Home>Discussions>INSULATION & HVAC>Open Celled vs. Closed Cell Foam In Attic For Living Space
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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 don’t 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?

Re: Open Celled vs. Closed Cell Foam In Attic For Living Space

When I saw that the New Orleans project was using open cell I was so shocked. I thought that allowing the moisture to drip through would cause so much damage that there's no way I would let the moisture to filter through when I could find something else that is weather tight. I mean, come on, if I'm going to put anything close to the one part of my house that deals with the most water, that insulation needs to be water proof because roofs fail a lot easier than we really want them too.

I've chosen closed cell when we finally get into that part.

Re: Open Celled vs. Closed Cell Foam In Attic For Living Space

Jolly, not sure if you will receive this (my first time on TOH discussions and I'm finding it a bit cumbersome) but I'm wondering what you decided between the open and closed cell foam.

Which did you go with and what has been your experience?

I live in Westfield, MA and I'm looking to do a similar project in my attic and have two contractors telling me two different things. Trying to find information on the web is a toss up as well. My biggest concern has always been how the foam will affect the slate roof--that and getting a decent R-value.

Anything I put up there will be an improvement over the cellulose in the attic floor and the last thing I want to do is put something in that damages the roof decking under the slate.

Any information you can pass along is appreciated.


Re: Open Celled vs. Closed Cell Foam In Attic For Living Space

I have 5-7" open cell under the roof deck and removed the nasty worthless cellulose.

I would now lean toward 3-4" closed cell instead. I'm found that when the sun heats hte roof, it causes the roof deck to act like a desiccant and drive moisture into the attic. It's not a lot of moisture, but enough that I'd recommend either adding a vapor barrier on the roof deck if you replace the roof, or go with closed cell.

Re: Open Celled vs. Closed Cell Foam In Attic For Living Space

the houses i renovate and build get spray foam installed regularly. you mentioned one of the installers states they can get r-19 out of 3.5 inches of open cell....... thats a first for me to hear that.. open cell foam has a maximum of r-5 per inch and has to be installed to a minimum thickness of 3" to be effective.. closed cell performs to a r-7 rating per inch unless in the last 2 months the engineers making the foam have been able to increase its density to get a higher r value,

as for better educating yourself, go onto www.finehomebuilding.com to see more info on using foam in attic spaces, they have a a few really informative articles regarding proper procedures and what product is best suited for the space

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