Building Envelope


Heat gained or lost through inefficient windows can increase the energy used to heat and cool your home by 25 to 30 per cent.

Energy-efficient windows have:

  • special coatings (known as low emissivity coatings, or “low-E glass”) and insulated frames and sashes which will reduce the cold transfer from outside and condensation on the glass.
  • more glazing (panes of glass) for better exterior noise reduction and even more energy savings.
  • special inert gases between the glass panes rather than just air for better insulation.
  • a label on the product to indicate where the model is certified for use in Canada.

What to Look For

  • A low U-value. The U-value is a measure of the window’s insulation value. Look for windows in the range of 0.25 to 1.25, with 0.25 being the best.
  • Buy windows certified for installation in Canada. In Canada, all windows should be at least double-glazed – two panes of glass.
  • Windows with more glazing (panes of glass) and low-E glass are the most efficient.
  • Hinged windows (casements, awnings, hoppers, tilt-turns) are more air-tight than sliders.

Things to Consider

  • Purchase ENERGY STAR®certified windows.
  • Windows that don’t open are more energy-efficient, but floors with bedrooms require at least one window that opens for an emergency exit.
  • The window frame affects a window’s insulation value, strength, maintenance and longevity. Wood and fibreglass frames are the most efficient.
  • Hire trained installers to ensure your windows and skylights will perform their best.
  • Window and supplier warranties vary. Compare before you purchase.
  • Consider installing high insulation value windows on the east and north sides of your house to reduce heat loss.
  • Consider getting a home evaluation to help you understand how your home uses energy and identify all improvement opportunities.
  • Check with your municipality, utility or retailer to see if rebates are available.


$300 to $700+ per window, plus installation.

Source: Natural Resources Canada