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r-values Post New Topic | Post Reply
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Leonard Stansbury
Posted: Apr 05, 2009 04:52 PM
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r-values
A lot of the insulators around here are spraying oc (1/2 pound) foam in a 2x4 wall.By my 2nd grade math the most u would get is a little over 12 .5 in r-value,but they call this good because of the ability to stop air movement. My question is this right or not? Iv been spraying roofs and i am just getting in to the insulating part so i want to be sure.
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mason
Posted: Apr 05, 2009 09:31 PM
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Open cell foam will range between 3.5 to 3.7 R per inch. So yes you can get R 13 in a 2x4 stud cavity with open cell foam. However, if you are in an area that requires R 20, you would have to go to a closed cell foam. (You may get a code official to accept performance equivalency if you have data that demonstrates that 3.5 inches of sprayfoam gives the same energy performance of R 20 fiberglass batt insulation. |
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andy buff
Posted: Apr 07, 2009 07:27 PM
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mason how do you get the performance factor and the data to back it. |
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mason
Posted: Apr 07, 2009 09:18 PM
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SPFA conducted tests at Oakridge National labs on sprayfoam in attics compared to fiberglass and at Architectural Testing Inc. comparing fiberglass insulated walls to sprayfoam insulated walls. The sprayfoam performed 15 to 30% better than the fiberglass. Contact SPFA for test reports. |
