AGG - 2006 - May/June

Volume 20 • Issue 3 • May / June 2006

Metal Matters

The Evolution of Thermal Isolation
by Dave Hewitt

As designers work to brighten living and working spaces with natural daylight, today’s new buildings boast more and more glass. As energy costs and environmental concerns also have mounted over the years, the importance of developing more thermally-efficient fenestration systems has also increased.

Glass technology has improved significantly to keep pace with the changes. Huge product improvements have been developed to reduce the exchange of energy, such as advanced coating methods, warm-edge spacers, and the use of inert gases like argon, krypton, and xenon to fill the spaces between lites. Framing systems are evolving as well, with innovative applications for proven technologies.

Thermal isolation has long been recognized as the key to enhancing energy efficiency in aluminum framing systems. This technology has benefited greatly from the introduction of glass-reinforced polyamide nylon components. As the name suggests, these thermal isolators are composed chiefly of nylon, for low heat conductivity, reinforced with glass fibers to add the strength a plastic component would otherwise lack. When used to join two extrusions into one thermally-isolated frame, such components help bring the performance of framing systems into line with the most demanding energy codes.

“Only recently have North American manufacturers like ourselves begun fully capitalizing on the compatibility of these insulating struts with aluminum,” explained Chris Fuldner, chief executive officer of EFCO Corp. “There are a handful of products, including our E-Strut thermal framing, that successfully integrate this performance into a product that delivers long-term efficiencies to the building owner and unique design solutions to the architect.”

“Insulating struts are by far the dominant technology used in the global aluminum industry to accomplish a structural, thermal isolation. Most systems that use insulating struts offer a 50 percent or greater improvement in thermal efficiency over competing technologies,” added Mark Silverberg, president of the North American division of Technoform, a manufacturer of glass-reinforced polyamide components worldwide.

The benefits don’t stop at enhanced energy efficiency, however. Superior structural integrity, increased condensation resistance, and improved acoustics also play into their appeal. From a designer’s point of view, one of the most attractive characteristics is that connecting the interior and exterior members with this type of thermal isolator allows more versatile finish options—such as different-colored finishes for the interior and exterior.

Exploring Expansion
Making thermal isolators compatible with aluminum framing members also has faced another particular challenge: the varying rates of expansion of the different materials during fluctuations in temperature. When materials within the framing system expand at different rates, the integrity of the seal and joint between members can be compromised. The advantage of glass-reinforced polyamide thermal isolators is that the material has a coefficient of thermal expansion nearly identical to that of aluminum, so temperature changes and thermal cycling stand no chance of causing gaps between the isolators and the frame over time.

“For nearly thirty years, insulating struts have had an exceptional track record for joint integrity and shrink-resistance. Thousands of buildings and millions of windows and curtainwall systems around the world use our insulating struts, without worry of field service issues down the road,” said Silverberg.

Because windows transfer about ten times the energy walls do, they are an obvious place for innovators to look for opportunities to improve the efficiency of the buildings in which we live and work.

Dave Hewitt, director of storefront and marketing for EFCO Corp., also leads product development for the company. He has 25 years of experience in the glass and glazing industry, and is a patent holder for a BIPV (building integrated photovoltaic) curtainwall system.