many individual tests and many individual noses of those sensitive have shown otherwise.

I know moderately sensitive folks who have looked at many houses with spray foam and been able to pick up the odor for two years.

And that’s when it’s done right. When it’s done wrong it’s a massive disaster that can end in a lawsuit against the company, plus an expensive imperfect removal of all the foam.

If you are extremely sensitive you would lose the whole house if this goes wrong, as the VOCs will soak up into other materials. This has happened to two of my clients.

Brands:

Icynene and Demilic are both 2-part polyurethane spray foam.

Whether they have soy or castor oils in them is insignificant in my overall view.

Icynene OC No Mix is still a 2-part polyurethane foam and although it appears to mix in the gun, the installation still has to meet all of the other parameters.

One part polyurethane:

One part polyurethane, which is the canned stuff discussed below, is much easier to tolerate, it’s used in small quantities, and it doesn’t have the same challenges and risks as the 2-part foam.

Insulating Around Windows and Doors – Non-Toxic Options

eight bottles of great stuff 1 part polyurethane insulation

Spray foam is often used around windows and doors. HandiFoam is GreenGuard Gold and will be tolerable for many folks after curing. In Canada, the best source is Organic Lifestyle.

I find this spray foam to be odorless once cured.

Other brands like Great Stuff, which you can find anywhere, seem very similar to me, if not the same.

Great Stuff does contain a flame retardant in some of its lines and Handi-Foam has declined to answer whether it contains a flame retardant or not.

a roll of polyethylene backer rod

Instead of using spray foam around windows and doors you can fill in the gaps with Backer Rod and seal with non-toxic caulk if needed.

I have a post on caulking if you need to test multiple brands.

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Corinne Segura is a Building Biologist Practitioner with 7 years of experience helping others create healthy homes.

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Filed Under: Healthy Building Tagged With: Healthy building, mold prevention

Non-Toxic Grout and Thin-Set Mortar

March 15, 2021 by Corinne 57 Comments

Updated Fall 2021

This post covers all of the materials you need to complete a tiling job without the use of toxic materials that offgas VOCs.

Luckily this is not too difficult to accomplish if we stick to the right kinds of products.

When tiling, first we lay down a mortar which is almost always a thin-set (not thickset anymore). We might need to use membranes or special backer boards depending on the project. After the tiles are laid, the grout is applied between the tiles. A non-toxic grout sealer is the final product needed.

This post contains affiliate links to relevant products that I use and recommend. Upon purchase, I earn a small commission at no extra cost to you.

For individual help on choosing the best products and materials for you and your home, you can schedule a consultation with me here.

Non-Toxic Thin-Set Mortar

Thin-set is the bonding layer that goes down under your tiles. Concrete-based thin-sets are the safest type and are also easy to source.

Thin-set mortar is also known as dry set and dry bond.

Brands

I used Custom Building Products CustomBlenc Standard thin-set mortar which is zero-VOC (and mildewcide-free). It had a light “wet concrete odor” when wet but it is safe once dry.

Unmodified Thin-Set (no Additives)

An unmodified concrete-based thin-set is concrete, sand, and lime and is not mixed with acrylic-latex additives.

The unmodified type is recommended for floors and may not be suitable for all applications. Schulter also makes SET, an unmodified thin-set mortar.

These non-toxic thin-sets are more prone to cracking than ones with additives, and you have to check if your application requires polymers.

On walls, thin-set usually has some acrylic (called latex) additive. Ceramic tile doesn’t need much acrylic-latex, porcelain tile needs more. Consult first with the tile manufacturer, if you don’t get a clear answer on which type you need then look to the advice from the thin-set manufacturer. You also need to consider requirements from membrane manufacturers. Source, JLC.

Modified Thin-Set

Ideally, I like to see full disclosure on what the polymers are in thin-set.

Ardex X 5 declares EVA as the polymer.

Other Types

Most chemically sensitive folks would want to avoid the toxic epoxy thin-sets and most mastics.

Although there are some safe and tolerable tile glues (mastics) like AFM 3 in 1. This can be used when applying tiles to a backsplash, however, you do need to consult with AFM on whether this will be suitable for your project (dependant on the weight of the tiles).

Non-Toxic Tile Membranes / Underlayment

Over the first layer of thin-set, I used Schluter DITRA (polyethylene with a fleece backing), an uncoupling membrane that will help prevent cracking in my tiny house (it worked well and did not have an odor to me).

Polyethelene is a very safe plastic. In regular-sized houses, you can use this as well to prevent cracking.

If you just need a waterproofing membrane, use Schluter Kerdi (a modified PEVA core with non-woven polypropylene).

Membranes for the Walls

For a tiled shower, the Kerdi shower system is recommended by architects to create a mold preventative shower.

Be sure to test all parts including Kerdi Fix sealant if you are sensitive to chemicals. With the Schulter systems you often need to use their thin-set and grout. Schulter All Set and Schulter Set do contain fly ash.

Integrated Membrane Boards

Instead of using the membranes over concrete backer boards (backer boards are discussed in this post), you could use Kerdi Board (also available through Walmart) or WEDI Panels (you can mention my name at The Tile Shop for 20% off).

Test for tolerability before proceeding. They will be behind the thin-set, tiles, and grout, which will render them safe for most people with sensitivities.

These integrated membrane wallboards help simplify things by replacing concrete backer boards + membrane with just one substrate that is easy to waterproof.

The panels are made of non-toxic zero-VOC polystyrene with a plastic membrane already integrated.

Concrete Based Non-Toxic Grout

Concrete grouts are the safest grouts and are generally non-toxic. You don’t need to go to a green building store for this product, these grouts can be found at all regular building supply stores and online.

You do want to look for a basic concrete-based grout in powder form. Never pre-mixed.

Top Brand

I used Custom Building Products Polyblend grout (or the new Polyblend Plus), it’s the same brand as the thin-set, and like the thin-set, is zero VOC and contains no mildewcides or antimicrobials.

It comes in sanded and unsanded and in different colors. (Unsanded is for marble and certain tiles types). You can find this at Amazon, Flooring inc, and Walmart.

It barely had an odor, though it does have polymers (listed as EVA). Almost everyone does well with this one.

Alternative Brands

Custom Building Products Prism is similar to their Polyblend with some additional aggregates and more of the polymers which makes it a little bit less water absorptive (a little bit less breathable but it’s not that big of a difference).

Mapai Keracolor (U and S) is another brand that lists the polymer – we know it is EVA.

If those don’t work for you, Bostik Hydroment is also recommended for people with sensitivities. However, it has a small amount of latex additive (this usually refers to EVA) and contains an antimicrobial, which appears to be silver-based.

Laticrete also makes a number of zero-VOC grouts and thin-sets. Many Laticrete products use Microban, which is this case almost certainly refers to Microban’s silver antimicrobials.

Make Your Own Grout

If you need to avoid all additives, you can make your own grout with Portland Cement mixed with sand, lime, and water for a totally chemical-free option. 

Here are the ratios from Craftsman’s Construction Encyclopedia. To mix your own unmodified grout it is a ratio of Portland cement to sand, 1:1 for 1/8th joints, 1:2 for 1/2 inch joints, and 1:3 for over 1/2 inch joints. Adding up to 1/5 lime increases workability.

What are Grout Additives and are They Toxic?

Those who are sensitive to chemicals will probably want a concrete-based grout (like those above) and then see which additives if any can be tolerated.

Since additives are trade secrets and polymer is a word that can mean a variety of chemicals (there are over 10,000 polymers that can be used in cement) you will probably have to test them against your sensitivities.

Common polymers in grout include: latex-based polymers, acrylate copolymers (acrylic eg. PVA), styrene butadiene rubber copolymers (SBR), vinyl acetate-ethylene copolymers (VAE), and ethylene-vinyl acetate (EVA).

The main polymer found in concrete-based “modified” grout is EVA.

Polymers can come mixed in or you might mix them in yourself. Mixing them means you can test the additive against your sensitivities in a more concentrated form, on the other hand, you may not want to test the polymers and the grout until it has cured.

Polymers are added to improve chemical resistance, reduce porosity, improve flexibility, and freeze/thaw stability (source).

You will have to find out when and where you need additives, which will depend on your specific project. I don’t consider most of these polymers to be toxic.

Are Thin-Set and Grout Safe – Why do They Have the Prop 65 Warning?

Sanded grout and thin-set contain silica (the same substance as glass) which is harmful to breathe in when in dust form; you will see a Prop 65 Warning on every product that contains silica dust.

Use an N95 mask (or better) when mixing it until it is fully wet. This is completely safe when it is no longer in dust form.

There may also be other minerals in there that are only a problem in dust form like aluminum oxide, which can result in a high health rating on the SDS and other warnings. Again, these are safe when it’s mixed wet and when it cures.

Some cement contains fly ash and some don’t. Plain Portland Cement does not have any other harmful additives.

Non-Toxic Thick-Set /Thick-Bed Mortar 

Thick-Bed mortar (also called thick-set or mud set) in its most basic form is simply Portland cement and sand. Custom Building Products makes a mix of 1:3 that is unmodified, it contains no chemical additives like polymers.

This is harder to source than thin-set. 

Alternative to Concrete-Based Grout

For something more waterproof check out QuartzLock; this won’t be tolerable for everyone. It is a urethane-based grout, not cement, and provides more waterproofing.

I personally would not use a premixed grout and I would keep a close eye on contractors to make sure that they use what you specified and don’t swap that out for a premixed option.

This grout is significantly higher in offgassing and it should not be necessary in almost every application.

Your waterproofing needs to be done properly behind the tiles.

Epoxy grouts are also waterproof, and may be selected when a clear grout is specified.

Non-Toxic Tile Types

I used concrete tiles from Morocco in my tiny house. Porcelain and ceramic tiles do not offgas VOCs.

For more info on choosing non-toxic tile types, my post on bathrooms goes into the most detail.

Tiles don’t generally have any offgassing. Lead is the biggest concern.

If you are looking for safer tiles, this e-book outlines the XRF lead testing results from 64 ties that are available now in late 2021/early 2022.

It shows the test results for each tile, alongside the photo, description, and where to buy it.

If you buy the same tile from a similar time frame, it is reasonable to assume that the test results could be similar or the same.

This can help guide your purchases towards low-lead, or lead-free tiles.

You can get it HERE!

Non-Toxic Grout Sealers

For a full review of all the grout sealer types (and where to use each kind) see my dedicated post on grout sealers.

In many situations, you don’t need a grout sealer, or you could even do more harm by blocking moisture.

If your situation does call for sealers to be used, the post on grout sealers will walk you through each type.

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Corinne Segura is a Building Biologist with 7 years of experience helping others create healthy homes.

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Filed Under: Healthy Building, Healthy Interiors Tagged With: Healthy building, healthy interiors, mold prevention

Mattresses for the Chemically Sensitive | A Complete Guide for 2022

February 21, 2021 by Corinne 145 Comments

Updated Winter 2021/2022

This post started out with my journey to find the best mattress that suited my own extreme sensitivities. There are so many more options now. Still, many I don’t think are good enough.

We will look at my top picks for the best healthy spring mattresses (no latex or polyurethane) with price comparison (2022), all wool mattresses, and other futons, and why I don’t use natural latex.

There is no all-around “best” mattress for those with sensitivities. Sensitive folks can have a hard time with any of the following main materials used: cotton, wool, hemp, natural latex, and polyurethane. You will have to find out which materials work for you.

The article includes a look at more unusual options for those who don’t do well with any of those main materials, or who just want something simple.

I recommend all of the products here, some products have affiliate programs and some do not. Upon purchase, I earn a small commission through affiliate links at no extra cost to you.

First, a Quick Backgrounder on the Chemicals in Our Mattresses

Conventional Mattress Materials

Conventional mattresses are usually made of polyurethane foam or, more rarely, synthetic latex which both offgas VOCs. It’s difficult to find out exactly which chemicals were used in a particular mattress.

The worst offenders are synthetic memory foams, followed by polyurethane (though almost all polyurethane can meet CertiPUR certification which I discuss here), and then synthetic latex, which usually does not meet any green certifications on its own.

Going with a spring mattress does minimize the amount of foam and therefore chemicals in it.

“Soy Foam” is polyurethane with some soy.

Flame Retardants Might be Added

Look for mattresses that specify no chemical flame retardants – I list them in this post. Sometimes boric acid is added but not disclosed. Newer flame retardants include Kevlar and silica which, from what we know, are safe.

Natural Latex Can be a Problem

Most “natural” or non-toxic mattresses contain natural latex which I have some concerns about and many chemically sensitive folks react to. I discuss that in the article as well as the best alternatives.

Chemical Coatings

You also want to avoid mattresses that are stain-resistant, as they contain harmful perfluorochemicals.

Some mattresses are also adding an antimicrobial agent which you would generally want to avoid, though there are some natural antimicrobials that might be okay for some people.

1. Non-Toxic Spring Mattresses

My top picks for a safe and healthy conventional feeling mattress are these five options below.

They don’t contain latex or polyurethane foam. I list options without wool for the most sensitive who are often looking to avoid this allergen trigger.

They are also free of flame retardants.

 i. My Green Mattress 

The Echo is made of GOTS certified cotton and GOTS certified wool with springs. No polyester here. It is $1,099 for a queen (firm).

