Passive House Tiny House - A Detailed Mould Preventative Build

Intro from Corinne

This post is about a meticulously built tiny home, designed to hold up in the long run to mould. The post is written by the owner/builder who did years and years of research and consulted with many building science experts. There was an extreme attention to detail on preventing mould. The main reason almost every house is mouldy is because of the many many mistakes made in most builds (in design and execution). These can be even more prevalent in tiny homes which are less regulated and often built by non-experts.

This post is mainly to serve as an example of the care, research, consultation and attention needed to build a house that will hold up to mould. The owner/builder, who would like to remain unnamed, also has MCS. There is a focus on healthy materials in this post.

This post may have ideas you can use in your own build and it may also be interesting to see the kind of detail needed to carefully build a house. The build itself took over a year. This house uses many practices from Passive House building so there are some unique aspects, but many of these aspects can be applied to most tiny houses. Never simply copy someone else’s building practices without consulting with your own architect or engineer who specializes in mould prevention. If you change the materials due to availability, or your own sensitivities, or you live in a different climate your house will likely be different. We are also not presenting this as the perfect house to copy. Any ideas here should be reviewed by you and your experts. That is not a legal disclaimer, that is just what needs to be done to build a home that will last. Keep in mind even among experts there is disagreement on building systems. However, I do think there are some unique and valuable ideas here.

This post does not go over every detail of the build, as that would take a whole book. But it does cover the main tricky areas, as well as the main materials used.

Even if you choose just to look at the pictures or watch the video (coming soon - I will post it to my Facebook page), I think this will be interesting to anyone looking to build or renovate, whether you are a beginner who does not know the full complexity of housing systems or an expert in building science.

I am very excited about this post. I think it adds something really important to the tiny house conversation.

The following is written by the owner/builder and has a few comments inserted by me. It has been edited for grammar and length by me. The owner himself will be away from the internet for the next 3 years, so he will not be available.

This post is not sponsored by any of the companies mentioned. The Amazon links are affiliate links. If you are going to purchase any of the items here, and if you found my site’s content useful, it will not cost you any more to make your purchases through these links.



About three years ago I set out to build a Tiny House to help with chronic health problems I’ve had since childhood. The structure would need to be free of chilling drafts during colder weather (it gets down to around -30 F), free of building materials that caused Toxicant-Induced Loss of Tolerance (TILT), have a good (and properly sized) supply of fresh air in the form of Heat Recovery Ventilation, and would need to be as efficient as possible. Early on we struggled to find materials that would fill these needs. We thought it seemed likely that we would have to wind up building more or less another version of the kinds of structures that have made life challenging for me in the past. But then a retired contractor mentioned Passive Haus/Passive House (PH) to me.

For several months, I’ve been living in the final product of what we built, and it has changed my life. It is by far the most beneficial structure for my health that I’ve ever lived in. Because of that, I really wanted to take the time to explain our build. I’d be really happy to know that others in the Tiny House community might be able build on what we’ve done, and improve it. They’re awfully small spaces to share with moldy surfaces and cavities of walls, roofs, and floors that have moisture issues over time. I have heard horror stories of how much these factors can impact Tiny House occupants.

The envelope design we settled on has a number of points where it differs from other Tiny Houses I’ve seen, so I’ll try to explain why, and how, it differs in this post.

I’ll start with how we went about planning the design.

Part I: Design and Testing

During the early part of the planning phase, the amazing and kind Hans at Pinwheel Structures in Ontario, Canada suggested that I try using U-Wert in order to test moisture and efficiency performance of my wall, roof, and floor assembly ideas. U-Wert (German for “U-Value”) is a program that people can use for free online to perform basic WUFI-style analyses of any given assembly in their building envelope. There are more advanced features available through subscription.

The English version of the program itself is still partially in German. There are full listings of analysis information for nearly all brands and styles of Passive House Certified Materials, as well as a wide selection of the other common building materials. The listings include factors like permeability, u-value, thermal delay, thermal mass, and nearly all the other important statistics for Passive House consideration. Once putting together a given assembly design, one can set interior and exterior temperature and humidity to see how the assembly performs under different conditions. Because I figured I only had one shot at getting our design right, I got a little addicted to the program.

At 475’s recommendation, I also bought a copy of the Passive House Planning Package (PHPP). The PHPP was learnable, with some real attention and effort, for a layperson like myself – and the amount of climate-based information it offered was invaluable for understanding what’s required to build a Passive House.

After working with the PHPP for many hours, I was able to get a sense of how much energy I’d be using for the plan I settled on. What I needed was a design that could be potentially mobile, was specifically designed around environmental health issues, and that fit into an incredibly small budget. The home will also be empowered by the fact that it can be physically moved (and therefore re-oriented) each season, to give it the best performance for any particular time of year.

After more U-Wert and PHPP test-runs than I could count, we settled on a design that has a few calculated risks, largely for the sake of maximizing foam-free efficiency. I want to be sure to explain those.

Part II: Walls, Roof and Floor


The first of these risks is that instead of using a continuous layer of exterior insulation, such as Gutex (covered by battens and siding as normally prescribed) we chose to go with Facade-Grade Thermacork. Facade Thermacork has essentially the same u-value as wood-fiber insulation, but can be left exposed to the elements for a lifetime, and is designed and tested to stand up to almost any kind of natural exposure (except woodpeckers…it doesn’t like woodpeckers!  Just put up some mylar balloons when it first goes in, and they’ll stay away).

This function of Thermacork is not a risk, it’s been relatively well tested in many places around the world and is undergoing some data collection in the temperate rainforest of Washington State. The risk for us is that we could not find anyone who had used Thermacork on a Tiny House and then moved it on the highway. Some of the people we spoke to about the idea seemed completely unworried about the material in highway conditions (after all, it survives extremely high winds on building exteriors all the time). Others felt we might want to plastic-wrap the house if it ever gets moved. We’re thinking we’ll probably be safe and wrap it, just as most conventional mobile homes are wrapped for transportation. This seemed like a reasonable risk to take, as we’re not planning on moving the house often (only once or twice in its lifetime, if needed).

Additionally, the Thermacork allowed us to save a great deal of weight over the normal exterior insulation-batten-siding approach – no matter how we sliced or totalled different materials. Thermacork also had a major advantage for sound: one inch of it cancels as much as 50 dB equivalent.

Most importantly, though, the Thermacork saved us space. After repeated U-Wert analyses, it became clear how important every inch used for insulation can be in a Tiny House, due to size restrictions. Tiny Houses generally need to be less than 8’6” total width, and less than 13’ 6’ total height for road legal transport in most areas. Additionally, since we were trying our best to make sure that the structure could be certified as a legal residence (we are now nearing receipt of a Certificate of Residence or Occupancy) we had to hit the International Residential Code (IRC) requirement of 7’ interior space in length and height of all habitable areas. These factors place a clear limit on how much space there is in a Tiny Home for insulation.

A note on foam vs other insulation: Under these circumstances, foam can be tempting. It’s light, it appears to have the maximum R-value per inch of all available insulations save for Vacuum Insulated Panels (VIPs). It can also come in differing forms (spray, board, roll, exterior roofing spray, etc.). However, even the most trustworthy professionals in the foam industry I spoke with emphasized that spray foam will lose significant R-value over the course of its life. It will be dimensionally unstable, eliminating its proposed air-sealing value, and potentially creating gaps in wall-cavities over-time. It is expensive. Almost all foam is heavily vapor-closed, and so does not allow breathing of moisture in most building assemblies like ours. It also outgases for the life of the product, and spray-foam can lead to disaster if minor aspects of the install go astray. For more information on why we chose to avoid foam in our build, please see 475’s excellent blog series “Foam Fails.”

