Outdated windows can lead to a ton of problems for a homeowner. Air leaks increase the cost of heating and cooling and light can be lost through old, dingy glass. Replacing these costly old fixtures could actually pay for itself with savings from the cost of your utilities. That being said, most people don't know the first thing about windows. In order to make sure you're making the best choice for the money, the answer may be in the Energy Star Program.
The United States Department of Energy and the United States Environmental Protection Agency designed the Energy Star program to decrease American ecological impact and enable the average American to save money on utilities. Glass products such as skylights and windows are all given a rating in five categories by a third party before being sold to the public. By learning how to read these ratings, you can be sure you're making the best investment when replacing old windows and glass.
The U-factor is basically an overall rating of the window's insulation. U-factors vary but generally range from .25 to 1.25 and are measured in Btu/h·ft2·°F. The lower the rating given here, the better the unit insulates.
Solar Heat Gain Coefficient (SGHC)
The solar heat gain coefficient calculates how much solar energy passes through a window to determine how well the glass blocks heat caused by solar gain. SGHC is always measured on a scale of 0 to 1 and ratings typically will range from .25 to .8. A smaller rating here means less solar heat will be transmitted and a higher one means more.
Visible Transmittance (VT)
Visible transmittance measures the amount of visible light that can actually pass through the window. Vt is also rated on a scale of 0 to 1, and values generally range from .2 to .8. The higher the VT rating, the brighter the sunlight passing through.
Condensation resistance tests how well the product resists water build-up. Always scored between 0 and 100, the higher the resistance factor, the lower the amount of condensation.
Air Leakage (AL)
Air Leakage is exactly what it sounds like. This number is a rating of how much air can pass through the joints in the product. AL is measured by volume, calculating the amount of air in cubic feet which passes through one square foot of window area in a single minute. The lower the number here, the less air is lost. Industry standards and most building codes require at most an AL rating of .3 cf·m/ft2.
With a better understanding of these ratings, you can be sure that you're getting the full picture of your new windows before you buy them. Whether you choose to install your windows yourself or have them installed by a professional, you'll be able to upgrade your home with secure knowledge that you're making the best investment. Contact a company like Alabama Glass Works Inc for more information.