For a proper spring mattress, this is the price to beat. They often run promotions, which I post the codes for here.

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You can buy directly through them.


ii. Naturepedic 

top non toxic mattresses no odour flame retardant free no offgassing

The Naturepedic Chorus contains GOTS certified organic cotton, organic wool (with lower odor than many other brands), and PLA polyester with springs. It’s $2,000 for a queen.

This is my top brand, as I like the construction, it’s high quality and it’s very well-liked and well-tolerated amongst many of the most sensitive.

In the kid’s mattress section they have one that comes in a full size that does not contain wool. For those who cannot tolerate wool, this is one of the top picks. This option is firm though!

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It’s $900 directly through them.

You can also find some of their mattresses through Amazon, prices fluctuate.


iii. Royal-Pedic

all cotton organic cotton luxury non-toxic mattress

Royal-Pedic makes a cotton spring mattress with no wool. The All Cotton line is not organic, the Natural Cotton line is organic but not certified.

They also offer options with wool.

This is known as a high-end and comfortable option, though like the others in this category they are firm.

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It is around $3,000. You can find the All Cotton on Amazon, prices fluctuate over time.


iv. Earthsake 

Earthsake is a unique mattress. They make a hemp spring mattress with no cotton and no wool.

For those with sensitivities to cotton and wool, or who are in a humid environment, this may be a better choice.

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A queen is $2,795 via their website.


v. The Futon Shop

The Futon Shop has a good variety of very affordable mattresses.

Those with springs and coils will be more comfortable than conventional futons.

You can choose ones without latex or “soy foam” (which is polyurethane).

They no longer use boric acid, which it seemed like some were reacting to in the past.

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Their prices are fantastic starting at $575. (US only. They don’t ship to Canada).

2. Chemical-Free Wool Mattresses

Wool is a natural and healthy choice, as long as you are not allergic to it or sensitive to the lanolin odor of wool.

Many brands that use wool process and wash the wool leaving it with almost no odor. Others use a less processed batting that does have that telltale natural odor.

i. Shepards Dream 100% Wool Futon

Image from Shepards Dream

When I was furnishing my tiny house I was extremely sensitive to toxins. I went with the purest and simplest option I could find, which is a 100% eco wool mattress from Shepard’s Dream. 

It is a (relatively) economical choice at $1,975 for a queen. (I have the skinny version pictured).

It does have a wool smell but it is not super strong. It is firm, as it gets compacted with time. If you don’t like firm mattresses I would recommend using a topper with it or using the thicker version.

Shepard’s Dream has offered a 10% discount to my readers, you can mention my name, Corinne Segura for the discount.

a black and white button that says buy that you can click on

Buy through their website.


ii. Heartfelt Layered Wool Felt 

Image from Heartfelt Collective

For those with extreme sensitivities, a layered option that can be washed can be very functional. Heartfelt Collective sells wool felts that can be layered and washed.

To put together what would come to about a conventional queen feel, it would cost about $1,900. But you may not need that many layers, or you can combine the woof felt layers with something else.

a black and white button that says buy that you can click on

Buy through their website.


iii. Savvy Rest Wool Futon (Cotton Cover)

Image from Savvy Rest

Savvy Rest makes a futon style organic GOTS cotton covered organic wool mattress for $1,800.

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Is Wool Chemical-Free?

When looking at wool qualifications you may want to know various factors, depending on your sensitivities, such as the chemicals used to process the wool.

Certified organic wool is becoming more common, GOTS has expanded to cover wool.

If a company claimsย all-natural, pure, or eco-wool, you will want to take a look at what they mean by that.

Wool doesn’t need to be organic to be free of harmful chemicals.

3. Natural Latex Mattresses

There are plenty of options for natural latex mattresses made in the US and Canada. In fact, when looking for non-toxic beds, it’s difficult to avoid natural latex.

Make sure it is 100% natural latex and has GOLS certification. And test for odors/sensitivities to make sure it is tolerable.

These mattresses range from $800 to $5,000.

Almost all of the green mattress brands offer natural latex, you can even find this now at Costco and IKEA.

These are the most affordable options:

i. The Futon Shop

Some of the most affordable natural latex options are by The Futon Shop.

Many of their latex options are paired with wool. Some are paired only with coconut coir or with hemp and coconut coir. Others include PLA and cotton.

The simple options start at $800 for a queen.

a black and white button that says buy that you can click on

Buy through The Futon Shop.


ii. Topper from Amazon

natural latex from Amazon, affordable topper to sleep on

The most economical option is to buy a 3-inch piece of latex. For a little over $200 (plus tax and shipping), you can get 3″ natural latex from Amazon (queen). I find that 3 inches is very comfortable to sleep on.

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It won’t have a cover, but for $450 you can get 6 inches of latex on Amazon.


iii. IKEA MAUSUND

This non-toxic IKEA mattress is 85% natural latex and 15% synthetic latex with wool wadding. If I was going to go with natural latex I would go with a large established brand like IKEA if not the super simple topper from Amazon.

You will want to check this out in person to make sure the odor of the natural latex and the synthetic latex works for you.

Update: No longer sold at IKEA in the US and Canada this option is only available in Europe.


iv. Avocado

If you want to go with a more purist natural latex bed, Avocado is the best in this category.

It’s 100% GOTS organic certified cotton & wool and 100% natural GOLS certified latex.

Avocado goes all the way on healthy natural latex, with the top organic certifications, no adhesives between the layers of latex (only on the top layer), and silica or wool as the flame-resistant barrier.

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A queen is $1,600. They currently have a discount code for $125 off.


v. Awara

Awara beats Avocado in price but it falls slightly short in eco cred. It uses glues in the construction, and the latex isn’t GOLS certified.

Still, those are not dealbreakers for most people in the grand scheme of things. This slightly more affordable option still meets most of the marks for a safe and healthy mattress.

The flame retardant is natural silica, and the top layer is organic cotton and organic wool.

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A queen is $1,300 through their website plus there is often a $300 off deal for new customers.

Is Natural Latex Mold-Prone?

After one of my pillows became covered in grey mold after two years in low humidity, in a new, non-moldy house I started looking into this. Over the years I have seen many reports like this.

I have seen melting, disintegration, and visible mold on pillows and on mattresses that were on slats in normal humidity, sometimes even when brand new. Including two recent reports of a popular organic latex brand.

There are other cases of this on a forum, many private messages from people writing to me, and reports in Facebook groups.

It is not clear if this is a defect (these were all different brands), or whether there is a certain condition that leads to the latex breaking down or going moldy.

I would not buy natural latex again myself after going through this, but I do have to say, I have not seen a report of this problem for years now (as of 2022).

Does Natural Latex Offgas?

Folks with MCS vary greatly in their ability to tolerate the natural smell of rubber and different brands work for different people. Here is a list of some of the ingredients that can be in natural latex.

Essentia, which makes natural memory foam claims that the VOC levels of their foam 36 ฮผg /m3, about the same as that of natural latex. From my research, this is around the same levels as outdoor air – but it is not zero VOC or zero offgassing.

There have been dramatically different odors from different brands and even from the same brand over time. So you may want to check out more than one option.

4. Natural Memory Foam

Photo via Essentia

Most memory foam is made of polyurethane and it’s usually more toxic than your standard polyurethane foam, though they are not all the same.

There are a range of chemicals added to produce polyurethane memory foam for different brands.

The only non-toxic non-polyurethane memory foam out there is Essentia, which is natural latex-based. The VOC levels are extremely low, 36 ฮผg /m3.  

When researching “background VOC levels” I did find this to be within background levels (though everything adds up). Here is one study and here is another study to confirm this.

Background levels of formaldehyde can be found here. 

This mattress contains essential oils – grapefruit seed, coneflower, and jasmine. I tested a sample and it has a noticeable scent (though it’s very faint). Though I would not say it is flowery, it is a bit sweet. 

It contains Kevlar as a flame retardant. 

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You can find them through their website and on Amazon.

5. Non-Toxic Polyurethane?

I would consider polyurethane as well. I personally would consider this material over memory foam (of any type), and usually over natural latex.

It does offgas a little bit, but for some folks who are less sensitive, this could still be considered non-toxic, especially if you give it some time to offgas. It will become tolerable with time.

If you have serious back or neck problems and need something with more cushion than the firm cotton and wool options, you may want to consider polyurethane.

This is the least expensive mattress type, so for some people, this is the only option.

If you don’t want or need a full bed, polyurethane slabs can be useful as simple sleeping solutions. I have used them many times.

White Lotus has a non-petroleum-derived foam that many have done well with.

i. IKEA

I would consider IKEA polyurethane beds. They don’t use flame retardants in the foam. Just go as simple as you can.

The MINNESUND for $75 is the least expensive. But for a little more you can add springs and reduce the amount of foam even more. The HASVร…G is $179.

Despite being a budget option, IKEA mattresses do not use fiberglass as the fire barrier. Some of the mattresses contain modacrylic fiber wadding and some do not.

IKEA mattresses in North America use an inherently fire-resistant barrier made of rayon/polyester batting. Flame retardant chemicals are only used for some stitch bonds, piping, and zippers.

I may use the aluminized tarps to sequester the offgassing, if needed.

a black and white button that says buy that you can click on

Buy through your local IKEA.


ii. White Lotus Eco-Foam

Image via White Lotus

White Lotus makes a simple mattress based on their naturally derived polyurethane. It also has a wool layer and cotton cover.

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It’s $986 for a queen through their website.


iii. Purple Mattress

The Purple Hybrid mattress is made of a non-toxic plastic grid and minimal polyurethane.

The Purple Hybrid with coils really minimizes the amount of foam used while keeping the comfort level high.

Moderately sensitive folks have done well with this brand so I certainly would consider it myself.

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You can buy the Purple Mattress (original) from Amazon or from their website.

The Purple Hybrid Mattress, which you can buy from their website, is $1,800 for a queen.


iv. Saatva

Saatva mattresses have been vetted by the chemically sensitive – a number of folks have reported that their foam seems to be very low in offgassing.

It does contain memory foam, which is usually higher in offgassing than standard polyurethane yet it still has good reviews.

Alternative Beds for the Chemically Sensitive

1. Buckwheat Hull Beds

Image via Open Your Eyes Bedding

Open Your Eyes Bedding sells organic cotton canvases and buckwheat hulls that you twist together yourself!

A mattress topper or pad may be needed for comfort.

You could fill the canvas with organic cotton batting, wool batt, Kapok, foam, or even recycled wool sweaters, and use the same twist system to make your own truly DIY chemical-free mattress.

What I like about this is it can be totally customized, as well as taken apart, washed, and refilled.


2. Cotton and Kapok Futons

Image via Zafu

Futons are more affordable than regular mattresses and often don’t use flame retardants. Look for organic cotton or wool filled. Avoid conventional (non-organic) cotton batting which still retains a lot of pesticide.

Look out for antimicrobial and even added pesticide treatments.

i. The Futon Shop is an obvious option for very affordable futons that many sensitive folks do well with. Starting at about $300.

ii. Rawganique has 100% organic cotton futons as well as cotton and wool. The company focuses on reducing chemical processing as much as possible.

iii. Zafu kapok fiber futons are really cool. They don’t compact as much as cotton and wool batting. They have an organic cotton cover, with eco wool and kapok fiber. This brand came recommended by sensitive folks.


3. Silk Mattresses

Image via Allergy Buyers Club

I have seen silk-filled mattresses in the past, though they are hard to locate. They may be good if you cannot tolerate cotton, wool, hemp, kapok, or latex.

Silk mattress toppers or pads are easier to find, and you could build them up to make a mattress.

This silk comforter from Allergy Buyers Club has a silk encasement (not cotton).

You can find them on Amazon or Allergy Buyers Club.


4. Cotton Sleeping Mat

Image via Dream Designs

This organic cotton mat by Dream Designs in Canada is thin but may be enough for some people who need a simple solution. It was recommended by someone extremely sensitive.

The futon companies above also make simple sleeping mats.


5. Hammock

An organic cotton hammock is a simple option that does work well for some folks.

A good brand that is clean and healthy is La Siesta. Try the undyed organic cotton if you want the purest option.

A metal hammock stand works well with many models (no trees necessary).


6. Camping Beds to Use Indoors

i. Camping Cots

For a quick and easy solution, maybe a camping cot will do!

Let it offgas a bit first. The plus side is there is not much to offgas there, so some time in the sun should do it.


ii. Camping Pads/Mats

Camping mats can be used inside regular housing for those wanting a simple solution, or for those with trouble tolerating regular beds.

They may also be needed high moisture locations like tents, trailers/RVs, and shelters.

a. Closed Cell Camping Mat

For sleeping pads, the most basic type is closed-cell foam.

This aluminized Thermarest is considered the most tolerable of the camping mats. I found it really good and very easy to clean.

They have non aluminized versions as well.

b. Open Cell Polyurethane Self Inflating Mat

I use the most deluxe Thermarest – the 10 cm thick Mondoking (it has polyurethane it in). I find it very comfortable.

It takes a bit of time in the sun to offgas, but many MCSers can use these. I used it after two days in the sun. After a week it was ideal for me.

Setting up a camping cot inside

The general consensus for those with sore backs or who need the most comfort is a Thermarest on top of a camping cot.

