As energy costs skyrocket, builders across the country are more vested than ever in helping homeowners control heating and cooling needs. Windows can be a source of significant heat loss in winter—and heat gain in the summer. According to the Partnership for Advancing Technology in Housing, energy lost through single-pane windows can account for up to 50 percent of the energy required to heat and cool homes.
Low-emissivity (low-E) glass is a first line of defense against window heat gain and loss. The glass has a thin, transparent coating that helps reflects solar radiation to varying degrees to allow for the amount of solar heat gain desired. Contractors will pay 10 percent to 15 percent more for low-E glass, but owners can save 30 percent to 50 percent on energy costs associated with the product during its lifetime, according to the U.S. Department of Energy.
“Our customers are definitely getting more knowledgeable about windows. About 50 percent of clients will ask for low-E glass and double panes up front,” says Matt Garcia, an executive with Mike Garcia Construction, Woodbridge, Virginia. “We are big believers in low-E glass because of the efficiencies.”
Energy Improvements
Double-glazed units with an air- or gas-filled space between the glass panes also improve energy performance, providing superior insulation, sound isolation and also protect against impact from wind-borne debris. The thickness of the air space determines how much insulation you get, and many window manufacturers have increased the thickness from ¼- to ½-inch or more. Beyond depths of about 1 inch, there is little additional gain in energy performance.
Instead of air, some windows have a gas fill between the panes, such as argon, krypton or carbon dioxide (CO2). These dense gases cut heat loss dramatically.
With new window products hitting the market all the time, how do you choose? Climate is the key factor in window selection. For example, low-E windows in Miami or Mobile have low solar heat-gain coefficients, to keep more heat out; in Maine or Michigan, use windows that allow high heat gain to cut winter energy bills.
“We definitely go with gas-filled every time,” Garcia says, noting that they work well in his Northern Virginia climate. “We usually select a double- or sometimes triple-pane window with argon inside, because of its insulating factor.”
Weather and Performance
Energy isn’t everything though; builders also want assurances that the products they install will be both well-designed and long-lasting. Fortunately, window manufacturers have stepped up, offering new styles, materials and state-of-the-art features. For regions prone to severe weather, advances in high-impact glass may be the most important new upgrade.
Many manufacturers, including American Craftsman, Jeld-Wen and Andersen, produce windows designed for coastal areas with impact-resistant glazing, a sandwich of glass panes adhered to a film of polyvinyl butyral (PVB) or a similar material. When standard windows would easily shatter from windborne debris, impact-resistant glass holds strong, protecting what’s inside.
Newly added severe-weather features from various manufacturers include steel reinforcements, interlocking tilt-latch hardware, and hide-away sash brackets that retract into the frame in calm weather. As a bonus, these storm-safe windows also reduce noise from outside.
Designing for Daylight
Design considerations top many homeowners’ punch lists, and two important aesthetic issues are preserving views and increasing daylight in the house. To increase viewable area with the same size windows, contractors can select narrower grilles and muntins, thinner frame profiles and even windows with blinds installed right between panes. Some windows have removable grilles, too, making cleaning easier.
New advances in insect-screen technology are making it easier to let the sunshine in. Andersen’s TruScene™ insect screens delivery more than 50 percent increased clarity compared to standard insect screens, but are as tough as the stainless steel they are made of.
“The TruScene insect screens are virtually invisible,” says David Nix, senior marketing manager for Andersen Windows, Bayport, Minnesota. “They improve not only the view through the windows from the inside, but also the appearance of the home from the outside. In addition, they provide more airflow for better room ventilation, yet keep out even the smallest of insects.”
Easy-Clean Windows
Other features that provide easier use and maintenance for homeowners include classic tilt-in double-hung windows that allow cleaning from the inside of the home, with no ladders required. But for those hard-to-reach, two-story-high Palladian units, or for customers who prefer to spend time doing activities other than cleaning windows, consider a low-maintenance glass such as Andersen Window’s High Performance.
Low-E4 glass, Jeld-Wen’s optional Neat Glas or American Craftsman’s ClearView These windows feature a titanium dioxide coating on the exterior of the glass that is designed to react with the sun’s UV rays to loosen dirt, while reducing water spots up to 99 percent. Not only does the glass stay cleaner longer, it helps lower energy bills, since the windows are more energy-efficient in both winter and summer.
Whatever window you choose, make sure to study the warranty and consider the long-term costs. As Garcia notes, “Nowadays you have to weigh every penny. People are willing to pay a little more up front so they won’t pay as much every month on that heating bill.”
Best Practices: Window Flashing
The most weather-tight window available will still leak if it is not installed and flashed properly – a callback no contractor wants. A few expert tips will keep moisture out and profits up.
- First, install house-wrap material. Cut it at the windows and fold it into the openings to keep water from entering.
- Shim the bottom of the window to create a channel for any water that leaks in to get back out.
- Add sill pan flashing at the base of each window opening. Some sill pan flashing systems feature sloping drainage channels and support ribs to drain moisture away from the interior wall.
- Place the window and install jamb flashing, a self-stick material that bridges the gap between the window and drainage plane. Make sure the window is square.
- Install head flashing under the drainage plane. The plane—cut away from the window prior to installation—should then be lapped back over the flashing, to help shed water.
- Use a good sealant with high elasticity to prevent water from seeping in through cuts and joints after the window has been installed.
Source: HousingZone.com