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By Nancy B. Solomon, AIA

Case study: Aerogel goes mainstream

“New” is something of a misnomer when it comes to aerogel, a highly porous solid made from a gel. Although the first architectural application of this material was introduced in January 2003 by Kalwall Corporation (www.kalwall.com), of Manchester, New Hampshire, the intriguing substance was originally developed in 1931 by Steven S. Kistler at the College of the Pacific in Stockton, California, and later used by NASA to insulate the battery system in the Mars space rover.

To visualize aerogel, says Marketing and Sales Manager Jim Litrun of Cabot Corporation (www.cabot-corp.com), a specialty chemical and materials company headquartered in Boston, imagine being able to remove the liquid from a bowl of Jell-O. The remaining gel structure would form a kind of wispy sponge that is 95 percent air and 5 percent solid.

 

Commercialization of Aerogel Overland Partners Architects specified Kalwall’s Nanogel structural-composite panels for a one-story office building and a public library (next page), both in Bozeman, Montana. Photography: Courtesy Overland Partners Architects

The result is a lacy matrix of extraordinary qualities. “It is the lightest, most insulating solid in the world,” continues Litrun. Its pores are only about 20 nanometers (one nanometer equals a billionth of a meter) in diameter. The miniscule air pockets trap individual gas molecules, preventing them from bumping into each other and transferring energy through convection. Energy cannot be transferred by conduction, either, because aerogel is typically made from poorly conducting chemicals, and because there is very little material present in the matrix anyway. Multiple tiny pores and minimal solid material makes aerogel a great sound insulator, as well. Yet diffused light can penetrate through it.

Cabot makes a proprietary version of aerogel from silicon dioxide, which the company calls Nanogel. Its granular formulation can be packed tightly into Kalwall’s familiar composite-structural-sandwich panel. The assembly offers up to 20 percent light transmission with a thermal transmittance (U-value) of a mere .05. Up until now, the most thermally insulated Kalwall panel—consisting of translucent fiberglass batt insulation sandwiched between fiberglass-reinforced translucent faces that have been bonded to a thermally broken frame—provided light transmission of 10 percent with a U-value of .10. “The Nanogel version can double the light transmission and double the thermal protection at the same time,” observes Litrun. A fenestration system fabricated with this new panel is detailed and installed in the same manner as any other high-performance Kalwall system and costs about the same, according to Kalwall vice president Bruce Keller.