Foam insulation – retro fit an old house
Over the weekend, I visited the Old House/New House Home Show. The parking lot was packed, as was the inside (visitors AND vendors). I asked some questions about foam insulation from 3 vendors. All 3 of them had the same answer. NO, I can’t retro fit my house using closed cell insulation. When I asked why, I was told because it expands out, whereas open cell insulation expands up.
I can’t quite wrap my mind around that. I would think the foam would expand the easiest way, in my case it would be up as siding would interfere outside and plaster would interfere inside.
Is there any literature out there about foam insulation for OLD houses? I also asked about vapor barrier (do I need it?) but got alot of hemming & hawing. No one really had an answer for me on that either.
“Go brush your teeth, comb your hair, put on dry clothes, and get the guns. We’re going to Wal-Mart.” On the Edge by Ilona Andrews
Replies
Seems like getting the same answer from 3 different vendors is a sign that they may be in agreement. I've seen a couple of jobs (not mine) where the foam was oozing out of cracks in the walls (both interior and exterior) and running down the wall surface. It wasn't pretty and looked like a major PITA to clean up.
Regarding your vapor barrier question, you might check Building Science Corporation's website for recommendations regarding your specific climate zone and building details.
Check out the slow rise closed cell foam from Tiger foam and a number of others. It is designed to insulate walls of existing houses.
the answer lies in the way the foam cures, some expand rapidly on application, the surface continues to grow, like bark on a tree, while in others, the entire product continues to expand. This is also why there are depth limitations to each application, too thick and the centermost portions of the foam are "insulated" by the surrounding foam, never curing properly, or expanding later causing the outer to crack ..
After having to re-do all the sheetrock on a kitchen remodel after the spray foam that was supposed to expand up decided to expand out instead, I would listen to your foam guys. Retrofitting old houses is a perfect job for dense-packed cellulose. If and when you reside your house, you can add rigid foam panels on the outside.