A final note on our framing design: it could be said that we took a risk by utilizing advanced framing techniques for a mobile design. This has become a commonplace approach among Tiny House builders, but it does require care. The architect who volunteered to help us, John at Rebuild Studio, as well as the seasoned framer we consulted with – took every opportunity to emphasize that. We made sure to install metal braces at pretty much every connection point (between floor and wall framing, between roof rafters and sill plates, etc.). Our framing consultant really did want to see us use 2x6’s – rather than the Tiny House standard 2x4’s – and for a lot of reasons (see the “Interior” section on Windows, Doors and Interior) we decided to go with that suggestion.

Here are more pictures of the framing.


This leads me to the second risk we took: an R-60-ish roof full of Roxul. If we had anyone nearby who could do dense-pack cellulose affordably (or there was a machine we could rent nearby to do it affordably ourselves), I would have insulated the roof with cellulose to be sure we got the weight balance right. Aside from the sheer lightness of cellulose, dense-packing cellulose or fiberglass might have also allowed us to save considerable additional weight by removing some of the secondary stick-framing we put in, in order to add additional layers of Roxul around an interior thermal break space. There are also fantastic cellulose batts on the market, but they would have cost us about twice as much as Roxul (due to the fact that we can easily drive across the border into Canada and buy Roxul near the factory).

I want to highlight this risk, because I would not want anyone else to take the same approach we did, only to find that their building is top-heavy and dangerous. I have not taken our Tiny House on the road yet, and so I cannot confirm that it will be functionally balanced. Based on our best weight calculations, and the considerable weight of the floor assembly and heavy-duty trailer we built on, we felt like the building would be alright travelling at moderate speeds. Here on the build site, it has never so much as swayed a millimetre. But I remain agnostic about how this aspect of our build turned out, and we may not know for many years how it will fare on the road.

That R-60 roof value was very challenging to reach without foam, we had weight restrictions, and it required some sacrifice in space. Many Tiny Houses really skimp as much as possible on insulation in the roof and floor, so that they can have enough space for a functional lofted living/sleeping area. A major factor that encouraged us to go with our approach is that, due to the IRC’s size requirements for habitable spaces, most Tiny House lofts are illegal for sleeping or any other habitation activity. Knowing that, we were willing to sacrifice a loft. Instead, we made what is essentially a permanent bunk bed – and since one of the main concerns I’ve heard with Tiny Houses is closet space, we made it into an inexpensive pull-out closet. There would have been no way to make a legal living space underneath. We could have also gone with the approach of putting the bed underneath a platform living space, and rolling it out on casters (to see how this approach works, see the Minim House. If I had needed a larger bed, that is most certainly how I would have done it (and I would have made sure to get an out-swing door, rather than an in-swing!)

Floor Assembly

Another aspect of our design that might require some explanation is the floor assembly. We went through a number of ideas for how to create a truly thermally broken Tiny House floor. Along the way, we also had to face the fact that there were no known ways around using vapor-impermeable materials for the interface between the floor frame and the trailer – at least none with proven longevity. I really wanted to be sure that the floor had vapor permeability because I’ve seen deconstructed Tiny House floors that had gone rotten after some years, due to impermeability issues. Floors, especially those elevated off the ground and exposed to air and wind, can really have a tendency to deal poorly with vapor drive. They are the coldest assembly in a Tiny House. After some great advice from many professionals, we decided on using ¾” marine-grade plywood for the underside of the floor assembly – with some added tricks and layers.

Floor Trick 1: We built the floor upside-down, in sections that we could manipulate without heavy equipment. While the marine-grade ply bottom was exposed, we taped all ply seams with Extoseal Finoc, as well as all parts of the ply that would interface with the trailer. The not only provides a great self-sealing water-proof layer but also enables meaningful amounts of capillary action to wick away any moisture that comes between the floor-frame and the trailer in those interface spots.

Floor Trick 2: We then coated the remainder of the exposed marine-grade-ply-surface with Prosoco R-Guard Cat 5, which was extremely impressive. As many Passive House Professionals have pointed out, relying upon liquid-applied layers for air and moisture sealing on walls and roofs can be unreliable. Many such layers can fail over time. Also, they are not produced in a factory (like Solitex Mento or Intello) and are essentially “manufactured” on site. This creates significant added potential for failure/error during application and curing. However, in our case, we were not relying on the Cat 5 for air sealing, since we would be taping all seams by the end of the install. What we wanted was a thick, durable protective layer over the ply surface that would completely repel water, and be moisture permeable from the interior. CAT 5 fit that description very well: it’s thick, water-immune but breathable, and incredibly strong (almost like dolphin skin when wet). Prosoco’s amazing field rep emphasized that Cat 5 should always be covered and protected by rain-screens, etc., as it can definitely be damaged. However, because our application was sheltered and downward facing, and we were not covering the surface with siding or anything of that nature, we felt all the more confident that we would be able to patch the material over time with a brush-stroke or two anywhere it might get damaged during sitting or road-travel. We figured we’d just schedule logical times to check the surface and see if it needs repair (zero repairs needed so far). Although the material should never be exposed directly to the sun and other elements, because we were installing on the underside of a floor-frame and taking the above precautions, Prosoco agreed that this was a feasible approach for our application.

Floor Trick 3: After a lot of consideration, we settled on putting the thermal-break layer for the floor to the interior. Placing a thermal break to the exterior of a THOW floor frame either left significant thermal breaks (as in insulating the trailer frame), created a danger of decay (SIPS), or other problems. Placing the continuous layer of insulation inside the building envelope allowed us to not only to ensure we had a robust thermal break but gave us the ability to build our floor sections with 2x8’s (again, without heavy equipment) because we would not need to lift the added weight of wood-fiber insulation board with the sections, during placement on the trailer.

Floor Trick 4: The engineer we worked with said that we should use stainless steel bolts and nuts to be sure we had enough strength, and he gave us a pretty large number to install. It was a really fail-proof way to ensure connection to the trailer – and will allow the Tiny House to be removed and put on another trailer or a foundation when this trailer reaches the end of its life. Because our floor frame was so thick, we had to use an extremely long metal drill-bit meant for aircraft, but it was available locally and worked very well (with a lot of elbow grease – Kangaroo Trailers makes a seriously beefy trailer). Dave at Kangaroo was able to get us additional attachment points via welded flanges on the sides of the trailer, and very well-made cross-bars going across the center. His design also saved significant amounts of weight over many of the other approaches we’d seen – while still keeping a maximum amount of strength on the main frame and the tongue.

We had been hoping to avoid the use of sheet-goods with formaldehyde of any kind on the interior of the structure, so we used tongue and groove pine instead. Above the pine, we installed the wood-fiber insulation, and above that we laid Intello Plus and connected it on all junctions with the wall membranes. This very effectively sealed the pine out of the interior living space. However, we were left with a surface that would have been difficult to install a conventional floor over (i.e. the top of wood-fiber insulation, with relative blindness to the studs and tongue & groove below).

Floor Trick 4: In the end, after a lot of research, we used Marmoleum Click for our finish floor. Marmoleum makes the only linoleum certified by several international health organizations – and takes great care to ensure that all materials used in their products are low-off-gassing. Running a simulation of the product in U-wert (using the top-surface, the low-VOC MDF, and bottom cork layer) tested to have acceptable vapor permeability – although we were never able to get official perm ratings from the company.

More pictures of the flooring process here. 

Part III: Air Sealing, Ventilation, and Heating

Because we wanted to avoid drafts, foster dry wall cavities, avoid the formation of mold throughout, and have good control over the interior air-quality of our Tiny House, air-sealing and ventilation were incredibly important to us. We were extremely happy to find products that worked perfectly for these purposes, and had extremely rigorous testing and research backing them.

Air Sealing

We used a carefully detailed continuous layer of Solitex Mento 1000 as our primary exterior air-sealing layer, and vapor-permeable secondary Weather Resistant Barrier (WRB).

