My Chemical-Free House

A Guide to Creating a Healthy Home

Tiny Homes and Trailers

The Best Tiny Prefab for Mold and Chemical Sensitivities

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These metal SIPS panel homes by Artspan come in various sizes from this tiny ice shack, like the one pictured/featured in this article, to a full-size house.

In this case, a client-friend, Shannon, used the ice shack kit as a safe haven for environmental sensitivities. Her house also has its own IG account here.

This article is a review of materials, costs, timeline, and challenges that would be useful for anyone building this ice shack or a bigger sized unit with these panels.

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

The basics

This ice shack shelter is 9’x12’ (108 sq ft) and this one has no plumbing in order to stay within the “no permit” zoning in Ontario, Canada. 

The R-Value of the panels is 28.5!! That is excellent. Your average North American wood-framed house has an R-Value of R-15.

This shelter, as well as their tiny houses and regular house options, are suitable for all climates. Including the coldest and wettest climates. However, if you are sea-side, the metal is a lot more prone to rust from the salt (and I would not use it in that location myself).

They currently have designs for 108 sq ft, 153 sq.ft, 162 sq.ft., 252, 954 sq.ft, 1,026 sq.ft, 1,458 sq.ft and 1,701 sq.ft. They make all kinds and sizes of homes and buildings made of these same metal panels. A 12 x 27 is the largest they can make it without interior framing of the SIPS, so it will be WAY more economical this way. Plus this size can be made without any wood whatsoever.

You can leave it as a bare box, or add the usual plumbing and electrical with or without a kitchen and bath, depending on your needs and local building codes. They only provide the shell.

The ice shack is around $7,000 and the panels ship from Canada. You can get 5% with Shannon’s code 3752, or message her to connect with the company.

Summary of Materials

The ice shack does come with everything precut for a 6ft roof. If you want to raise the roof to 7 or 8ft then you won’t have everything precut. The ice shack comes with windows and doors but if you want something different you will have to buy it.

The website says precut window opening and precut panels. The kit did come with all the fasteners and connection angles etc. It came with the Sikaflex 1a as well and 2 tubes of silicone (the guys used like 8 so that wasn’t enough for silicone). It also came with panel clamps.

You have to buy your own spray foam for the walls where they connect at the corners (unless your kit comes with the corner panels, this one didn’t, but that is a good upgrade to ask for).

The owner also ended up using spray foam between all panel joints, they recommend that on their large builds in the assembly instructions but that step is skipped in the ice shack kit instructions. The client wanted a good seal so she bought the spray foam and did this at joints even though they said I didn’t need to (I would do this for sure if you’re planning on using it as living space).

Roof Panel

Why it’s good for people who are sensitive to chemicals

The panels are made from rigid foam (polyiso specifically, which does not offgas) with steel on each side. Other than the glue that holds the foam between the metal panels there is no offgassing from these materials.

The paint on the panels is factory applied, it looks like it’s powder-coated to me, which does not have any offgassing.

You are going to have spray foam and sealant at the seams of the panels, and these do offgas, so it’s important to choose the sealants carefully.

Canned spray foam for most people is quick to offgas (relatively). Not for the most extremely sensitive. Sikaflex 1a is also recommended but lower offgassing sealants can be substituted like AFM Almighty.

Be sure to test all material ahead of time by getting samples.

You can add extra sealing to the interior seams to help block offgassing by sealing them with silicone caulk at the end.

Also, remember that in a small and very airtight space the offgassing of everything you bring in will be more pronounced.

Is it Mold Proof?

It’s about as mold proof as you can get. Be sure to stay under 12 x 27 feet to avoid all wood.

The other caution you need to take is that if you use AC inside you should not finish out the metal walls with drywall or wood as you could get condensation on the interior walls. Leave them unfinished.

You could also get condensation when it’s very cold outside at the corners potentially when heating inside. Another reason why it’s best to leave the walls unfinished and a non organic material for the flooring.

Build this up with the panel foundation that they make and not on a concrete slab which is safer for the panels and safer as a foundation type in general (since slabs often go moldy).

How long does it take to deliver from the time to order?

When the client asked, she was told from purchase to delivery it should take about 6 weeks. But when she placed the order that had changed to 12+ weeks. It arrived at 16 weeks.

How long did it end up taking to build?

In total it took 27 work hours and there were 2 guys working. The company says it takes 1-2 days which isn’t realistic if you have never installed this before.

Can you DIY? If you bought the ice shack kit with the 6 ft ceiling and the pre-cut everything then it’s possible you could do this yourself. Otherwise, you will at least need some knowledge of tools.

How much time does it need to offgas?

It was 3 weeks before the client could spend a long time in there (like an hour+ without the offgassing affecting her. She did use Sikaflax 1a caulking which is strong and slow to offgas (a better alternative is AFM Almighty Adhesive). The thing is it’s SO airtight that when she added a new couch in there this also added to the offgassing.

How much did it cost in total?

