Researchers at Oak Ridge National Laboratory (ORNL), working with two manufacturers—NanoPore, of Albuquerque, N.M., and Firestone Building Products, in Indianapolis, Ind.—have developed a 2-inch-thick polyisocyanurate board that provides an R-25 insulation value. The new rigid foam board contains "modified atmosphere insulation," or MAI, cores. Most insulation materials rely on air pockets. Normal polyiso board contains thousands of tiny air bubbles. Heat conducts slowly through an enclosed air space, so a material with lots of air pockets provides better insulating value than a denser material with few or no air pockets. The new MAI board goes one step further by creating tiny bubbles that have no air in them at all, vastly reducing the conduction of heat across the spaces. Radiation across the tiny voids are reportedly reduced, as well, by adding "opacifiers"—materials that render the system opaque—to further increase the R-value. According to an ORNL news release, the vacuum in MAI panels is produced by filling the porous core with a condensable vapor. This vapor condenses to liquid that occupies a fraction of its original volume, leaving the remaining space a vacuum. Read more.
