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Window Insulation Ideas to Reduce Energy Costs

The windows in your home may be your home's biggest energy waster. In the summer, sunlight pours in and heats your home. In the winter, your heat can quickly find its way outdoors through poorly insulated windows.

Windows not only waste energy through heat transfer through the glass, but air infiltration around the window sash and the space between the wall and the window frame.

Many modern windows are made with two or more glass panes with an insulating gas sandwiched between them. Single paned windows have an R-value of about 1. Dual glass panes roughly double the insulating value. Windows with low-e coatings and argon gas can reach an R-value of 4.4. While that is still less than half of the insulation value in most walls, it quadruples the insulating value over single pane windows. If you consider that windows can account for 50% of heat loss in the winter and 75% of heat gain in the summer, those few points can make a big difference in your heating and cooling costs.

Replacing windows is expensive, but the payback in energy savings can make it a net savings in two to ten years. In other words, you will potentially save more than what you spend in as little as two years. Naturally, there are a variety of factors such as where you live, the windows you choose and your energy costs, that will affect how long it takes for new windows to pay for themselves.

Not ready to replace windows? There are several things you can do to improve your window's efficiency, and some of these tips apply to new energy efficient windows too.

When your home was built, the framing went up and big holes were left open for windows to be fitted into. Those holes were made larger than the window so that the window could be properly installed. However, this means there are gaps all around the window frame that allow air infiltration. You should fill these gaps to reduce air infiltration. You can use fiberglass insulation or expanding insulating foam amongst others. These two are both easy and fairly inexpensive.

To insulate around the window frame, remove the interior moulding surrounding the window frame. This will expose the openings around the window frame. If you use fiberglass, fill all the open space, but do not pack it in tightly. The air pockets in fiberglas create the insulating barrier. Compressing fiberglass eliminates those air pockets. If you use expanding foam, follow the manufacturers instructions, but in general you point the extension nozzle into the crevice and fill the area while pulling the nozzle toward you and repeating all the way around the window frame. After you are done, simply replace the moulding.

Outside your home, the exterior moulding around the window should be sealed with caulk to prevent moisture damage. This also helps to reduce air flow. Use paintable exterior grade caulk. Clean dirt, debris and loose paint from around the moulding. Run a 1/8" bead of caulk around the top and sides of the window frame moulding. Some builders believe the bottom moulding should not be caulked across the bottom to allow drainage of any moisture that does accumulate.

Weather stripping is another improvement you can make with your windows. Older windows and wooden windows often do not seal very tightly. Adding weather stripping along the edge or bottom of the sash where it meets the window sill and the gap where two sashes meet is a good way to reduce air infiltration.

In cold weather climates, installing a plastic film and sealing the edges with tape is an effective way to reduce heat loss and drafts. Storm windows are another effective tool.

In any climate, the use of draperies and shades to either admit or reflect sun during the day and to block thermal transfer at night can also help to reduce your energy bills. Choose draperies that are heavy or lined and shades that fit tightly within in the window.

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