Here’s the materials we’ve used and/or researched, and what we thought of it in terms of chemical content, ease of use, weight, cost, etc. It does seem that the healthier choice is always heavier, so keep this in mind as you are designing your house! * Denotes a product we used in our house.
PVC (polyvinylchloride), can be used for supply or waste lines – pros: easy to install, flexible, lightweight, can tolerate temperature swings well, can theoretically be recycled; cons: super toxic stuff from the PVC itself to the adhesive used to join it – if inflexible, it is called vinyl in the US (such as vinyl house siding), but if plasticizers are added to make it flexible those plasticizers are highly susceptible to leaching (and the plasticizers are usually PHTHALATES! yippee!), and when PVC breaks down, it creates persistent organic pollutants (or POPs) which accumulate in the environment, as they are so toxic that they are not composted or metabolized in any way by any class of organisms. In fact, they have had better luck finding organisms that metabolize fossil fuel, take up heavy metals, or metabolize concrete. And if you burn PVC, it creates DIOXINS (PCBs are similar), extremely dangerous compounds that can cause all kinds of cancers and disease, and they are lipophilic so they like to accumulate in fat (read= mammals). We humans are doing ok because we eat a variety of foods, but seals and waterfowl are found to have very high levels because of the fish they eat, but thankfully not enough to cause their extinction (yet). Amazingly, PVC is the most common compound used for municipal water supply lines!
ABS (acrylonitrile butadiene styrene), usually used for waste/vent lines, and is the same plastic used in Legos and some golf-club heads, and even used in tattoo inks when ground down fine?! (if your tattoo is very vividly colored, then it likely has ABS plastic in it, according to Wikipedia) – pros: easy to install, flexible, impact resistant, can tolerate temperature swings well, lightweight, much less toxic than PVC, and can be recycled; cons: not UV resistant, has high embodied energy
Copper – pros: natural, relatively non-toxic, fireproof and not UV-sensitive; cons: expensive, requires skill to install, heavy, inflexible, must use lead-free silver solder to join together, if water is acidic can cause excessive corrosion
PEX – coming soon!
OSB, pressboard, particleboard or strand board – As far as I can tell, there is almost no redeeming value in these products except marginal cost savings. Tremendous VOC off-gassing, heavy, high embodied energy, turns to oatmeal when wet… don’t use it, even if you don’t have MCS. This also applies for indoor uses, as particleboard is commonly used as the housing for cabinetry.
*CDX/exterior grade plywood – pros: relatively inexpensive, relatively lightweight, easily obtained; cons: uses phenol-formaldehyde in the adhesive. This off-gasses slowly, but not to the degree that OSB or interior-grade plywood does. I haven’t been able to find a single manufacturer of a formaldehyde-free exterior grade plywood.
*Magnesium Oxide Board – similar to cement board only made with magnesium oxide, the kind of ‘natural cement’ that predated Portland cement. It’s what they used on the Great Wall of China, so you could say it wears well. Sadly, magnesium oxide does not occur in large deposits in the US; it does occur in China and to a lesser degree, Canada. However, the Chinese government has made it illegal to ship raw magnesium oxide, so it must be a value-added product. That is why you can’t buy anything but Chinese-made magnesium oxide board. Also, as is usually the case, some manufacturers feel obligated to “lace” their product with toxic compounds, so read the fine print. Here are some of the brands:
– MagBoard – pros: super performance characteristics (waterproof, rodent proof, fireproof, lightweight, high shear strength, highly insulating), extremely non-toxic and natural, this particular company owns their manufacturing plant in China and has done extensive performance testing on their product; cons: terrible customer service, only available on the east coast of the US
– *MagnumBoard – pros: super performance characteristics (waterproof, rodent proof, fireproof, lightweight, high shear strength, highly insulating), extremely non-toxic and natural; cons: limited availability on the west coast (nearest source is EcoAbode, LLC in Tacoma, WA. Contact Jim McCullough at (253)-606-6886), no performance testing results provided on the website.
-Strong’s EnviroBoard and Dragonboard – no personal experience, but some people have used to good effect.
Eco-Bond Multi-Purpose Adhesive – pros: relatively inexpensive, somewhat available (easily available online), zero-VOC, non petroleum-based; cons – unknown chemical composition
*Polar Industries, LLC Hi-Omega Epoxy – pros: made from linseed oil, zero VOC, dries quickly and has high strength performance, supports small business; cons: the company has poor customer service and the website is out-of-date and unhelpful, expensive, takes 2 weeks minimum from time of order for the product to arrive, requires mixing of epoxy with hardener.
*Fir or pine studs – pros: local to us, relatively inexpensive, non-toxic if not pressure treated; cons: heavy, some people are sensitive to the pitch odor/vapor
Metal studs – pros: strong, can use less material and therefore less weight, cons: much higher embodied energy in the manufacture, expensive, EMF sensitivity is suspected, I would avoid.
Airkrete – basically spray-foam insulation made out of magnesium oxide, air and water. Pros: super performance characteristics (waterproof, rodent proof, fireproof, lightweight, high shear strength, highly insulating), extremely non-toxic and natural; cons: only “licensed” franchisees can install so not terribly available, likely expensive. No installers provide any sort of pricing without having all of your contact information provided prior. Closest installer is in northern Washington from where we are.
Cellulose – pros: somewhat lightweight, natural; cons: settles with time, turns to mush when wet, rodents and insects like it, not fire retardant unless treated
*Wool – pros: natural, local (where we are), easy to install, expands with time and actually absorbs VOCs, doesn’t degrade when wet, insulates as well as fiberglass per inch, makes you feel like your house is wrapped in a cozy blanket; cons: expensive, not fire retardant unless treated with borax, somewhat heavy. We used Oregon Shepherd Natural Wool Insulation.
Spray foam insulation – pros: lightweight, waterproof, doesn’t settle, very good insulator; cons: there are companies that market nut oil-based spray foam insulations. However, from what I can tell, there is little research showing if the additional processing of the oils generates new toxic compounds, so I am hesitant to recommend this route although they can claim natural sources. Modern textiles are a perfect example of how natural raw materials can be processed to the point of becoming toxic.
Marine-grade coated plywood – pros: lightweight, easy to install, moderate expense; cons: super toxic
*Metal flashing, either aluminum or *galvanized steel – pros: steel is moderately inexpensive, non-toxic; cons: have to back the flashing with plywood or boards along seams in order to install it tight and snug, heavier, more work to install, aluminum is expensive
*Iron Eagle Trailers in Fairview, Ore did a beautiful job of making our trailer with undermount cross-members
If you call someone and ask if they can do undermount cross-members and they say “It can’t be done” or “What?” move on.
American Eagle was not open to making a custom trailer with undermount cross-members