R-Values

Use these values as starting points while designing and checking energy performance of structures and assemblies. Always consult product specifications for exact R-Values and verify numbers prior to final documentation.

• These values should be used as a starting place, and not the end result.
• Code and Energy Guidelines may present guidelines or other requirements to follow.

R-Value Degradation

R-Values may degrade over time due to settling, chemical changes (rust, staining), dust, or other issues.

*Air Gaps & Film

Air Spaces (Air Gap)

Air spaces are particularly difficult to estimate values of the R-Value as they depend on numerous factors, including size and shape of the surfaces, orientation, reflectivity of the surfaces facing the airspace, heat and airflow in/out of the airspace (air changes per hour), and other factors.

ICC A9.4.2 Air Spaces

ICC Ashrae TA9.4.2 Air Spaces Has been created to help deal with the difficulty of how to estimate air space values. Note that all air spaces under .5” thick are stated to have zero R-Value.

Air Film (Adjacent to Assemblies)

Air against a wall has an insulative property and is known as ‘air film’. Interior and Exterior accepted values are shown in the chart, and are generally used throughout various textbooks.

R-Value Charts

R-Value Per Inch

~Mid Value * Standard Widths