Centra Estimator Robin Buie from Langley, BC talks about the major difference Low-E glass and argon gas make in the insulation value of windows.
Many people ask me if they really need high performance windows. The quick answer is yes! If you are replacing your windows you need Low-E glass with argon gas, along with vinyl frames. This increases the insulating value of a double-glazed window by over 100%!
Emissivity in Glass
So what is Low-E glass? The ‘E’ stands for emissivity (to radiate energy). There are two main ways heat is radiated at the home: the first is by the sun, and the second is by your furnace or heat pump. In the summer, your home gets warm because the heat from the sun radiates through the windows, and in the winter, as we use the furnace to heat the home, we are losing the expensive heat that it is creating through the windows, which are essentially holes in the walls of your home. With inefficient single-glazed or basic aluminum or wood double-glazed windows, the heat loss is enormous. Low-E glass reflects heat from the sun while letting the visible light enter the home. This keeps heat out of the home during the summer and in the home during the winter months.
There are two different types of Low-E coatings: passive Low-E coatings and solar control Low-E coatings; they are more commonly called “soft coat” and “hard coat” glass. Soft coat glass has a coating of zinc and silver that is sprayed on the glass after the glass is made. Hard coat glass has zinc and silver added to the glass while it is in the manufacturing stage. This is the same kind of technology used to make one-way mirrors, but results in a thinner coating.
Convection in Glass
Convection is another way heat moves through windows. We may think of the air between the panes of glass as “dead” air, but in fact, it is not. In between the two panes of glass in a double-glazed window, air rises against the inside, warmer pane and falls at the top when it hits the outside, cooler pane. This process, called convection, “pumps” heat to the outside. Argon gas slows this method of heat loss. When it is cold outside and the warm heat created by our furnace or heat pump rubs against the interior surface of our windows, the warm air cools and becomes denser causing it to drop towards the floor. More warm air will then try to take its place at the glass surface again. This is typically known as a cold draft. Rather than the cold from the outside coming in, the heat is actually moving away from you. To eliminate convection in windows we will replace the air in the chamber of the window with argon gas, which is much heavier than “regular” air. Argon gas is an inert gas and will not move in the cavity of the sealed unit, eliminating the convection process.
What’s the difference between R-value and U-value?
R-VALUE
R-Value is a rating given in construction to indicate how well a material insulates. The higher the number, the more insulation you are getting and the more money you are saving in energy costs. Please be aware that a lot of window companies will say they have an R-Value of 25 on one component (say, just the frame of their window). However, you need to be sure to get the value of the window as an entire unit, which is realistically between 2 and 4.
U-VALUE
U-Value is similar to R-Value, but there are two major differences. First, the U-Value rates an entire window or door unit, whereas the R-Value only measures specific materials. Second, the lower the U-Value, the more energy efficient your home will be (as compared to the higher R-Value being more energy efficient). This difference in scale exists because R-Value rates how much heat is retained, whereas U-Value rates how much heat is lost.
If you would like to reduce your energy bills each month, there are many solutions that can reduce heat loss. The added bonuses are that new vinyl windows will increase the value and curb appeal of your home, and greatly reduce the heat from the summer sun! Call me at 778-549-9117 or email me at rbuie@centra.ca for a no-obligation consultation.
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