Though with the MondoKing, most people likely don’t need a camping cot under it (though I would raise it or put a waterproof cover on it).

Thermarest claims to be flame-retardant-free.

For a more permanent setup, the MondoKing fits into this inexpensive Amazon Zinus Daybed.


iii. Polyester Fill Mat

Another type of simple sleeping mat is a Nufoam polyester fiber mat.

This may be more tolerable than the camping pads that have polyurethane foam in them.

Plus polyester does much better with moisture than cotton, wool, and other natural fibers.

This is ideal for an RV.


iv. Airbeds

a. TPU Airbed

This phthalate and PVC-free TPU air bed by Lightspeed comes highly recommended by many chemically sensitive folks.

This is the alternative to PVC and foam mats.

I found it offgassed in 2 days. Which is faster than many types of beds with more material inside.

b. Polyester Airbed

Another PVC-free airbed is this polyester bed from Intex. Some tolerate polyester better than TPU.

How to Prevent Mold in Mattresses 

how to avoid mould in and under mattress

In any house or trailer, tiny or big, make sure your mattress can breathe underneath (slats or box springs are used for a reason). Only certain types of beds like an air mattress may be able to go straight on the floor.

When building a tiny house, find a way to incorporate slats under your bed. I see too many tiny houses with the mattress on a solid floor. This is not a good solution if you want your bed to stay mold-free.

The picture above is my loft. The slats are built right into the loft. It works great!

When camping, I do think a waterproof cover is the best idea, in a trailer you may be able to use something simple like this Hypervent for airflow, though I have heard that this does not create enough airflow in many situations.

Corinne Segura is a Building Biologist Practitioner with 7 years of experience helping others create healthy homes.

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Filed Under: Healthy Interiors, Mold-Free Interiors Tagged With: healthy furnishings, healthy interiors, mold prevention

Non-Toxic Flooring Underlayment

July 23, 2020 by Corinne 36 Comments

There are a variety of underlayments used under wood floors, click-together floating floors, as well as carpet and tile.

Underlay can serve various functions like cushioning, sound deadening, leveling, uncoupling, and moisture resistance.

These are the best non-toxic low-VOC options with a focus on the material composition.

This post contains affiliate links. Upon purchase, I earn a small commission at no extra cost to you.

Paper Underlayments Used Under Wood Floors

Silicone Paper

Silicone paper is usually used under real solid hardwood floors, but it can also be used under engineered wood. It is semi-permeable which is good, as you want your upper floors (over wood subfloors) to be breathable in almost all situations.

It meets perm ratings recommended by the National Wood Flooring Association.

Those extremely sensitive to chemicals have liked this product a lot. If you just need something simple that is not providing sound dampening or leveling this will do the job.

Red Rosin Paper

Tried a true, Red Rosin is the old school underlayment paper used under real wood flooring. It’s extremely low in odor and even that dissipates rather quickly. The extremely sensitive almost always do well with this, with only a few people mentioning that the undyed Rosin Paper was preferred.

This is what I would use under wood floors. Keep it simple and breathable.

Foam Underlayments for Click Together Floors

Basic Polyethylene Foam

For laminate, engineered and other click-together floating floors I prefer the most basic polyethylene underlayment. It’s very simple – it’s one of the safest plastics in terms of odors and offgassing (it’s zero-VOC).

This provides some cushioning which is necessary under flooring types like laminate.

It’s not a complete vapor barrier, so it can breathe, which is great for upper-level floors. Plus, it’s very inexpensive.

This is the type of foam that comes pre-attached in some laminate lines. I find that very convenient.

A “2 in 1” will usually have polyethylene foam and a thin layer of plastic. If you are looking for a vapor barrier, make sure it has one attached. The term 2 in 1 is rather confusing in this sense, as some are moisture-resistant and some have vapor barriers, but they are very thin.

Check with the flooring company and your contractor to make sure you have an appropriate vapor barrier, if one is required.

Cali Bamboo brand makes a good polyethylene underlay with foil as the vapor barrier, made for their floating floors. And Kahrs makes a polyethylene foam with 3 mil poly plastic for their engineered floors.

Some are just the foam, which is the type I would use over wood subfloors.

Polypropylene Foam

Polypropylene foam is another very safe plastic. It’s not as breathable as polyethylene and I have only seen it advertised as being a vapor barrier or as having a vapor barrier (another plastic layer) attached to it.

It’s used for laminate and engineered (mostly) when a vapor barrier is required. It can be used under solid hardwood floors to provide cushioning and sound dampening.

If it’s labeled 3 in 1 that usually means it’s cushioning, sound dampening, and a vapor barrier.

Floor Muffler has not tested their products with carpet. Their polypropylene underlayment is free of any added flame retardants.

They have a high acoustical rating, the one below can meet IIC up to (74) dB per ASTM E 492 / ASTM E 989, STC up to (73) dB per ASTM E 90. Mohawk Silent Guard is STC 73, IIC 71.

EVA Foam

EVA foam is another safe foam. Compared to polypropylene and polyethylene it does have slightly more of an odor.

EVA foam underlayment can be used under floating floors like engineered wood, laminate, bamboo, and vinyl as well as carpet.

IIC (Impact Sound Transmission Test) rating is 73, STC (Sound Transmission Class) is 72.

Felt Underlayment For Engineered Floors

Felt + Vapour Barrier

Quietwalk is felt and a vapor barrier made for under laminate and engineered wood as well as other floating floors like bamboo and luxury vinyl plank.

The felt and (polyethylene) plastic layers are quite safe even for the chemically sensitive. It claims to be zero-VOC.

This one does contain Microban (Microban can refer to hundreds of chemicals, so this could be anything from silver to something more synthetic). If you want it without antimicrobials you can get Quietwalk from Green Building Supply.

Because this has a vapor barrier it’s meant for on top of a slab or basement floor. If you do lay down laminate, engineered, or another organic-based click-together floor on a slab or basement you do need a vapor barrier.

Best practice, according to mold preventative architects, is not to apply flooring that requires a vapor barrier over a slab because a concrete floor is always trying to dry to the inside. As a mold-sensitive person, I can smell the mold that festers underneath when a vapor barrier is applied. And it happens in most homes in my experience.

Available on Amazon or Walmart.

Natural Material Underlayment For Many Floor Types

Breathable Cork

Cork underlayment is one of the most expensive underlayments. It provides good cushioning and sound dampening as well as some leveling.

It can be used under engineered hardwood, laminate floors, hardwood flooring, and ceramic tiles.

The small pieces of cork are usually pressed together with a polyurethane glue which I find to be quite strong in offgassing, so I don’t personally use this underlayment. However some brands are made with polyethylene as the binder, which is much much better in terms of odor and offgassing. Eco Cork Foam, says they use polyethylene as the main binder.

They also recommended to glue the underlayment down.

There are many flooring types and brands that come with an already attached cork underlayment, which also always has this polyurethane offgassing odor.

1/2โ€(12mm) cork underlayment has STC 49 and IIC 48 sound ratings.

Cork with a Vapour Barrier

Eco Cork Foam is not as natural as the pure cork above. This version combines cork with polyethylene foam and a 6 mil poly vapor barrier.

Pressed Wood Underlayment

This Steico product is a lot more unusual than the others. This is different from the old particle board underlayments. They claim it is more water-resistant than particleboard.

It’s a pressed wood product, but they don’t mention what kind of wax, oil, or glue is used to make it. They do claim it is zero-VOC.

It can be used under floating floors like LVT, laminate, and engineered wood, as well as hardwood floors.

It seems to be very good at sound dampening.

Available on Amazon or Walmart.

Vapor Barrier for Over a Slab or Basement Floor

6 Mil Poly

This is the most common vapor barrier for slabs and basements. If I was going to put down a vapor barrier (which I wouldn’t due to the reasons discussed above) I would go with plain 6 mil polyethylene plastic. There is no need for anything fancy here. Though it does not provide cushioning. If cushioning is required it makes sense to buy a foam and vapor barrier in one. I would make sure it’s 6 mil though.

Flooring with Attached Underlayment

Many click-together floors come with an attached underlayment. This really helps in simplifying things.

I like laminate floors with polyethylene foam backing attached, LVP with rubber underlayment attached, and engineered flooring with cork already attached.

Luxury Vinyl Plank (LVP) with a cork backing does not make sense to me in a basement, slab or wet area since one of the main benefits to LVP is that it is waterproof and very mold resistant.

Some LVP comes with a EVA underlayment.

Underlayment for Tile

I like the Schluter system under tile.

If you need zero-VOC acoustical control under tile Schluter DITRA-HEAT-DUO providers a ฮ”IIC contribution of 20. Cork underlayment can also be used under tile.

Many acoustical underlayments for tiles are rubber-based, and I would personally avoid those as they are one of the highest offgassing products in a home. (Whisper mat is one that is mostly foam with some asphalt adhesive, so that would be an improvement over most rubber underlays).

Laticrete Fracture Ban is not toxin-free but it’s the only one I have seen that is breathable.

They have different membranes that I discuss more in the grout and thinset post.

They are made of a non-toxic very low odor plastic that even chemically sensitive folks do well with.

Photo Schulter membrane from Amazon.

Underlayment for Carpet

The main healthy options are natural wool felt for wool carpet, polyethylene, EVA foam, low-odor synthetic rubber, or built-in synthetic felt.

My carpet post goes into detail on underlayment for carpet.

Corinne Seguraย is a Building Biologist Practitioner with 7 years of experience helping others create healthy homes.

Did you find this post helpful? If so you canย buy me a coffeeย to support the research behind this blog. Thank you!

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Filed Under: Healthy Building, Healthy Interiors Tagged With: Healthy building, healthy interiors, mold prevention

17 Non-Toxic Eco Prefab Homes Compared | 2022

February 4, 2020 by Corinne 22 Comments

how to build a healthy prefab, what to look for

This list focuses on healthy non-toxic prefabricated (“prefab”) homes. They must be both mold-preventative designs and low-VOC to be healthy homes.

I have reviewed them myself with input from customers and building science experts. Many need further closer inspection.

When considering a prefab, it’s important to see the detailed design of the build, tour the factory (or have an expert tour it), see pictures of their builds in progress, and if possible, tour a home that is already built by them.

They must be willing to work with a mold-aware architect. Some companies have their network of installers and some rely on you having your own builder.

Many will turn down severely chemically sensitive clients; I recommend bringing me onto the team before getting into materials with them to avoid that scenario.

Before digging into the reviews of 17 “green” prefab companies, we are going to look through what you need to know about the process of building a prefab and make sure the materials are safe and the design is mold preventative.

Building a home, even if prefabricated partially or fully offsite, is still a complicated process to navigate.

This post focuses on standard size homes. If you are looking for smaller and more affordable homes, my post on small and simple homes covers those.

This post contains no sponsored or affiliate content, and I don’t have a partnership or other ties to any of the companies listed.

Steps to Building a Healthy Prefab

  1. See the list below for some prefabs that I have prescreened, or start with one you like.
  2. Screen the prefab design for initial clues into its quality, including any errors in the photos (do an initial review with someone who knows building science). See the list of good signs and red flags below.
  3. Get sufficient photos and schematic details of the design of the build (walls, ceiling, floors). Take them to a qualified building science expert like Cheryl Ciecko.
  4. Talk to others who built with them. Look for reviews of the company.
  5. Talk to the company more seriously to gather more details about the plans if you didn’t get them in step 3.
  6. Get your specific house plans reviewed by at least two qualified building science experts, including the architect that you have hired independently. Plans are made specific to your climate and piece of land.
  7. I recommend bringing on an HVAC consultant to your team, too, to size and spec (or review) the HVAC, including the ventilation.
  8. Bring a builder on board early in the process of design to make sure they are part of the team. (Some companies have builders or work with a network of builders, if that is the case, vet them to see if they are good.) The builder needs to be really good and that’s not easy to find. Make sure that is in place early.
  9. You or someone with building knowledge should supervise the preparation of the land, the foundation, and the install of the shell or modular unit. Supervise all the stages of the build.

Good Signs and Red Flags

  • The age of the company is important to me. They should not be on their first prototypes. Ideally, you should be able to see some of their houses that are at least 10 years old. You should feel confident in the person running the company. They need to be in business (in the future) to honor warranties. There are two good companies, however, on this list that are less than 10 years old (Ecocor and GO Logic).
  • A company without architects or building science experts on the team needs to be looked at more carefully. Who is in charge of the design and how knowledgeable are the project managers? Steer clear of any company that doesn’t promote their building science expertise.
  • If the company provides the General Contractor or works with a network of general contractors, vet them just as carefully. If you don’t have enough choice in who you use to build it out on-site, you won’t get a well-built house.
  • While you should expect to make minor changes to the design with your architect as a consultant on the team, any major design flaws in their models is a red flag.
  • Talk to someone who built with the company recently. If the company is disorganized and the project manager could not coordinate all teams well, that’s going to be a huge mess. Things might not get done right due to this problem (which is a common one with prefabs).
  • I look for the ability to tour the factoryโ€”ideally the company owns the factoryโ€”and make sure you see a house that is built. Even better if it’s a hotel or Airbnb you can stay in.
  • You need to be able to see details of the building systems/designs system before committing any substantial amount of money.

