Monthly Archives: April 2019

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

PM Windows and Doors Kitchener Waterloo is your top choice for replacement windows and replacement doors.

What is the Purpose of Low-E Glass?

The quality of a window’s glass is of utmost importance. These days homeowners are obsessed with window replacement & upgrade since studies show the positive influence quality windows have on energy efficiency and home functionality. If you have an old wooden window with single pane glass and without Low-E coatings, you don’t have a properly insulated home, resulting in higher electrical bills, higher UV damage and significantly reduced comfort.

What is Low-E?

Window glass has the main role in heat transfer between your interior and the outside environment. Glass absorbs heat and reflects as little as possible. This results in disruption of ideal temperatures on the inside. To solve this problem, experts invented Low-E which stands for low-emissivity. This is a coating applied to the window glass. Its main role is to catch solar heat from the outside and reflect it, not letting it enter the home. Low-E reflects interior heat on the inside as well, keeping temperature forces separated and with minimum interaction.

With having Low-E glass, you maintain ideal temperatures at home, increasing efficiency and reducing the need for additional heating and cooling systems. The best Low-E windows retain heat, but also provide a comfortable amount of natural light on the inside.

Types of Low-E

There are 2 main types of Low-E glass: hard coat and soft coat. Each is applicable in different environments. For instance, hard coat works best for extremely cold climates since it lets some radiation pass through and heats up the house. The soft coat is recommended for hot or hot-to-cold climates, providing maximum UV protection and heat retention. The first one is also known as passive, while the second as solar control.

  • Hard-coat: A pyrolytic coating applied to the glass ribbon, fused with a glass surface. The manufacturing process creates a highly durable and strong connection.
  • Soft-coat: MSDV means magnetron sputtering vapor deposition. It is the process of creating soft-coat low-e. The coating is applied to the glass before it is cut. This Low-e is more solar efficient than hard-coat.

Additional Ratings

When choosing a window, one must not focus only on Low-E since its functionality depends on other values and glass characteristics. Here are some of the glass efficiency ratings you should know:

  • SHGC: When looking for Low-E glass, you should also mind SHGC. It is an acronym for solar heat gain coefficient and it represents the amount of solar radiation a window lets pass through. Higher numbers are better for homes facing North since they need maximum heat gain, while low numbers are those enabling minimum transmission of solar heat.
  • VT: This rating represents visual transmittance. It is expressed in percentage and the higher numbers, the more visible light entering a home. Usually, when purchasing Low-E, you will find that most of them have low VT ratings.
  • U-value: This rating stands for resistance to heat loss. If the value is lower, your home will be warmer in the winter and cooler in the summer.
  • R-value: Unlike U-value, R-value needs to be as high as possible to keep a healthy living environment. It stands for the ability to absorb and retain heat.

About PM Windows

PM Windows and Doors Kitchener Waterloo is your top choice for replacement windows and replacement doors.