Windows shape how a home feels. They bring in the light and the view, and they decide how warm the rooms are in January and how hot they get in August. In a new Vancouver house or multiplex, the window order is a large one, and every supplier's quote is full of numbers. In this post, we walk you through the three numbers that matter on a window label, what the ENERGY STAR label in Canada requires, and how to use those numbers to compare quotes and place windows around your home.
Every figure below comes from Natural Resources Canada's ENERGY STAR technical specification for windows, doors and skylights, Version 5.0, and its related pages, read on November 4, 2026. The City of Vancouver applies its own Building By-law with its own energy rules, and we did not read those rules for this post. Ask the City, or your designer and energy advisor, what your project must meet.
NRCan's specification defines each number, and each one changes how a room feels.
The U-factor measures how much heat passes through the whole window, frame and glass together, for each square metre and each degree of difference between inside and outside. It is written in W/m²·K in Canada, and sometimes in Btu/h·ft²·°F. The specification gives the conversion: multiply the Btu number by 5.678263 to get the metric number.
A lower U-factor means less heat lost. On a cold, wet January evening in Vancouver, a window with a low U-factor keeps the room warmer and the glass surface warmer to the touch.
The solar heat gain coefficient, or SHGC, is the share of the sun's heat striking the window that enters the room. It is a number between 0 and 1. A higher SHGC lets in more of the sun's heat.
This number works both ways. In winter, sun through a south window is free heat. On a summer afternoon, the same glass on a west wall can make a bedroom hard to sleep in.
Air leakage is the flow of air through the window itself, in litres per second per square metre. NRCan measures it both ways, air coming in and air going out. A leaky window brings in drafts and loses heat.
Canada also uses a fourth number, the Energy Rating (ER). NRCan describes it as a value that balances heat loss through the window, heat loss through air leakage and the possible heat gain from the sun. It applies to windows installed upright in low-rise homes.
The specification gives the formula:
ER = (57.76 × SHGC) − (21.90 × U-factor) − (1.97 × air leakage) + 40
The U-factor is in W/m²·K and the air leakage is the average of the in and out measurements at a set test pressure. In plain words, more solar gain raises the rating, and more heat loss and more air leakage lower it. A higher ER is better.
These two windows are examples we made up to show how the formula works. They are not real products.
- Window A: U-factor 1.20, SHGC 0.30, air leakage 1.0. Its ER is 57.76 × 0.30 − 21.90 × 1.20 − 1.97 × 1.0 + 40 = 17.33 − 26.28 − 1.97 + 40 = 29.
- Window B: U-factor 1.40, SHGC 0.50, air leakage 0.5. Its ER is 28.88 − 30.66 − 0.99 + 40 = 37.
Window A loses less heat through the glass. Window B lets in more of the sun's heat and leaks less air, so it scores higher on the Energy Rating. Which one is better depends on where it goes in your home.
NRCan's Version 5.0 specification has been in effect since January 1, 2020. To be ENERGY STAR certified in Canada, a product must meet these limits:
- Windows and doors: a U-factor of 1.22 W/m²·K (0.21 Btu/h·ft²·°F) or lower, or an Energy Rating of 34 or higher.
- Skylights: a U-factor of 2.29 W/m²·K (0.40 Btu/h·ft²·°F) or lower.
- Air leakage: for every product, infiltration and exfiltration of 1.5 L/s/m² or less.
Under these limits, Window A in our example meets the U-factor path (1.20 is under 1.22), and Window B meets the Energy Rating path (37 is over 34). Both could carry the label.
The specification also says products must be certified by an organization accredited by the Standards Council of Canada, or by the US National Fenestration Rating Council, and that each model must be registered with NRCan. Each product must have installation instructions available online or in the box. Products assembled on site are excluded.
NRCan also gives an ENERGY STAR Most Efficient designation to the best performing windows and sliding glass doors. For 2025, a product needed a U-factor of 1.05 W/m²·K or lower, or an Energy Rating of 40 or higher, and the designation ran from January 1 to December 31, 2025. Check NRCan's site for the criteria that apply in the year you order.
On October 15, 2026, NRCan posted a notice that Environment and Climate Change Canada is preparing a draft Version 6.0 of the specification for windows, doors and skylights, planned to take effect on January 1, 2029. A home designed in 2026 and built in 2027 will be ordered under Version 5.0.
The numbers help most when you match them to each wall.
A south window gets the low winter sun. A higher SHGC here can add free heat to a living room in winter. Roof overhangs and exterior shading can block the high summer sun.
West windows get the strong afternoon sun in summer. A bedroom or a home office on the west side may stay cooler with a lower SHGC, exterior shading, or smaller windows.
A north window gets little direct sun, so the U-factor does most of the work. A lower U-factor keeps these rooms warmer.
A skylight brings daylight into a stairwell or an inside bathroom that has no outside wall. NRCan's limit for a skylight is a U-factor of 2.29, higher than the 1.22 for a window, and the Energy Rating path does not apply to skylights. Ask for the skylight's own numbers, and plan blinds or shading for a skylight over a bedroom.
In a multigenerational home, the people on each floor use their rooms at different times. A grandparent's ground floor suite may be in use all day, while the children's bedrooms upstairs matter most at night. Talk through each room's daily use with your designer, so the windows suit the people who live behind them. Our post on three-generation multiplex design covers the floor plans.
Ask for All Three Numbers. For each window type in the quote, ask for the U-factor, the SHGC and the air leakage, plus the Energy Rating. A label that shows only "ENERGY STAR" tells you it met one of the two paths, and the numbers tell you which.
Compare the Same Unit. Make sure every quote states U-factor in the same unit. A number in Btu/h·ft²·°F looks smaller than the same window in W/m²·K.
Check the Registration. NRCan keeps a searchable list of ENERGY STAR certified windows and sliding glass doors. Look up the model in the quote.
Read the Installation Instructions. The specification requires them to be available online or in the box. A window performs to its label only when it is installed the way the maker intended, with the air and water seals done right. In Vancouver's wet season, the water seal around each window keeps rain out of the wall. Our post on building through Vancouver's wet season covers how we protect openings during construction.
Match the Energy Plan. If your project follows an energy target, your energy advisor will model the windows with the rest of the house. Give them the real numbers from the quote before you sign. Our post on the BC Energy Step Code explains how energy targets work for new homes.
Costar's process page lists ordering windows and doors in the construction stage, alongside framing and sheathing, while the client reviews details such as flooring, cabinets and lighting. Our team works with your designer or architect from the first drawings, so the window sizes, the numbers on the quote and the energy plan agree before the order goes in.
If you are planning a new house or multiplex and want to talk through your windows, our team is happy to help. Tell us about your project today. Book a consultation.
Related on this site: Custom home construction in Vancouver · Multiplex construction in Vancouver · Book a one-hour project consultation
