Concentration of CO2 in the Atmosphere

Remarks of a Windows Specialist

Photo by Ellen Strauss, architect.

New window technologies have improved both efficiency and comfort. We also have an ever-expanding range of options. Selecting the right window for a home requires tradeoffs among efficiency and other issues to achieve the most desirable results, so understanding of some basic energy concepts is essential.

We have asked the owner of a local window company carrying many different lines of windows to help us understand some of these things. Steve Cary, who runs Loewen Window Center of Vermont and New Hampshire, in downtown White River Junction, has been kind enough to help us out.

At the store website we are told, “We specialize in high performance windows and doors from North America & Europe. Our products emphasize quality, durability and exceptional energy performance at a range of pricing levels. Our philosophy is simple; provide solution oriented, extraordinary and friendly service before, during and after the sale.”

Steve knows the need to stand behind the window lines he carries, and this is an important factor to take into consideration when deciding where to purchase new windows. Many companies claim to have the “world’s best energy-efficient windows,” and not all claims are true.

Windows’ features or specifications are not all of what is important. Durability and the follow-up of manufacturers and dealers count for a lot. (One day I will tell you about how all my own windows, from another company, failed. My advice is, keep it local; keep it professional.)

Steve had these observations and suggestions on different subjects.

  • Insulating value and condensation resistance. The entire window structure has to be taken into account to measure thermal performance to get a U value, and the lower the number is, the better. The sealed units of the double or triple glazing are filled with argon or krypton gas to reduce heat transfer and eliminate condensation on the interior surface of the glazing. Good frames for thermal performance have low conductivity from thermal bridges. Solid aluminum does not perform as well in this regard as wood, fiberglass, or vinyl (PVC). [Aluminum cladding is a separate issue. -ed.]

  • Solar Control and Ultraviolet Protection. Thin, metallic,low-E coatings are important for solar control and ultraviolet protection. Typically, a greater number of low-E coatings reduces heat gain and will result in a darker tint. A further step for UV control can be taken by using laminated glass like that used for cars.

  • Daylight and view. The best performance means greater numbers of low E coatings, but that may darken the glass too much. A compromise to get more light in is to use triple glazing.

  • Ventilation and air-sealing. Window and doors can swing either in or outward, or they can slide. Large openings are in fashion and can provide energy efficiency. Manufacturers test for design performance (DP) and performance grade (PG). The PG test takes into account wind, water and structural performance. Usually a casement, awning, or tilt-and-turn type window will perform better than one that is double hung.

  • Sound Control. Double- or triple-insulated glass will definitely reduce sound. A special sound transmission glazing is available for greater reduction.

  • Privacy, Safety, and Security. For privacy there are dozens of choices such as frosted and sandblasted glass. Safety glass can be tempered and laminated to resist flying debris from storms or impacts.

  • Maintenance, Durability, and Lifetime. Wood windows should be made from decay-resistant species like Douglas fir. Pine should be treated with preservative and sealed well. Various exterior treatments include aluminum, vinyl, UPVC (plasticized PVC, which is a more durable and less harmful type of plastic), fiberglass, or a new solid composite material made of acrylic polymers called Compositewood.

  • Installation. Strictly follow the manufacturer’s instructions. Pay special attention to doors, as they are the industry’s greatest callback cause, and many problems relate to installation.

  • Economics. PVC is the lowest cost window-frame material, then composite, fiberglass, and aluminum-clad.

The website for Loewen Windows of Vermont and New Hampshire is Steve Cary has been in the construction business since 1977 and has been specializing in windows since 2000.

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