Clad Window Energy Efficiency

October 10, 2010

Heating and cooling can mean expensive monthly bills, and windows can account for 25 percent of that cost. Your options for energy efficient windows include clad windows. Clad windows energy efficiency can be increased by a number of factors.

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How Energy Efficiency Works

The materials your window is made from and the sash style affect the three factors that determine energy efficiency: non-solar heat transmission (the "U factor"), solar heat gain, and airflow. Conduction, convection, and radiation through your window affect the U factor. The sun shining through your window accounts for solar heat gain. Air passing through the open window counts as intentional airflow, and unintentional airflow is called leakage.

Clad Windows Energy Efficiency

Clad windows are a type of window frame material. Typically wood is "clad" with another material such as vinyl or aluminum on the weather-facing side of the window to reduce maintenance. Wood frames have high R-values (they resist heat transmission), but they generally require considerable maintenance to prevent them from rotting and warping, which can cause leakage and decreased energy efficiency. Clad windows energy efficiency may therefore prove better long-term.

The type of glazing in the window will also affect your clad windows energy efficiency. Look for low-emissivity (low-e) glass, and keep in mind that the lowest U factor will be more energy efficient. Also, the lower the air leakage rating on the label, the better. Leakage can also be a product of installation (which isn't included in leakage rating). To maximize your clad windows energy efficiency, consider professional installation.

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