You need new windows. You know the style that you’re interested in. You’ve booked some time to have a few window companies drop by to provide a quote. Now what? How do you decide which windows are right for you?

The rating for energy performance can help you choose the product which will be the most energy efficient for your home and be the best investment over time.

How is the energy performance measured?

In Canada, the energy performance for windows and doors and skylights is tested using the Canadian Standards Association (CSA) A440.2 standard. Performance is measured using the following values:

U-Factor: This is the rate of heat transfer from warm to cold areas - or more simply put; how much heat your window product loses. The lower the U-Factor number, the more efficient your window will be.

Solar Heat Gain Coefficient (SHGC): this is a ratio that shows the amount of UV heat that is passing through your window. In the case of the SHGC, the higher the number, the better. This is because the more heat your window allows in, the less energy you will require to heat up your home.

Energy Rating: ER rating is the composite rating that is used to compare windows. It combines u-Factor rating, SHGC rating and also includes an air leakage / infiltration rating for your window. The ER value is the best measure of the overall performance of your window. The range for most Energy Star approved windows is between 25 and 35 ER points. Once again, the higher the number the better.

Visible Transmittance (VT): This is the ratio of visible light allowed through your window. A higher value means that more light will enter through your window.

Centre-of-glass rating: This energy efficiency number applies only to the glass portion of your window and not the window as a whole.

Why should I focus on ER Value?

Some companies talk only about a window’s U-factor or SHGC. These individual ratings, in and of themselves, don’t tell the whole story. ER value is the only rating standard that combines all important test metrics into one comprehensive score. ER value is a measure of the overall energy efficiency of your window.

In Canada, we have three different zones and each zone has a minimum energy rating requirement. For your windows to be considered efficient in your climate, they will have to meet the minimum energy rating outlined in the chart below. Buying the right windows means cutting your energy usage, which ultimately means lowering your electricity bills, leaving you with more money in your pockets!

A graphic showing the Enery Star Zones across Canada.

Learn about Energy Star Qualified Windows, Doors & Skylights

Canada's colder climate means that space heating accounts for a remarkable 63% of the energy used in the average Canadian home. However, did you know that windows can account for up to 25% of your home’s total heat loss?

  1. Save time: The energy rating allows you to easily compare apples to apples when looking at different window manufacturers product offerings by only considering the top energy performers ( as rated by Energy Star ). Just make sure you compare windows from within the same product category.

  2. Save money: You’ll save money over time by purchasing the windows with the correct minimum energy rating for your climate zone.

  3. Help save the environment: When you reduce the amount of energy by buying energy efficient products, you reduce the amount of greenhouse gas emissions in the atmosphere - thereby reducing your carbon footprint.

  4. Save yourself headaches: With Energy Star you can be sure you are getting a product whose energy use is as claimed, because certified products are tested to meet strict efficiency standards and certified by an independent third party.

ENERGY STAR - “Most Efficient” rated windows

Windows certified to the ENERGY STAR Most Efficient specification are even more efficient—up to 40% more compared to a standard double-pane window!

NRCan has created a high performance category for windows that achieve the highest level of energy efficiency - they designate these windows as ‘Most Efficient’ rated windows which ensures that you’re getting a product that has demonstrated superior energy efficiency performance. Only a very small percentage of windows receive this designation.

Some final considerations:

While the ER Value is a great tool to help you choose replacement windows, a quality installation is just as important as a quality product. Even the best window in the world will have poor energy performance if it isn’t installed properly. Do your due diligence and choose a company with a great track record.

At Nordik, we manufacture, install, and service our products, so you will only ever have to deal with one company; from the initial quote until you sign off on the installation of your new windows!

Finally, make sure you fully understand your warranty - does it cover both the product and installation and does it include any and all service charges that might occur during the life of your windows. The promise of a ‘Lifetime Warranty’ is often not what the name implies.

Nordik WIndows offers a Worry-Free Nordik Warranty - one of the most comprehensive warranties in the industry.


If you need replacement windows, don’t hesitate to contact us to request your free quote , our staff will be able to walk you through any questions you may have!

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