This was the total cost of my client’s build in Canadian dollars in 2021:

ARTSPAN SIP PANEL BUILD: $20k

$6.6k 9 x 12 Kit (8 ft ceiling)
$1.3k Shipping from Manitoba to Ottawa
$4.1k Installation
$3k Windows & Patio Door (install included)
$2.2k Electrician to wire the 30 amp panel
$800 HRV
$400 LVP Flooring & Underlayment
$200 Flooring Install
$200 Gravel & Ground Cloth
$100 Concrete Blocks
$100 PVC Baseboards
$300 Wall Heater (1500 watt metal Stelpro Mirage convector wall heater.)$700 Other (including silicone, sealants, tarps, shims, paint, etc)

(Shipping to the US costs more, $4,900 CAD/$3,800 USD is the 2021 shipping quote to Charlotte, NC)

You can get 5% if you tell the company Shannon’s code 3752.

More Technical Details

Window and door install and flashing

In regards to the window installation, on the ice shack kit assembly guide it doesn’t mention any flashing at all, but on their “general” assembly guide the window instructions are more detailed and they use liquid flashing. It’s definitely a good idea to use liquid flashing.

Avoid acrylic latex caulks around the window and use 100% silicone instead and it will offgas faster. Sikaflex a1 is specified which is strong, and slow to offgas. (Also note, it needs to be over 5 degrees C to apply this). AFM Almighty would be better.

But going back and using silicone on every seam, inside and out will help to block that as well as keep it airtight. It might smell a tonne for the first couple of days but don’t panic about silicone smell, it will go away. (My post on caulking looks at silicone brands)

They are also calling for 1-part canned spray foam at the seams which for most people offgasses enough in a day or two. (Highly sensitive folks will need to test it for sure).  

If it’s the vinyl window itself that is offgassing you can seal that with pure shellac, SealCoat Shellac or BIN Shellac (and then paint over that if you like, or else just remove the pure shellac later with alcohol because it will look a little yellow). 

On the exterior, for windows they said they use Supra Professional. It’s a “thermoplastic” sealant. Thermoplastic is a very broad term they’re just trying to not say what it is. The client ended up using Sikaflex.

Interior walls

On their Instagram, they have a few examples of finished builds with what looks like drywall. Or you can just paint them with Annie Sloan paint or Allback linseed oil paint and leave the corrugated look. The electrical will have to be exposed that way. Regarding electrical if you want it concealed you would build out additional framing for the wires since there are only vertical channels built-in, not horizontal. I don’t think they recommend drilling horizontal holes in the panels. 

In the interior photo at the start of the article, the walls are not painted, they are the original white panel. The interior trim was painted white with Annie Sloan Chalk Paint which can go over almost anything.

Exterior Walls

Cheryl Ciecko recommends a drip edge flashing at the bottom of each wall on the outside side if you are on a raised foundation to move water away.

Foundation

I only recommend a raised foundation (a panel foundation with these metal SIPS). Building these metal panels directly on a concrete slab means they are are risk of getting wet and rusty (Cheryl Ciecko does not recommend that).

In regards to the foundation, the contractor said screw piles are kind of overkill for this size build and that he’d recommend the foundation in the Artspan video: https://youtu.be/K6vroAs1Tro

The owner ended up doing a very simple foundation, just two 12 ft long steel C channels (provided by Artspan) running the length of the build, sitting atop 6 concrete blocks (3 per channel).

The steel channels were purchased from Artspan for $75. Concrete blocks we bought locally. They did 6 inches of packed gravel under each of the blocks and then a couple inches all over top.

There is no exact requirement for how high off the ground something like this should be. I would err on the side of caution and I would try and make it a foot high so that there is not a lot of moisture getting trapped there and the ground could start to go funky/ swampy that way.

Adhesive for the Walls/Roof and Floor Panels

They said you could use a different adhesive if you wanted and have the Sikaflex costs refunded from your kit.

When looking up the Sikaflex 1a – they say it says “odorless” but it’s not in my opinion. The VOCs are less than 40g/l and this SIkaflex 1a offgasses for months in my opinion/to my nose. I would say it hit close to odorless between 2-3 months.

AFM Almighty Adhesive is a polyether which is far better.

Keep in mind that the longevity/life span of this whole house rests on the warranty of the foam and sealant at the seams.

Interior Flooring Material

The owner spoke with Artspan and they said they usually lay a plywood subfloor because the steel facing is not perfectly flat (the design has grooves). You can use plywood if you don’t plan to use AC inside.

You could also go with a really wide and really long non-organic plank flooring, for example, Cali bamboo has a vinyl plank that is absolutely huge called Longboard. If you run that perpendicular to the grooves that are already there, you won’t need anything else.

The client used Golden Select Antique Oak 18.2 cm (7.16 in.) Rigid Core SPC Vinyl Flooring. Plank dimensions: 122 cm × 18.2 cm (48.03 in. × 7.16 in.), thickness: 6.5 mm (0.25 in.) There was no need to fill in the groves in the metal, it was laid perpendicular to the groves with the DMX 1 step underlayment.

All of this is referring to the shallow groove side up – as one side of the panel has shallow grooves and the other side deep grooves.

They said it’s up to you if you want the thick corrugation side on the interior or exterior for the floor panels (for walls and roof it’s on the interior). They said for small builds like this they usually just do the shallow groove side up since it’s easier. If you do the larger corrugation side up it can take slightly more weight, but that doesn’t matter for making a small shelter or tiny house.

