Energy Tips
The sheer volume and misleading nature of window replacement advertising leads people to believe that windows are of utmost importance in conserving energy. Ads promise that installing replacement windows will save you lots of money on heating and cooling. This is typically not the case in New England, where windows account for only about 19 percent of energy costs in the home. The order of priorities for cost-effective, energy-saving improvements should be 1) air-sealing, 2) insulating, and 3) duct-sealing. Once these are done, evaluating window replacement would be appropriate.
If existing windows are in good condition but are leaky, it is often best to seal the windows with caulk and weather-stripping. People often assume that windows leak around the sash. Many do. However, air infiltration testing with a blower door test reveals that windows often leak between the window and the rough opening. Caulking where the inside window casing meets the wall is the easiest way to stop the air movement and conserve energy. If you want to remove the trim or have to remove it for window replacement, filling the gap between the window and the rough opening with low-expansion foam is best. Do not over apply it, as it may adversely affect the window casing.
If you have decided to go the route of window replacement, there are three key items to consider. The first is the frame. It should be wood, vinyl, or wood-clad because these materials conduct less heat than aluminum. The second and third items are the glass or glazing. Without spending a lot more money — probably $30 to $60 per window — it makes sense to get windows that have a Low-E coating and are gas filled. These two items alone will significantly increase the energy savings without a lot of extra cost.
The most important thing to look for when buying new windows is the U-factor, which represents conductive heat loss. The lower the U-factor the better, but as a rule, do not buy windows with a U-factor above 0.35. The most energy-efficient windows are as low as 0.15. More features that contribute to energy efficient windows are a third layer of glass, additional Low-E coatings, and nonmetal air spacers. However, these items may increase cost significantly. The bottom line is buying the best window that you can afford.
However, before you make your windows as air-tight as possible (either by replacement or by sealing), you should air-seal the attic and basement. If you don't, you will be enhancing the stack-effect — cold air enters at the bottom of your house and pushes warm (heated) air out at the top under increased pressure as outside air temperature drops. If you seal the sides of the house (i.e., make them more airtight with replacement windows or by sealing windows), you will have created a better "chimney" through which air will pass. You don't want to do this, so to make sure your basement and attic are not costing you important energy dollars, seal them first.
Tim Gould is director of Energy Egghead, an Amesbury-based company that can be found at www.ENERGYEGGHEAD.COM and provides professional energy audit and conservation services.
