Compare Thermopane Windows

Compare Configuration Options

• Fixed Thermopane windows offer the greatest enegry efficiency of all configurations because their air-tight design eliminates air leaks. The major drawback to this design is that the window doesn't open, which prevents homeowners from ventilating the home with fresh air. Awning, casement and hopper windows provide the lowest air leakage of all operable Thermopane designs, while hung or sliding windows have the highest air leakage rates, according to FineHomebuilding.

Review U-Factor

• The U-factor of a window is the inverse of the R-value. While R-value measures the window's resistance to heat flow, U-factor measures how much heat energy passes through the window. It ranges from 0 to 1, and the lower the value, the better the windows are able to keep heat from escaping, or keep unwanted heat from entering the home. Look for the lowest possible U-factor when choosing Thermopane windows to maximize efficiency.

Consider Solar Heat Gain Coefficient

• The solar heat gain coefficient reveals how much solar heat energy enters the home through the windows, and ranges in value from 0 to 1. In cold climate zones, look for Thermopane windows with the highest possible SHGC to take advantage of passive solar energy for home heating. The U.S. Department of Energy recommends a SHGC of 0.6 or higher in cold climates. If you live in a hot climate zone, look for a low SHGC to reduce air conditioning costs.

Evaluate Visual Transmittance

• The visual transmittance of Thermopane windows measures how much visible light passes through the window. The higher the VT value, the more light passes through the unit. A VT of 50 percent or below often is associated with a window that looks dark or reflective, while a VT of 60 percent or greater generally means the window appears clear.

Look for Tax Credits

• The added pane of glass and insulated airspace in Thermopane windows help to improve energy efficiency, which may allow you to quality for tax credits, utility rebates and other financial incentives. For example, Thermopane windows purchased in 2013 qualify for a federal tax credit of up to $200 as long as the windows are certified under the U.S. Department of Energy's Energy Star program. Check for local and state incentives in your area when choosing Thermopane windows to determine which models qualify.