Q: What is U-Factor, also referred to as U-Value?
A: U-Factor is a measure of thermal transmittance (heat flow) through a wall system or assembly, per unit area, time, and temperature differential, including surface boundary conditions. It is used to quantify heat loss during times of both peak load and normal mechanical operating conditions. Thermal Transmittance, or “U-Factor,” is determined in a guarded hot box test. In this test, the window unit divides a cold chamber (with fan-generated, 15 mph wind velocity) from a highly insulated/guarded, warm chamber. By measuring the energy input required to keep the warm side at a constant temperature, the U-Factor of the window unit is indirectly determined – the lower the U-Factor, the better the thermal performance. The required U-Factor for a specific application depends on code requirements, mechanical design parameters, and occupant comfort needs.
Steve Fronek, Vice President of Research and Development, Wausau Window and Wall Systems (www.wausauwindow.com), Wausau, WI
Q: What are the benefits of low-e glazing?
A: It’s an energy conservation option. It allows building owners to have lower energy costs, lower heating bills in the winter, and lower air-conditioning costs in the warmer months. And it also has some significant ability to reduce the transmission of ultraviolet rays. It depends on the formulation that’s used by the particular manufacturer but somewhere around three-quarters of the ultraviolet radiation that would normally get through to the interiors is blocked by low-e. So it means that an owner has fewer worries about fading of carpet or draperies.
Bob Saumur, Architectural Sales Representative, Marvin Windows & Doors (www.marvin.com), Eagan, MN
Q: How important is finding the right installer?
A: The window is only as good as the installation. You’re not going to have anything leaking through the glass, or through the window, but it might leak around the window if the installation is not tight – and that’s a real bad thing. Almost as important, if not more important than buying the right product, is making sure the right people install it.
Mark Hermes, Vice President of Sales, Maine Glass (www.maineglass.com), Park Ridge, IL
Q: Windows are a no-maintenance product. True or False?
A: A window is still like anything else you own; there is still a certain amount of maintenance required to keep that product in tip-top shape. Whether it be a clad window or vinyl window, on the exterior skin there is a seam between the window product and the exterior surface, [which is] typically the easiest point for caulking to break down. So there should be a maintenance schedule to continually clean up the old caulk and re-caulk the window to the structure so there won’t be any water penetration.
Greg Dahl, Commercial Projects Manager, Eagle Window & Door Inc. (www.eaglewindow.com), Dubuque, IA
Q: What are the primary benefits to applying window film in commercial applications?
A: For commercial building operators, the primary benefits delivered with the installation of solar control window film include:
Lower heating and air-conditioning needs, leading to substantial energy savings.
Window film provides a balance of internal temperature, eliminating internal hot and cold spots, leading to a greater comfort level within the building. Comfort within the building is further enhanced through a reduction of sun glare.
Building aesthetics can be vastly improved by creating a uniform look, by eliminating views of untidy, chaotic individual office windows and floors.
With the installation of solar control window film, the harmful effects of the sun’s ultraviolet rays can be virtually eliminated.
In addition to the solar control benefits provided by window film, the product is inherently a safety device that forms a protective shield across windows so that if a glass window or door were to break, the shattered glass would be contained.
Virginia L. Kubler, Director of Sales and Marketing, Window Films, CPFilms Inc. (www.llumar.com), Martinsville, VA
Q: How does self-cleaning glass work? And how do you clean it?
A: From our standpoint, one of the trends that we are promulgating would be the use of self-cleaning glass. The product breaks down organic dirt, dissolves that dirt on the glass, and then when it rains or with a hose, the water physically sheets down the glass, causing that dirt to run off.
What that delivers is reduced costs on maintaining the building because the product works to reduce the number of cleanings necessary. We’ll never say, “You’ll never have to clean the glass,” but it will significantly reduce the number of times you have to mechanically and physically clean the glass.
[When cleaning,] no metal objects such as razor blades [or] metal edges of squeegees should come in contact with the glass. You can use tough cleaners if necessary on the glass, and it will not impact the ability of the product to perform its function.
Paul M. Gore, Business Segment Leader, Building Products, Pilkington North America Inc. (www.pilkington.com), Toledo, OH
Jana J. Madsen (firstname.lastname@example.org) is senior editor at Buildings magazine.