September 15, 2007


This document summarizes the theory behind thermal insulation and building system heat flow control metrics and presents a literature review of selected research into this area. As the building industry strives to reduce energy consumption for environmental and economic reasons, building enclosures with high thermal performance, reliably and affordably installed in the field are required. The R-value was developed over 50 years ago to provide users and specifiers of insulation with and easy-to-compare, repeatable measure of insulation performance. The strength of the R-value is that it is simple to measure, easy to communicate, and widely accepted.