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 any offgassing.
Wood - Wood windows are usually treated with fungicides. You could use a sealer that seals in VOCs like AFM Safecoat Safe Seal, AFM Safecoat Transitional Primer, or B-I-N Shellac Base Primer & Sealer. You could go with custom wood windows to avoid fungicides, but they are more expensive and you still have to consider what kind of sealer you can tolerate on the inside and outside. Finding a suitable sealer for outdoor wood is tricky. AFM Safecoat Duro Stain or AFM Naturals Clear Penetrating Oil are two options. The outside would need to be re-stained on a regular basis.
Consider also the glue that is used in conventional wood windows could be irritating for the sensitive person. If you are having custom windows made see my post on safer wood glues.
Fibreglass - Fibreglass offgasses VOCs and most sensitive people do report reacting to it.
Vinyl - Vinyl offgasses VOCs and is not a healthy choice.
Gas filled - Windows filled with argon or krypton gas have a higher insulative value and both gases are considered non-toxic.
Silicone - My top choice for silicone is Eco-Bond but I review a few different options in this post.
Sealing around windows and doors - Wool products can be used instead of polyurethane foam. Some options are available at Loghome Wool.
I used NovaFlash which is a zero-VOC product.
|Source: Blinds Chalet|
Fabrics - Fabric curtain are usually treated with wrinkle-free chemicals and flame retardants. Natural fabrics do break down in UV light but are a better option.
Blinds and Shutters - Green versions include naturally finished wood shutters, metallic venetian blinds, and bamboo roll down blinds.
Between the Glass - Between the glass is a really cool option. Here is an example.
Non-Toxic Blackout Shades - This is a hard to come by product. Blinds Chalet blackout liner is PVC- free and they claim that it is environmentally friendly. Blinds Galore has a natural blind with a cotton/polyester blackout liner. (They have a .com as well as .ca)
Avoid vinyl roller shades and vinyl miniblinds, and conventional blackout curtains.