Architects Slowly Begin to Expand the Traditional Palette of Materials

New substances from high-tech labs enter the construction realm.

Architectural Record
November 2003
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.

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.

Testing conducted by Cabot demonstrates that Nanogel is moisture-repellent; resistant to mold and fungus; stable in the presence of ultraviolet light; and completely recyclable. It is not readily combustible, and no ozone-depleting agents are used in its manufacture.

With all these attributes, it may seem surprising that it has taken so long for aerogel to reach the architecture market. Initially, however, production of the material was extremely complicated, requiring a drying process under very high pressure and high temperature. Due to the expense, dangerous processes, and low volume of production, early attempts to commercialize the material failed. Spurred on by the public’s greater interest in energy efficiency, Cabot recently developed a safe, affordable process that yields sufficient quantities to make it a viable product for architecture.

In the first full-scale demonstration project—in which decades-old Kalwall panels over the pool area of a Comfort Inn in Manchester were retrofitted last year with the new technology—the Nanogel-filled structural-sandwich panels insulated so well that the warm pool interior could not melt snow that fell on the skylight panels. Owner Fred Bailey attests that while the new system seems to let in more light, the insulated area no longer has drafts, nor does it lose heat. And more recently, Overland Partners Architects of Bozeman, Montana, specified the high-performance, translucent panels in the first commercial installation in the country—another roof system on a one-story office building for the Security Title Company in Bozeman. The firm wanted to get the lowest U-value possible for this climate, where heat loss is significant during winter months. “The owner is interested in quality in general and environmental issues in particular,” explains principal Mark B. Headley, AIA, “so he was eager to use the innovative panels.”

Photography courtesy Overland Partners Architecture

For more information, contact:
Bruce Keller
Kalwall Corporation, 603-627-3861
(U.S. 800-258-9777)