Air Krete: Foam Without Plastics

Air krete insulation is not all that new—it has been around since the early 1980s. In that time, it has collected a small but very enthusiastic group of advocates, especially among the chemically sensitive. There are also skeptics, however, who are concerned about its long-term durability or just question whether it is worth the higher cost. Recent evidence about the product’s firestopping capabilities may provide the big break air krete advocates have been waiting for.

Air krete insulation is essentially foamed minerals: magnesium oxychloride cement, derived from sea water, and a particular variety of ceramic talc mined in Governor, New York. These minerals are mixed with a proprietary foaming agent—“glorified soap suds,” according to air krete inventor R. Keene Christopher—and sprayed with pressurized air through a foaming gun. The resulting foam has a density of 2.25 lb/ft3 (26 kg/m3). It takes a few hours to cure, so when it’s being installed in open cavities a fine screen is stapled across the opening to hold the foam in place. Air krete used to be pink, but some purists objected to the use of red dye #2 food coloring, so it now has a blue-green tint, achieved with an inert mineral pigment.