Windows & Doors Review: Peak PerformaceHigh-tech window glazings reduce energy costs and keep houses more comfortable.

Continued from page 1

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."

Easy Clean

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