Volume 49, Issue 4 - April 2014


Thermal Ratings May be Superior in Europe But Experts Say it’s Complicated

With glass performance for energy efficiency being comparable in the U.S. and Europe, window frames on this side of the Atlantic have been eyed as underperforming on the U-value front when compared with those in Europe. But the reason for—and even the very premise of underperformance—is complicated, say experts.

One general consensus that industry members point to is that codes are more stringent in Europe.

“[Europe doesn’t] have the same air-water structural requirements that we have in the U.S.,” says Patrick Muessig, vice president of global technical operations at Azon USA. “So if you can get away with a lighter frame, then it’s easier to get a better thermal rating.” Adding such factors as requirements in regions that may have earthquakes or hurricanes, for example, further complicates the equation.

Moreover, comparisons between the two continents can be apples-to-oranges. To start, the European market structure is set up differently, with frames and glass often marketed and sold separately. Therefore, if, say, you go to a European trade show, don’t expect a straight U-value for the whole window system. Rather than a label for a product with a comprehensive U-value for a unit, you may see a U-f value, referring to the frame alone.

Market differences also spill into the technical arena. As Helen Sanders, vice president of technical business development at Sage Electrochromics, explains, “In the U.S., the code requirements are based on whole window U-factor values, whereas in Europe there are specific requirements for both frame and center of glass.”

And then there’s the technology itself. Proprietary products notwithstanding, any high-performance technology available in Europe is available in the U.S. But with constantly evolving technologies, coupled with the multiple variables that make up window systems, comes the need to make everything work together toward a client’s end goal, says Mark Silverberg, president of Technoform North America.

Silverberg also points out other market-related elements that increase the complexity of the issue. It’s more than the codes in Europe simply being more stringent; it’s a matter of market economics at work. For example, in Europe building owners often are required to have energy certificates that stipulate energy consumption. If energy rises above caps, the building owner, not the tenant, may be responsible for the overages, giving the owner economic motivation to achieve high energy efficiencies.

In the U.S., meanwhile, developers are concerned most with lowest first-use installed cost and simple payback calculations. Energy costs typically are passed on to tenants, while developers may plan to flip the building within five or seven years, bringing such factors into play.

Public buildings, wherein the long-term operating and maintenance costs will be a priority, and large corporations with a strong corporate-responsibility ethos and brand are exceptions. Both are driving the use of high-performance technologies, Silverberg notes.

—Carl Levesque

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