R-values of Insulation and Other Building Materials

The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) provides R-values of building materials in their 1997 Handbook of Fundamentals.

R-values are additive.  For instance if you have a material with an R-value of 12 and another material with an R-value of 3, then both materials combined have an R-value of 15.

Many energy modeling programs and code calculations require U-values of assemblies.  The U-value is simply the reciprocal of the total R-value of the assembly.

Building Material R-Values

The R-values above for specific assemblies like doors and glazing are generalizations because they can vary significantly based on special materials that the manufacturer uses.  For instance, using argon gas in a double pane insulating glass unit will dramatically improve the R-value.  Consult manufacturer literature for values specific to your project.

The values in the table above were taken from a number of sources including: The ASHRAE Handbook, ColoradoENERGY.org, and Building Construction Illustrated by Francis D.K. Ching. Other minor sources were also used. Archtoolbox does not test materials or assemblies.

2004 CSI Masterspec Division

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