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Take the Energy High Road with Low-E Windows

By The Old House Web

Your archaic single-pane windows should be the first thing to go when you remodel an older home.

Low-E Windows Reflect Harmful Rays, Heat

Single-pane windows were the fare till the early 1970s, when double-pane windows, with inert gas separating the two panes, became common. Within a decade, manufacturers began adding a microscopic layer of a metallic oxide to the glass that served as a barrier to both ultraviolet and infrared light, thus spawning the Low-E window (low emissivity). Ultraviolet light is responsible for much of the damage to fabric and furnishings. Infrared is the source of the heat from light. A surface that you would expect to be uncomfortably hot under a broiling sun can be only slightly warm under a Low-E window.

Today, most municipalities require some version of Low-E windows to meet the U-factor (heat retention) in building codes.

Depending on how the windows are coated, they can keep the heat out of a house in hot climates, or keep the heat inside a house in cold climates. Windows can be formulated to insulate to some degree in both directions for climates where you want some heat protection in the summer, but also insulation from the cold in the winter. Many homeowners typically put "hot-climate" windows on the west (sunny) side of the house, and cooler-climate windows on the rest.

The Efficient Window Collaborative estimates that, with an outside temperature of 20 degrees, the inside of a single-pane window in a heated room should be 30 degrees. At the same external temperature, a high quality double- or triple-pane, Low-E window can have an inside temperature of about 65 degrees.

Low-E Windows: Stop the Window Weap

Besides the comfort factor, the warmer windows mean that you are much less likely to have the Great Lakes of condensation on your windowsill every the morning, as it is the cold glass that causes condensation. The experienced DIYer, should be able to replace the windows himself, at least with an assistant or two. Skillful use of the pry-bar and saws-all should let you pop the old windows out and replace them with a style of your choice without upsetting the siding and interior walls.

Modern Low-E windows can provide significant energy savings. Depending on your climate, you can save as much as 50 percent on heating and cooling costs. And they can be made to match any design, so you needn't worry about disrupting your home's style.

Sources • Efficient Windows Collaborative,
Anatomy of an Energy-Efficient Window • http://www.energystar.gov • Energy Star

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