Final Sealing Interior and Exterior

Any 100% silicone can be used on the seams. They come in clear or different colors so you might want to check that out. Some companies make custom colors.

Ventilation

You will need some air exchange unless you want to leave the window cracked at all times (which is what Shannon ended up doing in the end anyway, as it’s easiest! Be sure to monitor CO2 in such a small airtight space).

If you do use an air exchanger, you want a really really low CFM here. Even 20 CFM is going to be overwhelming and could make you quite cold in the winter. So I want that to dial down to 10 CFM or maybe even less. If it’s not comfortable you’re just going to want to turn it off all the time. Also, make sure that you can turn it off. I’m sure any of them could be wired into a switch but I would check or make sure they wire it that way! Think about the placement too, and make sure that it’s not blowing on you.

Without a kitchen or shower in there, with no wood and no AC, this isn’t about trying to control the humidity really, but just making sure the owner has enough oxygen and doesn’t have the CO2 go too high. However, that can definitely be accomplished by opening a window and turning up the heat. 

The CFM for the Blauberg Duo is 10-40. It’s cheaper than the Lunos because you only need one. It’s around $900 CAD.

Roof

The owner was worried about the roof, being that it’s just the same panel connections as the walls. She wanted to be sure to really seal those joints well. She considered an RV tape roof sealant on the seams like this:https://www.amazon.ca/gp/aw/d/B094XP9PR2 though didn’t install it.

The contractor siliconed the seams and they also did all the roof trim, roof panel seams/ wall panel seams (Artspan says just do roof panel seams but she wanted to be safe).

She did end up with a roof leak in the first year. I would recommend a liquid RV roof sealant at the seams.

Cheryl Ciecko said the cut edges where the steel is raw is vulnerable to rust so that may need to be painted. She also thought that it could use a drip edge on the edge of the roof panel, though she did not have an exact specification there.

Conclusion

Alright, so those are the main deets for this tiny house. This is really the best option I have seen for a fast, easy, well-priced prefab house that you can install as a safe haven for mold and chemical sensitivities.

Thanks so much to Shannon for going first and sharing the build with us. You can see more pics of her house here. Don’t forget you can get 5% if you use Shannon’s code 3752 when you talk to the company.

Addendum: Now We Are Getting into the Real Nitty Gritty of the Installation

This is for those in the throes of the install:

Dealing with Exposed Foam Corner Pieces

There are small air pockets on each corner between the female side of the panel (with exposed foam) and the trim piece. It’s at the corners of the build, so there’s a 3/4 inch gap of metal but no foam that runs the height of the build before it meets the trim that covers the corner.

Artspan says since it’s on the outside there will be no condensation there. My contractor seems to agree. And it’s covered by trim.

I suggested she cover the exposed foam with a paint so that it’s not permeable to water, and make sure that it has a drainage plane so that if water gets back there, and it will, that it can drain out at the bottom. Most exterior paints work on foam.

The problem is the panels sit directly on top of floor panels (vs just on trim). So to make a hole under would mean drilling through the 5 inch metal/ foam floor panel, in which case any water draining would repeatedly come in contact with the foam interior of the panel. So we could not go with a drainage point there. You could poke a hole in the bottom of the corner trim piece as low as you can go to find that out if you suspect it taking on water. 

In this video you can see the exposed parts before trim is placed. (At 30 seconds it’s the front 2 corners).  https://youtu.be/K6vroAs1Tro

For large builds, they actually have a “corner panel”. You can probably get them with any package at an additional cost (which I would recommend). The ice shack/ similar kits don’t come with them by default. Their larger builds also come with a heavy-duty metal frame on which the build sits on. The ice shack kit comes with “skids” and with this one the owner added 2 steel channels for $75 extra to sit it on (you can also put it on whatever you want, concrete pad, wooden frame, etc). 

The owner thought that they really need to do a better job with their instructions. There is a lot that’s not clear especially if the builder has never worked with these panels before. She said with clearer instructions we could have easily shaved a day off the build. 

Tips and tricks for Installation

The biggest issue is that they send drawings specific to your build but with no actual “steps” or order of how to do things. They have the measurements and trim angles etc. But it’s nowhere close to enough for someone who has never put one of these together.

She printed out their “general assembly guide” because she figured it was better than nothing. She thought that ended up being more confusing as it’s geared towards their huge builds that are like 20 by 40 and 20 ft tall. Eventually they told her to try to follow the ice shack kit instructions, as it was more in line with this build. By this point the guys had already put the base trim on upside down, but the ice shack guide did help. Except the base is different and the trim is different. So again they were confused. They had to call them to verify they had flush trim (ice shack shows a box type trim).

