Q. What happens to the R-value when you stuff R-19 insulation into a 2x4 stud cavity?
A. Mike Lacher, Technical Services Manager in the Insulation Group at Certainteed Corp., responds: What happens is that as you compress fiberglass batt insulation, the R-value per inch goes up, but the overall R-value goes down. For every x% that you compress the material, you lose approximately 1/2 x% of R-value. Refer to the chart below to see...
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