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Lighting Seattle since 1905 Jorge Carrasco, Superintendent
Seattle City Light Conservation | Tip of the Day

Tip 26 - Here's Looking Through You, Kid
The amount of energy that escapes through American windows every winter is the equivalent of all the oil that flows through the Alaska pipeline each year. Much of the country's energy goes right out the window.
  • Twelve times as much heat escapes from your house through a single-pane window as through a typical wall.
  • Even during a mild winter, you can lose as much energy through one single-pane window as a 75-watt light bulbs uses running seven hours a day, 365 days a year.
  • A double-pane window retains twice as much heat as a single-pane window.
  • New window coatings (thin films that are sprayed or baked on the windows during the manufacturing process) have been developed that reflect heat back into the house but let the sunlight through easily, cutting energy losses through windows to one-sixth of what they'd be without the coating.
  • Install storm windows.
    • If you feel thrifty and don't mind plastic on your windows, you can make effective storm windows by tacking clear polyethylene plastic over the outside of windows.
    • Glass storm windows are more expensive but they will save some energy and increase your comfort. Some types are attached in the fall and removed in the spring; others can stay on year round and open or close like regular windows.
  • Install new windows.
    • Double-pane windows are now available either with an insulating air space between the two panes or filled with a gas such as argon. In climates with colder winters, these can save considerabale energy.
    • "Low-e" windows are more expensive but provide even greater efficiency.
    • Frames are important. Standard aluminum frames leak twice as much heat around the edges of the glass as do the best wooden frames. If you must have aluminum frames, make sure there are thermal breaks, rubber gaskets between inner and outer pieces.
  • Getting reflective:
    • Window films stick on the inside of windows to block out some of the sun's rays in summer and can be applied easily to existing windows. They block the winter sun as well, so they make the most sense in areas where summer cooling is a bigger concern than winter heating.
    • A wide variety of other products are available to bounce those incoming sunbeams back to the sky. There are reflective screens, essentially a mirror surface with holes in it for visibility. There are louvered screens, like venetian blinds, whose slant intercepts much of the sun but little of the view. And there are fiberglass screens, which are like regular bug screens, but thicker and whiter, to reflect the sun.
    If only 100,000 homeowners installed one storm window, they would save some 50 million cubic feet of natural gas every year and they'd keep more than 6 million pounds of carbon dioxide out of the air. If one percent of U.S. households installed three storm windows, it would save one Exxon Valdez full of oil every year.

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