What do Window Energy Ratings Mean?

What do Window Energy Ratings Mean?

Many people have probably told you to only purchase energy rated windows. And those people are right, the safest window for your home is the one with high energy ratings. But what do these rating truly signify? To help you out here is some information:

What are They?

Window energy ratings or WER are basically points that a window gets after it has been tested for efficiency. And as usual, higher points means better quality. The rating is done with specific algorithms for calculating solar heat resistance, air leakage, visual transmittance and so on. After a window has been tested in a special laboratory, it gets a specific amount of points, then it is placed on a scale from G to A (G being the lowest and A the highest). Another important thing you should know about these ratings is that the whole window is tested, not just the glass or the frame, but the window as a complete entity.

The Important Factors

As mentioned before, windows get Energy Ratings based on specific calculations. When a window is up for testing, these 5 things are of utmost importance:

  • U-value: This value signifies the resistance to heat loss. The lower value, the better window since you don’t want the heated air on the inside to exit through your window on a cold winter day.
  • R-value: Unlike U-value, R needs to be higher. This value signifies a window’s ability to absorb and retain heat. The best windows have high R and low U values, providing an amazing atmosphere for saving up on the electrical bills.
  • SHGC: This is an acronym for solar heat gain coefficient or the amount of solar radiation a window transmits. The ratings are from 0 to 1, with lower numbers signifying less transmission. Windows with high SHGC are placed in rooms facing North because there, the amount of natural light is limited and insufficient.
  • VT: Another acronym, but for visual transmittance. Expressed in percentage, VT represents the amount of visible light transmitted through a window. If the percentage is lower, less light will enter your home.
  • Air leakage: The name speaks for itself since Air leakage represents the amount of air leaked through a window. The higher the numbers, the more unwanted air loos through a window.

What about Energy Stars?

If you have heard about Energy Ratings, you have probably also heard about Energy Stars. These are marks given to a product only if it exceeds a certain point limit. For instance, if the window exceeds a score of 5, it gets an Energy Star. This point limitation varies from country to country and while in Canada a window must exceed 6, in the USA only 5. (These numbers are only used as an example, for getting the point across, they aren’t true). Many products can get energy stars, including kettles, water heaters, laptops, and even buildings.

About PM Windows

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