Updates to Energy Star Windows Guidelines for Canadian HomeownersIf you are a homeowner in Oakville, chances are you know about Energy Star windows. Most likely, you have invested in energy-efficient Energy Star certified windows for your home in order to keep your heating and cooling costs to a minimum. 

Recently, some changes have been made to the standards for Energy Efficient windows, which will affect Oakville area homeowners. In the following article, we shall discuss these changes from Energy Star and the impact they will have on Oakville windows and doors.

Changes to Energy Star Windows 

In order for windows to be certified as Energy Star Windows Canada, they must adhere to at least one of three climate zones, or energy efficiency levels. When purchasing new windows for your Oakville home, you will want to make sure to purchase the right windows for your climate zone.

Following are the standards for climate zones. They can be determined by a formula that configures the average daily temperature for any day that falls below 18°C calculated with the quantitative HDD value (heating-degree day). This means the colder the area in which you live, the higher the HDD value.

Zone 1: 3499 HDDs and below

Zone 2: Between 3501 and 5999 HDDs

Zone 3: 6000 HDDs and above

In the 1990s, Energy Star set these standards to help consumers choose products that were energy efficient. These products reduced energy costs for homeowners in the United States and were soon adopted by both the European Union and Canada. Most Canadian companies label the products that have been identified as Energy Star Certified. 

Window companies in Oakville are not only to comply with the standards for Energy Star Windows, but they also must meet those requirements that have been implemented by the NAFS (North American Fenestration Standards). Together these standards guarantee that homeowners can save a great deal of money on their heating and cooling costs while ensuring that their homes are energy efficient. 

Guidelines for Energy Star Windows

The following terms are used to identify Energy Star Windows. Windows companies should have these products labeled accordingly. 

In coherence with the guidelines below, Energy Star Windows must also be certified as airproof and watertight.  

Visible Transmittance (VT)

Visible Transmittance is the amount of visible light that passes through the window pane and is measured from 0-100, with 100 being the maximum level of light. 


The U-Factor determines the process of heat transfer to a cold area from a hot area. The higher the U-factor, the faster the transfer, which makes it more energy efficient. 


The value of the insulation is measured by the R-factor. Thus, the higher the level of insulation, the greater the R-factor.

****Keep in mind that heat gain as a result of natural light does not determine either the U-Factor or the R-Factor.

Solar Heat Gain Coefficient (SHGC)

The Solar Heat Gain Coefficient specifies the amount of solar heat gained via the glass pane. SHGC ranges from 0 to 100.

Energy Rating (ER)

Ranging from 0 to 50, the Energy Rating is an average of the SHGC, U-factor, and airtightness of the window. The higher the rating, the more energy-efficient the window. 

Having insight as to what these terms mean will provide you with the knowledge you need to install the proper Energy Star Windows in your home. To make your windows even more energy-efficient, you should upgrade to triple or double pane windows with Low-E coatings that have been filled with inert gases for added insulation. 

Energy-efficient windows that meet the above criteria will keep your home warm during the bitterly cold nights we are so used to here in Oakville. Moreover, they will prevent heat and humidity from entering your home during the summer, thus keeping it cooler and putting less wear and tear on your HVAC system.

Optima Windows and Doors in Oakville has the largest selection of quality Energy Star Windows. Call us today to set up a time for us to meet with you in your home to provide you with a free assessment and quote for the best energy-efficient windows.

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