Joseph Strama couldn't believe his eyes. His company, Woodland Logcrafters in Medford, Wis., was installing drywall on a stick-built house in 20-degree weather. The source of his surprise? Completely dry windows.
Normally, with so much heat and humidity from the drywall process, the windows would be dripping with condensation or even frost in the cold weather. But the Weather Shield windows he had installed, which feature the manufacturer's Zo-e-shield high-performance glazing with a gas-filled air space and low-conductive spacers, were nearly room temperature. "During the process, [the interior of the] windows was never wet," Strama says. "I was totally amazed."
Chalk up another convert to the newest generation of high-performance window glass. It's been decades since the introduction of insulated glass units and transparent low-emissivity (low-E) coatings, and window and glass manufacturers continue to improve the energy efficiency of their products while lowering the prices.
"Low-E coatings have gone from an upgrade product to where it is almost standard now," says David Koester, brand manager at Weather Shield. "Consumers know they should have low-E glass." In fact, a market study from the American Architectural Manufacturers Association (AAMA) and the Window and Window and Door Manufacturers Association (WDMA) found that low-E use in the residential market stands at about 56 percent as compared to clear, tinted, and reflective glasses, up from 51 percent two years prior. That number is actually closer to 70 percent for non-aluminum windows, according to Jeff Lowinski, vice president of technical services for the WDMA.
A lot of those low-E windows are being speced for retrofit applications, Koester says, where they are replacing windows that could be up to 25 or 50 years old. But with energy prices on the rise and green building a full-fledged trend, new-home buyers are asking for high-performance glazings as well.
"They're thinking about the cost of heating 4,000-, 5,000-, 10,000-square-foot homes," says Roger Widing, owner of Widing Custom Homes in Traverse City, Mich., which builds large, high-end homes. To upgrade from standard low-E glass to a glazing package with a gas fill and low-conductive spacers, "it's 3 or 4 percent more to do it, but in the long run it's worth it," he says.
SUPER WINDOWS
Window manufacturers are packing the most technology into what Alex Wilson, president of GreenSpec Directory publisher BuildingGreen, calls "super-high-performance windows." These top-of-the-line windows start with three panes of glass with multiple gas-filled insulating spaces. The units are filled with argon or krypton gas because it's heavier and denser than air, so it slows down the convection current in the window. Krypton performs better and has been coming closer in price to argon, Wilson says, but krypton should only be used in small air spaces — less than 1/2 inch between panes.
High-performance windows also have several low-E coatings applied to one or more of the glass surfaces facing the air space between the panes. The transparent silver coating is attached to the interior and/or exterior pane depending on climate.
The latest generation of window glass, like Cardinal's LoE3-366 and PPG's Solarban 70XL, feature three low-E coatings to further improve the window's solar-heat-gain-blocking properties. Perhaps most impressive, however, is that unlike previous generations, the new glass improves the window's visible light transmission. "It reduces the SHGC [solar heat gain coefficient], and it's only slightly darker in terms of a tint," says Brian Hedlund, a product marketing manager for Jeld-Wen, which began offering the 366 glass in March.
Extra-efficient windows also can offer savings elsewhere, Wilson points out. "If you go to the extent of designing a super-high-performance building envelope, you can often really downsize your heating and cooling system," he says. "You spend more on the envelope but reduce the cost of the mechanical equipment."
DIRECTIONAL CHALLENGE
To achieve optimal efficiency, windows should be speced depending on their location in the house and the customer's individual climate. Gary Lee, sales manager for California Energy Consultant Service, a window dealer and installer in Rancho Cordova, Calif., says the setting sun in the hot summer months in his area bakes the west side of an already-warm home. "One guy said, 'I've got three windows on the west side. Can we change the glass in just those three windows?'" Lee says. Even though the customer already had new low-E windows, "it's worth the money for them to upgrade even after the fact."
In fact, he says at least half of his customers upgrade their windows for comfort reasons, rather than energy efficiency. "They say, 'Now we can sit at that table with the window behind it,'" he says. "You don't feel the heat or the cold."
Other clients are excited about protecting the interior of their homes from the damaging effects of sunlight. While laminated glass has always been able to block 99.9 percent of UV light, new high-end low-E glass can block up to 95 percent or more of UV light, reducing fading of carpet, draperies, upholstery, and artwork.
An added bonus of high-tech windows: Northern builders have discovered that high-efficiency window glazings allow their customers to keep the humidity at a more comfortable level without having to wipe the window sills for frost and condensation. "Even at 25 to 32 degrees, there was virtually no moisture on the windows," Strama says.
DYNAMIC MARKETING
Manufacturers say the future of specialty window glass is in dynamic coatings that can become dark or light at the flip of a switch. And the future is already available in skylights. Velux has partnered with Sage Electrochromics to create an electrochromic coating that lets in 62 percent of light in its open state, but only 4 percent of light, and very little of the sun's heat, in its darkened state.
