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Energy Efficiency

Energy Efficient House

Energy-efficient windows and doors from Carter Lumber keep your home cool in summer months, warm in winter months and help maintain appropriate moisture control. Quality windows and doors can:

Increase energy cost savings
Minimize heat loss and air leakage
Improve comfort
Minimize condensation

Low-E Glass

Low-E glass provides the best year-round performance and lowers energy costs by at least 13 percent (based on savings over clear glass). It features transparent, microscopic layers of silver placed between layers of anti-reflective metal oxide coatings.

In Warm Weather
These coatings block 83 percent of harmful UV rays and 96 percent of the sun's infrared heat, so homes stay cooler in the summer and interior furnishings fade less.

In Cold Weather
In the winter, Low-E glass helps keep homes warmer for improved comfort and reduced condensation.

Rating Energy Efficiency

Most manufacturers rate the energy efficiency of windows in terms of their U-values (the rate of heat loss from your home through the window), R-values (resistance to heat flow) and the Solar Heat Gain Coefficient (how much heat your house gains from the sun as a result of the window's performance). A NFRC (National Fenestration Rating Council) label provides window energy properties for product comparison.

U-Factor: U-factor measures how well a product prevents heat from escaping. The rate of heat loss is indicated in terms of the U-factor (U-value) of a window assembly. U-factor ratings generally fall between 0.20 and 1.20. The lower the U-value, the greater a window's resistance to heat flow and the better its insulating value.

Visible Transmittance: Visible Transmittance (VT) measures how much light comes through a product. VT is expressed as a number between 0 and 1. The higher the VT, the more light is transmitted.

R-Value: The R-value indicates a window's insulating value. If the R-value is high, it will lose less heat than one with a lower R-value. The higher the R-value, the greater the insulating value. Make sure the R-value is calculated for the entire window, including the frame, and not just for the center of the glass.

Air Leakage: Air Leakage (AL) is indicated by an air leakage rating. Heat loss and gain occur through cracks in the window assembly. The lower the AL, the less air will pass through cracks in the window assembly.

Solar Heat Gain Coefficient: Solar Heat Gain Coefficient (SHGC) measures how well a product blocks heat caused by sunlight. SHGC is expressed as a number between 0 and 1. The lower a window's solar heat gain coefficient, the less solar heat it transmits.