Pros and Cons of Building Prefab

Benefits to Building Prefab

  • Mistakes are limited in the really good factoriesโ€”computer planning, precise cuts, fabrication by machines, and panels put together by highly trained technicians limit mistakes that are extremely common in traditional builds.
  • Build out of the rainโ€”the wood and other components are stored inside and stay dry (in theory, if it’s a good company). The panels or modules will be built in a climate-controlled factory. It goes up faster on-site, during a dry time, and should be watertight before it rains.
  • Enjoy cost savingsโ€”it would be very expensive to build a house at as high of a quality as some of these on this list from scratch, with high-quality craftmanship like that accomplished in the factory. If you go with a predesigned layout (not custom), prefab helps you save even more. With many companies, you may also have a more fixed price than in a conventional build where many things tend to change.
  • It’s fasterโ€”the whole process from start to finish is likely to be faster than with a conventional build.
  • There’s less work for you โ€” while you do have to tour the factory and have the plans reviewed by an architect, you don’t have to supervise as many parts as in a conventional build. Wall and roof panels, and in some cases whole modules, will all be done in the factory setting and, if the factory is good, it’s likely to be done very precisely and correctly. That is almost never the case on-site at a conventional build. Since most homeowners don’t have the knowledge to supervise a build, this can be essential.

Downsides to Building Prefab

  • Have less controlโ€”while it might be possible to be in the factory during the manufacturing of your specific panels, you don’t have full control here over supervision in the same way you would on-site.
  • If you are extremely sensitive, you need to have confidence in the factory that they are only using clean wood, stored correctly, etc. (The same goes for all the components, but with the wall systems the wood is clearly the most important part).
  • Ability to analyze and review/change the plansโ€”with some companies, you cannot see the full details of the plans (or the walls, ceiling, floor system) until you put down a deposit. This is a huge problem. The good companies do show their designs.
  • Some companies will not allow you to bring your own architect as a consultant on the plans (though most will). That would be a deal-breaker for me.
  • Supervision is still neededโ€”assuming you were able to have your plans reviewed by multiple experts, and feel confident in the factory making the panels or prefab, you still have a fair amount of planning and supervising on-site, making sure the local team knows how to put this together properly, that the foundation is detailed right, the land was prepared properly, and the final on-site details (like the roof) are done right.
  • On the topic of supervision, if the prefab is a very unusual system, it becomes more difficult to have it confidently reviewed and to supervise it.
  • Possible lack of coordination between teamsโ€”with some companies that don’t have a strong process in place and strong project managers, and/or if your builder is not on board from the start, you may have a lot of difficulties arising between the parties, with no clear person/company responsible when things go wrong.
  • Prefabs aren’t typically inspected in the usual wayโ€”they are inspected in sections, and the companies have individual agreements with the states to allow them to do “inspections” out of state and/or off-site. When the local inspector checks in order to give you a certificate of occupancy, they are only checking things at the finished level, not the construction level.

Building with Environmental Sensitivities

If You Have Chemical Sensitivities

  • Another thing I look for is to make sure we have control over the finishes in a way that suits your environmental sensitivities.
  • You should have control over: flooring types, all wood finishes, all sealers, all paints, some glues, the shower system, the cabinet company, and the countertops. This is where you want to know how customizable they are (usually very).
  • Elements that are fixed are likely: framing type, insulation, flashing tapes, house wrap/WRB, and possibly window and door types. With these, you want to know if you can tolerate the materials specified. In general, don’t try and alter the main components. Though there might be a little bit of choice here, for example, with the window framing material.
  • With most companies, you have a choice with the siding and roof types.
  • Some of the best companies are reluctant to work with someone super chemically sensitive. Sensitive customers can demand changes that compromise the integrity of the build; a good company won’t allow this and won’t want to deal with it. Bring me onto the team early in the process, possibly before you speak to them. I can work with the whole team to make sure you get products that are healthy for you and they don’t compromise the building system.
  • Prioritize QUALITY over extreme modifications to make something perfect. It’s better to have to wait for your house to offgas, and have a house that will last a long time, than the other way around. Many people are making this mistake – building something too modified for chemical sensitivities that will go moldy and not get them out of the toxic loop.

If You Have Mold Sensitivities

  • The design of the prefab system is the most fundamental part that needs to be done right.
  • Bring your own architect on board, even if just as a consultant. Make sure the designs are solid (reviewed by more than one building science expert) and the final design for your climate and land is solid.
  • Bring your own HVAC consultant to review the system.
  • You need an excellent builder.
  • You need supervision of all parts of the build.
  • You need to know which party is taking responsibility for each part that could go wrong.

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Definitions: Prefab, Manufactured, Mobile, Kit, and Modular Homes.

Prefab (Prefabricated)โ€”This is the general term for all of these building types that are made partially or fully offsite:

  • Panelized Prefabsโ€”Panelized construction is the most appealing type to me. The exterior walls and ceiling pack onto a truck and are usually assembled with a crane. Some have windows and doors installed at the factory (most of the ones I looked at do), while others have those parts installed on-site.
  • Manufactured and Mobile Homesโ€”I don’t cover these types in the post. Manufactured homes are usually the type of prefab that is in mobile home parks, and are not usually good quality. Mobile homes are homes on wheels (including tiny homes on wheels) and are covered in this post.
  • Modularโ€”Modular homes are more complete than panelized. Modules or boxes are built in the factory and wrapped and taken by a flatbed truck to the construction site. There might be just one module for a small house or many modules that fit together. They are lifted by a crane and set on a foundation. Some modular homes are almost complete when they arrive and others are finished on site.
  • Kit Housesโ€”With a kit home, all of the materials for the house are built in the factory, numbered, and shipped to the site. A kit home doesn’t come with walls or a whole module built (or partially built). Instead, it comes with all the materials you need to build the house, stacked up, and labeled.

Review of 17 Non-Toxic Prefab House Companies

1. Bensonwood Passive Homes

https://www.instagram.com/p/BrnztsHnkTD/

Bensonwood is at the top of my list because it is the most established company making well-made Passive Houses (and other types). They are well detailed for mold prevention, made in a factory that they own.

They came to my attention because the builder Matt Risinger toured their factory and worked with them. You get to see a bit about how one of their models are made in this video. This is the house made by Matt Risinger’s company (which you can see during the house tours Matt puts on).

You can tour the factory yourself, too.

This is a panelized custom prefab. The walls and ceilings are made in the factory and they go up on-site at a dry time of year in one to two weeks. The houses can be built to Passive House standards and they use timber frame construction.

Build Type Options

They have three ways to build:

1) Bensonwoods fabricates the custom-designed shell and installs it (this includes the walls, roof, floors, windows, and door). Your builder does the rest of the finishing, as well as the foundation and site prep.

2) The enhanced shell option includes the shell plus some prefabricated components, such as window casings, stairs, and doors (you can see these options on the website).

3) The whole house option, where the house is completed by one team.

Geographical Area

The whole house option is a finished house, but it is only available in the area around Walpole, New Hampshire. The other options can be shipped to 49 states.

Design & Materials

A typical Bensonwood wall panel would have a service cavity that may or may not be insulated, then an airtight layer of OSB, then a structural framed wall of I-joists or sawn lumber.

The exterior sheathing might be OSB (typically, Huberโ€™s Zip) or a continuous layer of wood fiber insulation. Cavity insulation is dense-packed cellulose. 

Roofs are made with either EPS or dense-packed cellulose.

See my posts on pressed wood products and insulation to see if these materials would work for your sensitivities.

Windows are Marvin Integrity, Unilux, or Wasco. My window post reviews the toxicity of window types.

The wall and roof systems can be seen on their website. It’s important that they do show the wall designs, so they can be evaluated.

Factory. The panels are made in their own factory, called Tektoniks, in New Hampshire.

Established. They have been in business since 1973. They have been building in this factory since 2000.

Build time. The shell goes up in one to two weeks. The typical time frame from 3-D model to construction completion is 5-10 months.

The Process. It is important to have secured your land before developing any formal plans (as with any good prefab company). Decide between the shell, enhanced shell, or whole house package. They take the design and create a 3-D model and then send that to be fabricated in the factory.

Here is a video of their process of installing the shell.

2. Their Sister Company Unity Homes

https://www.instagram.com/p/BcvKRTElubm/

This is the more affordable wing of Bensonwood that was started in 2012. The models are predesigned, as opposed to the custom Bensonwood designs. However, you can still mix and match some of the elements to make the house more personalized.

The houses’ designs range from 500โ€“3000 sq ft. I love that they took high-end wall panels and made them affordable by keeping it to predesigned packages. The smallest house is $150,000. If you want an affordable prefab, go with predesigned.

The models can be made to Passive House standards.

Design and Materials

This company is a sister company of Bensonwood, using the same technology. The panels are manufactured in the Tektoniks factory.

Most of the clients they build for are sensitive, a representative said. You can bring materials home to test them.

The interiors are very customizable.

Just like Bensonwood, they use the same high-quality mold preventative design, airtight builds, and balanced ventilation (air exchange).

Geographical area. New England is easiest, but they can serve a larger area.

Factory. They have factory tours (the same factory as Bensonwood) in New Hampshire. They also have a show house in New Hampshire.

Process

Just like Bensonwood, they offer three options: the shell, the shell with some finishes (both of these completed by your GC), or the completed house, which is only possible local to their site in New Hampshire.

In the most simplified process, you can choose one of the interior collections, including finishes, in its entirety. This is the fastest and least expensive way to do it.

They also have โ€œPersonalizedโ€ and โ€œSemi-customโ€ design paths, in which you can substitute choices from outside the collections. If you would like the interior design to be completely customized, they recommend that you go with the Shell Package and you can finish the interior with materials and fixtures locally.

3. EcoCor Solsken Passive Houses

https://www.instagram.com/p/BfMaqHejHdq/

Another panelized Passive House prefab is at the top of my list. Passive House design is focused on well built, well-sealed, moisture preventative design. And this one is certified as well as vetted by well-respected building science experts.

I have heard feedback from three professionals about this house, and they were all positive regarding the design.

What I have heard is that the product is well-made and the knowledge and experience of the team are on point. The management may or may not be great, depending on who is working there.

Materials and Design

They use healthy materials and they minimize the use of paint, varnishes, and formaldehyde to near-zero VOC, they say.

They use the Zip system, with the Zip OSB layer close to the interior (it will offgas to the interior).

Dense-packed cellulose is used in the exterior wall assembly and Rockwool in the interior service wall. No spray foam insulation.

The bulk of their insulation is on the outside. They do not have sheathing on the outside. They use a WRB to hold in the insulation (under the siding).

Moisture-management

Detailed modeling of plans is done in WUFI softwareโ€”this is a way to model how moisture moves and could condense in the walls/ceiling/floors. They used moisture monitors in the walls of early houses to verify this.

Essentially, they use “out-sulation” (exterior insulation), with a very dry-able (breathable) exterior assembly.

They use mechanical ventilation (HRV).

It’s an excellent design, with knowledgeable team members.

Factory. They manufacture their panels in their own small facility: the Ecocorโ€™s facility in Searsmont, Maine. You can tour the factory.

Here is a video tour about the company.

Geographical Area. Ecocor’s custom designs are delivered anywhere in North America. Check with them about the predesigned models.

How long have they been in business? Ecocor started around 2012, with the Solsken branch of designs launched around 2017.

Costs. One of their 2 bedroom, 1192 sq ft models is about $408,000.

It sounds like they tend to work for upscale houses only (which is not uncommon when you find a really good builder or system, since good quality costs more). This tends to be more expensive than BrightBuilt or Gologic.

This is not your budget option, but it’s not overpriced either if what you want is quality.

4. Morton Metal Siding Structure

https://www.instagram.com/p/Bvb4gS2gM68/

This company makes fairly standard construction metal siding homes and structures and have been reviewed by Cheryl Ciecko. They have worked with her and they are willing to work with her again to make sure itโ€™s designed right.

Process

With the Morton process, many materials are manufactured in their plants (which they ownโ€”this is a large company). Building components are shipped to the job site using their trucks. Construction is executed by their construction crewsโ€”vet your local crew well.

Construction management is provided by themโ€”again, vet the local management well. This is a design-build firm, which means they take care of the whole process.

They use Allied Design Architectural & Engineering Group, but they will allow your architect to have input on the plans.

Design & Materials. This is a conventional build; it’s not high performance or Passive House. It’s stick framing, regular insulation, metal siding, and drywall. There’s nothing especially unique here other than they are willing to work with Cheryl.

Established. It’s a well-known brand, around since the 1940s with a robust warranty and little risk of the company going out of business soon.

Factory. They are fabricated in Morton, IL.

5. Holz100 All Wood Houses

https://www.instagram.com/p/Bz-y6YYjJl3/

This panelized and module prefab is something a little different. This company makes panels that are made from all wood: walls, ceiling, and floors. No adhesives. No nails. Just wood. Siding and roofing materials might not be wood.

They claim a 50-year warranty on condensation and mold in the walls. The company has not been in business for 50 years though, about 25 so far.

The next step here would be to see if a building science expert (actually, more than one) can look at this wall system, which is a series of pieces of wood with some air gaps, and see what they think about moisture management in that type of wall.

