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Efficient Window Performance

By George Harvey

Choosing new windows for a retrofit or new building can be a daunting experience for an ordinary person. There are numbers of choices that seem to go on endlessly. We can choose among installers, manufacturers, and designs. We can pick different materials, components, and construction.

On top of everything else, there are different standards used, which are not directly comparable. Most of us know simple conversions, such as changing a distance from kilometers to miles. Others are a bit more difficult, but pretty straightforward because a simple formula does the trick. But comparing window standards between those used in Europe and what we have in North America is somewhat daunting. Fortunately, there are professionals who are well-educated in these matters, and who are available locally.

What we need is not to understand window construction and the meanings of all of the standards. What we need is to be able to connect with professionals who understand the issues and can advise on them with reliable advice. These are experts in installation and manufacture.

Tanner Lauda Tilt/Turn windows. Photo courtesy Loewen Window Center of VT & NH.

Tanner Lauda Tilt/Turn windows. Photo courtesy Loewen Window Center of VT & NH.

Loewen Window Center of Vermont & New Hampshire

Steve Cary, of Loewen Window Center of Vermont & New Hampshire, is an expert on the subject. He told us, “It’s apples versus oranges on the testing.” Explaining this further, he pointed out that the European standard was developed with Passive House (PH) standards in mind. German engineering, in particular, is careful and thorough. Nevertheless, he also says many of the North American products are very good, and added, “While many European products are indeed very good – it’s not as [greatly] spread as commonly thought.”

He explained, “Many of our lines have been used in PH projects, but only one (Tanner) has a certified PH window. The performance claims are only as good as the certification and in the North American market that’s the NFRC label.” He is referring to the National Fenestration Rating Council. Though the ratings are different, they are nonetheless useful for comparing windows rated under the same standards.

Cary says the Tanner products, which are certified for PH, are the most expensive. They are of “tilt/turn” design, with minimal framing showing to the exterior and are engineered to European standards. He says Loewen’s own products are less expensive, but the company has been manufacturing triple-glazed windows since 1973, making it the most experienced major maker of such windows in the United States. Even less expensive are the Comfort Line Fiberframe, the oldest US fiberglass window manufacturer; they are followed, among the products Cary represents, by Kohltech windows, which include triple-glazed models in a number of product types, including tilt/turns windows, casements windows, and a new single-hung series.

The web site for Loewen Window Center of Vermont & New Hampshire is

Menck Window’s clad wood window with triple glazing. Photo courtesy Menck Windows.

Menck Window’s clad wood window with triple glazing. Photo courtesy Menck Windows.


Menck Windows, based in Chicopee, Massachusetts, manufactures high performance, German engineered tilt-turn windows, win-doors, swinging doors, and lift and slide doors. With their designs, product quality and performance is guaranteed through European testing and trade federations. Their tilt-turn type windows provide superior performance with wind and water infiltration and are tested to withstand high loads.

Alan B. Wall, Director of Sales and Marketing, spoke to the importance of triple-glazing, saying, “Not only does triple glazing increase thermal performance, it increases interior comfort (the interior pane of glass ends up being much warmer, so you do not feel the ‘convected cold’ that’s present with double glazing on cold days) and a much quieter interior.”

Menck’s website is


Intus is a window manufacturer based in Fairfax, Virginia. Marketing Executive Ema Klimaite pointed out the importance of proper window and door installation as a very important part of the process. “You may purchase the most expensive products, but if they are poorly installed it will result in a potential loss in energy savings.” She also commented on the importance of efficient design. “A typical dual pane window has a R-value of R2 to R3. Intus Windows’ triple pane lineup have an average R-value of R7.”

There are a number of choices that can be made, and there is no single choice that is best under all circumstances. Perhaps the best advice is that unless you are an expert on windows, it pays to have the help of someone who is.

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