What is R Value?
The Federal Trade Commission (FTC) considers R-value to be an integral part of spray foam measurement, and the FTC defines how R-value is reported and tested. The thermal performance of insulation is measured by R-value.
R-value is a test performed under laboratory conditions and measures resistance to heat flow. The testing methods were developed by the American Society of Testing and Materials, and must be performed at a mean temperature of 75 degrees Fahrenheit with a temperature differential of 50 degrees, plus or minus 10 degrees. These tests must also be performed on aged material for spray foam products. More information on these testing standards may be found here on the e-CFR website.
What are typical R-values? Here are a few:
| Minimum | |
| Brick | R-0.2 |
| Softwood (most) | R-1.41 |
| Fiberglass loose fill | R-2.5 |
| Polyethylene foam | R-3 |
| Icynene spray | R-3.6 |
| Open cell polyurethane spray foam | R-3.6 |
| Closed cell polyurethane spray foam | R-5.5 |
Nearly all closed cell spray foam has higher r-values because it traps insulating gases in the foam. These insulating gases conduct less heat than air, which is an integral part of most insulation.