I would also like to see computer modeling of moisture in the walls, and why it doesn’t hit dewpoint in those spaces, or real-life data from the company showing how moisture performs in the walls.

I want to know how they deal with the roof since it looks like they are putting an exterior vapor barrier on the flat roofs that could get tricky for mold fast. The underbelly of raised up wood houses can also be vulnerable to condensation.

If this system holds up the way it says it does, it will be a very interesting option.

I am really rooting for this company, as I think it looks really cool.

Although I’m reluctant to be a test person for something we don’t know enough about I was happy to see Matt Risinger tour this style of home (a company called Holzpur. With the green light from both Matt and SIGA (who sponsored the video), it would make me want to proceed with the next steps of review.

Geographical Area

Most of their buildings are in Europe and you could go see some of the buildings there, including a hotel in Austria, a hotel in Belgium, and a rental. That would be crucial as well, to see how this is holding up in real life. And you can sleep there to see how you feel.

They are also available in the US and Canada.

Cost

The small little room that is just under 100 sq ft is 35,000 CAD.

A tiny house is 39,000 Euros. They make houses of all sizes, including apartment complexes and hotels.

6. GO Logic GO Home

https://www.instagram.com/p/B4fr_hAg4Xt/

These are Passive House-level panelized prefabricated homes. This is another highly respected company. They are a design-build company in Maine. Outside of Maine, they assemble the shell only. Your local contractor does the rest.

Materials and Design

2ร—8 wood stud wall. Dense-pack cellulose insulation in the stud cavities. Rigid mineral wool insulation between the sheathing and siding.

Taped Huber Zip OSB air barrier. See my post on pressed wood products to review the offgassing of these materials.

The roof is made with prefabricated wood trusses with blown-in cellulose insulation. See my post on insulation.

You can choose from many different design options. Windows are aluminum/PVC or aluminum/wood (triple glaze).

Flooring is concrete and real wood, Marmoleum or tile.

They use high-quality finishes like solid wood stair treads and solid wood trim. Interior walls are gypsum with 0 VOC paint. IKEA cabinets.

You can upgrade or change most of these interior finishes.

Moisture Management

They use meticulous air-sealing between the attic and living spaces and ventilation beneath the sheathing to eliminate the risk of moisture buildup and ensure a durable roof.

They seal the critical joints at window openings, between the foundation and exterior walls, and between the wall and roof structures.

Wall assembly is designed to avoid moisture build-up.

They use mechanical ventilation – HRV. Electric heat (like most Passive Houses).

On-site blower-door testing meets or exceeds Passive House standards.

Costs. Size is 600-2500 sq ft from $179,000 to $567,000.

How long have they been in business? Go Logic (founded 2008) company launched the GO home prefabs in 2017.

Geographical area. Delivered and assembled in Maine. Outside of Maine, they deliver the shell only in New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, or eastern Pennsylvania. Your local contractor would provide the site work, exterior, and interior finishes.

7. BrightBuilt Homes

https://www.instagram.com/p/B6gHgsPA8L5/

BrightBuillt appears at first to be a competitor of Ecocor and GoLogic. They make net-zero ready homes that are a bit better than code. Less expensive than EcoCor and GoLogic.

The house arrives in modules as opposed to panels.

Materials

Double-stud walls insulated with dense-pack cellulose. It looks like fiberglass in the roof in some pictures. Some have rigid insulation on the exterior.

Moisture-Management

Air sealing, some use Zip system, some use Blue Skin or Typar. Drainage plane below siding, mechanical ventilation. They have pictures of blower door tests, but it’s not clear if they test all of them.

The lack of information on materials, cross-sections of the walls and ceiling, and details on building science on the website is a red flag for me.

Will they allow prospective customers to tour their factory? Yes.

Customer feedback

They try to be accommodating, but a customer was not happy with their attention to detail or efficiency. Their own photos online show modules arriving with damage to the house wrap and exterior foam.

They claim low VOC, but if they don’t have good enough oversight of their module producer, building for a sensitive client might not go according to plan. You can totally customize the finishes, though.

When a design problem cropped up during the building process, there was no go-to person to address it, a BuiltBright customer claimed. The customer was stuck between the designer and builder, with no one to advocate for them.

If there isn’t a designated project manager or contact person to oversee the project, like what this customer claims, you won’t have the efficiency of what you might expect in a prefab process.

If the management changes in the future this could change.

Process

You have three primary routes you may choose: a pre-designed BrightBuilt Home (from 9 models), a modified BrightBuilt Home, or a custom home.

If you are happy with one of the standard designs, you will simplify the pricing. If you would like to make some modifications to the existing designs, you can make changes to the finishes, spaces/interior design. Or do a totally custom design.

They help you identify a builder.

BrightBuilt designs the modules, passes it on to a company that makes the modulesโ€”if anything goes wrong there, BrightBuilt may not be responsible, reports a client. The builder may have to pick up the mistakes made by the other two.

Factory. Subcontracts the manufacturing of their panels/modules out.

Established. They have been in business since 2013. Their parent company (architectural firm) has been around since 2004.

Geographical area. At this time, they construct, deliver, and complete within Maine and the Mid Atlantic region.

8. Module Homes

https://www.instagram.com/p/B601GTCBh7p/

Module uses both wood-based panelized and modular construction. Their houses are built off-site at the Bensonwood Tektoniks factory.

Their first home, the Latham house pictured above, was built to Passive House standards. In the future, all of the homes will be built to the Zero Energy Ready Home standards.

Geographical area. Based in Pittsburgh, modules are made in New Hampshire, they deliver to any area of the US. 

This is a design-build firm: they manage everything “from the first shovel to the last coat of paint”, they claim. Though it’s not clear in which area they provide the full service. The company did not respond by email yet to the question.

Materials

Zip panels with cellulose insulation.

The base model option has fairly standard materials (like IKEA cabinets and laminate countertops). The upgraded options have healthier materials like custom cabinets and solid surface countertops.

Factory. Just like with Bensonwood and Unity, you can tour this factory.

Tektoniks factory is owned and operated by Bensonwood; it’s not owned by Module.

The companies design the panels and send the design specs there to be made.

Cost. One of their two-bedroom homes is $250,000. An estimated 50K more for site work, foundation, and permits.

How long have they been in business? Since 2017.

You can see a video of their first house here:

9. Haus.me

https://www.instagram.com/p/B18aFNzFNUo/

I’m waiting for a prefab like this to really work for those sensitive to mold and not be too high in offgassing. Something like this has the potential to be very waterproof, with nowhere for moisture to condensate in solid plastic walls.

This prefab is modular; it arrives totally complete. It has a metal frame and then they show a spray foam “composite” that makes up the insulation and the exterior. It’s not clear what that is.

They claim it’s a 3-D printed composite polymer (which means some type of plastic). They don’t say what polymer this is. At first glance, it looked like fiberglass. On closer inspection, it does not look at all like fiberglass. They claim it is VOC-free.

The windows are 6 layers of tempered glass!

It’s mobileโ€”not on wheels, but it can be moved anywhere.

You can schedule a visit to one of their demo units at this link.

Geographical area. They deliver from the facility which is in Reno, Nevada. It takes 2-3 weeks within the US to deliver a house. But they are currently backlogged 9 months.

It is possible to ship an assembled haus.me to any international seaport, which also makes this an interesting option for those relocating to Latin America/the Caribbean.

Warranty

For House Frame and Windows: Five year warranty or lifetime warranty.

Maintenance and Warranty Plan: One year of base warranty and free maintenance for home appliances and dรฉcor, including furniture and equipment or ten years of extended warranty and free maintenance.

Year Established. They have been in business since 2016 and this is the first prototype.

Keep your eye on them. When something like this passes the test of time, I will share it on my Facebook page and in my email list.

10. Log Cabin Kits

https://www.instagram.com/p/BxgFZ5Ljb9H/

Although log cabins don’t have a lot of insulative value, and they don’t completely skip past the need for intricate detailing, I like the simplicity of solid wood walls with nowhere for moisture to accumulate and hide (in theory).

The logs need to be debarked and stored properly in good mold-free conditions before the build.

And, as always, pay special attention to the roof and foundation which are done wrong in almost all assemblies, whether it’s in the design or execution. Most foundations have water damage.

They are prone to moisture damage in cold climates. Around windows, doors, and building corners are vulnerable areas. Thermal mass improves the performance a bit, but air leakage more than counters any benefit. Cool surfaces + a source of moisture = mold.

I don’t know which log cabin company is the best, but I would use the same criteria of evaluation as with more conventional prefab houses outlined in the beginning of the article.

You still want to have this evaluated by a building science expert to see how log walls will perform in your climate and hold up to moisture and mold.

You also want to evaluate the companies based on their specific “log” system. As these walls are usually square or rectangular, not the classic real round logs.

I pictured Confederation Log Homes because they have a long record and have been in business for a long time. They look like they are building good quality homes, from what I can see in their photos. They passed the initial screening.

11. Method Homes

https://www.instagram.com/p/B5qe0Y3AJUf/

Method makes modular homes that can reach Passive House standards.

Method will build anything an architect designs, as long as it can still be shipped.

Process. You can use their design-build company, Method Contracting, or go with a local builder or general contractor of your choice (“under our direction,” they say). Method has an internal team of specialists and they have an external network of contractors throughout the Pacific Northwest (the US and Canada) that they can recommend and work with.

They don’t say quite as much on the website about building science as the others, but they do say they avoid thermal bridging through either double-stud walls, rigid foam wrap, or a combination of the two.

They do blower door tests to measure airtightness. In order to achieve a very tight envelope, they use the specialty (high performance) tapes like those used to seal the seams of the plywood during framing.

They also use โ€˜flash and battโ€™ which is a very tricky method to get right, explained here. I don’t use spray foam in walls due to off-gassing concerns as well as technical difficulties.

They use ERVs or HRVs for ventilation.

This has been reported to be highly customizable.

Materials. Real hardwood floors, 0 or low VOC paints, and glues. In a message, a company rep said, “While we use no VOC products, we are not fully set up to build homes for the environmental sensitive community”.

Area served. Method has experience delivering and building in challenging and remote sites, including the San Juan Islands and British Columbia Islands.

Their manufacturing facility is located in Ferndale, Washington. They service the western US and Canada including Washington, Oregon, California, Alaska, Idaho, Montana, Wyoming, Nevada, Colorado, Utah, Hawaii, British Columbia, and Alberta.

Cost. Base price $162,000.

12. Artisans Group

https://www.instagram.com/p/BeFD8D9AjHr/

Artisans Group is a design-build firm in the Pacific North West. They build prefabricated panelized homes to Passive House standards. They can do custom designs or you can choose from their pre-designed plans. I had to email them to clarify: any in their current portfolio is a predesigned plan.

They work with their network of selected prefabricated Passive House builders who deliver the floor, wall, and roof assembly systems to your site.

They use the design-build model because communication between the design team and the construction team is extremely important in order to get things done right.

The assembly is overseen by a Passive House expert.  

Year Established. They are a large firm, in business for 20 years. They claim they have designed more homes to the Passive House Standard than any other US firm. (Ecocor makes the same claim).

They have a good team that is highly educated on building Passive Houses.

Materials. They have been using low and no VOC finishes since the days you had to special order them. (Another good sign they know materials well).

There is not a lot of detailed information on the website about the wall assembly and design. Like all Passive Houses, they do use HRVS (air exchange). I would make sure you can find out more before committing.

You can tour their houses during their yearly tours.

13. Phoenix Haus

https://www.instagram.com/p/BpPi1p9g3hV/

Phoenix Haus is a panelized system that is Passive House certified.

Design & Materials

The Phoenix Haus Alpha System is lightweight timber frame construction, insulated with cellulose, mineral wool and wood fiberboard. The system uses solid timber supports with timber I-beams in the roof. With a ventilated rain screen on the exterior.

An airtight membrane (Intello Plus) is used on the inside of the supporting joists (behind the service cavity). Tescon Vana tape is used on joints. The exterior water-resistive barrier is Solitex.

These are all low offgassing (or practically 0), very common Passive House materials. Most passive houses use these same membranes and tapes.

They do show the cross-section of the designs, which is important information to have.

Geographical area. They can work anywhere from the Midwest to the Rocky Mountains and Pacific Northwest.

Process

Phoenix Haus does the architectural drawings, makes the panels (the panels come with windows and doors), and they deliver them to the site.

The company assembles it and helps you find a builder from their network. You can also choose your own builder.

The general contractor does finishing work (mechanical, electrical, plumbing, flooring, drywall, etc.).

They are open to working with your architect.

Year established. Phoenix Haus has been in business since 2011.

Cost. A 1,500 sq ft cabin costs about $150,000, which usually totals $375,000 with finishes, excluding land and design fees.

They have no pictures of completed houses on their website or Instagram, which seems very unusual to me.

14. BONE Structure

https://www.instagram.com/p/B7WYat5B3Mz/

This is a Canadian company that can ship the components to the US. This is a non-wood-based design that uses metal framing and spray foam. My post on insulation talks about spray foam, which I tend to avoid.

Materials and Design

They use both spray foam and rigid foam. They say they have reduced thermal bridging.

They don’t quite make Passive House airtightness standards, which seems strange to me for a house that uses foam as the only insulation product.

