Airtight casement windows are the greenest windows.

Cynthia and Eric Wice chose the most airtight option when they installed six new casement-style windows.

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casement windows, energy efficient, Energy Star windows, green homes, replacement windows, windows

Shopping for Replacement Windows

Look for glazing and wood frames when buying the best energy efficient windows.
By Rhea Seymour

When Cynthia Wice and her husband, Eric, moved into their 25-year-old Oakville, Ont., home two years ago, replacing the original single-pane windows topped their reno to-do list. “They were leaking, with water pooling on the frames, and they’d become bowed,” recalls Wice. They noticed an immediate improvement after installing six vinyl tripled-glazed casement windows: the tighter seals keep out the wind and street sounds, like the newspaper slapping the front porch every morning.

Installing new windows can definitely make your home more comfortable, but the impact on heating bills will be modest. Energy-efficient windows reduce a home’s energy costs by just seven to 12 per cent, according to Natural Resources Canada. “Replacing your windows is one of the more expensive things you can do with a lower return on investment,” says Vancouver’s Chris Higgins, program leader for LEED Canada for Homes at Canada Green Building Council. “It’s worth doing, but there are other things worth doing first, such as installing better insulation. Thirty dollars’ worth of blown-in cellulose in your walls has a higher R-value and would reap the same benefits as a $1,000 window.” Find out how to improve your windows without replacing them.

Energy Efficient Windows Checklist

The energy you might save varies: replacing, say, nine single-pane windows with triple-glazed versions will have a bigger impact on heating bills than swapping out one double-glazed window for another. The more inefficient windows you replace, the greater your savings. To maximize efficiency and get the best windows for your budget, here’s what to look for:

☑ Frame material

Since they’re the least expensive, about 90 per cent of windows are vinyl. However, says Higgins, vinyl is the least eco-friendly due to toxic fumes it releases during manufacturing. Aluminum frames are rarely used because the metal conducts heat. Wood windows and fibreglass frames, often found in custom homes, are better choices environmentally but they cost more; a comparable window will run about $250 with a vinyl frame versus $700 in wood or fibreglass. Wood windows need repainting every five to seven years. Fibreglass is lower-maintenance; expect to repaint after 20 to 25 years.

☑ Zone rating

In Canada, Energy Star windows are rated for four climate zones. The mild parts of southern B.C. are considered zone A; southern Ontario and most of Eastern Canada are in zone B; the prairie provinces are zone C; and the three territories, with the coldest temperatures, are zone D. Zone A windows are the least energy efficient, and zone D are the most, says Higgins. “If you put a D window in an A zone, you’ll get greater energy efficiency, and sometimes there is little or no premium cost.”

☑ Glazing

The more glaze, or layers of glass, the better. A double- or triple-glazed window (a few Canadian manufacturers also make quad-glazed) is a sealed unit filled with gas, which has better insulating properties than air, says Higgins. “Argon, the less expensive gas, is almost as good as krypton gas.”

☑ Style

The way a window opens affects the quality of its seal and ability to minimize drafts. Pivoting casement windows come with the tightest seal and highest cost. Single- or double-hung windows are second-best and mid-priced. Sliding windows have the least effective seal and lowest price.

casement window, single-hung, double-hung window, sliding window

☑ Low-e coatings

For about $4 more per window, order glass with low-e (emissive) coating, a thin metal-oxide finish that reflects heat back into your home for warmth. This may pay off in lower heating bills, says Higgins.

☑ Local manufacturers

While most big-box stores sell vinyl windows made in the U.S., it is possible to find windows manufactured in Canada, says Higgins. Check to find Canadian manufacturers of energy-efficient windows.

Window Shopping Checklist

Look for these features to find the greenest windows in your budget.






Wood or fibreglass



Triple- or quad-glazed

Gas fill



Made in


Your province


Single- or double-hung


TIP: For added energy efficiency, install windows designed for a climate zone colder than the one you live in.

See more green home improvement ideas:

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