We applied a similarly detailed interior layer of Pro Clima’s Intello Plus as our interior air-sealing layer and intelligent vapor control layer.

We then applied Tescon Profil tape for all our window connections to the interior and exterior membranes (taking care to seal and connect the junctions between Mento and Intello). We also used Tescon Vana to seal the seams of the exterior sheathing as a back-up, to help ensure we got a good air-seal – since it was our first time around the air-sealing-block. 475 believes in redundancy, and although taping all plywood seams below a layer of Solitex Mento is not a step they suggest, we really wanted to be sure we got a proper air seal, regardless of any novice mistakes.

Along the way, we sealed all seams and penetrations of the interior and exterior membranes with Tescon Vana as well.

Extoseal Encors was used for all the window and door sill-pan details. Encors is able to flex and shape itself around corners in ways that are genuinely unbelievable, especially when compared to normal materials – and it’s self-sealing and waterproofing capabilities are essentially superpowers.

We also wanted to experiment with trying to save vertical space by using Solitex UM on the roof. This allowed us to save the inches of vertical space that would have otherwise been taken up with battens, while still allowing moisture from under the roof panels a pathway out from under the standing seams. We had to take special care when lapping the drip-edges to be sure the moisture would escape on the mesh, as planned, and also had to take a lot of care while installing the roof panels over it, but we all wound up being impressed with the functionality of the membrane design Because we had to have some extended conversations with 475 about how to detail this particular process, and we haven’t seen it elsewhere on the 475 blog, we wanted to list the steps here:

Install Wood-Fiber Insulation properly over the roof sheathing

Properly stretch, mechanically fasten, and tape the Solitex UM over the wood-fiber insulation.

Make sure to properly connect the Solitex UM (or plan so that you can connect it later) to the air-sealing layer over the walls.

Be sure that you are placing the edge of the mesh so that it allows water to drip properly over the edge of your roof, and not down behind any part of your wall.

Integrate the fabric part of your Solitex UM properly with your wall’s air and weather barriers so that there are no gaps.

Follow manufacturer’s instruction for the proper order of installation of the Standing Seam Roof panels, drip edges, etc, while taking the following steps:

Each time you fasten any material through the Solitex UM, cut a small slit in the mesh layer above the fabric, to be sure that your fastener doesn’t catch a strand of the mesh, and leave a pathway for moisture to travel along the fastener, and below your fabric.

As you place the roof panels, fasten them through backer plates to ensure that the fasteners do not damage or puncture your insulation board.

A final note on Solitex UM: If you’d like to experiment with saving wall space, you can also use this on the exterior of your walls, instead of battens, and apply your siding directly on top of it.

Here are some detailed pictures of the roof install. 


For ventilation, we went with a pair of Lunos E2 units, and an eGo for the bathroom fan. The units provide pressure-balanced ventilation, and the upper end of their CFM capacity is more than what we wanted for the tiny space, even given how much I appreciate fresh conditioned air. Despite that, I would not recommend using just the E2 units without a proper bathroom fan of some kind. E2 pairs are not rated for enough moisture to be used in a bathroom. In the warmer shoulder months – when it’s often too cold or wet to comfortably open a window, and too warm for the air to tend towards dryness - it’s really important to get shower moisture out of the bathroom effectively. Using both the E2 and a bathroom fan (especially the eGO) made the humidity manageable. With the smallest 25 pint Kennmore Dehumidifier (Note from Corinne, they no longer make this size but this is another good dehumidifier) the house has been able to maintain 50% humidity or below at all times, even during the wettest moments of the summer months (most of the time the dehumidifier is not needed, but when it is, it clears out the humidity quickly, and much more effectively and reliably than any of the smaller options I looked into.) Here is a good and well priced humidity meter. A bathroom fan also ensures that unpleasant bathroom odors do not become a problem. (As an important side note: Lunos HRVs should always be located at least 1.5’ from the ceiling in any location. These are often not placed correctly.)

The final piece of the ventilation picture was a 24” recirculation range by Summit (Note from Corinne, I prefer for this to vent the humidity to outside like this one). It’s the only model we found that was small enough for us, and in our price range, and it does the job well enough. I had to remove their foam filter (which was supposed to be what caught non-oil food-particulate, but was shockingly diffuse, and wasn’t even cut to the right size) and replace it with cut-to-fit carbon. I was happier with the carbon than a cheap foam filter anyway. Overall, the quality is a bit lower than I had hoped, and it doesn’t effectively catch all the cooking vapors, but with our mini-split circulating air (see the next section for more information) an E.L. Foust 160R2 air-purifier, and the Lunos units running, I’m able to get the air fresh within a reasonably short amount of time after cooking. I’ve lived in tiny houses before that became very moldy as a result of not being able to effectively vent and/or filter the steam from cooking – and the food particulate within it that creates the odors.

Heating and Cooling

For heating, we decided on an LG Artcool Premier mini-split heat pump, which is LG’s highest efficiency model. Mitsubishi makes the lowest BTU output model on the market at 6,000 BTU’s, and their models have fantastic quality and durability. I have relatives who’ve owned their units for years now and have also made many calls to local HVAC companies, as well as Mitsubishi and Ecomfort’s customer service staff. All the agents I spoke with were very candid about the different brands and models. Given all of that, as far as well could tell from initial research, the smallest Mitsubishi unit seemed like the best for tiny spaces. So why did we choose the LG Artcool Premier? It turns out that even though the smallest LG Artcool Premier model puts out 9,000 BTU, the inverter LG uses allows the unit to step down heat output to just a bit less than the Mitsubishi Unit (at least at the time of my research, that is what both companies confirmed for me, when I contacted them about the numbers.) This actually put the LG unit closer to the number the PHPP gave for the total BTU’s we’d need to heat our house will tell you exactly how large your heater needs to be, among many, many other useful things.) So in this case, the LG unit will be able to almost match its output to our exact needs, under any circumstance. As it turned out, the small amount of research I’ve seen from the Department of Energy indicates that having units be oversized for the space and unable to step down to the given needs, is a major factor decreasing efficiency.

Another factor is that the Mitsubishi unit automatically shuts off at around -13 F according to the submittal. The LG unit does not have an automatic shut-off, and field reports from users as well as the company would indicate that it can continue to put out enough to heat a tiny space like ours down to as low as -20 F. So in the end, the fact that our unit puts out 9,000 BTU is not a problem due to the inverter flexibility, and the extra BTU capacity also gives us some extra breathing room to keep using the unit as temperatures drop into negative digits.

Beyond all that, the LG was significantly less expensive, which I appreciated. You also get some additional items that cost extra with Mitsubishi (like the drain-pan heater.) The folks I’ve spoken with who’ve installed these units have emphasized that they tend to have very few problems – IF, as with any brand, they’re properly installed by a professional, and well maintained. At this point, we can heat and cool (and ceiling fan!) the house for around 200-300 watts in most cases. This is amazing. The dehumidification function is disappointing, and in general please remember to use the “self-cleaning” setting on the remote if you buy one. Running A/C and dehumidification on these units can lead to them developing some mold after a while, if you don’t run the fan enough to dry the fins out.  The “self-cleaning” setting does that to some degree, but I try to run the fan function as much as I can, and that also keeps really good air-mixing going in the house (and helps make up for the fact that we placed the Lunos Units too close to the ceiling!)

One final note about mini-splits: our installer seemed short on time, and insisted that he wanted to put the indoor unit on the same wall as the exterior compressor. This is not what we had previously planned on, and came as a surprise. Unfortunately, this meant that it was not only right over the foot of the bed, but would be somewhat obstructed by the only cabinet we had installed. The location worked out fine, and it heats the space wonderfully regardless. However, I hope that if you’re thinking of getting a mini split for your Tiny House, you might be able to account for putting it in the spot that will be most straight-forward for the installer (and least expensive for you.) By having the lines from the indoor unit come straight out the wall above the outdoor unit, we saved him an immense amount of time on working with the copper lines, etc..

