R-value

R-value is a measure of thermal resistance and is used to measure the conduction characteristics of various building materials or systems. The higher the R-value of a material, the better it is at resisting heat loss (or heat gain) due to conduction. R-values are measured by testing laboratories; most notably the government sponsored Oak Ridge National Laboratory.

There are several different approaches to measuring R-value, each of which yields different performance results. The most comprehensive approach is referred to as “whole wall” R-value, which measures the thermal performance of an entire wall, including structural supports, or studs, as well as a variety of typical building envelope interfaces, such as wall corners, wall/floor junctions, wall/roof junctions wall junctions with windows and doors, where heat gain/loss is typically most prevalent.