There was a time when the measure of a window was its ability to fit the architectural style of a house. That is still important today, but other factors now carry as much weight.
Simply put, the window is an integral part of the building envelope. Thus, along with the roof and walls, it’s part of the first line of defense against moisture, air, sound, and—most important for energy efficiency—heat gain and loss.
“The high prices for natural gas, electricity, and home heating fuel that followed the first oil embargo in the early 1970s made energy a high profile, pocketbook issue,” says the National Fenestration Rating Council (NFRC), a nonprofit organization that provides information about the energy performance of windows. “Many consumers became aware of R-values—a measurement of a product’s resistance to heat loss—and learned that materials (floors, walls, and roofs) with higher R-values are more energy efficient.”
Energy awareness may have started in the ’70s, but it has escalated in recent years with growing concerns about rising energy prices. “And this has affected windows. The state of affairs in the glazing market has changed quite a bit in the past few years,” says Brian Hedlund, product marketing manager for windows at Klamath Falls, Ore.–based Jeld-Wen. “Green [building] is tremendously important, and energy efficiency is a big deal.”
The average energy-efficient window uses a standard glazing package that includes low-E insulated glass, and it is more energy efficient than windows from 15 or even five years ago. But in conjunction with their glass-producing partners, window manufacturers are now able to offer glazing that increases energy efficiency or addresses specific situations.
LOCATION, LOCATION
Home buyers in different regions, for example, have different needs. In the North, a window’s U-factor, which measures how well a window prevents heat from escaping, is important. Buyers in warmer states, on the other hand, should be concerned with the solar heat gain coefficient, which measures how well a window blocks heat from the sun. And in the central regions, a window must do both. “There is no one option that is ideal for every climate,” says Tom Sinning, director of dealer sales for Warroad, Minn.–based Marvin Windows and Doors.
Because buyers and climates have different requirements, manufacturers have come up with ways to meet them. For example, Jeld-Wen says its high-performance low-E insulating glass is a good general purpose glazing because it “helps homes stay cooler in the summer and warmer in the winter.” But for warm regions, it offers LoE³-366.
“This glass features three transparent, microscopic layers of silver placed between layers of anti-reflective metal oxide coatings,” the company explains. The coatings block UV rays and reduce window heat gain.
Medford, Wis.–based Weather Shield Windows and Doors claims its Zo-e-shield is the world’s best energy-efficient glass, offering the lowest center-of-glass U-factors and solar heat gain coefficients. The line uses a combination of components such as warm-edge spacers, gas-filled airspaces, and laminated interlayers to fill various types of performance needs.
Earlier this year, Bayport, Minn.–based Andersen expanded its glazing options with SmartSun. Unlike standard solar glazing, SmartSun has an additional layer of silver that controls the amount of infrared energy transmitted, the company says.
LABEL GAZING
An easy way to see if a window meets your needs is to look for the NFRC label, which lists a product’s performance such as U-factor, solar heat gain, air leakage, condensation resistance, and visible transmission. The Energy Star label also lets buyers know that a window has met certain energy-performance requirements.
Unfortunately, high-performance glazing will likely cost more money than standard packages. Even low-E may add to the cost, Sinning says. “Low-E has become the standard energy-efficient glazing, but it may not be a standard offering from all manufacturers,” he explains. Plus, offering the high-performance glazing is only half the battle for window manufacturers; they still need to build a good window. “The trick for manufacturers,” Hedlund says, “is how to package the glazing with the window” to make them work as a system.
Smart aleck: The manufacturer offers a wide variety of glazing options on its 400 Series products. The recently introduced SmartSun control glass rejects unwanted solar heat while allowing the light to stream through. Other glazing options include Low-E4, Low-E4 Sun, and Low-E4 insulated impact-resistant glass. Andersen Windows and Doors. 800-426-4261. www.andersenwindows.com
Get Lo: In addition to its low-E insulated glass, the manufacturer offers LoE3 366 glass on custom wood windows. Made with three layers of silver placed between anti-reflective metal oxide coatings, the windows block 95 percent of UV rays and reduce window heat gain by 64 percent. Jeld-Wen. 800-877-9482. www.jeld-wen.com
Coat of arms: The manufacturer says its Integrity windows come standard with Low E II coated glass, which can reduce heating costs by 34 percent in cold climates and 38 percent in warm climates. The Energy Star–rated windows feature wood interiors and a virtually maintenance-free pultruded fiberglass exterior called Ultrex. Standard-sized products include casements and double-hungs, among others. Integrity by Marvin. 888-537-8263. www.integritywindows.com
Shields up: Zo-e-shield is custom-engineered to improve a home’s energy usage, the manufacturer claims. The line features such components as Real Warm Edge Spacer systems, EasyCare coating, multiple layers of low-E coating, and inert gas-filled airspaces. Three performance levels are available: Zo-e-shield 5, Zo-e-shield 6, and Zo-e-shield 7. Weather Shield Windows and Doors. 800-477-6808. www.weathershield.com
Triple protection: Designer Series triple-pane windows are the manufacturer’s most energy efficient. The triple-glazed windows offer energy efficiency and noise reduction. Between-the-glass blinds reduce heat gain by 43 percent and minimize airborne allergens. Pella Window & Door. 888-847-3552. www.pella.com