Part IV: Windows, Doors, Interior and Framing Details


Windows, for a Tiny House on Wheels (THOW), were items that we had to research and reflect a great deal on. There are many different standards for what counts as “high performance” windows, depending on who you’re talking with. For a certain section of the market, Marvin and Andersen are considered high performance and efficient. We’d had experience with them in the past, and although we were pleased with the workmanship and quality of service, they always became drafty in our region and could be frigid to sleep near.

In sections of the truly high-performance market, we found triple and quad-pane windows that were of incredible quality, but also way outside of our weight allowance and budget. Luckily, we found that there is a small section of the Passive Haus and high-performance market that has been working with Heat Mirror technology – which is essentially a special kind of heat retentive film used in place or ordinary sheets of glass. It is cost-effective, and comes close to being in the same range of efficiency as panes of glass. However, after speaking with some fantastic (and very honest) engineers at companies with some experience in Heat Mirror use, it sounded like most of them hadn’t really figured out how to make the technology reliable in the long-term. Right around then is when we were referred to Alpen High Performance Windows.

Alpen (formerly Serious Windows) has arguably more experience with Heat Mirror technology than any other company in the industry. They’ve learned how to secure and seal the Heat Mirror film properly, as well as suspend the film so that it does not sag or cause distortion over time. They’re accustomed to using Heat Mirrors between glass of varying thicknesses and types, for all applications – and they do so for both triple and quad-pane units. This saves enormous amounts of weight. Their manufacturing takes place in-house at their factory in Colorado – so they are able to have wonderful levels of quality control over both the process and the product. After a lot of pricing and research, I honestly cannot recommend any other company for high-performance windows to be used in THOWs.

They were also able to work with me to eliminate PVC from the windows I bought (replacing PVC glass stops with aluminum ones – the rest of their windows are made from an amazing low-toxicity fiberglass). I found the PVC used in many PH windows to be a major problem in a tiny space, and many companies unavoidably include PVC, and do not offer any flexibility to allow you to eliminate it. All of the people I spoke with at Alpen were wonderfully kind, and either had the information I was looking for or readily put me in touch with someone who did. If you’re looking for PH Certified Windows that will fit into the weight constraints, efficiency standards, and budget for a Tiny House, I just can’t imagine buying anything else. For those who are very sensitive to off-gassing VOCs from window seals, there will be some of that with Alpen windows – as with any window. People like us just need to plan some time in for things of that nature to off-gas before moving in. It didn’t take long before they were fine for me. I’ve never felt uncomfortable in front of one, even in -20 F weather – and I haven’t yet seen even a speck of condensation on them (although the space has been extremely dry during the winter much of the time, often sub 30% humidity).

Here are more photos of the window install.


Researching high-performance doors for a tiny space was similarly challenging. Again, weight was an issue for the extremely high-quality PH certified doors I saw – we just wouldn’t have been able to balance it properly, or account for it in the overall weight budget. They were also incredibly expensive and outside our budget.

Due to a recommendation from Alpen, and other folks we spoke with, we began looking into local ProVia dealers. They make high quality, well-crafted steel and fiberglass doors with R-values around 5, solid air-sealing values, and options for quality multi-point locks. Just about a year before we contacted them, ProVia began manufacturing what they’re calling the “Embarq Door.” They claim that it’s the highest R-value unit on the US market, and many at their company seem to consider it to be the ultimate in high-performance entryways. Although I feel someone at the company should inform these employees that there is an entire world of PH doors out there – many of which blow the Embarq away in pretty much every category. I hope more people get a chance to look into it, and see if it’s a good fit for their projects. It has some improvements to make, but it’s a very high-quality American made door, for a decent price (depending on where and how you buy it).

The Embarq door is R10. ProVia built it more or less like a vault-door: with a tapered interior edge Based on our research into door options, it came in at between ½ and ¾ the cost of a certified PH door, depending on the given model and quote. The Embarq makes use of ProVia’s impressive Signet fiberglass technology – which is not only light but can also imitate a number of different wood grains, to the point of being almost indistinguishable from wood from six or more feet away.

On the downside, ProVia hasn’t yet figured out how to use multi-point technology in the door (due to the vastly increased thickness over their standard doors.) Because of this factor, and the fact that they're still tuning their manufacturing process for such a thick slab, the air-sealing figures suffer a bit compared to their normal doors – despite the multiple layers of seals they use. They seem to be figuring out the manufacturing process and how to work around the slab thickness and seals, which can make for tricky installs – especially if you’ve ordered a wide-jamb door, as we did.

For our interior bathroom door, we picked up a free slab with hinges from Craigslist.  I apologize to those who were hoping for something prettier!

Interior Framing Details

On the interior of our envelope, after much debate and reflection, we decided to go without a service cavity in the walls.  This is not a choice that we made lightly, and I wish we’d been able to include one. Because we had the space, we were able to use a service cavity in the ceiling – and we packed as much electrical into that as we could, and fit 100% of the plumbing into the interior bathroom and countertop space. For what little wiring was left over in the exterior walls, we settled on surface-mounted outlets which allowed us to avoid large holes in the membrane. Air-sealing a Romex cable is pretty straight-forward with Tescon Vana and it saves a lot more air-leak risks than a larger hole. We did use one air-sealing outlet-box from 475, and it was awesome (i.e., sleek, space-saving, easy, effective, etc.). If I had the chance to go back to the electrical phase, I’d just use the air-sealing boxes everywhere instead of the surface mounts If I had a chance to do the whole project all over again, I would want to do a full-on service cavity in the walls.

Here are more pictures of the electrical.

Using a service cavity is the best way to assure a fully intact and functional interior membrane, and it just makes everything in the finish phase more straight-forward. In our case, we would have either had to trade the 2x6’s we used (to increase structure and insulation) for the service cavity space, or make the interior an illegal living space by making it smaller than 7’, side to side. We made the best choice we could at the time, and I was very focused on trying my best to get as efficient and moisture-sound as we possibly could.

As an additional note on where I was coming from, no matter how I configured it, U-Wert consistently showed us significantly better efficiency and moisture numbers for a 2x6 wall cavity with 2” of exterior insulation, than with 2” of exterior insulation, 2x4’s and a 1.5” service cavity. I don’t know if this was just a glitch in U-Wert, but especially the moisture performance calculated as clearly superior, even when using a 2.5” service cavity. I think this might be due to the fact that the inboard membrane had all of the insulation to the exterior of it so that the total amount of wall insulation was not broken up by a second set of framing members, and the membrane. U-Wert also showed a clear improvement in moisture performance when the service cavity was left un-insulated, so I imagine that the additional insulation on top of the Intello created more of a temperature difference between the inside air and the Intello’s interior surface, which made for greater condensation risk there in the winter. I hope those who are much more in the know than myself, and with expertise in WUFI, will chime in with their thoughts. Obviously, both wall cavity sizes are far, far smaller than any truly Passive House in the Northeast. Based on my tinkering with U-Wert, I do not imagine anyone with a Passive House in this region would see moisture dynamics of that kind in their assemblies, due to the much larger amount of insulation exterior to the Intello. The U-Wert analyses certainly support that idea – and I can see that principle at work in how the numbers for our roof assembly worked out.  Because of the greater amount of insulation exterior to the Intello membrane, we could have easily insulated the service cavity without much condensation risk. However, given that we wanted to squeeze as much insulation into the walls as we could, we just couldn’t see making wall service cavities and not insulating them.

