Energy-Efficient Windows near you

Each part of the window affects how much heat gets through. Natural Resources Canada's guide to upgrading windows describes the main levers: extra panes, low-e coatings, an inert gas such as argon or krypton between the panes and spacers with thermal breaks at the edge of the glass. It notes that triple-glazed windows can have U-factors as low as 0.8 W/m²·K.

ENERGY STAR is the simplest filter. Under version 5.0 of Natural Resources Canada's specification, a certified window must have a U-factor of 1.22 W/m²·K or lower, or an Energy Rating of 34 or higher, and meet an air leakage limit. NRCan says certified windows are about 20% more energy efficient than the average window.

Within that group, NRCan recognizes ENERGY STAR Most Efficient windows and sliding glass doors as the best performers among certified models and lists them in its searchable product list. Look up the exact model and configuration on your quote, since the ratings depend on the glass and frame options chosen.

Certified windows carry ratings calculated for the whole product, glass and frame together. Keep in mind which direction is better for each: a lower U-factor means less heat escapes, a higher ER means better overall performance once heat loss, solar gain and air leakage are balanced, and the solar heat gain coefficient and visible transmittance show how much of the sun's heat and light pass through.

Condensation forms when moist indoor air meets a surface that is cold enough. A better-insulated window keeps its inner pane and edges warmer, so it can handle more humidity before water appears. Natural Resources Canada says ENERGY STAR certified windows have less condensation than ordinary models, pointing to triple glazing, low-e coatings, inert gas fills and thermally improved spacers.

Efficient windows don't cancel out a humidity problem, though. NRCan's window guide warns that tighter new windows can raise indoor humidity because the old leaky ones were letting moist air out, so ventilation has to keep up. NRCan also notes that condensation may form on the outside surface of high-performance glass around sunrise.

Sunlight through a window is free heat in winter and unwanted heat in summer. Natural Resources Canada's rule of thumb is that a solar heat gain coefficient between 0.3 and 0.4 is optimal for new homes and homes substantially renovated for energy efficiency in Canada. It suggests a higher SHGC, above 0.4, in homes built before 1980 or not well insulated and air-sealed, in mainly sunny areas with a short cooling season and mild summers, and in homes designed for passive solar heating.

In Quebec, the Government of Québec's Rénoclimat program was still accepting new applications when this page was reviewed, and it includes financial assistance for replacing doors and windows with ENERGY STAR certified models. The order matters: you need a pre-retrofit energy evaluation before starting and a post-retrofit evaluation once the work is done, and your home's EnerGuide rating must improve to qualify. Keep the invoices and the ENERGY STAR labels from the new windows.

Elsewhere in Canada, programs are run by provinces, utilities and some municipalities, and their conditions change often. Natural Resources Canada's directory of energy efficiency programs shows what is available where you live. Whatever the program, confirm the eligibility rules and any evaluation it requires before you sign, because work started too soon may not count.

Windows are only one part of the building envelope, and not always the part losing the most heat. An EnerGuide home evaluation, carried out by an energy advisor, rates the home's energy performance, usually includes an airtightness test and produces a list of recommended upgrades, so you can see where windows rank against attic insulation, air sealing or the heating system.

The evaluation also helps sequence the work. Replacing windows at the same time as the siding, for example, allows the joint between window and wall to be sealed properly, and a tighter house may need its ventilation reviewed so condensation doesn't simply move from the old windows to the new ones. In Quebec, the same evaluation is the entry point to Rénoclimat.