energy rating
Window and Door

Window Efficiency Factors

Although doors and windows do not consume energy, they may be a significant source of energy loss. If you consider energy efficiency when purchasing windows, ER will assist you in comparing standardized window products.

Energy Star Certified Products

Energy Star certified products are tested by authorized neutral organizations using standardized procedures to meet strict efficiency standards, making it easier to compare similar products from different companies. Considering energy efficiency, Energy Star certified windows can save you energy costs and help reduce carbon emissions together.

According to data from the Natural Resource Canada (August 2017), Energy Star certified windows can save an average of 8% in energy costs compared to standard windows. Windows that meet the Energy Star’s most efficient window standards are 40% more efficient than standard windows.

The Energy Star certification (CSA A440.2 Standard) process measures 3 variables that are applied to a formula that calculates a windows Energy Rating (ER):

The Energy Star Certification (CSA A440.2 standard) process measures three variables that are applied to the formula for calculating the Windows Energy Rating (ER):

  1. U-factor (UF) – measure of the rate of heat loss. The lower the number, the slower the heat loss. 
  2. Solar heat gain coefficient (SHGC) – heat transmitted and absorbed and subsequently released inward
  3. Air leakage (AL) – cold air hot air moving through the window or door

These variables are used to calculate Energy Star’s Energy Rating (ER) – a value representing the overall energy efficiency performance of the tested doors and windows. The ER 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

Want to window comparisons? Take a look at Energy Star’s most efficient window products.

Summary on window selection:

  • Select window with lower U-Factor (lower heat loss)
  • Select window with larger ER rating (the more energy-efficient)

Do you want to replace the most energy-efficient windows? Please consult vertex Window. We will help you find the best fit window to maximize your home comfort, and minimize energy costs.

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