Can “Equivalent R-Value” be used to determine compliance with mass wall energy code requirements?
In short, no. The Equivalent R-Value of concrete masonry assemblies (or any mass wall system) cannot be used to determine compliance with energy code requirements. Despite the prevalent use of the term Equivalent R-Value, there is no single, standard method of determining such a property for material or assembly.
While Equivalent R-Values can help to illustrate that concrete masonry mass wall assemblies do not require the same level of insulation as non-mass assemblies while provided the same or better level of thermal efficiency, they cannot be used to determine compliance with energy codes.
What’s important to note is that building codes and standards use the term Equivalent R-Value in the context of steel frame construction. In this context, the term effective R-Value is accounting for extremely high level of thermal bridging that occurs in steel stud construction.