Evaluating the Energy Efficiency of Windows

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Lowering heating and air conditioning bills is probably the single largest benefit in replacing your old windows. Consider the following factors in choosing the windows that will provide you with the greatest return on your investment.

What makes windows energy efficient?

Factors such as how the frame and sashes are engineered and build, the type of glass used (single, double or triple pane), the weather stripping, the type of low-emissivity coating on the glass and the presence of argon or krypton gas determine the energy efficiency of windows.

What is Energy Star?

Energy Star is a program created by the U.S. Department of Energy and the U.S. Environmental Protection Agency to help people make smart, long-term choices for their home. The Energy Star rating is only granted to products that reduce energy use. For more information, visit their web site at www.energystar.gov.

What is Low E II Glass?

Low E stands for low emissivity. Low E II glazing is a simple means of minimizing summer heat gain and reducing heat loss in the winter. Think of them as microscopic shutters that allow warming low-angle winter sun into a home while filtering high-angle summer light. At the same time, UV rays are screened to reduce fading and damage to upholstery and carpets.

What is R-Value?

R-Value refers to the ability of a building material to resist heat transfer. The greater the R-Value, the more effective the insulation.

What is U-Value?

U-Value refers to a measurement of heat transfer through a building material. The lower the U-value, the more effective the insulation.

What is UV Light Transmittance?

The UV light transmittance is the percentage of invisible, damaging ultraviolet light that passes through a window, leading to fading of carpets and upholstery. The lower the number, the better. Both low-e coatings and tinted glass help to reduce UV Light Transmittance. Impact-resistance glass virtually eliminates UV rays.