"It's a very exciting development," says Wilson, whose organization named SageGlass a top green building product last year. "Electrochromic glazings offer the potential to get the best of both worlds." The durability of electrochromic glass sets it apart from other dynamic technologies like suspended particle devices, says Joe Patrick, senior product manager for Velux. Whereas a suspended particle device must be protected from UV exposure, an electrochromic glazing is made of bits of ceramic particles that are not broken down by UV rays, he says, adding that U.S. Department of Energy and Department of Defense testing indicated the glazing could last for more than 100,000 cycles.
The glazing also has a better solar heat gain coefficient than other technologies in its darkened state, according to Velux. It even outperformed the company's exterior heat block awnings, Patrick adds. The biggest obstacle, of course, is cost. Patrick says a typical $800 venting skylight would cost $2,000 with the electrochromic coating. However, he points out, "the technology has the potential to drop in price significantly once the volume is running high, much as static low-E did."
For such a great concept, self-cleaning glass hasn't always lived up to expectations. Early generations were very delicate, manufacturers say, and the technology's benefits were oversold.
"When the stuff came out early on, it was advertised as, 'You never have to clean your windows again,'" says Rod Clark, wood windows product manager for Jeld-Wen. When homeowners discovered the windows still required a little hosing down or wiping off now and then, "that left a bad taste in some people's mouths," he explains. But glass manufacturers have since addressed the kinks and durability issues. "Like low-E, it's matured to the point now where it's pretty durable and pretty effective," says David Koester, brand manager at Weather Shield.
With the improvements, some additional window makers are rolling out the technology. Andersen's Low-E4 and Jeld-Wen's Neat glass, for example, come with a titanium dioxide coating that fills in the microscopic cracks in the glass, causing water to sheet rather than bubble up or roll off. The result is a reduction in water spots up to 99 percent, says Paul Landgraf, product line manager at Andersen.
In addition, "The interaction with the sun and the titanium dioxide will actually work at degrading organic material," Landgraf says.
Weather Shield includes an EasyCare silicone dioxide coating as part of its Zo-e-shield glazing. "If they're interested in energy performance, but not quite convinced on the price, the easy-clean is a tipping point," adds Weather Shield senior brand manager for architectural marketing Jeff Williams.
Still, some installers are weary of customers having unrealistic expectations for their windows. "If it leaves a couple of water spots, they're calling you," says window dealer and installer Gary Lee.
Manufacturers are doing their best to explain the true benefits, and contractors should do the same when marketing the feature to homeowners. "Your windows will get dirty eventually, but generally you can just hose it off," Williams says. "You will have to clean your windows, but much less frequently".
-- BUILDING PRODUCTS
Anderson Windows
Andersen Windows. Low-E4 glazing, now standard on all 400 series windows, deflects radiant heat, reduces glare, and cuts ultraviolet light by 83 percent, while incorporating a sunlight-activated exterior coating that reduces dirt buildup and water spots, the maker says. The 400 series also includes a clear protective film applied to the interior and exterior sides of the glass, removed after installation, to provide additional protection against installation hazards and construction site debris. 800-426-4261.
Marvin
Marvin. The manufacturer's standard glazing options include insulating Low E II glass with argon gas fill; triple-pane glazing is available as an upgrade. The manufacturer also offers simulated divided lites with or without spacer bars; authentic divided lites; removable grilles; and grilles between the glass. 888-537-7828. www.marvin.com.
Hurd
Hurd. ClimaGuard SPF, a glass coating technology proven to block 99.9 percent of UV-A and UV-B rays, according to the firm, is available on almost all of the company's wood and vinyl windows. ClimaGuard SPF windows will prevent sun damage to typical household furnishings for 15 years or more, the maker adds. 800-433-4873. www.hurd.com.
Great Lakes Window
Great Lakes Window. Maxuus 10 is a triple-pane assembly combining two lites of multilayered vacuum-deposition soft-coat low-E insulating glass with an interior glass substrate, creating two insulating chambers of krypton gas. The result is an insulated glass unit that is nearly 10 times more energy efficient than single glass, according to the manufacturer. 419-666-5555. www.greatlakeswindow.com.
PGT
PGT. WinGuard impact-resistant and vinyl and aluminum windows and doors are available with a choice of high-performance glass tints that reduce solar heat gain, increase comfort, and help manage energy costs, according to the manufacturer. WinGuard units with vinyl frames feature heavy-duty multi-chambered construction and come standard with laminated insulating glass. Laminated insulating glass is an option for WinGuard with aluminum frames. 877-550-6006. www.pgtindustries.com.
Velux
Velux. Electronically tintable skylights allow control of the amount of light and heat that enters a room. Applying a safe, low DC voltage via a control switch, remote, or automatic timer causes the electrochromic layers on the skylight to darken, and reversing the voltage polarity causes the layers to lighten. The skylight allows 62 percent light transmission in its clear state, and 4 percent light transmission in its darkened state. 800-888-3589. www.veluxusa.com.
