When choosing non-toxic window frame materials, windows made of thermally broken aluminum are the top choice, and that is the preferred choice of those highly chemically sensitive. My second choice would be Accoya wood windows. Some vinyl and fiberglass brands can be considered, since they can be low in offgassing.
For sealing around the rough openings, polyurethane canned foam is the norm, which does cure quite well. The least toxic option is backer rod plus caulk.
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1. Metal Window Frames
Aluminum windows are the healthiest, safest option, especially for the chemically sensitive. It is what I used in my tiny house (pictured left). On the interior, I added wood framing trim.
Thermally broken aluminum windows are all aluminum on the outside with a foam like polyurethane inside.
What is used in the windows as a thermal break is blocked by the glass and metal so there is no need to worry about offgassing from that aspect.
Non-thermally broken aluminum windows are not a good idea to use as they conduct heat and cold and easily condensate.
Brands
I used DYG windows from Canada. Milgard is another popular brand that makes thermally broken all aluminum windows (US and Canada). Other high-end aluminum thermally broken window brands include Western, Arcadia, and Fleetwood.
Aluminum Clad
Aluminum clad means there is an exterior of aluminum which usually has wood as the interior side framing.
Marvin has a line called Modern which is fiberglass on the outside, and aluminum on the inside (either powder-coated or anodized) which some sensitive folks have liked.
Non-Aluminum Parts
The most extremely sensitive clients can pick up the seal, PVC stop, and some glues used. The gaskets are made out of rubber or PVC. Though this is still the window type that the most sensitive go with.
The final finishes I have seen on aluminum windows are baked-on enamel, resin paints, powder-coated, and anodized. Some baked-on enamel finishes and paints can offgas, the other two are considered safe.
2. Wooden Windows
Wooden windows are usually treated with fungicides, pesticides, and insecticides.
You could use a sealer that seals in those chemicals like AFM Safe Seal, AFM Transitional Primer, or Zinsser Shellac (the Bullseye Shellac is waxed and harder to paint over, the SealCoat is dewaxed and easier to paint over).
Standard wood is also prone to warping and water damage.
Safer Wood
Accoya wood used in some window brands uses a non-toxic process called acetylation to naturally provide rot resistance.
They use no chemical fungicides or mildewcides and they claim this process helps to reduce shrinking and swelling compared to most solid wood windows.
Loewen is one of the brands that uses Accoya wood and allows you to choose your paint brand.
Custom Wood
You could go with totally custom-made wood windows, but they are more expensive and you still have to consider what kind of sealer you can tolerate on the inside and outside.
For an exterior sealer see my post on paints and sealers.
Problems with Wooden Windows
All wood (through and through) windows are not a good idea as they do not hold up well to moisture in the long run, Accoya wood claims to have solved this problem.
You can also consider ones that are wood on the inside and a more weather-resistant material on the outside (aluminum clad) if you like the look of wood inside.
Consider also the glue that is used in conventional wood windows could be irritating for the sensitive person.
Chemical Wood Treatments
Marvin’s wood windows (which have aluminum on the exterior i.e. aluminum clad) are treated with TimberTreat pesticide, tebuconazole, and propiconazole fungicides, an unlisted insecticide, and mineral oil.
Pella and Anderson also make wood windows that are treated with the same or similar chemicals (they are also aluminum on the exterior, aluminum clad).
3. Fiberglass Window Frames
Fiberglass and vinyl are the next best choices – they do offgas, but some brands will cure quite quickly or be low enough emissions to not cause any issues.
Some types and brands are better than others (in terms of offgassing) and this could result in a preference of fiberglass over vinyl or vice versa.
Some chemically sensitive folks do perfectly well with these options.
Marvin’s Ultrex was not tolerated by one very sensitive person though some less sensitive have done well with it.
Marvin has two different kinds of fiberglass, one has an acrylic component and one has a polyurethane component. You may find them to be different – with the polyurethane one being better tolerated for some.
Pella fiberglass is tolerated by some sensitive folks.
Kolbe has their own fiberglass called Glastra which is mixed with another polymer (plastic).
Zenith fiberglass by Alpen is pictured above. I couldn’t pick up any offgassing myself.
4. Vinyl Window Frames
Vinyl is often not a healthy material, but since this is a hard, usually unplasticized, vinyl, it does not have much of an odor or offgassing at all.
I did not pick up any offgassing on the vinyl windows I tested (and used in a little camping trailer).
uPVC indicates vinyl without plasticizers, which is the most harmful part of the vinyl for chemically sensitive folks.
I can pick up the offgassing in some of them used in apartments under one year old. Others have reported reacting with new ones. Some let them offgas for a while before installing.
Personally, with a bit of time to offgas, I find these to be good. Often better than fiberglass (depending on the brand), but not as good as aluminum.
Fibrex is a PVC and wood composite made by Anderson which some sensitive folks have reported being too high in offgassing for them.
Tyrol is a fiberglass-reinforced uPVC with EPS foam in the interior by Alpen (pictured). I couldn’t pick up any offgassing.
Vinyl Components
Vinyl components can be used in any window frame type. Look into the gasket, window stops, jamb liners, and tracks which can all be PVC. I have seen some companies (like Alpen) replace the PVC stop with aluminum.
More details on Alpen (which makes fiberglass and vinyl windows) and other low-toxin “High Performance” windows in this post on Passive Houses.
Window FAQs
What are High-Quality Trusted Window Brands?
High-quality window companies recommended by architects include: Marvin, Kolbe, Anderson, Pella, and Wasco. Alpen for High-Performance windows.
Are Gas-filled Windows Non-Toxic?
Windows filled with argon or krypton gas have a higher insulative value and both gasses are considered non-toxic.
Are Low-E Coatings Non-Toxic?
The two main types of Low-E coatings are both non-toxic. The “soft coat” is a mechanically applied silver coating that is within a double pane window system. You will have no exposure to the silver. A “hard coat” is a layer of tin oxide that is applied while the glass is still hot. The tin is a more integral part of the glass in this case, and is therefore not a risk.
Sealing Around Windows
Caulking
The first two I would test out are AFM Caulk and silicone. Silicone caulks all have different odors/offgassing and rates of curing. My top pick is a neutral cure silicone – Chemlink. GE is also quite good.
I have a post on caulking that goes into more detail.
Sealing the Rough Opening
Plastic backer rod (polyethylene) can be used to seal around windows. This is a non-toxic and odorless alternative to polyurethane canned spray foam. It is sealed with caulking. It’s not a substandard method, with some of the best architects like Christine Williamson preferring this method.
Many people do tolerate the canned spray foams after some offgassing (give it 24 hours to cure or more). Great Stuff is a common one to find easily online and in stores.
Handi-Foam is another brand, that is certified with Greenguard Gold for more assurance (but I cannot tell the difference between the two).
Some people use wool around windows. I prefer not to have wool around windows. The sealing around windows is meant to be airtight to prevent moisture issues, so wool would not suffice.
Window Flashing
For zero-VOC window flashing use TYPAR AT.
They do not recommend this being used in the rough openings, and it doesn’t fit all building codes.
Non-Toxic Window Film
I tested out the Sunshield Energy Control window film which does not offgas any VOCs. The reps said there are no adhesives with this film, the bond is created when applied to the glass using a soapy water solution and covalently activated once exposed to solar heat.
The films selectively inhibit the infiltration of ultraviolet, infra-red, and visible light to protect artwork, fabrics, furnishings, to provide protection from UVA and UVB, as well as energy conservation and temperature control.
Corinne Segura is a Building Biologist Practitioner with 8 years of experience helping others create healthy homes.
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