They spent almost a whole day trying to figure out if the wall panels were pre-cut or not. She was under the impression that all the panels were totally pre-cut— the only cuts on site would be rough openings. On the drawings the only mention of cutting is a generic “some field cutting may be required”. You then have to piece together which panels require cutting. They finally figured it out by looking at the measurements on one of the drawings, and seeing that one panel on each wall measured less than the others, then they measured those corresponding panels on site and found they were the same size as all the others. So they deduced they had to cut them down to size. But this made no sense because by that point they had the floor assembled, and no cutting was required. Why are the floor panels cut to size but not the walls? She then found out from calling Artspan that all the panels are cut to height or length only, NOT width. For the floor and roof panels, no cutting was required, but 4 wall panels needed to be cut. It would have helped it they said “Panel 1, 5, 6, and 8 have to be cut to size on site.”

The next issue came as they were assembling the walls after they’d made the appropriate cuts. The contractors started with one corner and worked their way around clockwise. At the end of the day they had done all 4 corners and just had 2 more front panels to do. She figured out that one of the end pieces had to be the last to go in to make it work, as the end pieces are only connected on one side and just exposed on the other, nothing to slip into. It should note: “The last panel placed must be one of the corner panels”.   

Non-Toxic Travel Trailers for the Mold & Chemically Sensitive

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graphic with a trailer that says homes on wheels for chemical and Mold Sensitivities

This article focuses on the healthiest trailers. The first priority is that the trailer holds up to mold. If it doesn’t hold up to mold, no amount of natural wood, or wool, or other eco-friendly material really matters.

Conventional trailers are extremely mold-prone. They use wood within the walls, roofs, and floors with a design that is not airtight. Condensation usually forms in the cavities. They are also prone to leaks.

The Designs That Best Hold up to Mold are:

  1. Sandwich construction – Airtight cavities of metal or fiberglass with rigid foam insulation. Ideally laminated together.
  2. Fiberglass shell campers – Solid fiberglass body trailers are single or double hulls. A single hull has no hidden cavity where condensation or mold can form. The double hulls can work well too. I list brands that have minimal wood or where the wood does not become a mold risk.

Low-VOC Trailers:

No well-made trailer is extremely low in VOCs. Some are better than others.

The interiors of all-metal trailers can be lower in offgassing compared to trailers with other wall materials. But don’t underestimate the odors of the glues used in all metal trailers.

There is no getting around the offgassing. The best strategy is to give it some time to offgas or buy a used one if you are highly sensitive.

You certainly can compare models though if you are chemically sensitive since we all are reactive to different chemical combinations. You definitely could find some brands more tolerable than others, even if the total VOC count is the same.

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Non-Toxic Tent Brands (No Flame Retardants, Low Offgassing)

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After having spent two years of close to full-time camping while I was highly chemically sensitive, I have a lot of opinions on tents! I tried a lot of different styles during that time.

This article looks at different style tents and which ones are easier to keep mold-free, which brands are low in offgassing (and chemical odors), and which ones are free of flame retardants.

There are so many more options now than when I started!

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Passive House Tiny House – A Detailed Mold Preventative Build

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Intro from Corinne:

What it takes to Build a Mold-Preventative House

This post is about a meticulously built tiny home, designed to hold up in the long run to mold.

The post is written by the owner/builder who did years of research and consulted with many building science experts.

There was an extreme attention to detail on preventing mold.

The main reason almost every house is moldy is because of the many mistakes made in both design and execution.

These mistakes can be even more prevalent in tiny homes – which are less regulated and often built by non-experts.

This post serves as an example of the care, research, consultation, and attention needed to build a tiny house that will hold up to mold. There is no other article like this online nor in books so I’m very grateful to Terran!

The owner/builder, Terran, also has TILT (also known as chemical sensitivity). There is a focus on healthy materials in the build as well as mold prevention.

This post may have ideas you can use in your own build and it is also interesting to see the kind of detail needed to carefully build a house.

The build itself took over a year.

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Non-Toxic Alternatives To Vinyl Sheet Flooring (for Vans, Trailers, Kitchens, Bathrooms, Schools)

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Usually, vinyl sheet flooring is used in trailers and RVs. Vinyl sheeting has significant offgassing. The post outlines healthier options.

Metal and fiberglass homes have unique challenges with thermal bridging and humidity, and often require waterproof flooring that can hold up to some moisture.

The following list is the flooring I would specify in vans, metal trailers, fiberglass trailers, and any other tiny house made of metal (like SIPS), plastic or fiberglass.

This type of flooring is often used in commercial buildings and schools and can of course be used in residential kitchens and bathrooms.

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Emergency Housing for Chemical and Mold Sensitivity MCS / CIRS

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Here is a list of some housing ideas for those with environmental sensitivities needing immediate or temporary safe housing.

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

KOA Cabins

KOA cabins are located across the US and Canada. The cabins are made from mostly safe materials (mostly wood) and have been reported to be good places to stay for those who are environmentally sensitive.

Ask if the wood has been stained recently. The bathrooms are separate and may or may not be mold-free, depending on the location.

Recently I’m hearing reports of these having gone moldy. If the foundation or roof is not done right there is a high chance these could go moldy. Often newer is better for mold.

Home Made Tents

Regular tents can be difficult because of the chemicals used on the fabrics, the lack of insulation and the tendency for them to go musty very easily and be a lot of work with the airing out and drying out.

I have a preferred tent which is an off-the-ground tent in my post on camping gear. Here are some alternatives:

Reflectix Tent 

Reflectix provides some R-value and reflects light so that should work in a lot of different climates, though the seams will reduce the insulative value and add more glue and more potential for leaks. There are simpler designs for the structure that will reduce seams.

