ENERGY STAR windows have been independently tested and certified to be among the most energy efficient on the market. Major benefits of energy efficient windows are:
• Save money
• Increase comfort
• Cut down noise levels from outside
• Reduce condensation in cold weather than standard products
• allow fewer ultraviolet rays to pass through
For a typical home, choose ENERGY STAR windows and save:
- $126–$465 a year when replacing single-pane windows
- $27–$111 a year over double-pane, clear glass replacement windows
Energy Star Windows can save up to 12% on their energy bills compared to standard products. For windows to become ENERGY STAR certified they must meet technical requirements for both thermal and structural performance. Windows are qualified based on either their U-factor or their Energy Rating.
The U-factor is a measure of the rate of heat loss. The lower the number, the slower the heat loss. The heat transfer per time per area and per degree of temperature difference in BTU (the amount of heat necessary to raise 1Lb of water, 1 degree F. Btu’s are a total amount of heat, not a flow rate)
Energy Rating is a formula that includes the U-factor, air leakage and the benefit of potential solar gain. The higher the value, the higher the potential annual energy savings. Windows and sliding glass doors must also have an air leakage rate of ≤1.65 cubic metres per hour per metre of product opening or ≤1.5 litres per second per square metre of product area.
Also ENERGY STAR qualified products must meet specific energy efficiency levels that have been set for four climate zones (A, B, C and D) in Canada. In addition, all products must be certified by an accredited agency for their energy efficiency. The four climate zones were developed using heating degree-days, a measure of annual average temperature (HDDs). The efficiency levels measure how well a window, door or skylight insulates against the cold or how well it uses the sun’s heat to supplement the home’s or building’s heating system. The four climate zones will be converted to three climate zones as of February 1 2014.