Energy efficient windows are an important consideration for both new construction and existing homes. Heat gain and heat loss through windows are responsible for 25%–30% of residential heating and cooling energy use.
If you are selecting windows for new construction or to replace existing windows, it’s important to choose the most efficient windows that work best in your climate.
Replace Your Windows and the Selection Process
In addition to choosing the window type, you also need to consider design, energy use and labelling, warranties, and proper installation.
Ensure your windows are covered by ENERGY STAR label when buying new windows. Then review ratings on the energy performance label from the National Fenestration Rating Council (NFRC) to find the most efficient windows for your needs.
NFRC ratings are included on all ENERGY STAR certified windows and provide a reliable way to determine a window’s energy properties and compare products. Learn about energy performance ratings for windows to understand how to read the labels and energy-use information.
In colder climates, consider selecting gas-filled windows with low-e coatings to reduce heat loss. In warmer climates, select windows with coatings to reduce heat gain.
Choose a low U-factor for better thermal resistance in colder climates; the U-factor is the rate at which a window conducts non-solar heat flow.
Look for a low solar heat gain coefficient (SHGC). SHGC is a measure of solar radiation admitted through a window. Low SHGCs reduce heat gain in warm climates.
Select windows with both low U-factors and low SHGCs to maximize energy savings in temperate climates with both cold and hot seasons.
Look for whole-unit U-factors and SHGCs, rather than center-of-glass U-factors and SHGCs. Whole-unit numbers more accurately reflect the energy performance of the entire product.