You can’t buy these – you would have to look online for the metal structure, then buy the Reflectix, foam, aluminum tape, and duct tape and then have someone make it for you. The tape may make this intolerable for some. And this also lacks airflow. 

You would also make at least one triangle out of polyethylene or an EVA Shower Liner so that you have some light. But have a flap of Reflectix over it that you open and close over this “window”.

Plastic Tent

A woman sitting outside of a tent that she made from Tyvek plastic
Kim’s tent via Paradigm Chage.org

Kim was severely sensitive to chemicals. She made a tent out of Tyvek which she tolerated well when extremely reactive. She explains how to make it here. Through extreme mold avoidance, Kim made a full recovery.

This is a plastic used as house wrap.

There are so many options here on what you can build an emergency tent out of. It all depends on what you can tolerate.

It may not last forever but it may give you some time to find another option or even bring down your MCS which will open up options. 

Other materials you could use: polyethylene, tarps, even hemp fabric if you are not expecting rain and don’t have high humidity.

Foam Tent

A A frame foam box that I set up inside my cargo trailer for sleeping in

When Sara was an extreme reactor (also now recovered), she made a simple structure out of XPS foam boards. The two-inch boards of XPS (usually Owens Corning brand can be found easily) have a high insulative value.

She arranged them in a tent shape, the groves in the edges holding them together. Rocks at the base pressing them together. Of course, you could use tape if you can tolerate that or put plastic over the whole thing.

Above is my version made of polyiso foam. This is a “foam tent” used inside a non-insulated trailer that was cold and still offgassing.

I hooked up a Panasonic ERV and ran fresh air into the tent at night via a 4-inch aluminum tube. The opposite end of the tent had a 4-inch hole for air to exit.

This is a highly effective way to deal with offgassing – fresh air is pouring through, though it can be difficult to control the temperature and humidity this way. 

Coroplast Tent

This Youtuber built a foldable shelter out of the safer plastic Coroplast. The downside is the amount of tape needed to form a shelter like this.

Simple Wood and Foam Shelter

The actual wood frame which was the cover of my foam shelter

Inspired by the idea of a foam shelter, I have made two highly insulated shelters with ridged foam, raised off the ground and covered in a tarp.

A wood structure like mine pictured above, may be needed to protect from wind and snow. 

The frame was covered with a tarp and inside on the plywood platform was a box made out of foam. This shelter worked extremely well though there are things to keep an eye on in the long term.

Here are some video tours and here is a post devoted just to this shelter (the second one had no wood framing above, just a tarp).

A digital sketch up of a wood A frame on a platform that my foam shelter went inside.

The whole thing was completed with some volunteer and some paid labor for 1000 CAD. 

Such a robust frame is not always necessary. You can build the plywood platform, with foam box on top and simply string a tarp over this if you don’t have strong winds or lots of snow. 

This is the same structure with a tarp over it and the XPS foam box secured with tape inside. The design can be improved by fixing the tarp, painting the foam structure and using clear tape. Please contact me for details if you want help setting something like this up.  

Here’s another example of a foam box. Just don’t put it right on the ground like they did here, and you want another cover on it. This is polyethylene foam which is much more unusual. 

Insulated/Aluminum Tents

These WeatherHyde tents are insulated and the foil on the inside will also block most of the VOCs from the fabric on the outside.

They say you can sleep in them down to 0 degrees Celsius.

They are 600 USD.

They look like they would have problems with airflow and condensation inside. As well as being straight on the ground, but they may work for some people. 

The shift pod for 1300 USD is similar but with the reflective layer on the outside.

This will help reflect the sun and keep cool in sunny weather when there is no shade.

But I don’t know how this will perform well with condensation inside.

The best of the typical tents have an internal mesh layer, then a gap with a rainfly on top. If you don’t use that system you usually end up with condensation. 

There are other similar tents cropping up that were designed for Burning Man festival.

For a lot less you can get a simple aluminum-lined small sleeping tent. It’s not insulated but the aluminum on the inside is more tolerable than the usual tent materials and does reflect heat inside. 

Regular Tent

My tent outside an cob house at OUR ecovillage
My first tent CC BY-NC-SA

There is no perfectly chemical-free tent, The most tolerable brands include Ozark, Big Agnes, REI, LL Bean, Colman, and Lightspeed. Everyone is different. 

My post on tents looks at the lowest offgassing options and which ones are free of flame retardants.

In the post, I also discuss canvas cotton and hemp for really dry climates (or temporary use) which may be where the most sensitive need to start.

I would also check out the cuben fiber tents mentioned in the camping post.

Yurts & Huts

A green plastic yurt on a platform at OUR Ecovillage on Vancouver Island
Me at a yurt at OUR Ecovillage CC BY-NC-SA

Yurts are often tricky for a few reasons. They are normally made out of PVC which takes time to offgas.

On top of that they are difficult to insulate, although one could just use them as an uninsulated tent.

The wooden framing can be susceptible to mold if there is a lot of condensation inside or with high humidity inside, which can happen when heating up a small space.