Simonton
Simonton. The manufacturer offers several glass packages. The triple-glazed glass package features krypton-filled, triple-paned glass; two double-strength, low-E surfaces; a single-strength clear divider; a solid silicone foam spacer; and a 1-inch insulating glass unit. It offers a center-of-glass U-value of .11, an R-value of 9.09, and a solar heat gain coefficient of .33, the manufacturer says. 800-746-6686. www.simonton.com.
3M
3M. Prestige series Ultra films are clear, metal-free window films that help hold the glass together to protect against would-be intruders and flying glass during severe weather, while measurably reducing the heat and UV rays that enter the home, according to the manufacturer. Because the films are clear, they do not change the appearance of the home. 888-364-3577. www.3m.com.
Silver Line
Silver Line. Series 9500 replacement double-hung windows come with standard double-strength, LoE2 glass that provides both energy savings and improved sound control, according to the manufacturer. The 7/8-inch insulated glass uses Intercept Warm-Edge spacers and is Energy Star-compliant in all 50 states. Other options include tempered glass, tinted glass, obscure glass, laminated glass, and argon gas fill. 800-234-4228. www.silverlinewindows.com.
Kolbe
Kolbe. LoE3-366 glass is now available as an option for the manufacturer's windows and doors. Providing year-round, all-climate comfort, the specially formulated glass allows 66 percent visible light transmittance, minimizing exterior reflectance to avoid heavy bronze or smoke-colored tints that may darken a home's appearance and view, the maker says. It also blocks 95 percent of the sun's damaging ultraviolet rays. 800-955-8177. www.kolbe-kolbe.com.
Jeld-Wen
Jeld-Wen. The ImpactGard window system includes laminated glass, which has an interlayer sandwiched between two sheets of glass to deliver extra impact resistance. The interlayer is 100 times more rigid than the industry standard, according to the manufacturer, so it delivers five times the tear strength. Even if the glass cracks under pressure, the fragments will adhere to the interlayer. The insulated version also uses a low-E coating. 800-535-3936. www.jeld-wen.com.
Loewen
Loewen. The manufacturer's windows are available with numerous glazing options: a sound-reduction system; the StormForce series; and Heat-Smart Plus Window Systems 1, 2, and 3, which use argon gas and Low E2 technology. Each of the three systems delivers a different level of thermal performance, according to the manufacturer. 800-563-9367. www.loewen.com.
Pella
Pella. The Designer series collection has both double- and triple-pane glazing options to help keep a home warmer in the winter and cooler in the summer, according to the manufacturer. Windows and doors with triple glazing and laminated glass can reduce exterior sounds by more than 80 percent, the maker adds. The series also offers snap-in/snap-out blinds, shades, decorative panels, and grilles. 800-374-4758. www.pella.com.
Weather Shield
Weather Shield. Zo-e-shield glazing systems are custom engineered to improve a home's energy usage while protecting and enhancing comfort levels according to the manufacturer. They use multiple layers of low-E coating and inert gas-filled airspaces. Zo-e-shield is available in three performance levels, and also comes with EasyCare easy-clean coating. 800-222-2995. www.weathershield.com.
Milgard
Milgard. SunCoatMAX low-E insulating glass is now an upgrade option on the manufacturer's full line of windows and patio doors. The triple-coating technology provides a new level of solar heat gain control, energy efficiency, optimal UV protection, and year-round comfort, and it will yield up to a 34 percent solar heat gain reduction over two-coat low-E technology, the manufacturer says. 800-645-4273. www.milgard.com.
Gorell
Gorell. The manufacturer's newest and best-performing triple-glass system, Ultra Master III, features two of the industry's most advanced low-E coatings, a proprietary spacer system, and krypton gas between the glass panes. The system achieves U-values as low as .15 and excellent solar heat gain coefficient ratings, according to the company. Ultra Master III is one of five glass systems offered. 724-465-1800. www.gorell.com.
Windsor
Windsor. Using high-performance material from Cardinal Glass Industries, windows featuring the Windsor glazing system include 3/4-inch dual-pane LoE2 insulated glass with argon gas and are designed to meet or exceed Energy Star guidelines in all zones. The windows will use all-foam Super Spacers that reduce heat and cold conduction. 800-283-3399. www.windsorwindows.com.
CertainTeed
CertainTeed. The Thermaflect glazing system was created to balance all the benefits of low-E glass-saving heating and cooling costs, protecting against UV damage, and keeping the room bright, according to the manufacturer. The system is a double-pane insulated unit with low-E coating on the inside surface, an argon gas fill, and a spacer between the panes made of low-conductance material. 800-233-8990. www.certainteed.com.
Southwall
Southwall. Heat Mirror, a technologically advanced low-emissivity and solar-reflective film, can be applied inside an insulating glass unit to provide insulating values ranging from R-6 to R-12. For maximum insulation, the dual-film unit creates three insulating cavities that provide 95 percent of the insulation performance of an R-19 insulated wall. 800-365-8794. www.southwall.com.