Process

BONE Structure will collaborate with 3rd party architects. They will go over their design with your architect.

The company will provide a project manager and can introduce you to builders, or you can find your own builder.

Time to build. On average, the envelope of a BONE Structure home of 3,000 sq ft is assembled in less than 10 days, they say.

I would have this design carefully analyzed by a building science expert before proceeding.

15. EcoCraft

https://www.instagram.com/p/Bf8joQzHvYW/

EcoCraft uses prefab building techniques, but the houses are all custom designed. They build in modules, as opposed to panels. They can be Passive House certified.

Process. They work with local architecture firms. This sounds like they don’t have an in-house architectural team.

They take care of all the building (and the cost includes this): basic excavation, an unfinished basement, walls, roof, finishes, plumbing, electrical, appliances, delivery, installation, and all finishes if you are in the Pittsburgh area.

Materials and Design. They use continuous exterior insulation (rigid foam). Like all Passive House homes, they are built airtight, with a heat recovery ventilator.

They use un-faced formaldehyde-free fiberglass batts within the walls and floors, and blown fiberglass in the attics, along with spray foam insulation to seal air leaks. (You will want to see how much spray foam is used and what kind.)

Fiberglass is a step down from Rockwool/mineral wool.

They use thermal imaging and blower door testing to test for air leakage (which leads to vapor movement).

On the interior, they use low or no-VOC paints and low or no-VOC adhesives and sealants.

Factory. You can tour the factory. You can even be there while your home is being constructed and take photos. The modules are manufactured in a factory located about 90 miles out of Pittsburgh.

Geographical area. They are based in Pittsburgh and build within a 60-mile radius of Pittsburgh. Sometimes, they build outside that radius, or you can use the panels outside of the radius, but they will not be able to complete the build.

Warranty. They carry a 10-year structural warranty and 1-year cosmetic warranty.

Cost. EcoCraft Homes start at $285,000.

16. Bamboo Living

https://www.instagram.com/p/BudE2i5HH_D/

This Hawaii-based company makes panelized bamboo homes. They have insulated walls and uninsulated wall options.

When going with a traditional indigenous building technique, keep it close to the original way of building. Bring in current experts in building science to analyze it, as well. That means no insulation for me with bamboo.

Bamboo is a traditional building material in a huge part of the world. This leads me to believe there is a way to build this in a mold preventative way.

But, bamboo being bamboo (quite the finicky material with moisture), probably means there are a thousand ways to mess this up. That means more research is needed here than usual.

I personally would not ship bamboo panels very far from where they are built.

Warranty. They give a 20-year structural warranty.

Tour: You can tour their homes. You must check out other bamboo buildings first, including a hotel made by this company, and, when they have listings, you can check out this condo made by them too.

Year Established. They have built 400 homes they say. The company started in 1995.

Cost. Base price of $89,000

17. Plant Prefab Living Homes 

https://www.instagram.com/p/BqptxXmll1F/

LivingHomes is Plant’s in-house design studio. I’m mentioning this company because it’s usually on non-toxic prefab lists, not because I’m particularly impressed.

Materials

The construction is standard. From what I can see, they use OSB, Knauf Ecobatt fiberglass insulation, and regular drywall. They use exterior rigid foam insulation, house wrap, furring strips, and Jamies Hardie siding.

They use Anderson Windows (you can upgrade to aluminum windows). Doors are by Thermatru, flooring Millstead Cork Floors (I’m not a fan of cork floors, explained here), kitchen/bath cabinets by Merillat Cabinets.

They claim to be low VOC by using 0 VOC paints and stains, millwork and engineered wood without (added, I’m assuming) formaldehyde, no wood-burning fireplaces. Vents in the bathroomโ€”every house should have a vent in the bathroom, so this should not be their main claim to fame on mold prevention!

These materials are all very standard and any builder can build with these.

They say they include indoor plants to absorb “dangerous compounds”. This is a big red flag for me for greenwashing and lack of knowledge about VOCs, as these plants do almost nothing.

Process

They can work with your architect to create a custom design, or you can choose from one of their standard designs.

You can find your own contractor or they can help you find one.

They coordinate with the general contractor in charge of site work and foundation; they resolve any design issues and maintain oversight and quality control during the construction process. This is good: if they have this much control over the process, assuming they know what they are doing, oversight is good. A clean line of responsibility between parties is good.

Factory. All Plant Prefabs are built in their factory in Rialto, California. You can visit the factory and see your home being built. (I like this part.)

Warranty. In addition to the standard warranty required by code, they provide a ten-year structural warranty and offer double warranty protection from 2-10 that ensures your warranty will always be covered.

Geographical area. The area they serve is the West Coast of the US and “select places elsewhere”.

Cost. $438,520.00 is the estimated total price for the C6 which has 3 bedrooms and is 1288 sq ft.

So, Which Ones are My Favorite?

Top picks for a regular, conventional house are Bensonwood and Ecocor.

Top pick for something simpler, less conventional are the log cabin kits.

I have my eye on Holz and Haus.me as potentially simple elegant and unique solutions to the safe housing crisis.

Join the mailing list and Facebook page where I will share updates on the companiesโ€”which ones have worked out well for folks and stood the test of time.

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Those that Didn’t Make the List

Reasons why these didn’t make the list: Insufficient focus on building science. Evidence of poor building practices or lack of anything to demonstrate “above and beyond” mold prevention.

Don’t repeat the past with poorly made manufactured homes

Flex house | Delivered complete. The house is made with FSC certified lumber, low or no VOC materials and low Global Warming Potential. BaySeal closed-cell insulation. I’m not a fan of spray foam.

IdeaBox | These are modular homes that don’t look different than mobile homes or your average tiny home. The photos of the build appear to show standard construction with saggy fiberglass insulation. (Not good if it’s saggy).

Greenfab | Some info on green building, but insufficient evidence on advanced building science and mold preventative building.

Blu Homes | Make nods to green building and mold reduction by using wood floors and by “building well” with no actual evidence of how they build differently; how they build well; what their walls, roof, floor systems are; and how they are mold preventative. They do use metal framing, which is especially tricky to manage condensation and thermal bridging in.

Clayton homes | From what I can see from the video, it looks like an exterior vapor barrier, there is no rain screen, and the roof looks like it also has a plastic barrier. These look like typical mobile/manufactured homes.

Dvele | A new company, it sounds like they have display homes as of 2018 in California. They founded in 2016 after running a Canadian prefab company. They are Passive House certified. Use Roxul on all 6 sides, they say. They use some high VOC materials inside like epoxy. You can tour the factory. They use moisture monitors in the walls. Insufficient information on the website to make a call on this. This company might be decent, but if they are building to high standards, they should make this more obvious.

Deltec | Looks really standard. They make wall panels. Tyvek, plywood, regular framing. Not sure how those panels come together, still have to finish the rest of the insulation and everything as usual. They have pictures of what looks like vented crawl spaces (that’s a no from me), and gutters coming off the side close to the house with no kick out (that’s a no for me). I don’t have a lot of confidence in these panels, or the installation, from what I have seen.

MADI Homes | This flat pack house is beautiful and temptingly simple. But from what I could pull out of them in emails and from photos, it sounds like flash and batt insulation plus a poly interior vapor barrier (that’s a double vapor barrier). A no-no for mold prevention in my books.

IT House | I liked the IT House initially, because of the large amount of glass used, and elevated off the ground designs. The structure is metal beams. The panels which are not load-bearing are made of cement board 3form resin panels, and solid wood thin paneling (I don’t really know what that means).

Finish panels are either fiberboard cement or 3Form eco-resin (for interior wet location). I’m still confused on how they build and what the panels look like. Reportedly, they have changed the system since then. That’s why I don’t like prototypes. They have not bothered to update the website.

Their display house is a bnb. A friend checked out the display house and wasn’t totally satisfied with the construction. The website says IT House is $150/sf but a client found it to be more like $400/sf in actuality.

The company has not updated the webpage or Instagram for a very long time. A reader reported that they are still very much in business and are busy and backed up.


Concluding Thoughts

Look at the story of Greenterra homes, a company on many green prefab lists just a couple years agoโ€”the company went down epically.

My private notes on this company said “donโ€™t see anything green about themโ€”external foam on metal frame, with poly on the interior, double vapor barrier (no). Laminate flooring with OSB.”

They were clearly building cheaply. It turned out to be even worse than that.

Do not rush into a prefab purchase. As tempting as it can be with all the beautiful and affordable models, and the urgency of safe housing, you have to build this right.

Prefabs are not necessarily better or worse than custom houses. They can easily be worse than most, while many are better than what the average builder can produce. A really good prefab design has benefits, mainly being built out of the rain and with fewer mistakes.

If you need to build something less expensive and smaller see my post on small prefabs.

Corinne Segura is a Building Biologist with 7 years of experience helping others create healthy homes.

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This post took 30+ hours to research and write and is not sponsored or affiliated with any companies.

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Thank you to Bethany from Building Literate who contributed as a researcher to the post.

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Filed Under: Healthy Building, Mold-Free Building Tagged With: Healthy building, mold prevention, tiny homes and trailers

Designed for Mold-Prevention – Corbett’s Tiny House

January 15, 2020 by Corinne 3 Comments

building a high performance mold preventative tiny house

This post contains affiliate links. Upon purchase, I earn a small commission at no extra cost to you.

Intro

Corbett and Grace Lunsford’s tiny house on wheels (THOW), called the Tinylab, was made as an educational house to teach folks about home performance.

In this article, I’m going to outline the areas of this tiny house’s home performance that are relevant to mold prevention.

These mold preventative aspects of the house are:

  • Air sealing to prevent vapor from entering the cavities of the enclosure.
  • Using vapor retarders wisely, to prevent condensation in walls and the roof.
  • Insulation installed without significant air leakage (air leakage = vapor movement = condensation potential).
  • Windows flashed and taped correctly to prevent water infiltration.
  • Using ventilation to reduce humidity, and avoid negative or positive pressure which can push or pull air through the walls and cause consequences.

I also outline some other facets of the house that make it a healthy home. These are:

  • Low VOC materials
  • Improving indoor air quality by reducing carbon dioxide, carbon monoxide and VOCs
  • Controlling humidity
  • Managing microbial growth in tanks
  • Energy/Power system which provides for flexibility of location

I haven’t seen many tiny homes on wheels built really well. This is only the second one after Terran’s house that I have featured as a mold preventative build.

Air Sealing is Key

In Corbett’s High Performance house, air sealing is incredibly important. Air sealing is how you prevent air from entering the wall and other cavities. This is important because air carries vapor, and it’s usually at a different temperature.

Air leakage brings with it vapor that can condense on hidden surfaces.

This build used materials that are made for Passive House design. Passive House is a design process that includes a major focus on controlling for moisture and condensation within the walls, ceiling, and foundation.

The Exterior Water Resistant Barrier (WRB)

Solitex Mento membrane and tapes were used, just like in this detailed example.

Solitex Mento is a breathable house wrap/WRB that comes with a line of high-quality tapes for sealing around all seams and openings.

Most houses should have a breathable exterior water-resistant barrier over the sheathing, with a vented rainscreen system. A rainscreen is battens that create a gap behind the siding. This lets moisture escape and dry out.

These products are good at air sealing and they are also lower VOC than liquid applied barriers. Many high-quality builders are now using liquid applied barriers in many areas of the house, and that might not work for all chemically sensitive folks.

Interior Vapor Retarder

Inside, the Intello brand smart vapor retarder was used to prevent moisture from entering the cavity in the winter and let it breathe more in the summer, preventing condensation within the wall cavity.

We want to get away from using vapor barriers that trap moisture. Instead, these two permeable membranes, one on the outside of the wall and one on the inside, control air flow, and slow vapor flow but don’t stop it completely.

The Insulation

With Rockwool R 15 in walls and ceiling, the Tinylab house can be moved around the US to multiple climates. You always want to design the house with one climate in mind to optimize all the systems (and the whole house as one system).

This house was built for Atlanta. As they moved the country they had the most difficulty with humidity and condensation in very humid and very cold climates. They attempted to follow the weather to reduce this challenge before returning to Atlanta.

Rockwool is easier to pressure fit into cavities compared to cotton batt. They tried the recycled blue jean insulation at first, but it was sagging in the ceiling, and leaving a little bit of air gap in the wall cavities. You can see that here.

Rockwool holds itself in well with a friction fit in both the ceiling and the walls, without sagging and leaving air gaps. The tighter it is to the framing the better.

If your insulation is not tight to the framing air leakage can lead to moist air moving through the wall and condensating. A lot more moisture moves into the wall with air leakage than with diffusion. Diffusion itself moves very little moisture, not enough to cause problems in a well-designed wall. Matt Risinger explains that in this video.

You need to take your time to cut and fit the insulation as perfectly as possible so that you don’t have air leakage.

They didn’t use spray foam, even though folks like the idea of insulation that in theory is an air sealant and a high R-value insulation product in one.

In reality, spray foam often pulls away from the walls, in which case you lose the air seal. And in a tiny house on wheels that is moved around, it’s going to crack and come apart from the studs almost for sure. Bad idea.

Here is the interior air barrier and air sealing:

Low-VOC Materials

There was a big focus on 0 and low-VOC materials throughout the whole build which I appreciate seeing, even though the Lunsford family is not chemically sensitive.

