Guide to Choosing Energy-Efficient Windows

Worker installing energy-efficient windows

Whether you live in a hot or cold climate or a mixture of the two, energy-efficient windows are one of the best ways to reduce heating and cooling costs.

That's because traditional windows allow the sun to heat your home in the summer and allow warmer air to escape through your windows in the winter.

Indeed, Natural Resources Canada estimates that up to 35 percent of all residential heating and cooling is lost through inefficient single or double-paned windows -- and replacing your existing windows with energy-efficient windows may help you save almost 10 percent on your home's energy bills.

Energy Efficiency Factors

Insulated walls and roofs do an excellent job of keeping out the hot air in the summer and the cold air in the winter. Unfortunately, traditional windows are not generally known for their energy efficiency.

If you've ever put a bare hand on a window during a winter cold snap, you know the feeling. It can be perfectly comfortable inside, but the window feels cold to the touch.

If it's hot outside and you've got the climate control set to a comfortable 22 degrees Celsius, your window will likely feel warm or hot to the touch, even if the sun isn't beaming down on it.

That's because all windows, doors, and openings to the outside experience heat loss in one of four ways:

  • When your window’s glass absorbs heat energy, that’s known as radiation.
  • The heat energy that moves through solid materials, such as your window frames, is called conduction.
  • Convection is when heat energy is transferred to the air surrounding or between your windowpanes.
  • When heat energy escapes or enters through a gap in the frame, that's known as air leakage.

Increasing Energy Efficiency in Windows

More than anything else, the type of windows found in your home play a large factor in how much energy is lost.

Sliding windows are generally less efficient than hinged windows.  The same holds for hinged doors which tend to have better seals than those found with most sliding doors.

Window location and window size are also important considerations. Having larger windows may leak energy outside. Which could happen if they face the sun (summer months) or the wind (winter months).

However, an increase in window size can mean an increase in energy savings with new improvements to today’s windows.

Newer window frames made from vinyl or fiberglass are much better at protecting your indoor atmosphere than traditional metal window frames. That’s because these new window frames can be filled with insulating foam or created as one solid piece with no air pockets. Metal window frames, on the other hand, conduct heat much more than other materials, making them less efficient. Their popularity has more to do with building and fire codes than energy efficiency.

Perhaps the most important aspect of energy-efficient windows is glazing, or, the glass used in window installation. Older windows are typically single-paned and lack any coating. Newer, double-paned windows are better, but the gap between the panes must be airtight, which may not be the case for windows that are decades old.

Triple-glazed glass, on the other hand, can be up to 50 percent more efficient than a double-paned product, and if needed a thin layer of polyester film can help save weight when substituted for one of the panes.

Furthermore, low-E glass, which is a metal coating applied directly to the window's surface, can reduce heat loss in both summer and winter by up to 30 percent when used in energy-saving windows.

The space between the glass panes can be filled with inert gas -- so-called IG units -- which typically use argon or krypton to reduce glass heat transfer. Spacer bars that hold each pane can also be made from different materials to increase energy efficiency.

Even those metal grilles that give a stained-glass look have a purpose -- they reduce the surface area and subsequently the amount of heat that enters through the face of the window.


Here in Canada, it's easy to shop for energy-efficient windows.

Just look for the ENERGY STAR® rating, which is the standard mark of high-efficiency windows.

Like in the U.S., all ENERGY STAR® windows are readily marked and meet strict technical specifications for energy performance.

In order to determine what window is going to be the best option for you, consider your geographic location and purchase the right ENERGY STAR® certification to match. If you would like increased performance or if you live at a higher elevation than the surrounding area, purchase windows that are better equipped for colder climates.

If you have any questions about the energy efficiency of your favorite product, just ask your local retailer or contractor what they think are the best energy-efficient windows for you.

The Direct Energy Way

Here at Direct Energy, we're not just a power company in Alberta. We also provide heating and cooling services such as duct cleaning, water heater, and HVAC maintenance, as well as repair services and replacement.

We also sell protection plans for your home's heating and cooling systems, so you won't have to shell out hundreds or thousands of dollars if your HVAC system bites the dust during a heatwave or cold snap -- and plans start at just $21.95 a month.

So, whether it's increasing your home's energy efficiency by maintaining your heating or cooling systems or getting the most out of energy-efficient windows with a renovation project, Direct Energy has the right services and education for today's energy-conscious world.

Visit us online to see how we can help you, and, read our Energy-Efficient Home Series to see what projects are best for your home.