Rigid insulation boards have been a standard component in commercial construction for years. One of the most common variants, polyisocyanurate (“polyiso”) foam board, contains thousands of tiny air bubbles, which limit heat transfer. This results in an R-value – the measure of heat transfer through a material – of about 6 per inch. Over three inches of polyiso board are typically needed to reach the R-value of 21 required for walls by building codes in Washington.
However, researchers at Oak Ridge National Laboratory, a branch of the Department of Energy, are developing a new type of insulation designed to reach an R-value of 12 per inch. The product, dubbed “modified atmosphere insulation,” or MAI, utilizes air bubbles that are filled with nothing at all – they are vacuum-sealed. A vacuum greatly reduces heat transfer versus a sealed air space.
Vacuum-sealed insulation is not new, but has historically been prohibitively expensive due to its complex manufacturing process. The MAI boards developed at Oak Ridge solve this problem with a much simpler technique: the air pockets in the insulation are filled with a condensable vapor, which is then allowed to cool, reducing its volume greatly and leaving a vacuum to occupy the bulk of the enclosed space.
Buildings account for about 40% of U.S. energy consumption, so reducing heating and cooling loads through better insulation provides a great opportunity to minimize our carbon footprint. For more information on the new insulation, check out this news release by Oak Ridge, or this article in the Journal of Light Construction.