I have a cathedral ceiling comprised of 2×12’s with R38 fiberglass batt, foam baffles, and interior 3/4″ 1×6 T&G. This system melts too much snow, and I have been considering ways to fix that. So, as an experiment, I added 2″ rigid polyiso insulation board to the interior of our master bathroom. It seems to have helped reduce heat loss and resulting icycles, but it smells. While it might dissipate over time, I don’t want to put more effort into it only to be left with a rotten smelling bathroom. Apparently XPS would have been a better choice, but I was looking for the highest R value per inch.
So, should I take it out, now that I have foamed in the gaps, or try to cover with an ice and water barrier, or some other membrane prior to installing a new finished 1×6 ceiling?
I appreciate your thoughts.
Brian
Replies
Yeah, some foam smells, and I suspect polyiso tends to be worse. In part it's the basic chemical composition, and in part it's the quality. If foam board is cheaply made the chemicals in it will not be well balanced and there's apt to be an excess of smelly stuff that doesn't chemically bond with other stuff. In general the odor will abate over time, but it's sometimes hard to predict whether that's 3 days or 3 decades. Odor will tend to be stronger in hot weather, of course.
Foil facing will help to contain any odor, though it will cause small amounts of odor to linger longer (since evaporation of the odorific compounds is slowed). Presumably any other impervious barrier on the "conditioned" side would also help keep the odor out of the house. I would think I&W is apt to have its own odors, so plain old plastic sheeting is probably a better idea.
Rock and finish over it with something thin to seal out the offending smells, then put the wood over that.