4 window technologies that can lower your energy bills
Susanne Clemenz | Improvement Center Columnist | March 19, 2012
The most spectacular, in-your-face view of Sedona, Arizona's, Cathedral Rock formation is to the east from a nearby 30-year old home. However, the 15-foot high double-paned view windows created a solar oven in the 1,750 square foot home, especially in the open great-room. Double cell pleated shades helped, but often hid the famous view.
At the opposite end of the great-room, a tall, rust colored sandstone ridge one block away shaded the kitchen sink window by about 4:30 p.m. on summer days.
Although the home was tightly insulated, its double paned air-filled windows with wood frames were state-of-the-art window technology -- 30 years ago! At a summer party last year neighbors were comparing utility costs between newer and older homes on the street. For the home described, heating and cooling costs were definitely higher than those of newer homes. One new-home neighbor mentioned the U.S. Dept. of Energy (USDE) website had been a great resource in helping them choose their windows. Perusing that site lead to detection of an obvious energy hog in the older home: the windows. The not-so-obvious solution? Several different replacement windows with different features to lower inside temperatures were needed.
Match your window solutions to specific problems
Your home may be a California ranch with many east and west facing windows, a north-facing Minnesota, lakeside home, or a Fort Lauderdale, Fla., house with flying debris hazards. In any locale, each side of your home is exposed differently to heat, cold, and prevailing wind and rain directions. Bigger windows create different demands than smaller ones. Today there are energy-wise solutions for any architectural style.
- Number of panes: Double panes were an initial step in improving window performance. Like layered clothes, trapped air or gas between panes creates insulation. For really large windows, triple panes bump up performance. The USDE website says, "Select windows with both low U-factors [entire window assembly performance] and low SHGC [solar heat transmittance] to maximize energy savings in temperate climates with both cold and hot seasons." Bingo -- Sedona! To decrease heat gain from the Sedona home's view windows and reduce heat loss from the big guest bathroom window, the owners chose triple-paned glass. Smaller windows got new double-paned glass with features mentioned below.
- Gas fill: Air is used less often in today's multi-paned windows. Inert gasses like argon and krypton are more dense, creating improved thermal resistance. Argon is cheaper and krypton is more effective. An online chat with window manufacturer Jeld-Wen helped narrow down choices when Dayna, the Customer Service rep, commented that "The Premium Vinyl Energy Saver Max is our only window type that has both Argon and Krypton in it. We offer just Argon filled ones in all of our [other] window lines. If you choose neither gas then it will only have air in between the two panes of glass." The Sedona home-owners bought argon-filled smaller windows and used krypton and argon-filled windows in the big living room and guest bathroom.
- Frame material: The USDE details the capability of window frames stating, "Overall, vinyl, wood, fiberglass, and some composite frame materials provide greater thermal resistance than metal." Aluminum is very strong and new designs have thermal breaks to improve performance. Wood -- even with exterior claddings of vinyl or aluminum -- swells, contracts and can rot or become infested. The Sedona family got fiberglass frames on the big windows, insulated vinyl elsewhere.
- Coatings: The USDE website states that low-emission metallic particle coatings (low-e) on glass can reduce energy loss by 30-50 percent. The Sedona home's huge great-room windows got a low-e coating. For other climates, impact-resistant windows have an inner membrane to keep glass shards contained.
In mild climates one type of window may work throughout your home. The Sedona couple prioritized the huge living room window and selected other window features according to size and compass orientation. Learn how to read Energy Star and National Fenestration Rating Council labels. Then choose efficient replacement windows that lower utility bills while boosting the comforts of home.