Energy efficient windows have become a standard request of homeowners looking to buy new windows. Natural Resources Canada estimates that if consumers make responsible buying decisions, such as ENERGY STAR rated windows, they can reduce their greenhouse gas emissions by 20%! That means you can reduce your electricity consumption and heating bills by hundreds of dollars every month simply by using energy efficient windows – and live in a more environmentally responsible way.
But what are energy efficient windows? Glass is glass right? There are three things that you need to know when you are considering energy efficient windows (sometimes called ‘thermal windows’).
- Low Emissivity or Low-E coating (also called ‘Low-E glass’)
- Double and triple-glazed windows (with two or three panes of glass)
- ENERGY STAR rating (a rating that evaluates a window’s thermal performance)
These three technologies/aspects are what make windows efficient – and help you find the right windows for your budget.
What is Low-E glass?
Low-E or Low Emissivity refers to a coating on glass that enhances its insulation properties and helps reduce UV rays and infrared rays entering the home. This means your home will be cooler in the summer and warmer during winter.
‘Low-E glass’ refers to glass that has been treated with the Low-E coating. The level of coating and on how many panes you have it applied will affect the overall thermal performance of the window.
One by-product of Low-E glass is that it also reduces the amount of light that enters the home somewhat. For some that means increased privacy; for others it may feel like a reduction in natural light. Speak to an Eco Choice Window and Doors consultant to find the right amount of Low-E coating for your home.
In Canada, there are six values that measure the effectiveness of Low-E glass:
U-Factor – Heat insulation property of the window (higher is better)
Visible light transmittance – How much visible light can pass through the window (higher is better)
Coefficient of solar heat gain – How much heat from sunlight is passed through the window (lower is better)
Light to solar gain – Ratio of solar heat gain and visible light transmittance (higher is better)
Energy Rating – Number showing balance between U-Factor, solar heat gain and air leakage (higher is better)
Centre-of-glass rating – Energy-efficiency value of only the glass, not the product as a whole
Now you know how to compare windows with different Low-E ratings.
Anecdotal reports from homeowners have shown up to a 30% reduction in heating bills in winter time, once energy efficient windows have been retrofitted.
ENERGY STAR windows
ENERGY STAR® is a program developed by the United States’ Environmental Protection Agency. It provides energy ratings for a wide range of products – from appliances to doors and windows. It also means that product complies with certain requirements laid down in the standard.
For a window to be ENERGY STAR rated, it must be certified by an independent laboratory. If you are considering eligibility for home improvement rebates and grants from the government or from your energy company, ENERGY STAR windows are likely to a requirement. Moreover, you will be required to work with a window installer that has been accredited to install ENERGY STAR rated windows, such as Eco Choice Windows and Doors.
Double and triple-glazed windows
Double- and triple-glazing refers to the number of panes that have been incorporated into one window unit. With glazing, two panes of glass will sandwich a layer of inert and insulating gas, usually argon or krypton.
Double-glazed windows have two panes with one air chamber. Triple-glazed windows have three panes of glass with two air chambers. No wonder, then, triple-glazed offer several times better thermal performance.
Studies for the Government of Canada have shown that triple-glazed windows have an edge of glass temperature that is 3.4°C higher than a comparable double-glazed. In real terms, it means the innermost pane of glass will feel less cold to touch. That’s a sign of triple-glazing effectively insulating your home.
For the most energy efficient windows, opt for triple-glazed windows with high levels of Low-E coating. Speak to an Eco Choice Windows and Doors representative to understand what configuration of energy efficient windows will strike the right balance between insulation and budget. Call us at +1-855-691-1914 to schedule a free consultation for new or retrofitting windows.