In trying to figure out how to make my improvised shelters more efficient, I came up with an idea that, while not the most convenient or environmentally friendly, certainly seems to hold promise.

I've been using spray foam insulation on things like truck canopies, plastic buckets, molding blanks, and it occurred to me that a 12 oz can of spray foam might be just the ticket for "hardening" my more immobile sheltering needs.

It used to be that I would pack a couple of large plastic garbage bags, some wire ties, and some duct tape with me in order to build a "quansit hut" type e-shelter using branches as the frame to drape and secure the opened bags over. Unfortunately, the bags didn't last long, especially in high winds, and sometimes my shelters ended up being more duct tape than garbage bag. Switching to mylar sheets made a little improvement in the durability and rigidity of the shelter, but the sacrifice was I couldn't make holes in the mylar without it self destructing.

However, if I use the mylar as a molding surface and spray the outside with urethane foam, the resulting structure should be quite rigid, fairly wind and waterproof, and provide insulation against the cold. One 12 oz can should cover the entire shelter (roughly the surface of two 33 gallon opened garbage bags). The foam expands to 120 times it's volume and is tack free in less than two minutes, yet still flexible for maybe 15 minutes or so, depending on conditions. Even if you can't apply it uniformly, it should do a lot for the strucure integrity nonetheless. Another drawback is it would be difficult to apply under less than optimum conditions.

Tell you what, I'll give this a go, take some pics, and let you see how it turns out.