Walls and Cabinets

Purebond plywood which is made with a “soy glue” (probably a polyurethane glue) was used for the interior walls and cabinets as well as the interior door.

If you are sensitive you should test this out for yourself. I prefer plywood made with phenol-formaldehyde which has a defined short period of offgassing before it cures, compared to an unknown glue and VOC that we know less about.

For the walls here I would have preferred just a solid tongue and groove wood. With plywood only used for cabinets.

Flooring

The floor is APC Cork, which looks awesome and is great for sound dampening. For most moderately to severe chemically sensitive folks, cork flooring is too high in polyurethane glue (and VOCs).

There are many similar floors you could put down in a tiny house that are extremely low (lower than this) in offgassing. I list them here in my flooring post.

Insulation

Both Rockwool and EPS (polystyrene) foam insulation are used in the house. Both healthy choices. Rockwool is my go-to insulation to consider before moving on to more unusual options.

My insulation post goes more in-depth into insulation choices and why rigid foam is still a good choice for most sensitive folks.

Rigid foams are frequently used as exterior insulation (outside of the framing) as part of the system design to prevent thermal bridging and to help prevent condensation.

This video has some good information on the insulation:

The Devil is in the Details (Like Window Flashing)

When designing and building a mold preventative house, the devil is always in the details. Flashing is an area that is more often than not done wrong on new builds (along with the air sealing layers like the house wrap).

I liked this detailed video below on how to properly install a new window to prevent future moisture issues.

Maybe this looks simple and like anyone who can follow instructions can do it, yet almost every builder makes mistakes here.

It’s rare that I see a build in progress with the house wrap/WRB and all flashing done right. You should supervise this part of any build.

When windows and other openings in the exterior are not detailed right, water that gets behind the siding finds its way to the plywood or OSB sheathing. Enough moisture will cause water damage and mold here. As damage continues it will get into the framing and wall.

In regular builds, other openings in the wall for vents or wiring are often left without any sealing (flashing)! Big problem for water and air getting in.

Water is expected to sometimes get behind the siding – that’s not a fatal situation. It’s supposed to be able to drain, dry to the top and bottom, and stay out of the walls.

The windows are Pella brand wood windows with aluminum cladding on the exterior. The caulking recommended for this combination of materials is DAP 3.0 Window, Door, Trim & Siding High Performance Sealant.

Here are the WRB instructions from 475 if you prefer diagrams to video. All the brands come with detailed instructions, there is no excuse for a builder to not know how to do this.

Exhaust and Ventilation

What Happens if you only have Exhaust Fans

The object in the Tinylab is to have active balanced and controlled ventilation.

It’s easy in a tiny house to create negative pressure with a high CFM (CFM is the amount of air it’s moving) bath fan or range hood. This pulls way too much air out for such a small space. This can happen in any well-built air-sealed house, but it’s exaggerated in a small space.

The problem with that is that you start to pull in air back through any gap that the air can find a path through. And back through places you don’t want to pull through – like exhaust vents or even the composting toilet in this case! You might also be pulling in moist outside air.

You aren’t getting healthy make-up air this way (which is the air that’s coming in to make up for that exhausted air).

Why you want Air Moving In and Out

Without enough air exchange (air coming in and going out) in a small space, you can also raise your carbon dioxide.

Having air exchange (meaning you replace the indoor air with fresh outside air in a controlled way) is the best way to reduce carbon dioxide, VOCs and other pollutants, like those produced by a gas stove.

This house has a number of high tech ways to manage the air quality and replace the air.

An Energy Recovery Ventilator

A Broan HRV (later switched out to an ERV) exchanges indoor and outdoor air in a balanced manner. The ERV is working better for them in their climate because it buffers both humidity and temperature.

You need to look at the house as a system and your climate to determine which one you need.

The negative air (exhaust) side of the ERV is venting out of the bathroom, and the positive air (incoming air) is coming in over and under the loft.

The fresh air comes into the loft area with a damper to control whether it goes down to the sleeping area below.

This video explains what an ERV and HRV do and what the difference is.

Exhausts and Make-up Air

The composting toilet and kitty litter box area has a 3 CFM exhaust vent to keep that air moving out (a very small fan, just enough to keep it moving out).

The gas stove has an exhaust fan venting out over it, to pull out moisture, carbon monoxide and other pollutants and particulates from cooking. When this fan kicks on, it opens up a damper that brings in fresh air right under the stove. This keeps air circulating and moving out right where you want it to.

You can see it in action here:

Monitoring the House

The house has a number of cool monitors that help you know that everything is functioning as it should be.

Carbon Monoxide

Defender brand low-level Carbon Monoxide monitors detect low levels of carbon monoxide. This is important if you are running appliances on fuel. Your carbon monoxide level should be 0 in a healthy home.

Elderly, children and those with compromised health are more affected by low levels of carbon monoxide. The cheap monitors are only going to show you when the level is already too high.

Radon

Corbett has a radon monitor from Trutech tools, which is useful in a regular house. Though here it is used for teaching purposes. If you are not on a foundation you don’t need a radon monitor. (Though if you have a granite countertop this might be interesting to see!)

Corbett is aiming for 0 radon in all his houses.

C02 & VOCs

The Foobot monitor tests for carbon dioxide (what you breathe out, this will show you if you have enough fresh air), VOCs, particulates, temperature, and humidity.

Pressure

Retrotec manometer measures the pressure inside, making sure it’s where you want it to be. In the Tinylab they are making sure it’s more or less equalized.

It also monitors the pressure of the incoming air through the ERV. Just an extra data point to show Corbett that everything is functioning, and for educational purposes. For most people, this extra step would not be needed.

Though it would be interesting to see the pressure in the house as a whole. Just seeing that would tell you if something is wrong with one of your fans or exhausts.

Temperature

Two Dwyer temperature gauges measure the temperature of the incoming air through the ERV, and the air inside the wall on the backside of the insulation. These show how well the house is managing the temperature.

The temperature gauge on the inside of the sheathing can help you to calculate if there is a risk of condensation on the sheathing or exterior vapor barrier (if you have an exterior vapor barrier). Especially if that is coupled with air leakage (which you can use an infrared camera to check for).

A third gauge wraps around a plumbing pipe under the stove to see if there is a chance that pipe will freeze. Smart!

Mechanicals / Systems

Greywater & Blackwater

The greywater tank is on the exterior and is portable and on wheels. I like this idea as you don’t have and scum build-up inside hidden tanks. And not having a blackwater tank definitely cuts down on the kinds of bacteria and mold you might be fermenting in your tanks. (They use a composting Air Head toilet instead).

Freshwater

The freshwater tank, stored inside under the sink, won’t freeze. It uses chlorine to keep it bacteria and fungi-free, it’s not for drinking unless you want to filter the chlorine out.

In the last section, you can see the major leak they had with this tank and how they put more precautions in place after that.

Fuel & Electrical Systems

They have three solar panels that are portable, on a long cord and are set up on the ground. They can be moved around to maximize sun exposure. It’s not a great idea to put panels on the roof; more holes = more chance of leaks there.

You can also plug the house in; the whole house runs on one extension cord that runs off a regular house outlet (15 amps). That is an impressive (low) amount of power usage. It gives you the ability to be super flexible with where you live. Either going off of solar and propane, or one plug into any house.

The stove and hot water heater run on propane, which cuts down on electrical usage.

The Mitsubishi mini-split only needs to produce 5000 BTU of heat, 4000 BTU of cooling to keep this house warm and cool enough for their climate. It runs off only 200-300 watts.

This is something you need to calculate in at the design stage. You don’t want an oversized or undersized system.

Mini Split heat pumps are ductless systems, they do not bring air in or out of the house.

This does a little bit of dehumidifying, and in some conditions, the ERV helps too. But they also found they had to add this desiccant dehumidifier.

This video shows the mechanical systems and is a good overall tour:

Design of Walls, Ceiling, and Floor

Floor Design

The base of the house was designed to use the trailer cavity as an insulation cavity. EPS foam with foil backing was placed in between the metal trailer joists.

Underneath the whole trailer, there is a metal barrier to prevent water from splashing up. There is no thermal break underneath the metal trailer framing. This is a typical design for tiny homes on wheels.

On top of the framing, plywood is placed against the metal. It looks like there might be a slight gap between the EPS and the wood.

I wouldn’t recommend this design of the floor system in terms of preventing condensation and mold.

In fact, the flooring system is where you should put the most thought and planning. Bring in an architect like Cheryl Ceicko, or Passive House designer like Mike Maines.

It’s easy and common to have condensation in the flooring of a tiny house on wheels. The metal trailers make this difficult. There is a lot of thermal bridging. You need to decide between thermally breaking this underneath with foam or building up a breathable system on top.

Those who have designed with mold prevention as the main goal have all built up on top of the trailer. This post shows a detailed example.

EPS is also used around the metal wheel wells, a place that is prone to condensation.

Roof/Ceiling

The roof has plywood decking with foam exterior insulation on top (1 inch EPS), then Solitex Mento, then a rainscreen, then 26 gauge metal roofing.

Walls

The walls are regular 2 x 4 framing with Rockwool, plywood sheathing, a rainscreen, and is breathable to both sides with the Solitex and Intello products.

Make sure your rainscreen is vented, it’s a tricky detail in tiny houses on wheels.

What went Wrong?

A Flood

The Freshwater bladder did leak and it was quite the flood. After that, the Lunsfords put some precautionary measures in place.

Anyone preventing mold would want to do this from the start, making sure a leak-prone area is a waterproof protected area and you have these leak alarms.

Mattress on the Floor!

The foam mattress was put right on the floor. Always a no-no! This causes mold underneath. They changed over to an air mattress which does not let moisture transfer through it.

Condensation in Storage

They also had condensation on the wall in the backside (at the back of the drawers that were full of clothes and things) on the really cold days. That’s a place to keep an eye on. You may even want to design your storage a little differently in a cold climate.

Realistic Expectations

Corbett doesn’t have unrealistic expectations on how long a tiny house will last. He says no more than 30 years.

They put a lot of miles on the house but it was designed with an engineer to make sure that it would hold up to those forces. In that sense, it was designed well for the motion.

Building a tiny house when you have sensitivities is in a way a trickier endeavor. You are in a much smaller air space with all the items that offgas that you can’t avoid – appliances, flooring, caulking, glues, windows, doors.

You are also in a much smaller space with EMFs and you cannot get away from that.

In the end, I still like tiny houses for those with mold and chemical sensitivities, but only if you know full well what you are going into and have taken the time to design a detailed mold preventative build.

There’s a lot of work involved here – you are designing a full system. Just about as complicated as a regular-sized house.

The only part that is easier due to the size is that you have an easier time supervising the build. The HVAC is also less complicated.


I am currently taking Corbett’s course in Home Performance to become certified with the BPI as a Building Analyst. Corbett consults on home performance, and you can contact him here.


Corinne Segura is a Building Biologist with 6 years of experience helping others create healthy homes.

healthy home build consult

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Filed Under: Mold-Free Building, Tiny Homes and Trailers Tagged With: Healthy building, mold prevention, tiny homes and trailers

Get Rid of Mold in Your Car, Including AC System

January 8, 2020 by Corinne 6 Comments

prevent and treat mold in vehicles

This article covers the sources of mold growth in vehicles – AC system, high humidity storage, spills, leaks, and design malfunctions – and how to prevent them.

I go into detail on the four methods used to clean the HVAC system out, as well as methods to clean mold and cross-contamination in the vehicle as a whole.

The AC is usually the most difficult area in the vehicle to manage microbial growth. While there are certain makes and models of vehicles where this is more of an issue, to some degree it’s a problem in all vehicles due to the inherent design of the AC system.

This post contains affiliate links, upon purchase I earn a small commission at no extra cost to you.

Preventing Mold in Vehicles

Preventing Mold in the AC and Heating System (HVAC)

prevent mold in the car's AC system

The fungi and bacteria grow mostly in the evaporator core and immediate surrounds, due to humidity and moisture that forms when AC is in use. Mold can form in the ductwork as well.

To help reduce mold formation in the AC system, run the fan for the last 10 min after using the AC. (Defrost is also AC, so you need to run the fan for 10 minutes after defrost as well). This helps the evaporator dry out.

Using recirculate can worsen the problem in some situations. Bringing in fresh air (if the outdoor air has drier absolute humidity) as opposed to using recirculate can help the evaporator to dry out.

Another thing you can do is to avoid parking in areas where a lot of debris can enter the air intake.

Similarly, when driving through very dusty areas, you are bringing in dust and spores through the air intake. You may want to turn off the HVAC system completely in those conditions.

Maintenence on the vehicle should include changing the cabin air filter as needed (when it’s dirty).

I would include one of the four HVAC cleaning methods below as a preventative (before you start smelling or reacting to mold) if you do use the AC system regularly.

For those Extremely Sensitive to Mold in HVAC – How do you Turn off the AC?

Many folks who are extremely sensitive to mold do not use the AC system in their vehicle at all. If you refrain from using this right from the start with a new car, you will avoid most of the problems here.

