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Author	Comments
Judy Hackney Posted: Jul 26, 2008 07:09 PM	How Much Is Enough How thick should the closed cell insulation be applied to the roof deck in new home construction in West Texas? I have a contractor telling me that 1" of 2.0 lb closed cell polyurethane will be equivalent or better than fiberglass insulation to R-38. Is this right?
mason Posted: Jul 26, 2008 09:29 PM	Nope, You should have around 4 inches to take care of the cold and hot weather expected in your area.
Dan Hansen Posted: Jul 31, 2008 11:13 PM	I need an answer to the same question different location. I am in northern Illinois. My spray contractor wants to put in 2” in my walls and in a sloped section of my ceiling 5.5”. In the rest of the attic floor he would blow in an R 38 of cellulose. At an R 6.4 for the closed cell NCFI foam that would only be R 12.8 in my walls. I had other quotes that were similar. They all claim that the R value is meaningless when you are talking foam. I feel they quote less to try to keep the price down to be competitive. What should I have for my climate?
mason Posted: Aug 01, 2008 02:37 PM	The R value of sprayfoam is not meaningless, but it doesn't tell the whole story. Insulation is measured for its conductive heat transfer only and does not take into consideration, radiation, convection, air infiltration, thermal bridging and moisture that will reduce the insulation efficiency of any insulation. SPF has a high energy performance relative to other insulations when these factors are considered. There is some test data available to demonstrate that SPF can provide 15% to more thane 50% greater energy efficiency than the most commonly used insulation depending on the climate, use of building, type of construction and other factors. For more information read some of my articles on R value and SPF on my website masonknowles.com Check out he blogs I have written on the Honeywell website as well.

Author

Comments

Judy Hackney

Posted: Jul 26, 2008 07:09 PM

How Much Is Enough

How thick should the closed cell insulation be applied to the roof deck in new home construction in West Texas? I have a contractor telling me that 1" of 2.0 lb closed cell polyurethane will be equivalent or better than fiberglass insulation to R-38. Is this right?

mason

Posted: Jul 26, 2008 09:29 PM

Nope, You should have around 4 inches to take care of the cold and hot weather expected in your area.

Dan Hansen

Posted: Jul 31, 2008 11:13 PM

I need an answer to the same question different location. I am in northern Illinois. My spray contractor wants to put in 2” in my walls and in a sloped section of my ceiling 5.5”. In the rest of the attic floor he would blow in an R 38 of cellulose. At an R 6.4 for the closed cell NCFI foam that would only be R 12.8 in my walls. I had other quotes that were similar. They all claim that the R value is meaningless when you are talking foam. I feel they quote less to try to keep the price down to be competitive. What should I have for my climate?

mason

Posted: Aug 01, 2008 02:37 PM

The R value of sprayfoam is not meaningless, but it doesn't tell the whole story. Insulation is measured for its conductive heat transfer only and does not take into consideration, radiation, convection, air infiltration, thermal bridging and moisture that will reduce the insulation efficiency of any insulation. SPF has a high energy performance relative to other insulations when these factors are considered. There is some test data available to demonstrate that SPF can provide 15% to more thane 50% greater energy efficiency than the most commonly used insulation depending on the climate, use of building, type of construction and other factors. For more information read some of my articles on R value and SPF on my website masonknowles.com Check out he blogs I have written on the Honeywell website as well.

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