Open Celled vs. Closed Cell Foam In Attic For Living Space
I have read the insulation threads, but I have not yet decided to go with open or closed cell foam. I own a victorian in Northampton, MA and I have an attic (with a slate roof) that I would like to turn into living space. My rafters have at the most 5.5 inches of space for insulation.
I have looked at three foam contractors - two that are closed cell advocates and one that prefers open celled (some people refer to all opened cell foam as Icynene). The closed cell quotes on the job are almost twice as much as the opened celled! The numbers that are used by the different contractors are confusing, but the closed cell operators say that they only need 3.5 inches of foam to get a true R-19 effect along with a good air seal (closed cell is 2 pounds per cubic foot).
In contrast, my opened cell contractor says that in 11 years of installing he has never had any problems with opened cell leaking water in roof applications and he can spray in 5 inches of the less dense opened cell foam (a cubic foot equals a half pound) for a fraction of the cost of the closed cell companies. Also, my opened cell guy says that his quote will be much lower (more Rs per buck) because the opened cell is easier to work and less dangerous for the workers and wont off gas in the attic like the closed cell material.
I wanted to get information on the two products from unbiased sources including my local Center for Ecological Technology, but they were barely more informed than I was and they did not have much data on the two different products. In addition, I tried getting the articles from the industry newsletter, Energy Design Update, about a failure of opened celled foam in a Vermont cabin, but I donít know where to get this newsletter. The opened cell contractor says this Vermont cabin story is not representative of a good open celled job. On the other hand, the closed cell contractors say that TOH unfairly painted a positive picture of opened cell application in one of their episodes.
I may go with closed cell because I think that the unbiased sources are stating that there can be real problems with open cell and moisture. I have a slate roof, which can have a great deal of moisture transfer. The quotes from the closed cell contractors are hard to swallow, but I want to do the job right. Does anyone have any other opinions or any unbiased sources similar to Consumer Reports that can help me further my research?