If you want to avoid AC use altogether, using just the heating system should be fine. But, keep in mind many new vehicle models have automatic climate control which will use both heating and cooling under many different conditions (not just when defrosting). If you want to turn off the AC, look for a vehicle where this can be done – new cars have a way to disconnect the AC compressor. Ask a mechanic how to do this.

Does the auto setting on cars use AC and how to turn off AC

If you have already used the vehicle’s AC or you bought a used vehicle that has some funk in the HVAC system, then even the heating setting will circulate the fungi and bacteria throughout the vehicle.

Buying a vehicle with heated seats is a good idea in case you become sensitized to the vented HVAC and need to turn it off for a while (and try and clean it). Some very sensitive folks have had to turn it off permanently if they have not had success with the cleaning methods.

One other hack is that you can externally mount the HVAC system to get easy access to the evaporator. This is a very unusual hack. You can find photos of it in the group Mold Avoiders on the Road.

Alternative Ways to Stay Cool in the Car

Cars that Come with Cooling Seats

Some of these built-in systems blow unrefrigerated air through the cushions. And some use refrigerated air that is tied into the main AC systems. The unrefrigerated air system may be safe in terms of mold prevention.

Safer Cooling Seats (or Heating)

You can also add your own cooling and heating seats to avoid the use of your car’s HVAC system.

Cooling seats that you add yourself work simply by adding a fan that blows unconditioned air which helps to cool you down.

Some use fans and those can be affordable. (Though they might be made of vinyl).

The heated seats use coils, just like a heated blanket or heated jacket. Some models do both.

Then there are gel seats, I like the idea of the ones you put in the freezer first, then you bring it out to the car with you. This is a kids version. If you know an adult version let me know, I think it’s a good idea. You will want to dry those off though, when they come out of the freezer they are probably going to condensate.

Cooling Vests

When I used to have severe heat intolerance, I used cooling vests on my body – both active and passive vests work.

The active vests provide more cooling but are more expensive.

They were life-saving for me until I healed from heat intolerance.

Preventing Mold in the Car (as a Whole)

does mold grow in cars just from sitting in humid climates
Many of us stored our vehicles in the humid winters of the Pacific Northwest, to come back to moldy cars

Why Mold Grows Inside Vehicles

There are a few ways your vehicle can become moldy inside on the seats and upholstery. Sometimes just leaving a car to sit in a very humid place for long periods of time can cause mold to start growing on the seats.

More common though, is a spill or window left open that wasn’t dealt with fast enough.

Other sources of water damage are less common:

  • Debris accumulating in the air intake areas and connected drains (keep your air intake area clean, and change the filter). The cowl intake and drain area can collect debris. Those areas are connected to body cavities that can harbor microbial growth. Thus structural mold is possible in a vehicle, though this is less likely than mold growth in the HVAC and inside the vehicle.
  • Rainwater that has gotten into the HVAC ducts and car interior in some past Ford models – causing hidden pooling of water.

Ways to Prevent Mold Growth in Vehicles

Prevention here is key. Once mold is actively growing and has made it through to the foam in the seats, it’s a huge problem that is hard to fix.

When storing your vehicle for long periods of time in a constantly humid climate, it’s best to leave it in a sunny spot and leave it with a dehumidifier. Climate-controlled indoor storage is of course ideal.

Though generally, a vehicle should be able to withstand a good amount of humidity while being stored, really high humidity for long periods has been a problem. I left a truck in 70-95% humidity for a couple of months and came back to mold growth. No known water intrusion.

Many others in the Pacific North West or in semi-tropical and tropical areas have left vehicles sitting to come back to visible mold growing (and not from leaks).

Both active (electricity-powered), and passive dehumidifiers will help. You can also monitor the outdoor humidity.

I would check on the vehicle (or have someone check on it), both to empty the dehumidifiers and possibly to dry the vehicle out actively with heat and airing every few days if necessary.

When you spill something or leave the window open, just do everything you can to dry it out within a day, which includes the above: usually sun and air, or heat and air. Add dehumidification only if it’s going too slowly.

Decon/Clean Mold or Cross-Contamination in a Car

DISCLAIMER: Some of the cleaning methods discussed in this article, which include ozone, chlorine dioxide, hydrogen peroxide, and quaternary ammonia, require knowledge of safety precautions for handling the materials, and executing these methods. Please take full responsibility for your health and wellbeing and make sure you understand the risks, precautions, and procedures – not all of which are explained here in full (please research them before proceeding or consult with an expert). Full disclaimer here.

use a HEPA vacuum to decon mold in a car

If you do have some light surface mold in the car or cross-contamination, I would start with a deep clean.

If you had a big spill that didn’t dry out, or you suspect someone else did in your vehicle, you might want to open the seat covers to check on the foam. Some have zippers. If they don’t you would have to cut them open to check.

Mold in the foam cannot be properly remediated other than with replacement.

Deep Clean your Vehicle

You can remove light surface mold or cross-contamination by steam cleaning or shampooing the seats.

Make sure it is dried out quickly after that. Car detailing shops can do this. Just make sure you know which products they are using, as some might not be acceptable, toxin-wise.

A mechanic I talked to near Vancouver BC, does a shampoo of the seats with high temp extraction, then an enzyme spray on the seats instead of ozone to reduce odors. I use natural enzymes to break down odors.

DIY HEPA Sandwich for a Car

If it’s not so bad as to warrant a steam clean or extractor shampoo, use a HEPA vacuum, which you can do yourself. Vacuum the seats, carpet, and upholstery.

For a vehicle, you want a rather flexible hose. I would use a shop vac. I’ve used one before with the HEPA filter and HEPA filter bags.

You can then wipe down all surfaces with quats or the cleaning product of your choice. A proper “HEPA sandwich” clean would involve another round of vacuuming.

Having your car or truck professionally detailed can help, as they do a very thorough clean, though I haven’t seen them do HEPA vacuuming.

Using Ozone on Cross Contamination

If those methods don’t cut it, and you are still sensing mold in the vehicle, you will want to use the methods below.

Many people do use ozone and it does work, but it leaves behind oxidation, which smells quite terrible.

Depending on how long you ozonated it for, it can take a while to die down.

I don’t agree with some who say that you will damage the wiring easily, you would have to use extremely high levels for a very long time to do damage like that.

Many mold-sensitive folks have ozonated vehicles at very high concentrations for 24 hours, many times. I have done a couple of 24-hour treatments on my truck.

Car dealerships use this all the time as well (but normally in much shorter treatments, like 1 hour). Many people only do 2-hour treatments for mold, which should not cause damage to the plastics, and would only cause minimal oxidation odor after.

There is more info below on pumping ozone through the HVAC. If you don’t need to pump it through the HVAC, just see my general post on ozone and run it inside the vehicle. I use many of the little ones from Amazon (like this one).

Please read through the precautions thoroughly, since ozone is a dangerous gas that can be deadly.

Another oxidization method, though it is a weaker oxidizer than ozone, is to use chlorine dioxide gas. That method is explained below, in its own section.

Other Fogging Methods for Mold

If you have another decon method that has worked well for you in decontaminating your house from mold, it’s likely you can use that here – like thieves oil fogging, Concrobium fogging, or using quats.

Silver Hydrogen Peroxide though, is likely too much oxidation for most vehicles, though it can be used in the empty part of metal cargo vans.

Chlorine Dioxide Gas to Treat Mold

Chlorine Dioxide, like ozone is an oxidizer. Like ozone, there is evidence that it breaks down mold and mycotoxins.

Although it’s weaker than ozone, you should take the same safety precautions outlined here. It is dangerous to breathe in and it’s explosive in certain concentrations.

You may not need to be so far away from it like with high doses of ozone, which is an upside. It’s also cheaper and easier.

Keep it simple and buy the ready-made tablets or packets on Amazon. They are inexpensive and work just as well as mixing it yourself. NosGuard is one brand, Reset is another one.

Read the safety instructions carefully on the product and make sure you understand them. Never use a chlorine dioxide product in occupied spaces.

If you want to make it yourself, please take full responsibility for your safety and wellbeing. Here are the instructions:

How to make chlorine dioxide gas treatment for the home or car: 6.5 oz (roughly 3/4 cup) Oxine plus 3-4 tsp citric acid in glass or heavy plastic container, one for each room. Leave it for 3 hours for a shock treatment or 24 hours for a deep treatment.

You can make a smaller batch for smaller spaces with the same ratio. It takes about a minute for the reaction to take place, the liquid will turn yellow, and for about 3 hours it will release chlorine dioxide as a gas. Take similar precautions as with ozone for airing it out and re-entering.

Four Methods for Cleaning Mold from the AC (HVAC) System of the Car

1. Take it to a Dealership – Have them Clean out the System

Skill Level – Easy. Results – Can work, depending on which methods they use.

how to clean mold out of the AC system of a car

There are a number of different cleaning methods used by automotive repair shops to clean out the AC system. Some use ozone and even run it through the HVAC in the same way as described in the next section on ozone.

There are also treatments that are similar to #4 on this list, introducing a product into the system to clean the evaporator.

One mechanic explains: “one is a mist treatment, using a product which foams up. You drill a hole in the case and then introduce the mist to the evaporator core and let it sit, give it time to work, and then flush it out.” (source).

Some of these might have fragrance of other toxic additives but others would be acceptable for many folks who are sensitive to chemicals.

2. Using Ozone Through the HVAC

Skill Level – Intermediate. Results – works on most mold and bacteria.

how to use ozone to clean out a car or AC system

This is a technique used by some car detailers and dealerships and mold-sensitive folks.

The simplest way to do it is to run an ozone machine in the car while the vehicle is running so that the ozone is pulled in through the air intake. Most people would run this through for a couple of hours. Depending on the amount of ozone and the time you run it for, you may need a window open to provide oxygen.

If you are running the machine in the car I would use a small machine like the ones on Amazon for under 100$.

Instead of running the vehicle, you could alternatively, hook up the battery to a battery charger to run through the HVAC settings that way.

For any serious contamination or if you want to blast this more directly through the HVAC, mold avoiders tend to use an external ozone machine that pumps in the gas, giving the machine full access to oxygen outside. Bioblaster is the most popular one.

If you are in the Facebook group Mold Avoiders, you will be able to see an example of a Bioblaster hooked up right to the air intake here.

That machine is overkill for me. But others may need this. I would have no problem running the smaller ones on Amazon that I have used many times and pumping those through the HVAC system with tubing from the outside.

To get it through all the different parts of the HVAC system, the ozone needs to run through it on all settings (heat, AC, recirculate). Run it through each setting for at least 20 min. The next section explains more about how to access the air intake.

This is tricky because of how far away you need to be from the ozone. Let it air out each time before coming close enough to the vehicle to change the settings. Again, ozone precautions are here.

3. Spray Through the Air Intakes

Skill Level – Beginner to Intermediate. Results – May or may not work.

spray in the air intake to kill mold in a car
The air intake is usually right under the front windshield

In this method, hydrogen peroxide or quats are sprayed through the air intake.

Some very mold-sensitive folks have had success with 10% hydrogen peroxide sprayed into the air intake with these video instructions (not with toxic products like scented Lysol). Seeing the process in a video really helps to make sense of it.  

Spray the hydrogen peroxide through each setting for 3 min. You can use this mister.

You will be using 29, 30 or 35% peroxide (depending on what you can source) and diluting it down to 10% (here is the dilution table). Please research and take full responsibility for handling and spraying this concentration of hydrogen peroxide.

Some people found this worked better with quats (a type of ammonia). This ACDelco product was recommended.

4. Greg Muske’s Quats Cleaning Strategy

Skill Level – Very Advanced. Results – Likely to work if you do it right.

how to clean the evaporator core
From http://biotoxinjourney.com/clean-driving-machine/

Greg Muske from Biotoxin Journey has a detailed and more complex method of accessing the entire HVAC system and runnings quats (i.e. quaternary ammonium) through it.

You need some mechanical expertise for this method as it does involve drilling into specific parts of the system, which differ depending on your make and model.

You need someone who can understand the heater core diagram for your car, which you can look up online. You’re going to locate the evaporator core. Then drench the two cores by running about one gallon of quats solution into 3 access holes. Followed by a water rinse.

Greg also misted quats through the ductwork via the vents and the opening for the cabin filter directly above the blower (after removing the filter), and air inlet holes located under the hood next to the firewall. Unlike when cleaning the cores, this was not rinsed out. It was dried out by running the heater and fan on high.

Greg then cleaned out the rest of the car by using a steam cleaner on the carpet with Thieves Oil Cleaner. (You can use the cleaner of your choice). All other surfaces in the vehicle were wiped down with quats.

Full instructions and a video can be found here: Clean Driving Machine. This section was printed with permission from Greg Muske.

Corinne Segura is a Building Biologist with 7 years of experience helping people create healthy homes.

This post was written with input from two engineers, a mechanic, and a car detailer.

Did you find this post helpful? If so you can buy me a coffee to support the research behind this blog. Thank you!

Filed Under: Mold Avoidance Paradigm, Mold-Free Interiors, Tiny Homes and Trailers Tagged With: mold avoidance paradigm, mold prevention, vehicles

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ABOUT ME

Hi, I’m Corinne, I am a Certified Building Biologist Practitioner with 7 years of experience helping people create healthy homes.

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  • Healthy exteriors/gardens
  • Healthy Interiors
  • Mold Avoidance Paradigm
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