Cold, drafty windows have been plaguing Canadians for decades. Not only do they make your home uncomfortable, but they also cost you money. In fact, windows can account for up to 25% of the total heat loss in your home. That’s a lot of heat—and a lot of cash!
The good news is that window glass technology has come a long way. Keep reading to learn more about the most common ways to make your windows more efficient, and your home more comfortable.
First, let’s explore the basic composition of the glass in your windows. A double pane window consists of two pieces of glass that are separated by a spacer. This creates an air gap between the panes, which acts as an insulator. This type of glass is often called a sealed unit or insulated glass.
Triple pane windows are basically the same, except for the addition of a third pane of glass and a second spacer. This creates a second air gap which makes the triple pane sealed unit an even better insulator.
Air vs. Gas
To further increase the efficiency of the sealed unit, air is often replaced with gases such as argon or krypton. Argon is an inert, slow-moving gas that is denser than air. These properties increase its thermal performance, making it a better insulator than air. Argon is quite affordable, usually increasing the cost of the window by only 3 or 4 percent.
Krypton is even denser than argon and therefore does a great job of preventing heat loss. Unfortunately, it’s also much more expensive and typically increases the cost of the window by as much as 10 to 15 percent. Due to its high price tag, krypton is usually only used in extremely cold climates where energy efficiency becomes even more important.
Traditionally, a metal spacer was used to separate the panes in a sealed unit. Although metal spacers are strong and long-lasting, they are also excellent conductors—and therefore, they negatively affect the insulating properties of a window. To make matters worse, metal spacers also tend to have an inferior seal compared to warm-edge spacers. Having a reliable seal is crucial since it will keep the argon or krypton gas from leaking out, and prevents condensation from entering the sealed unit.
Warm-edge spacers are usually made from rubber or structural foam, and can be filled with desiccant materials. This helps create a better seal, and can be as much as 950 times less conductive than traditional aluminum spacers.
Low Emissivity (Low-E)
Emissivity is a measure of how much a glass surface transfers radiant heat. It’s important that your windows let light in but keep radiant heat out. Low-E coatings can be applied to the glass in your windows to help prevent your house from turning into a sauna in the summer, as well as heat from escaping in the winter. Typically, a Low-E coating is applied to only one pane of glass, but it can be applied to multiple panes within the sealed unit for increased performance. Low-E coatings are relatively affordable and usually only increase the cost of the window by about 7 or 8 percent.
It’s pretty easy to see the benefit in having three panes of glass in a sealed unit rather than two. The addition of a third pane creates a second air space which significantly increases the insulating properties of the window, especially if it’s filled with argon or krypton. It also gives you another surface on which you can add additional Low-E coatings. All these efficiencies can translate into a window with an R-value around 4 to 6, a significant increase from double pane windows which usually rate between 2 and 4.
When Triple glazing first hit the residential market it was expensive, often costing as much as 40% more than traditional double pane windows. Fortunately, the cost has dropped dramatically over the years. Upgrading from double pane to triple now only costs about 12 to 15 percent more, a much easier pill to swallow.
Windows will always be one of the weakest links when it comes to your home’s energy efficiency but as technology advances and as prices continue to drop it’s getting easier to choose warmer, high quality windows. Make sure you consider all the options when replacing your windows so that you can enjoy the view not the weather.