R-Value and RSI Table for Roofing Materials
And Building Insulation
To learn more about R-value, see Roof Online’s R-value page.
The following table provides typical R-values (and RSI) for various materials. These R-values were taken from manufacturer technical data sheets and are the reported R-values per inch of actual products. In a few cases, the R-values we give were taken from a non-manufacturer source that we consider to be trustworthy and accurate. In all cases, this table is intended only as a general guide to material R-values. When calculating the R-value for a real-life installation, always refer to the manufacturer's data sheets for the actual, specific product you intend to use, or contact the technical department of the product manufacturer or material provider.
R-value is used in the United States. RSI (R-value Système International) is the metric equivalent. To convert the R-value of a specific thickness of a material to RSI, divide the R-Value by 5.67826. To convert RSI to R-value, multiply the RSI by 5.67826. For example, two inches of extruded polystyrene, with an R-value of 11, has an RSI of 1.93721.
Please note that the R-values for roof membranes, shingles, tiles, air films, and roof deck materials might or might not be permitted by your local code to be included when total roof assembly r-value is being calculated for the purpose of satisfying energy code requirements. Always check with your local code authority.
Note: While the R-Value for a material is typically given per inch, the RSI is typically given per millimeter, so please be aware that the R-Values and RSI values for the materials in the following table are not for equivalent thicknesses.