New Home Windows - Energy Efficiency is the way to go
July 25, 2010
When it comes to new home windows, ones that are energy efficient are best.
An average home can lose 30 percent of its heat or air conditioning energy via its windows. However, today's technology makes windows capable of retaining heat in the colder months and blocking heat but capturing light in the hotter months--all the while making your home more comfortable. As a result, energy-efficient windows save you money on your heating, cooling, and lighting energy costs. You can recoup your initial financial outlay for the windows over a period of two to ten years. In some cases, windows are even net energy gainers.
For your new windows to be deemed energy efficient, they must meet your state's performance ratings for U-factor and SHGC (Solar Heat Gain Coefficient). The U-factor, or overall heat transfer coefficient, describes how well a window conducts heat. The SHGC measures the solar energy transmitted through a window. These measurements may differ for one or more areas in a single state due to the climate differences in those regions.
The following performance numbers will help you determine and select what type of glass, frame, coating, and glazing to choose for windows that will perform best in your part of the United States. For example, low-E coatings improve the insulating value of a window, and glazing reduces winter condensation. It is not unusual to find windows off the shelf that block more than 75 percent of ultraviolet energy.
Because a window's frame comprises about 25 percent of the its area, it should be thermally nonconductive. Wood and vinyl tend to perform the best, aluminum not so well.
To achieve the maximum energy benefits possible, window installation must be done well. As part of that window installation, your windows should be properly sealed and flashed to eliminate water and air leaks. The windows themselves should provide a thermal barrier between indoors and outdoors. They should be labeled so any window contractors who service them in the future know what they are dealing with.