Volume 14, Issue 7- September 2013

Energy & Environmental News

Passive windows
Is Passive the Next "High-Performance” Window?

As a window manufacturer or dealer you may have thought “high-performance” was the holy grail for which to strive—and you achieved that pinnacle by producing or selling a product that met this criteria. But then came the “super window” as one company calls it or the “passive window.” No, this isn’t one company’s made-up term designed to move its products. Passive homes, which of course include passive windows, are being sold by builders, certified by associations and overall gaining momentum and interest.

The Earth Advantage Institute (see box page 22) describes a passive house as “a building that is primarily heated through ‘passive’ energy gains from the occupants, lightbulbs, windows and appliances versus an ‘active’ heating system. Originally developed in Germany as “Passivhaus” the standard represents the world’s most advanced high performance ultra low energy standard,” says the Institute.

“A typical passive house has a reduced energy consumption of 80-90 percent over a building built to code … Worldwide, over 25,000 passive house buildings exist but the concept is relatively new to the United States,” according to Earth Advantage.

Intus Windows, a window manufacturer that produces windows found in passive homes, explains the concept further. “The term passive house window relates to the thermal insulation characteristics of the window. A window with passive house standard features has a particularly high thermal insulation value. The heat transfer coefficient Uw has to comply with the European standard and be less than or equal to 0.8 W/m2K. Every window with an Uw-value less than or equal to 0.8 W/m2K is therefore a passive house window and suitable for installation in passive houses and is eligible for support through corresponding programs,” explains Roland Talalas, co-founder, Intus Windows.

Although based on European standards, passive windows are found in the U.S. Intus manufactures and sells its windows worldwide from its manufacturing facilities in Lithuania. The company, anticipating the U.S. demand, opened an office in the U.S. in 2010. Talalas points out that passive house windows are not restricted to installation in passive houses only.

“Windows complying with the passive house standard can be used in refurbishment projects on old buildings as well as in any new building. Passive house windows enhance living comfort and help reduce heating costs substantially,” he says.

The outstanding thermal insulation properties of a passive house window are first and foremost due to its high quality frame technology in combination with triple glazing. The U-value of the finished window is a function of the U-value of the frame, the glazing and the spacer installed for the edge seal, says Talalas. As an added benefit, building owners will reduce energy and heating costs.

Triple Threat
Planners at the Capital City Charter School in Washington, D.C. did just that when it decided to improve indoor quality and cut future energy costs by replacing old windows with new triple-pane, high-performance windows manufactured by Intus. The school is saving close to $50,000 annually because of improved energy performance. Students are also benefitting from improved indoor air quality and more comfortable learning spaces.

Triple windows however weren’t what building owners originally had in mind—those involved in the project had envisioned traditional double-glazed aluminum windows due to a perceived lower cost says John Brayer, school official.

“The low solar heat gain coefficient of Intus Windows Eforte glazing combined with the low U-values, reduced heating and cooling demands significantly,” says Joseph Khoury, MCN Build. “The cost of the system proved to be 30 percent less than the otherwise installed aluminum double-paned system; thus saving both the builder, and even more important, Capital City Public Charter school, as much as $300,000.”


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