For the past five years, researchers at the Building Science Corporation (BSC) in Massachusetts have been testing the thermal performance of a variety of wall assemblies as part of an ambitious project to develop a new metric to replace R-value. (I last reported on the project in my August 2011 article, A Bold Attempt to Slay R-Value.)
BSC researchers recently released information on the multi-year project:
The BSC project is financed by a group of five insulation manufacturers and one trade organization — Dow, U.S. Greenfiber, Honeywell, Huntsman Polyurethanes, Icynene, and the North American Insulation Manufacturers Association — known collectively as the “Thermal Metric consortium.” While BSC hasn’t yet published a peer-reviewed paper reporting on their research project, the consortium has released enough details to draw a few conclusions.
The BSC researchers set out to measure the rate of heat flow through a variety of wall assemblies under different conditions — for example, at different rates of air flow. The intent was to compare the performance of a wall when air was leaking through the wall with the performance of the wall without any air leakage. The researchers also hoped to test wall assemblies at different outdoor temperatures and to quantify the effect of thermal bridging.
Eventually, the BSC researchers hope to propose a new metric for wall assemblies — something akin to the NFRC label now found on windows. “The window industry was in disarray a decade and a half ago, and it was very difficult for practitioners to select windows,” said Joseph Lstiburek, a principle of BSC. “Then the window industry came up with the NFRC ratings for windows, so that today it is fairly straightforward to get information on the three most important characteristics of windows. That labeling came from the industry, and it provides a tremendous example of…