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Windows make our homes bright, cheerful places to live, but they are also responsible for almost 25 per cent of heat loss.

Since the average window lasts 20 years or more, replacing it just to save energy may not add up.

Illustration of a man looking out the window

Draw the curtains in summer heat

In the morning, open windows to let cool air in. Then close them, and draw your blinds, during the day. Your house will hold much of the cool morning air.

Illustration of a window

Fill the gap

Check your windows’ trim for gaps. As much as 13% of your home’s heat and cooling loss could be escaping though them. Stuff insulation between the window and your home’s frame. If that is not possible, caulk around the window.

Illustration of a snowman outside a window

Trap warm air inside

On sunny winter days, open your window coverings to let the warmth of the sun in. Once the sun goes down, close them to keep the warmth in. Think of your curtains as the best way to insulate your windows.

Illustration of a man sealing the window

Build a barrier against cold

An inexpensive option is to seal your windows with plastic sheeting in the winter. All you need is a hair dryer and a staple gun. There is indoor and outdoor sheeting available, so be sure to read the label.

Invest to Improve

If your windows are more than 20 years old, investing in new ones is worth considering.
Not all windows are created equal, so before you start planning, here are some differences to consider.


Call a contractor

For most window projects, you will likely need a reliable contractor, so be sure to get a number of quotes and check references.


More than a window on the world

There are many types of windows. One of the largest innovations in energy-efficient windows is Low-Emissivity or Low-E glass, which prevents heat generated by people and appliances in a room from escaping. The Low-E coating also filters out most of the damaging ultraviolet sunlight, which helps defend your furniture and drapes from fading.

Glass and gas

Some windows are filled with gas. Argon and krypton are used to fill the space between panes. The higher insulating value of these gases improves the efficiency of the window by cutting down on the heat lost through both convection and conduction.

Be Window Wise

You should look for window manufacturers certified by the Siding and Window Dealers Association of Canada’s Window Wise program, which identifies quality energy-efficient windows. Learn more about Window Wise manufacturers.

See Also:
Insulating Your Home

Find out how to further seal in your energy savings with thorough caulking, weather-stripping and insulation

Learn More

Time-of-Use Tips

  • Reducing energy transfer through your windows (heat coming in during summer, going out during winter) is most important during on-peak times. Use your curtains or blinds to help control the temperature in your home.

  • If you have large windows that get a lot of direct sunshine in the summer, you may consider adding adjustable awnings on the outside. It is an old-fashioned idea that works.

Shopping Tips

Replacing or adding windows
  • Take the time to research the selection available to you. Look for the Energy Rating (ER), a rating system developed by the Canadian Standards Association (CSA) together with various energy utilities.
  • The rating takes into account the size of the window, the performance of the glazing, the frame construction, and the spacers.
  • A window’s ER rating is a measure of its overall performance, based on three factors:
    1. Solar heat gains;
    2. Heat loss through frames, spacers and glass; and
    3. Air leakage heat loss.
  • The higher the rating, the more you will save on operating costs. Make sure that the rating is for the whole product, not just the “centre of the glass.”
Purchasing a new window
  • Look for acceptable ER values for your geographical area.
  • The vast majority of Ontario is identified by Zones B and C.
  • Look for an ER value of at least 21 if you live in Zone B, and at least 25 if you are in Zone C.
It is all about the labels
When it is time to buy windows, be sure to look for windows with the Canadian Standards Association (CSA) label. The CSA Certification Program is based on rigorous product testing. The tests include air tightness, water tightness, and wind load resistance.

energuide star Look for the ENERGY STAR® for highest efficiency

The ENERGY STAR program identifies the most energy-efficient windows on the market. There are three climate zones in Ontario.  They are based on heating degree days (HDD), a 30-year averaged annual temperature indicator. 

Illustration image of the map of Ontario and its three climate zones

  • Zone B: 3501–5500 HDDs

  • Zone C: 5501–8000 HDDs

  • Zone D: 8001 HDDs or more

  • The higher HDD value, the colder the location and the longer the heating season.

  • Zone B is the warmest region and Zone D is the coldest region in Ontario.

  • The vast majority of Ontario is in Zone B and C.

 Ask your salesperson for more details to ensure that you are getting the right window for the climate of your geographical area.