To moderate the risk we faced by not using a service cavity on the walls, we worked with John Kingsley, at Kingsley Woodworking in Ithaca NY, to come up with a creative approach. John was the only person we found who could mill us ½” Poplar T&G panelling (or ½ panelling in any wood species). He did a beautiful job milling and sanding it. Because John knew we were trying to save weight, he mentioned to us that he could remove a small rectangular portion of wood from the back of the panelling, without compromising the structural integrity. He calculated that this would save us quite a significant amount of weight over the whole structure. Once we saw the kind of thing he was talking about, we also felt like the extra space behind our panelling might provide a least a little bit of additional room for moisture and air exchange, which helped us feel a bit better about not having a service cavity. Because we knew at least some of the panelling would have to be in direct contact with the Intello during its least permeable mode, we made sure to paint all four sides of the panelling boards with highly permeable Romabio mineral paint. Romabio felt that the paint did a good job of protecting wood from liquid moisture, while at the same time remaining vapor open. We won’t know whether this approach worked until some years have passed, or we cut a panelling sample to see what it looks like on the underside. We look forward to seeing what the results are though.

There were a lot of approaches we took with the interior, in order to try to maximize the efficiency of the space, or minimize weight while maintaining high-quality.


Eco Supply Center, which was the source of our Facade-Grade Thermacork, also very kindly walked us through the process of buying and DIY-ing Richlite for our countertop. Richlite was by far the best material we found for this purpose, after a lot of searching and ordering samples. Richlite is 0 VOC, waterproof, far more durable than wood, and weighs a tiny fraction of stone or other high-quality non-paper-based solid-surface options. Cutting and installing it ourselves was a little daunting, but between the amazing assistance from folks at Richlite, and the great people at Eco Supply Center, we were able to do it (at least to our standards!). In the end, we were able to use a totally normal saw blade for the cuts, but it did need to be high-quality, and sharp – at least in the beginning. After making our cuts, the Richlite dulled our blades to the point of them being basically useless. We certainly took that as a testament to how robust the material is, and it was great to be able to DIY it, since most other non-wood countertop materials must be cut with professional equipment.

Part V: Water and Electrical

Water Heater

The folks at Stiebel Eltron were an incredible resource for water heating. I searched an awful lot for a hot-water heater that would allow us to avoid plumbing propane (and re-filling propane tanks) and would give us on-demand levels of efficiency for the small amount of hot water I needed. All the on-demand electric water heaters I found required much more amperage than we would be able to run to the THOW, even the amazing range of on-demand units that Stiebel Eltron makes (their lower-flow, lower-power sink units just weren’t designed to put out enough water for showering).

After using an incredibly effective little 6-gallon water heater in India, I started looking into similar options on the US-market but found them to be generally unreliable based on reviews. They were disappointingly inefficient. They were also not built for long-term serviceability and became trash as soon as most anything needed to be replaced. Stiebel Eltron makes by far the most efficient small-tank water-heaters on the market, and during my search, they released their 6-gallon model. It is serviceable across the board, and replacement parts are available through Stiebel Eltron for anything you might need.

In my experience, with a low-flow shower head from Niagra I can have all the water I need to take a more-or-less normal (though by no means long) shower, so long as I make sure the tank is up to temperature before I start. It takes some care and practice playing with the hot and cold, and my preference is to keep the tank temperature right about 115 through most of the day, then turn it all the way up before taking a shower, and wait for it to get up to temperature before jumping in (there is a light on the side of the unit, so you can tell when it’s running, and when it’s up to temperature).

The unit has been extremely quiet and draws 1300 watts when in use (according to the literature, it has around ½ KW standby usage per day, at 120 F if you leave it on all the time). That was low enough to fit within the bounds of the underground electrical service we were able to run to the house, and I am extremely grateful for that.


Along with an induction cook-top, and the previously discussed heat-pump mini-split, everything fit just fine into a 50 amp service. With some care, we could run the house on an extension cord in the future if needed – and we’re now all set to run on renewables like solar, if I ever have the money for them. After talking with a number of people in the industry, it seems like with decent sun exposure, we would need very, very little in the way of a solar array to off-set the entire foot-print of the THOW.

And here is one last album with general construction details!

Closing Thoughts

I hope that we might have shared something here – either through the text, video, or pictures – that will be helpful to others. There are so many good intentions in the Tiny House community, and I worry that far too many people wind up with spaces that fall short of what they expected in terms of comfort, health, and efficiency.  I’ve been inspired by folks who broke out of the main-stream to experiment with addressing those problems – like Robert and Samantha at Shedsistence, and Leaf House in Canada. I hope we can all work together to make tiny structures live up to their potential, and become healthy, comfortable, efficient, affordable, and legal spaces for people to live.

Camping with MCS and Mould Illness

I am updating this post after lots of experience camping. The orginal focus was more on MCS (which is still in the post) but I am adding more usual camping equipment and techniques for avoiding mould.


For my first tent I decided to buy a used tent off Amazon. It turned out to be a new/returned tent so it was perfect for me. I bought this tent. I went for the cheapo option here just to get started quick. I used it after one week (with the doors all open at first for air) but it was about 1 month before I found it offgassed and could close up the doors. I was super sensitive at this time. There are a few other better quality brands in this style tent which is super easy and quick to put up and has a great design with the amount of ventilation. Lightspeed and Coleman have this style and are recommended by sensitive folks. Mine leaked in a heavy rain so I don't like this style of tent, other than the fact that it is very easy to pop up and if you get a good tarp over it you will be waterproof. Anyone super challenged with putting up tents might want to start here. Start with Lightspeed for the super sensitive.

For a heavy rain, a tent with a really good fly is needed (that comes down almost all the way to the ground) like many of the REI or MEC brands or this or this. Sometimes the rain fly smells stronger than the tent and sometimes it smells less. Sometimes a super beefy tent bottom is the hardest part to offgas. It depends on the brand. I have used many tents in this second style. You want a good rain fly that comes all the way down and you might also need a tarp. Water that soaks the tent walls with then soak anything that is touching the walls.

Some MCSers wash the tents to remove some of the smell but this also removes some of the waterproof coating so I decided not to try that. The mesh makes it easier to tolerate a tent sooner and prevents condensation. I like putting tents in the sun to offgas them. Smell thm and also touch them to make sure they don't cause a burning sensation.

Make sure you know how and that you can put up your tent alone (as well as set up other supplies like a stove) before you get to the campsite. I have showed up to campsites with tents that are defective or missing parts so I would check for that reason as well.

Staying Mould-Free
I bought a tarp for underneath to keep dew from getting the tent wet from below, and a tarp for over the tent for heavy rains. The bottom of my tent has stayed nice and dry. I take out and turn over the sleeping mat every day or two. If the bottom of the tent gets wet you will want to dry it in the sun within 24 hours. There are footprints made for underneath tents, but tarps are generally cheaper. (Your tent may come with a footprint). You want the tarp underneath to be a little smaller to tucked in so that is is under the tent. No water should get between the two. Some people tuck it and then raise it a little with sticks or rocks so that no water gets in between.

Some people find they still do have to move the tent every couple of days due to condensation or grass dying underneath. Keep a backup tent that is offgassed in case of mould or damage to your primary tent. I found regular tarps from the hardware store has a strong smell but offgassed within a few days. A silnylon tarp may be more tolerable but is more expensive.

Generally you string up the tarp in an A shape so that it's touching neither the tent or the ground. Some people dig a small trench around so that the water that drips off does not go towards the tent. Without a tarp I had a lot of problems including saturation of the tent and water coming through especially where anything was touching the tent. Digging a trench won't do much in a big storm, in very swampy land you need to raise it off the ground.

Brands of Tents for the Chemically Sensitive

Brands that MCSers have done well with are Moonlight (no FR, which is rare. Coated with silicone on the outside and polyurethane (PU) on the inside), Lightspeed (polyesters with PU coating) and REI Basecamp (polyester, rainfly and floor coated with PU), the most sensitive should try one of those three brands with some of the most sensitive people I know using REI.

