What does ENERGY STAR® certified mean for windows and doors?

An ENERGY STAR® certified window or door has been independently tested and proven to meet a published energy performance threshold set by the Government of Canada. A manufacturer cannot declare it on its own.

Certification differs from a general energy efficiency claim in a few ways.

• The performance is measured by a third-party professional rather than estimated by the manufacturer.
• The testing is done by a certification body accredited by the Standards Council of Canada or by the National Fenestration Rating Council.
• Certification applies to a specific model rather than to a company. A manufacturer can sell certified and non-certified products side by side.

Certification also sits above minimum building code, which sets a floor rather than a target. According to Natural Resources Canada, certified windows are about 20% more energy efficient than an average window, and certified doors are about 15% more efficient than an average door.

Certified products also go through post-market verification testing, and a model that fails can lose the label.

What does a window need to meet to earn certification?

A window qualifies by hitting one of two performance targets, plus an air leakage limit it has to pass.

U-factor

U-factor measures how quickly heat escapes through the whole window, frame and glass together. Lower is better. To be certified in Canada, a window needs a U-factor of 1.22 W/m²·K or lower.

Think of it as the leak rate. A low U-factor window holds warm air inside on a February night instead of bleeding it into the yard.

Energy Rating

Energy Rating, usually shortened to ER, is a single whole-window score with no units attached. Higher is better. A window certified in Canada needs an ER of 34 or higher.

The formula balances three things at once, which are heat loss through the window, useful solar heat gained through the glass, and air leakage. A south-facing window that lets in winter sun does work for your heating bill, and the Canadian rating gives credit for it.

A window needs to clear either the U-factor threshold or the ER threshold. It does not need both.

Air leakage

Every certified product has to keep air infiltration and exfiltration at 1.5 L/s/m² or less. Good glass cannot make up for a poor seal. A window with excellent glazing and a leaky frame is still a draft.

What about SHGC and visible transmittance?

Solar Heat Gain Coefficient measures how much of the sun’s heat the glass admits, on a scale from zero to one. Visible transmittance measures how much daylight comes through. Both appear on the label. Neither is a pass or fail number on its own in Canada, though SHGC feeds directly into the ER calculation.

NRCan cautions that windows with an SHGC above 0.45 facing south or west can make a room uncomfortably warm and push up summer cooling costs. Orientation is part of the decision.

How are doors rated differently from windows?

Windows and doors share the same headline thresholds in the Canadian specification. Three practical differences change how the rating works once the product is in your home.

Hinged doors are judged on U-factor

NRCan’s labelling requirements state that the Energy Rating must appear on a certified window, sliding glass door, or skylight, but the ER is not required on a hinged door or sidelite label. A swinging entry door is assessed on its U-factor, with no solar gain credit behind it.

Sliding patio doors are grouped with windows

A patio sliding door carries so much glass that it behaves like a window, and it is rated accordingly. It gets an Energy Rating on its label, the same as the window beside it.

Comparing a sliding door to a hinged garden door means comparing two products measured slightly differently. Check which number you are reading before you put the stickers side by side.

More glass means a harder number to hit

Doors are grouped by how much glazing they carry. The industry categories are opaque with no glass, half-lite or less, and more than half-lite, which covers three-quarter and fully glazed panels.

A solid door rates better for a simple reason. Even the best sealed glass unit, with low-E coating and gas fill, insulates worse than an insulated foam core. A fibreglass door with a small doorlite will reach a low U-factor more easily than the same door with full glass, two sidelites, and a transom above it.

None of that is a reason to skip the glass. If you want the light, you can still get a certified door. You just need better glazing to get there, and the number on the label will tell you whether the manufacturer delivered it.

Custom entry systems carry one more wrinkle. Transoms taller than 700 mm are classed as windows rather than door components, so a tall transom is rated on the window side of the standard.

What is ENERGY STAR® Most Efficient?

There is a tier above standard certification. ENERGY STAR^® Most Efficient recognizes the strongest performers on the market each year.

In Canada, a model needs a U-factor of 1.05 W/m²·K or lower, or an ER of 40 or higher. NRCan describes certified windows and sliding glass doors at this level as up to 55% more energy efficient than average models.

How do you read the label on a new window?

The temporary label on a certified window carries the numbers you need. Leave it on until you have checked what it says.

• The ENERGY STAR certification mark, confirming the model is certified in Canada.
• The performance values, meaning U-factor, SHGC, ER, and visible transmittance.
• The manufacturer or brand name.
• The frame type, such as vinyl or vinyl clad wood.
• The operator type, such as double horizontal slider or casement.
• The glazing description, covering the number of panes, the gas fill, the low-E coating and which surface it sits on, and grille details.
• A unique model code or NRCan reference number.
• The test standard used, such as CSA A440.2-19.

Why does any of this matter in an Ontario winter?