The wood also might be treated and could cause reactions. There are yurts that have metal framing which may be preferable for some people.

Here is an example of a metal-framed yurt.

You can create your own outer yurt cover by using a more tolerable material, although it will not be as long-lasting as PVC.

You can use materials used to make a tent, or polyethylene sheets that are used for greenhouses, or tarps. You could also go truly traditional and use hides.

One really positive design feature of yurts is that they are lifted off the ground on a platform. All metal yurts may work for some. I have looked at those in the post on simple shelters. 

These glamping tents by sweet water bungalows are PVC, with a canvas top (prone to mustiness), but the guide and framing could be used to create a tent with a plastic of your choosing.

Just keep in mind polyethylene is not as durable, but is less toxic. 

I wouldn’t use canvas for anything other than a short and dry camping trip but without the breathable roof these are prone to condensation.

Conestoga huts have a simple design for a little hut/glorified tent. A simple design that goes up fast is a big benefit.

I have not been able to review these plans for mold preventative building, but it’s an interesting design. If you have the plans for these will do a free review.

If you don’t insulate this it shouldn’t be a problem. If you do want to try these with insulation please reach out to me or an expert in building science. I am not presuming these are a mold-safe design.

Simple Metal SIPS Shelter

Two walls going up of the small metal SIPS house

You can easily put together click-together metal SIPs to make a fast, clean and fairly durable structure.

SIPS are structurally integrated panels. Metal SIPS are made of steel-styrofoam-steel sandwiched together. A highly tolerable material for those with severe sensitivities.

Because these are structural you don’t need to build a frame. Pour a concrete slab, and then once you have the panels it’s fast.

To create a long-lasting structure you would add siding but if you need something done fast, just put it up.

This little shelter is made with Structural Building Systems panels.

A small metal SIPS house in the desert

Sheds

Steel sheds can be bought from Amazon or hardware stores for 700-1000 dollars.

You will also need to build a foundation (you could also just leave it as gravel), pay for labor to set it up, caulk the whole structure and likely put in some insulation.

For everything you need to know about setting up a shed to live in see this post by EI Wellspring.

Sheds are not as easy to take down as you would expect.

There are also wooden and plastic sheds. I have seen some good little wooden shed kits made of solid wood.

Raise them off the ground and cover with a tarp above that is not touching the shed.

I like cedarshed.com for those who can tolerate cedar because it’s a highly rot-resistant wood.

Check out the wood first, see how it was stored and test it for reactions. 

Hard plastic sheds will work for many people. The more flexible the plastic the more it offgasses. PVC should be avoided where possible.

Glass Enclosures 

A greenhouse in the desert used as a shelter
www.buildahealthyhouse.com

A greenhouse can be used for backup shelter, it gets very hot when the sun hits them in warmer seasons and can dip really low at night in colder temps.

But some people have used them successfully. Margaret (another person who used this strategy to heal and make it back to indoor housing) talks about her experience with them here (her greenhouse pictured above). 

Other glass/metal enclosures brands are Handi Hut and Four Season.

Small sketch up for a glass and foam stucture with glass as the interior walls and foam on the outside with a tarp over it.

I designed an all-glass on the interior shelter with insulation on the outside. This was designed for a time that I could not have metal or wood inside touching me.

The walls and floor were glass. The ceiling would be easier to make out of metal.

The shelter was raised off the ground on a platform. Outside of the glass was 2 inches of foam insulation. To hold this insulation on, the exterior framing (outside of the foam layer) was attached by drilling through the foam and glass. The foam needs to be airtight to the glass. A tarp should cover the shelter.

Back of a Pick-Up Truck

Try and find an aluminum canopy for the back of the truck, which is the best-tolerated type.

The bed liner may need to be offgassed or can be covered with Reflectix.

If ordering a brand new truck you can request no liner.

Cargo Trailer

A cargo trailer that I converted into a RV

Details on converting a cargo trailer safe in this post. 

The company WeRoll can customize these and they have more robust roof lines compared to the standard models. 

Ambulances and Refrigerated Trucks

A decommissioned ambulance used as an RV home

The benefit to these two options is that they are already insulated and ready to go.

A decommissioned ambulance is insulated and offgassed since they already have quite a few years on them by the time the government sells them off.

Refrigerated trucks could be found either new or used and they are well insulated and also ready to go.

If you went new you would have to check out the offgassing levels to see if it suits you, but I would expect it to last longer.

Creating a Safe-Room in Your House 

To create a non-toxic room in your home you can use Denny Foil, or heavy-duty aluminum foil on the walls/ceiling/floor.

These materials block VOCs (chemicals/toxins including mold).

Heavy-duty aluminum foil is much easier to work with than the type used in cooking. You may need several layers to totally block smells. 

You want to use green Painting Tape for this as it will not damage the walls and is easy to remove – a healthy person could rip off/take down the whole room is probably 20-30 min (small room). The blue tape is toxic so I wouldn’t use that. You could use aluminum tape but it is very sticky and will leave a residue and will be hard to take off. Aluminum tape also smells and offgasses more than green tape.  

I would not do this where you have colder air inside than outside (AC use). 

