Hello!

I am building out a shipping container house. After much research on the pros and cons of polyurethane spray foam insulation, I think it will be an efficient choice for my circumstances. However, I'm curious if anyone has experience with coating the polyurethane foam with some sort of other sealant--something else to seal in any potential toxins from the polyurethane. I've read that once the polyurethane sets it is no longer toxic/smelly, however I don't wholly believe that and I want to do my best to protect my asthmatic partner who will be living with me in the structure. I am thinking that maybe ceramic paint would be an option, and would incidentally increase the R rating too...? Any suggestions?

Thanks!!
H

Put it on the outside or use another type of foam. According to www.epa.gov:

The potential for off-gassing of volatile chemicals from spray polyurethane foam is not fully understood and is an area where more research is needed.

At the very least, have a continuous supply of fresh, filtered air - containers have very little natural air exchange (a little leakage around the door).

The foam goes on the outside of the cargo can. Use 3lb density polyruethane with a mop-on/spray-on UV-protective coating to keep it from breaking down in sunlight. This is a standard method of insulating & rain-sealing flat roofs, but works fine on walls too. The UV protective paints need to be re-applied every 5-10 years.

Steel is gas-tight- only less-than tight seams or weatherstripping would let any of the foam-gases indoors.

There is effectively zero thermal performance to be gained from ceramic paints (NONE!), protestations of some manufacturers notwithstanding. It's a new form of "magic mouse milk, cures what ails ya, WAY better than standard snake oil" kind of marketing.

http://www.greenbuildingadvisor.com/blogs/dept/musings/insulating-paint-merchants-dupe-gullible-homeowners

http://www.greenbuildingadvisor.com/blogs/dept/musings/insulating-paint-salesman-tripped-his-own-product

There are some finishes with measureable benefits, but they're not about ceramic nanospheres, but rather their raw emissivity & solar spectrum reflectance. CRRC rated "cool roof" finishes have a thermal benefit during the cooling season, but a heating energy cost during the heating season- best used only in cooling dominated US climate zones 1 & 2.

See: http://coolroofs.org/