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Weighing the Merits of Spray-Foam Insulation
comments (1) January 23rd, 2012 in Blogs
Scott Gibson, contributing writer
Mulling the benefits of foam A homeowner has bids from several contractors for insulating his home with spray foam insulation, but conflicting advice has left him puzzled.
Scott Jacobs is facing a question many homeowners wrestle with: How to get the most bang for the buck as he weighs his insulation options.
More from greenbuildingadvisor.com
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The 1,100-sq. ft. Cape has been gutted, and Jacobs has contacted three insulation contractors for bids on installing spray-foam insulation. Two recommend open-cell foam, the other suggests closed-cell foam. Closed-cell foam costs more, but it packs nearly twice the insulation value into the same space as low density open-cell foam.
In a post in the Q&A forum at GreenBuildingAdvisor, Jacobs looks for advice.
A key concern is whether using open-cell foam in fairly shallow rafter bays will allow Jacobs to meet energy code recommendations for his climate zone.
But is that essential? Not really, some posts argue. In fact, some claim, using more than a few inches of foam is a waste of money, and the codes themselves are written by office-bound experts rather than contractors.
That conversation is the topic of this month's Q&A Spotlight.
posted in: Blogs, energy efficiency, insulation, spray-foam
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Comments (1)
Look at ASHRAE 90.1, find your climate zone and follow the R-value recommendations in the table (for attic in this case, because if you are using spray foam, you are insulating between the rafters and not Continuous Insulation, or c.i.). This gives you the recommended R-value you need for the insulation ONLY, from this you can deduce the thickness of insulation necessary. A few inches, lets say 3" of closed-cell is only about R-18 or so, which may be okay, 3" of open-cell is only like R-10 which is almost nothing. check the code!
Posted: 8:40 pm on March 7th
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