Cover outlets. As for light fixtures, I would go around them. 

The only thing in the room should be clean bedding i.e. a new non-toxic mattress or camping cot (etc). New non-toxic bedding and pillow.

Be careful that when you open the window or the door that the air coming in might not be good, so this won’t be a long-term solution. 

If you can’t foil the walls you can make a room within a room and use positive pressure as explained here in this post. The picture above shows how pressurized rooms keep out contaminants.

You can use foam, plastic or any airtight material. Isolate that by using positive pressure which will work to reduce chemicals like offgassing.

That can be a solution for someone extremely sensitive who has trouble with offgassing (when the issue is offgassing rather than mold).

You can find more information by researching isolation rooms. 

Ecovillages

A cob house at OUR Ecovillage on Vancouver Island
A cob house at OUR Ecovillage CC BY-NC-SA

Staying in a cob house (or straw bale, adobe, light straw-clay house) can be a really good option 

Ecovillages may rent out rooms in natural homes and there is a possibility of getting in on the communal meal plan as well. Search for some in your area and ask about monthly stays.

I have seen some natural homes listed on AirBnB as well as on lists of intentional communities/ecovillages. 

Always ask about propane, natural gas, cleaning products, and water damage. I have found that is wet/cold climates cob and similar materials do not hold up to mold after a few years.

Slabs and roofs often have mistakes that lead to mold. Green roofs can be very problematic. Amateur built houses are especially prone to mistakes that lead to mold.

This type of building is best when raised off the ground, or with a simple roof, otherwise, don’t bank on this being safe if more than 1-3 years old. 

Ecovillages are also a good place to set up a tent where you might have access to outdoor bathrooms and kitchens that are more MCS safe than campgrounds.

It may also be a safer environment for those traveling solo. I have used the Intentional Communities website, Google for places near you, and the site wwoofing.

If you have physical energy you can work on a wwoofing site in exchange for free rent (camping or small cabin usually) and often food.

Another option for those who have energy to do work is remote cabins that are advertised on Craigslist where you do some house and yard work in exchange for rent. The cabins might not be safe, but this could be a free spot to camp or live in a trailer. 

Other Emergency Housing

We should have emergency and long-term safe housing for people with MCS, but in reality, there is very little.

Check out the Environmental Health Association of Québec if you are a Quebecer. 

For housing listings in the US and Canada, join EI Safe Housing on Facebook. 

When I come across AirBnBs, hotels and short-term rentals that look safe I list them on my Pinterest page.

While many turn to Airbnb or other short-term rentals, in the beginning, this can be a difficult and sometimes impossible road if one is super sensitive and/or masked to mold. 

Corinne Segura is a Building Biologist Practitioner with 8 years of experience helping others create healthy homes.

I spent two years in tents and small structures in order to heal from extreme chemical sensitivity. 

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

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How to Offgas that New Car Smell

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This post will go through the techniques used to help promote offgassing of the volatile organic compounds (VOCs) in a new car.

That “new car smell” is made up of VOCs and we can speed up their release or mitigate them with a number of hacks.

Not all toxins in new vehicles are gasses (VOCs) however. We will also look at avoiding, cleaning, and sealing nonvolatile toxins like metals and flame retardants.

[Read more…] about How to Offgas that New Car Smell

Designed for Mold-Prevention – Corbett’s Tiny House

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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.

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

a graphic with different color squares that have words in each square: insulation, air tight, temperature, high performance house, ventilation, flashing, power

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 Practitioner with 8 years of experience helping others create healthy homes.

Did you find this post helpful? If so you can buy me a coffee to support the research and writing behind this blog. Thank you!

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How to get Rid of Mold in a Car, Including AC System

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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)

a close up of a typical car's manual heat and AC controls

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.

a close up of the digital controls for heat and AC in a newer car

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)

a cooling seat that you can add to a car

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

a cooling vest worn by a man

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)

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).

a small dehumidifier

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.

a man vacuuming 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

a vacuum that can be used in a car

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

a hepa vacuum

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

a little ozone generator

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.

the component inside the car seat area opened up and ready to clean with a fog master junior and bottle of squats

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.

a pick up truck with an ozone generator outside pumping ozone into the car

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.

a close up of the air intake on the outside of the car where the hood meets the window
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.

the hood of the car open, cleaning the evaporator core with fog master
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 Practitioner with 8 years of experience helping others 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!

What are the Causes of Mold in Tiny Houses?

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common areas that go moldy in tiny homes

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

1. Built by Non-Experts

Highly skilled builders are rare. They tend to focus on upscale houses because that extra work and time they spend to build something right does translate to more expensive homes.

Most tiny house companies I have seen were started by contractors who don’t have much experience, they certainly don’t have the expertise in building science (which is mold prevention), and high craftsmanship.

Most small companies I have looked at started with someone who had not even managed a whole house build before! That was the case with my builder.

Even if a company is well established, it’s rare that an architect or other building science expert is recruited as a designer and consultant on a tiny house build. It is necessary to have that building science expertise to building anything that will hold up to mold, no matter the size.

My resource page contains links to architects, builders, and building science experts who I think are good.

I certainly wished I had chosen an experienced builder who really cared about details, and hired an architect to design and manage the project.

