The finer points of insulation

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Q. My house is always drafty, and a pipe froze and my whole kitchen was flooded. The plumber fixed the pipe but said the insulation wasn’t done right and the pipe could freeze again. I was wondering if spray foam would help, but the plumber said the pipes (in foam) were too close to the outside. He cut out some foam to move the pipes and put a foam rubber cover over them. Should I put foam back, and what about my crawl space? We were flooded, and the foam they sprayed cost a lot more. Did I do the right thing? What’s the best way to insulate?

A. Great question, big problem. I’ve discovered that the foam insulation, which is a great vapor barrier, keeping condensation from forming on the warm side of the insulation, isn’t a good water barrier. Condensation (vapor) evaporates in the presence of relatively dry air, but water from flooding or high tides gets locked in as it’s drawn into the wood fibers of your wood-framed floor and wall structure. Because of the capillary action that sucks it into the fibers, like a sponge, water is very difficult to remove, and doesn’t evaporate easily because the foam prevents air from getting to the moisture.

I find that foam insulation works great in walls and ceilings above the first floor, and is great for attic floors and roofs. In crawl spaces I recommend rigid, closed-cell foam panels with a vapor barrier, uninterrupted by gaps and firmly attached to the underside of the flooring above. This works best in areas where the potential for high tide is greater because the panels can be removed, washed and put back. Because they’re closed-cell panels, impurities from sewage and saltwater don’t penetrate. For less money you can put in 6- to 10-inch-thick fiberglass batting insulation, but it will collapse in water and will then need to be disposed of and replaced with new material.

As for your piping problem, spray foam around pipes isn’t best, but if done, the pipes must be kept as close to the warm side of the wall or floor cavity they run through. I don’t recommend foam around pipes because it makes getting to them in an emergency difficult while you carve and discard the foam. Aside from having to throw out the more expensive foam, a plumber is one of the most costly services you can pay for in your home, and prolonging the time it takes them to locate a problem adds up. If you still want to foam, just be sure you can see the pipes from the inside of the house, to be sure they’re as close to the warm side, before putting back the finished wallboard. Same thing for wiring, which I advise be put into conduit so it can be pulled if work is done. Good luck!

©2014 Monte Leeper. Readers are encouraged to send questions to yourhousedr@aol.com, with “Herald question” in the subject line, or to Herald Homes, 2 Endo Blvd., Garden City, NY 11530, Attn: Monte Leeper, architect.