LL Bean (polyester with PU from what I have seen) and Big Agnes (nylon, polyester with PU and some silicone) have been tolerable for some. The jury is out on Coleman, some people tolerate it and others don’t. Some people find cheap Walmart tents  espeically Ozark brand are more tolerable than ones for hundreds of dollars. I have found Ozark tents to be very tolerable. The Sierra Tensegrity is FR free and uses silicone and nylon with no polyurethane which may be better for some.

Gear Aid silnet silicone seam sealer and some footprints are coated with silicone.

For those doing extreme mold avoidance or living somewhere very damp you might want to go with the more disposable option. Expensive tents from REI and MEC tend to pack smaller and lighter and should be higher quality, however if they do go mouldy it is a bigger loss. If I am traveling with a tent I want one that's not going to break unexpectedly as many places around the world do not have stores that sell tents. Check also how much wind and rain they say they can withstand.

Unconventional Tents

These 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 269 USD. They do not have any mesh for ventilation which I imagine would be quite the problem for condensation and fresh air. For 18 USD you can get this aluminum lined small sleeping tent. The aluminum on the inside is more tolerable than the usual plastic. Others have made homemade tents with materials they can tolerate like Tyvek, Reflectix or XPS sheets. More info on that here.

Some folks who cannot handle the synthetic tents have tried canvas tents. These do not hold up well to rain and high humidity and I would not use them in those conditions nor expect them to last very long at all. Some companies people like are Reliable Tent and Kodiak Tents. In my experience canvas tents go mouldy quickly.

My Mondo King
I bought the Lightspeed air mattress which is the one all the MCSers use. It offgassed quickly (2 days in sun) and felt comfortable. It's good quality but I had back problems with it. I ended up buying the thickest Thermarest instead and LOVING it. This is as comfortable as a bed to me, though many people put Thermarests over a camping cot, that seemed excessive with the Mondo (though cots can also help you get off the ground). I’m not that picky about beds so I was surprised that the airbed hurt. The Thermarest has a decent R value to keep you warm, the more insulation you have under you in the cold the better.

The Mondo is very comfortable and I usually wake up forgetting I’m in a tent. It has polyurethane in it but offgassed quickly in my opinion. I used it after 2 days of airing out (not ideal), in one week I found it to be really good, and one month to be near odourless to me. This is a super good mat for a trailer or other tiny home as well.

Safest bet
I bought the repair kit for it as well because this is going to be my main bed in the trailer. When it was hot and sunny I had no problems with condensation if I turned it every couple days and some days left it standing up to air out. As it got cold and I moved it into a trailer it became very challenging to keep this dry and mould free. It needs to have slats underneath and a waterproof cover without a doubt in a cold damp environment (or cover in mylar). You will want to flip or air out your sleeping bag in the day too to prevent mould, if you are extremely sensitive you need to encase it. If you are very sensitive to mould or very unmasking encase the sleeping mat right away. You can use plastic but I prefer thick aluminised tarps as they also block the smell.

For the ultra sensitive to chemicals, an aluminized Thermarest is the safest camping mat. People usually go with the solid foam or the small inflatable ones as they pack much smaller than the delux one I bought and are more affordable. Here is a good overview of the closed cell foam pads. I stil prefer the Mondo King or the next best option is the Lightspeed version. Other very sensitive folks have tolerated the small air mats. I was very impressed with how little this one smelled (less than the air mattress) but I did not find it anywhere near as comfortable as my Mondo Thermarest. The solid foam over a camping cot is a set up to consider.

None of the Thermarests have flame retardants.


I'm extremely pleased with this sleeping bag which is warm and offgassed after sitting in the sun for a week or so. I never even washed it. I used this in the summer and some days it was too warm. I use these polyester sheets. But there are specific sheets for Thermarests and other brands of sleeping mats. They are also polyester. You don’t want any cotton in your tent it doesn’t do well outside for long. I bought a polyester camping pillow which is small (and it has cotton on the outside!) I use waterproof pillow cases to prevent mould which I aired out and washed before using. They do smell at first but polyurethane coating does offgas to many people's standards.

Others like a silk sleeping bag liner which keeps you warm and keeps your sleeping bag cleaner. Is much easier to wash a liner than the sleeping bag. I'm using this one and it's quick to dry (surprised by how chemically it smelled, needed more washes than most fabrics). You can also make a liner by sewing a queen flat sheet in half. You can either use a liner to get inside of first or to encase a blanket. This will keep the sleeping bag good for longer.

I keep backups of everything.

Staying Warm and Cool

I use a heating blanket and was toasty warm in the tent. I thought the biggest problem for me would be stabalising my temperature but that ended up not being a problem at all. This is the heating blanket I use. After going through a lot of these, the trick is I want one big enough to cover me and I want the 10 hour shut off not the 3 hour shut off to keep me warm all night. They are challenging in how strong they smell when new and since they can't go in a dryer they can be difficult to clean in cold weather camping. For those concerned about EMFs you can use this to heat the tent without putting in on your body. It won’t be as warm but it is likely safer than a stand alone heater in a tent. Or, the fancier and possibly healthier option is an infared mat.

This 60 watt heated blanket (the smaller type) will run for most of the night off this solar kit. I have an extension cord running to my tent. Hot water bottles can be put inside the sleeping bag at night. This one has been reported to be very tolerable.

You can also set up a small heater - you want to check the wattage and if it has temperature control, or a portable AC (make sure your tent is big enough. If it’s your first time around the block, read the dimensions carefully, they run small). It's safer to place the heater up on a small table or round of wood to keep it from knocking over or blowing directly onto something that could melt or burn, make sure the tent is big enough to accommodate a heater with lots of space around it and it has an auto shut off when it falls over. For the AC you will need to cut a hole for the exhaust and seal around it.

Some people do use wood stoves in a tent. I'm getting this one for the cargo trailer but I do not have experience setting up a wood stove in a tent.

Use heaters, heating blankets or woodstoves at your own risk of fire or electrocution if they get wet. They are not recommended for tents.

Camping Supplies

Other items I use for backyard camping
- I cooked everything in an Instant Pot when camping which I could do on my one extension cord
- Travel Berkey is still on my wish list
- Non-cotton fast drying travel towel, I use this one.
- Eye mask and ear plugs, and for really loud situations the triple down method of (foam + silicone + ear protectors (or noise cancelling headphones). The foam contoured eye masks smell and need some time to offgas, the fabric ones can be offgassed by washing. I always keep a backup mask. The construction ear protectors do smell quite strong. One benefit of noise cancelling headphones is some noises cannot be blocked without adding white noise over them.
- I still love this outdoor dryer
-Washable wool or silk long underwear, wool socks and wool hat, gloves to stay warm in cold weather

Flame Retardants

To avoid flame retardants you may consider the Moonlight tent or Sierra Tensegrity. Some of the canvas tents do not have flame retardants.

For sleeping mats, none of the Thermarest mats have FRs. Wildkin sleeping mats and sleeping bags are also FR free.

Two other sleeping bags that are FR free are Holy Lamb Organics (but they use cotton), and Kelty.

More Resources

Lisa Petrison's excellent series:
Part 1: Transportation and Organization
Part 2: Shelters and Furniture
Part 3: Bedding and Clothing
Part 4: Storing and Preparing Food
Part 5: Cooking
Part 6: Comfort and Hygiene 

Lisa Petrison's camping supply list
My guide to and list for a mould sabbatical
Planet Thrive MCS Survivalist Guide for Tent Camping
From EI Wellspring Safer Camping and Safer Camping Equipment

Thank you to Emily Snelling for content support and the members of Mold Avoiders on the Road for all the advice along the way.


Some of the links to products and supplies on this page go through my affiliate partners. Whether a product has an affiliate program or not does not influence my recommendations. I do buy all my gear through Amazon. If you are going to purchase any of the items listed here and if you found my site’s content useful, please consider purchasing through my links - it will not cost you any more. Thank you.