2. Building Codes not Followed 

Building codes are not perfect, they are only the bare minimum requirements and even though they are just the absolute bare minimum of what needs to be done on a house, they are not usually followed.

To build a truly mold-resistant (regular) building you have to hit many of those codes right on and in many other areas go above and beyond those codes if you want the house to hold up to moisture and mold.

Tiny houses don’t even meet those codes on some of the most basic building standards. If you are having trouble finding a regular house that does not have mold, I don’t have good news, tiny houses are built even more poorly.

For some areas of the build, RVIA certification could help ensure things are done better. But some RVIA codes are not mold preventative (like the requirement a vapor barrier), that could make things even worse!

Look at RVIA codes and see if that will work with your moisture management system. You may have to forgo that certification. There may be important guidelines to follow there for general quality (plumbing, electrical, fire safety), but not necessarily for mold prevention.

You can build a mold preventative build (like this one) and also meet the International Residential Code (IRC) (which would be a good idea).

 3. The Trailer is Tricky to Insulate

All Tiny Homes on Wheels are built on a metal trailer – that’s a tricky interface for condensation in most climates. Building the house by using that trailer as a floor cavity is a bad idea.

The house should be built up on top of the trailer, and even then there are many very detailed decisions and details to consider and execute. See this post on a Mold Preventative Tiny House for details on the trailer base.

4. Metals Frames 

Many THOWs are also made with metal framing. That is really tricky too! Now you have a whole house with thermal bridging and the possibility of condensation in the wall. Even if you go with all foam for insulation, this has to be well thought out and designed well.

I have seen trailers with a metal frame and then an organic insulation! No!

The wheel wells, another metal area, are also particularly difficult to insulate and are usually done wrong. The wheel wells in my tiny house went moldy within the first 3 years. They need to be thought out and detailed right.

Hire a building science expert to design your building envelope.

5. Which Climate is it Built for?! 

Tiny homes are often moved throughout many different climates in the US and Canada. Which climate was it designed and built for?

Even if some thought was given to design the building envelope and HVAC for that climate, will it now be moved to many different climate zones? How will the house perform in those?

If the house is made for multiple climates that has to be factored into the design of the entire envelope and moisture management system as well as the HVAC right from the start.

WUFI is one program that you can use to model the moisture in the house and see how it will perform in various climates.

6. Movement is Not Your Friend!

Taking a house and then jostling in on the highway does not lead to something very durable. All those little details that need to add up to have things perfectly sealed and flashed do not benefit from a lot of movement.

You can easily lose the integrity of your sealing or flashing here, you may even have trouble with your framing or siding. Problems with your framing could lead to problems with your doors and windows and more…

7. A One Year Warranty??

Many tiny houses are very expensive and only come with a one year warranty! What!

What other 60K item would you buy that only has a one year warranty? Builders can get away with a lot because major mold problems will take longer to show up than one year.

My house had a few problems in the first year, but there were other major problems that took more than a year to show up. Mold above the shower in the ceiling, mold on the framing, an insulation system in the floor that was not done right – I fixed these myself on my own dime.

Ben Garrett (Tiny Healthy Homes) who built my house only paid for things that went wrong in the first year. He then changed the name of his business (and so I could not sue him). That’s another reason these small companies are very risky. I lost 100k as a result of the building defects in that house.

Though I did learn a lot about building science when I took it apart! And this did lead me to become certified as Building Biologist to help others build low offgassing, mold-safe houses.

The most helpful course in mold prevention is Cheryl Ceicko’s Building a Healthy Home.

8. Siding is Prone to Mold

Siding is frequently done wrong on tiny houses. Mold preventative siding almost always has a rainscreen with very few exceptions.

Regular wood-framed houses almost always require a vented rainscreen siding system to prevent water damage and mold. This is rarely done on a tiny house.

Most houses I have seen have siding right up against the sheathing. Sometimes it’s permeable siding, meaning solar vapor drive can drive moisture in, but even if it’s not, it prevents drying from the inside out. And you are losing your layer of protection from water entering behind the siding.

A rainscreen helps water that will get behind your siding drain out.

I highly recommend Cheryl Ciecko’s course on building a mold preventative house which is now evergreen, you can start the course at any time.

To hear about future course you can sign up for my email list:

9. Roofing Prone to Mold 

Regular sized houses have a fairly complex roof system that often has venting. An unvented roof (like tiny house roofs) would have to be done really carefully.

In a small space, your roof cavity can start to mold fast. Mine did over the shower as the builder had no interior vapor barrier and the breathable roof sheathing membrane was enough to trap moisture there.

Many tiny houses also have roofs that are flat or don’t have the right material for the slope.

Here is an example of a highly detailed mold preventative roof.

10. Details not Done Right 

The devil and mold prevention are in the details. Window flashing, house wrap installation, house wrap taping, metal head flashing, the detail below the rainscreen, flashing on any permeations going through the wall, details around the door- all of these are super crucial.

It’s especially important to get right due to the lack of overhangs over windows and doors on most tiny houses. This means everything has to be done perfectly. The overhang on a regular house is insurance against too much rain hitting these vulnerable areas.