Volume 35, Number 11, November 2000
The Importance of Structural Warm-edge Glazing
by David Mills
The oil-producing countries of the world (OPEC) are once again reminding us who
controls the worlds fossil fuel energy resources. Crude oil costs have almost
tripled in recent months and show no sign of recoiling soon.
Our consumption of energy and its effect on the environment has decreased dramatically on some of our most energy consuming products. In the past 20 years, for example, the automobile has improved its fuel efficiency by 80 percent, all the while increasing horsepower and performance by 50 percent.
Our energy saving products continue to grow in their development and capabilities. In the window industry, manufacturers of windows and components, code bodies and various industry associations, long have recognized this and continue to focus on energy reduction. It begins with design. For example, the American Institute of Architects (AIA), has established the following creed as its guiding principle:
Return to well-established methods of design that conserve energy and natural resources.
The Department of Energy (DOE) also follows this path. It has put restrictions on decreasing fossil fuel consumption as it relates to transportation. In addition, they have raised public awareness with the ENERGY STARŪ program and now are focusing on the energy consumed by commercial buildings.
Next to the transportation industry, commercial edifices are the largest consumers of energy in the world. The DOE is in the process of road-mapping an energy reduction strategy for commercial buildings.
According to the DOE, the built environment consumes 30 percent of our countrys energy. The goal of the DOE will be to reduce the energy consumed in commercial buildings by 50 percent, before the year 2010. Windows are the targeted products for improvement. Window manufacturing that utilizes energy enhancing components has become the norm. Thermal graphics show the dramatic improvements when using energy saving components to the manufactured windows (see figure 1). By incorporating these energy saving components into their products, fenestration producers have reduced their products U-Factor from 1.25 Btu /hr ft2 F to as low as .30 Btu /hr ft2 F. Using conservative calculations and entering the data into the software program RESFEN, on a 20-story commercial building the annual savings in energy consumption for this structure alone would exceed $15,000. This applies to only one relatively small structure in a single city; the effects on energy savings are staggering when multiplied throughout the world.
In addition to energy, structural performance in the design and construction of fenestration products in commercial buildings is of prime concern. The windows and insulating glass units must be designed to withstand greater wind loads, deflection and stresses not found in non-commercial construction. Framing materials usually are made of thermally-improved aluminumlong known for its lightweight, extremely high structural performance and its energy efficiency.
Insulating spacers can have a big impact on the overall performance of the insulating glass, both in U-Factor and condensation resistance. All warm-edge spacers provide energy saving benefits. The concern for commercial construction comes when structural requirements, which take into account wind loads and structural stability of the overall unit, need to be considered. They must withstand the rigors of testing to ensure the structural integrity of the overall unit. There are a limited number of warm-edge products on the market today that also improve the structural capabilities of the overall unit. Deflection and compression need to be taken into account. Simple calculations can reveal the properties of these products (as in figures 2 and 3).
These spacer products not only provide the warm-edge benefits for energy and condensation improvements, they provide even more improved structural performance than conventional aluminum spacers. The addition of a structural polyurethane provides the needed warm-edge requirements and allows for added structural performance at the severe conditions that are encountered in the most monumental buildings.
As we move into the next cycle of energy conservation, the commercial construction industry is ready and able to provide the products necessary to help us continue our path of independence from foreign energy producing nations.
David Mills is president of AZON USA INC. located in Kalamazoo, Mich.