A Green View on Windows
Today’s environmentally conscious homeowners seek green builders to construct their homes with sustainable, recycled and energy-efficient materials. The following tips can help you select a window manufacturer with solid environmental products and manufacturing processes.
• Understand the numbers. The window industry uses certain criteria, developed by the National Fenestration Rating Council (NFRC), as a guide to understanding the energy efficiency and performance of a window or door. The U-factor is a measurement of the rate of heat loss through the window. The lower the U-Factor, the better the window is at keeping heat from escaping. The R-Value measures a window’s resistance to the passage of heat. The higher the R-Value, the better the insulating value of the window. The Solar Heat Gain Coefficient (SHGC) is the fraction of available solar heat that passes through a window. The lower the SHGC, the better a window’s ability to block heat from the sun. Windows in warm climates should have low SHGC, while windows in cold climates should have higher SHGC in order to bring in the heat of the sun to heat a home.
• Choose energy-efficient glass. Insulating glass (dual-pane) and low emissivity (low-E) coatings can significantly improve the energy efficiency of your windows.
• Materials matter. The material of a window’s frame plays an important part in a window’s overall performance. Two great options are wood and pultruded fiberglass. Wood—desirable for its warm, traditional look—provides solid energy efficiency. “As wood is a renewable resource when managed correctly, ask questions about the manufacturer’s commitment to purchasing from reliable lumber suppliers who subscribe to groups such as the Sustainable Forest Initiative,” advises Scott Walbridge from Marvin Windows and Doors.
Pultruded fiberglass frames offer superior energy efficiency because fiberglass expands and contracts at the same rate as the glass in extreme temperatures, decreasing stress cracks or seal failures. Silica sand is the primary component in the manufacturing of fiberglass and is an abundant resource.
• Staying power. Choose durable windows that have the quality craftsmanship and strength to last.
• Choose manufacturers with a conscience. Look for a company with environmentally responsible manufacturing processes. Companies that actively promote recycling, clean manufacturing and waste management are often recognized by government or industry awards.
Use the following guide to help you understand the number on your window’s NFRC label (numbers listed are optimal for the Chicagoland climate):
- U-Factor: At most 0.35 (the lower, the better)
- Solar Heat Gain Coefficient (SHGC): Stay in the range of 0.3 to 0.55
- Visible Transmittance (VT): No requirement, but the higher number, the better
- Air Leakage (AL): At most 0.3
Source: Efficient Windows Collaborative
Rick Baumgarten is the president of Lee Lumber and Building Material Corporation. He is a past chairman of the National Lumber & Building Material Dealers Association and holds an MBA from the University of Chicago. Lee Lumber is an independent supplier of home-improvement materials. www.leelumber.com.