Cargo Trailer Conversion

Converting a Cargo Trailer into a Travel Trailer

Part 1: Getting it up and Running
My current project
I'm converting a small cargo trailer into a tiny trailer that can be used for sleeping and living.

The cargo trailer is a TNT brand DBL 'A' 6x12, White, 12" extra height making it about 7 ft high on the inside. The extra height is well worth it I think for a sense of space. Side and roof vent (side vents are so small that they bring in very little air. The roof vent can only be wide open if it's not raining). RV door lock that locks from the inside (vital) and barn doors that lock from the outside (easier to handle than the ramp door). You may want to move the lock to the inside when living in it. Front and roof are curved in this one.

Costs in Canadian Dollars:

$6100 cost of trailer
$3600 cost of renos at trailer shop - metal floors, install window, take out plywood (much cheaper, and probably faster if you have the factory do these.)
$1500 cost of insulation
Labour for insulation and vapour barrier, foil and glue - lost track
$1300 Electrical (+ $185 for CSA inspection and approval - allowing me to legally park the trailer in Canada)

I have seen better prices in the US, you can go smaller and get a better price, but for me 6x12 is the minimum amount of space needed to make a happy little home.

Joey was able to do this for $7000 with the factory doing most of the work. In the Facebook group Mold Avoiders on the Road you can see people having smaller trailers renovated for under $4000.

Necessary Renovations:
Dreaded plywood
between frame and
Remove plywood.

Install window - 24 x 30 vinyl awning style to stay open even during the rain (you're going to need air in such a small space). It’s vertical so that the framing did not need to be cut. I do not find the hard vinyl has a smell but you can use aluminum. I wish I had put in two as it's nice to have windows. One does bring in plenty of light though, along with the vent on the roof. You can look for an RV window or you can use a tempered glass house window and reinforce the framing around it.

Install metal flooring 3/16 hot roll plate steel flooring, 1000 for the metal + welding. See this thread for an in-depth discussion on what type of metal to use.

Electrical work - 30 amp panel with a campground plug and 4 outlets inside. You may be able to make do with fewer outlets but the electrician wanted a dedicated outlet for the fridge and one for the heater. Then I have one near the bed for computer etc, and there is one up high to string up a light and run any kitchen appliances.

My electrical
Have these renos done by the factory and not after you buy it. This was a huge mistake that costs me a lot of money and didn’t save me any time like I thought it would. I should have known better as I had read Joey's conversion story (highly recommend reading that for another version of a conversion and some ideas on what you might want to add. I disagree that foam doesn't provide a lot of protection from the cold and heat. 2 inches of XPS is R-10, that is really good). How long it will take to customise one depends on the brand, the factory and the time of year. Add 2-3 weeks on to their estimate.

The back door in mine has structural plywood so that still has to be removed and needed metal reinforcements. The front end had plywood between the frame and the skin which was a major pain to remove. Look for a brand that does not have these two issues and you will save a lot of money.

If you want to do it yourself check out this thread (you have to sign up). Watching someone's account of doing it herself is well worth it. You will see tips on taking out the plywood and choosing a metal for the floor.

Do the Walls Need Reinforcement?

A big question with cargo trailers is if you need wall reinforcement when you remove the plywood. There are two answers to this. The first is that it depends on the brand, some brands will tell you that their trailer is good to go with no plywood, these have thicker frames like the steel CM trailers. Or some companies can customise it with thicker frames. See pictures below.

The second answer is that the companies might say they are not strong enough but people leave it un-reinforced anyway. Erik Johnson, me and two other mould avoiders have taken out the plywood and not added anything that would replace it structurally. Mine started leaking and the company that sold it to me claims that the reason it leaked is because the plywood was taken out and this means there is less stability and it's easy for pieces to come apart and caulking to come loose.

If they won't customise it without plywood, remove that part yourself and reinforce it (or don't) yourself.

The first picture is a customised trailer reinforced with aluminum frames. Very robust. If you look closely you can see tape between the frame and the exterior, a mould risk.

The second picture is a CM all steel trailer with a robust steel frame, the frame is standard and the company does not recommend reinforcement.

The third picture is a standard frame, with plywood removed. Though it's not reinforced the owner is doing just fine with moving it around frequently. The brand is Victory.

This picture is my trailer it has the least robust frame of the bunch, while the seller advised that it could be reinforced for longer trips (he told me this after the insulation was up).

Toxicity of a New Cargo Trailer:

A cargo trailer smells much stronger than someone might anticipate a new metal box to smell. An extreme avoider in a hot climate would leave it sit for about a year before using. I have seen two people who have turned around and sold them soon after buying due to the strong smell. Mine is now a year old and not totally offgassed.

The smell comes mostly from the body of the trailer. It is a glue smell and may also be oils on the metal. There are many other parts that are non-metal (differ slightly between brands) that may include:

Caulk of different types, double-sided tape (you do not want to buy a cargo trailer with tape in the frame - this is a mould risk), plastic on the back of the RV door, plastic and glue (very smelly) in the vents to the point that you will likely not be able to use these vents for air, rubber and foam (glued on) can be found around the RV door, around the barn doors, and possibly around the window on some models, there may be tape holding up wiring, there is the usual plastic coating on the wiring, plastic light and light switch may be included, there may be spray paint on wiring, there may be caps on bolts, screen on top vent, there is also exterior paint which some people have said they are offgassing but I could not pick up a smell on. In such a small space there are also the tires on the outside to consider - on a hot day you will smell these. Rustproofing chemicals may also be added to the frame. (Thanks to Madonna Ramp for some of these materials from other brands).

A lot of this can be covered and you can see in mine that it is almost completely sealed up. If you buy one and it smells strong, give it time and/or seal it up like I did mine.

Every trailer takes time to offgas. Someone was able to get the company Mirage to build without glue or caulk, but she was not able to tolerate the trailer brand new. I would not recommend leaving out glue and caulk.

Buying a Used Cargo Trailer: 

I did not see any used cargo trailers in my area when I was looking but you can sometimes find these. You would want to know what it was used for. Look for gunk and rust that will accumulate at the bottom around the frame.

Building out the Interior - How Mine was Done (The Second Time)
XPS with Great Stuff
  • XPS Owens Corning Foam 2 inches on walls and floor (you can also use polyiso, the most well tolerated foam, or EPS which is not a vapour barrier on its own but is usually faced with foil or plastic). 2 inches XPS is R-10. If you are going to a climate that is extremely cold, add another layer of foam - polyiso or XPS on the inside until you get a high enough R-value for your climate. The reason I chose XPS is that is has a high R-value and it doesn't lose its R-value in very cold weather like polyiso does. I also could not find polyiso in my town. 
  • 1 inch Foil backed EPS on ceiling (because I needed something thin enough and flexible enough to be curved on the ceiling) (Note: This is backwards, there should be more insulation on the roof but I wanted the roof to stay curved and the insulation to stay between the frame so I kept it simple.). The brand was R-Tech but I can't find a link for this. I can add another layer of 1-inch foam if it gets too cold.
  • Great Stuff spray foam on the gaps of the rigid foam (airtight so no moisture gets behind the foam). There is one for small gaps and one for larger gaps you will need some of each.
  • Heavy Duty aluminum foil glued up to seal in everything. I don't recommend this method after trying it. Blocking moisture between the foil and the foam is a mold risk. There are other ways you could totally seal in the smell with metal walls and silicone as a gasket. The problem here is not being able to check for leaks.
  • A Fantastic Fan in the roof vent would be helpful for ventilation, drawing air out of the top will draw it in the window and turn over a lot of air. The fans also help with humidity. This has to be wired in with the electrical.
How we Installed it:
First layer of foil on seams
The foam is not being held in place by anything other than the power of it being held between the floor and ceiling. You can use some tape or glue if necessary. The canned spray foam is filling in the gaps (leave that to cure for at least 24 hours). Over the seams we put heavy duty aluminum foil.

We used natural glue to attach the foil - I don't recommend this.

There is a rumour that spray foam will crumble with movement in a trailer but speaking with the company Great Stuff and some folks who have taken apart trailers they have not seen this be a problem.

In an ideal world you have 2 competent people working on this full time you could get it done in 4 or 5 days. Add extra time for real world problems.

Here is a video of where the trailer is now (in progress) - hard to show in photos:


All this metal and foil did not stop wifi or cell phone reception - it lowered my wifi connection only slightly. If you are concerned about EMFs consult with an EMF specialist and test out a metal structure before buying. In theory, it is a Faraday Cage that blocks out some external sources of EMFs and may intensify what is on the inside.

My First Attempt and What Went Wrong:

My first attempt totally failed. I tried to buy a cargo off the lot and sleep in it within three days. We put up XPS over the plywood (sealing it in in a dangerous double barrier system), we used tuck tape to tape up the foam. This absolutely reeked. Then we covered the entire interior with mylar blankets and taped that up with aluminum foil tape - that absolutely reeked as well. So from there we took everything down and did the renovations properly (which means taking out plywood and putting in metal floors and a window). I found out taping up seams was not going to work. Even the most tolerable foil tape in a small enclosed space becomes overwhelming (I am very sensitive but not by any means among the most sensitive). The second attempt with foil wallpaper failed as well. The trailer started leaking at various points and I could not see this because of how well it was sealed up. Mold and rust started growing under the floor. We tore it all up a second time. The third iteration is in progress now (summer 2018).

Erik Johnson's Cargo Trailer (MECU):

Erik's story
Erik is the pioneer of cargo trailer living. He called his trailer and camper MECUs (Mobile Environmental Containment Unit). Erik used EPS foam without flame retardants. I don't know how he sourced this but I would think this is the kind used for packing, not insulation. In Erik's trailer, he left a gap (like I did) between the foam and the exterior. He put in weep holes at the bottom in case condensation did find its way to the back. Some trailer like mine come with weep hole. He has said that there has not been any condensation at the back and he has had this for more than a decade. I put the insulation in front of the frame which created a space naturally behind it (though my floors and ceiling have no space). In my third attempt, I'm going to put the floor insulation under the trailer.

He has an interesting (non-toxic) method of putting up the foam: Erik says: "I riveted small strips of aluminum to the steel wall studs that are four inches long. For two sheets of two-inch styrofoam. Put the styro in place and riveted one-inch aluminum angle to the four-inch strip, using the "L" of the angle to secure the styrofoam. This vertical angle then gave me a place on the wall to attach shelves." This eliminates the need for spray foam, caulking or tape to seal up or hold up the foam, it also means it's not air tight. This has not been a problem for Erik. Though I was worried in my set up about it not being a perfect vapour barrier.  Erik used wooden floors and not metal.

Here is a video of his camper which is done like his cargo.

Other Trailer Options:

You can build out the interior as much or as little as you like.
  • You could add batteries but consider how long these will last you away from plug-in power.
  • You could add solar panels but this doesn't get you a lot of power, it may be easier to just buy a solar kit that is portable that is made for camping.
  • If showering in another building, campsite bathroom, or outdoor shower is not an option for you, you could install basic plumbing. You would want to avoid tanks and have very simple plumbing that goes directly out to a bucket or pipes out into a grey water system. You will have to make sure you are following the rules with grey water here. I want to avoid all cooking, showering, and clothes drying inside to keep humidity down.
  • Options for outdoor showers include simple bucket showers, passive solar shower (that one is PVC-free, unlike most of them), active portable hot water shower (this one comes recommended by mould avoiders), or an outdoor tub big enough to bathe in. A privacy tent can be used to shower outside or set up a toilet outside. You can also DIY and set up something simple like wrap house wrap around 3 trees, or tie string around 3 trees and the string holds up shower curtains.

Finishing the Interior:
    WALLS: I was going to tack up these posters and some regular wallpaper - Farrow and Ball is a well tolerated non-toxic wallpaper. It is way too humid in here to put wallpaper though. I think that is unlikely to work in almost every climates. I am not eager to cover my walls with metal panels or plywood because I want everything to be simple and easily accessible. Other options for the wall: the grey side of housewrap, paint foil or metal walls with AFM metal paint, these polyethylene wall tiles (if you can tolerate the glue), seal everything with shellac and then paint over, or, other plastics made for RV/vans tacked or taped up. I will be using plastic RV panels.

Marmoleum from

FLOORS: For now I’m using these mats on the floor temporarily. They smell like straw. I am currently offgassing Marmoleum (takes one month in sun to offgas) but I don't like that there's a jute backing under the Marmoleum against the metal, that's a mold risk) and had considered Cali Bamboo Cork (not sure yet how long it takes to offgas, definitely much longer than Marmoleum). Note: Flooring I ruled out: Thermacork decorative cork the only cork I know of that is heat-pressed with nothing added - not good for floors. It flakes easily and won’t last long. Cork underlayment - I bought this and tested another one that claimed 0 VOC. It is going to need a lot of time to offgas despite these "0 VOC" polyurethane glues (not at all). A year later I have not offgassed the cork floorings (thought they were not out in the sun for a year).


    BED: My original plan was to customise a locally made solid wood bed with storage underneath - the bed will be up about 2 feet and take up more than half the length of the trailer, creating a large storage space underneath. I would like it to be made partially of Purebond plywood but even that needs to offgas, so I am planning a solid wood bed instead. Cedar is the best bet for holding up to high humidity environments and not going mouldy, but pine should work as well. I will seal it with shellac to seal in as much of the wood smell as possible. (I will do a post just on shellac.) A metal bed frame would be a safer option. In the third try here I think I will go with a metal bed. 

Heating, Cooling, Lighting, Laundry:

  • I’m have this light bulb up (the cord smelled strong and offgassed in my car for a while but then was fine for me). I also like this little nightlight but it won't provide much light.
  • In the summer I will use a portable AC, I like this one for the level of offgassing. I throw them away every fall as they tend to go mouldy after one season or two and I have nowhere to store them. 
  • I’m using this to dry my clothes and I love it. I don't want to add humidity in the trailer so I am using it outside under cover. It works well even in humid and cold outdoor temperatures (and it's not as mini as it looks). I have used this successfully down to freezing. I have not tried it much before freezing but I'm still really happy with it. 


  • I bought this fridge which needed a lot of offgassing outside including running it outside. This one smelled more than other brands I have tried like Danby. I like Walmart for fridges as well. 
  • I'm using this kitchen island which offgassed fairly quickly but you could use a metal version if you want to avoid wood (and wood sealers and glue). 
  • I offgasesd this cutting board pretty fast. I'm just posting that because I love it so much
  • Thrift shop bowls 
  • I’m using a pressure cooker to cook - you can make almost anything in this. If you use it outside or at least release the steam outside you will have very little or no added moisture to the trailer. You can get away with no other stove, oven or microwave. You just need an extension cord to use it outside.
  • I’m going to buy the travel Berkey for drinking water, there is no plumbing in the trailer. Berkey is ideal for well water and water from campsites if you are not buying water. 

In a high humidity situation like a trailer, tent or other camping structure it's important to have a bed and bedding that will not go mouldy. My bed will be up on slats soon (right now I am turning the Thermarest over every few days - it went mouldy so it is crucial to get it off the ground onto slats). Cotton does not hold up well in high humidity, so I have used more mould resistant materials.


I am available for consulting to help customise a little "safe room" cargo trailer or custom made trailer. I can help with everything from choosing materials to managing the whole build. I also help you to decide between different housing options, from building a conventional house, tiny house, trailer to setting up tent camping. Here is my consulting page.

Part 2 will show the finished product with all the interior design and furniture


Making purchases through affiliate links helps support me and this blog. Amazon and Walmart are affiliates.