Windows make up 25-30% of the total heat loss of a home. It’s a big issue in Toronto, Vaughan, Scarborough and the GTA at large — furnace systems are already overworked in cold winter months and it’s not unusual to get temperatures down to -25°C again.
Climate Zone 6 is one of the most severe climates in Canada, making Ontario one of these areas. This requires that your windows have a very high R value and U factor. This isn’t a choice between Energy Star Canada certified and not, it’s a requirement.
The impact of the wrong glass can be noticeable within your house:
- Increased heating costs due to uncontrolled heat loss through obsolete glazing
- Surfaces of glass windows getting frosty or cloudy because of cold snaps in the interior
- Cold drafts around window frames, which negates comfortable living area
- Wetness around sills and frames due to freeze-thaw events
- Wind- and weather-induced noises that leak in through a single or thin pane glass door or window.
Most people in the GTA who have a house don’t know that their windows are the most vulnerable thermal conduction point in their home wall assembly. Yes, upgrading windows is one of the best value for money improvements you can do to achieve year round comfort.
How Window Glazing Works: The Basics
Just a few key terms will help you make the window type comparison easy and practical.
The more panes the more insulation between indoor heat and outside heat. Between the panes, there is an insulating gas that provides a significant reduction of thermal transfer across the glass surface and retains heat within the pane.
Gas Fills: Argon vs Krypton
- Argon — the industry standard; heat transfer is reduced by ~34% compared to air. Highly popular and affordable in Energy Star windows in Canada.
- Krypton — Denser, slightly higher thermal performance, higher cost.Installed in high quality triple pane applications where each 1/10 of a U-factor point counts.
U-Factor & R-Value
- U Factor: indicates how fast heat can escape through a window – the lower the better
- R-value: Indicates resistance to insulation – the higher the number the better the insulation.
- Canada’s recommended U-value for winter is 0.25 or less. The typical performance of triple pane Low-E windows is 0.15-0.20.
Low-E Coating A thin film of metal that is applied to one or more of the glass surfaces. In the winter it radiates heat back into the room and in summer it shades the sun’s heat — it is not just a winter accessory.
Double Pane Windows: The Standard Option
Double pane windows (two glazes separated by a space filled with gas) has been the standard window type for many years. They’re significantly better than single panes and are offered in all window types and frame styles.
Advantages
- Lower initial cost than triple pane windows
- In all of the styles – casement, slider, awning, picture, and fixed
- Energy Star when combined with Low-E and Argon fill
- Lighter weight puts less structural stress on frames (benefit in older homes)
- Uses significantly better performance than a single pane in both insulation and noise reduction
Limitations for Canadian Winters
- A single gas cavity provides less thermal resistance in extreme cold
- More condensation during cold weather (T < -15°C)
- Typical U-Values are 0.30 to 0.45 (on the edge of Climate Zone 6)
- Not as effective as usual at noise barriers on busy roads and transit corridors in the GTA
Ideal for: Homeowners on a budget, mild GTA microclimates or short- to medium-term homeowners. Combined with Low-E coating and Argon fill, double pane windows can remain Energy Star Canada compliant and achieve significant energy savings, but they are not always the best choice for the coldest months in Ontario.
Triple Pane Windows: Built for Canadian Winters
Triple pane windows feature two interposed gas-filled spaces and three pane glass. This set-up (nearly) eliminates the cold zone between inside and outside temperatures during extended periods of below freezing weather.
Advantages
- Standard U-values of 0.15-0.25, much lower than the Climate Zone 6 requirements!
- Prevents indoor frost and condensation on glass windows in almost all weather conditions.Excludes interior frost and condensation on glass windows in almost all conditions
- Residents say they save 20-30% on their heating bills annually following upgrade
- High-performing noise reduction, essential in GTA streets, highways, airports and transit lines
- A significant rise in comfort around windows; no cold air coming out of the window on very cold nights
- Perfect for all Ontario climate zones, even Northern Ontario’s coldest climate
Limitations
- More expensive to install than double pane windows
- High weight of glass demands strong and well fitting frames as well as expert installation
- Minimal difference in performance — in truly mild climates, but not during the Canadian winter.
Ideal for: Toronto, GTA, and Ontario’s cooler climates. Triple pane windows generally break even with energy savings after 5–10 years during the lifespan of your home, especially if you apply government incentives.
Low-E Glass: The Year-Round Upgrade
Low-E glass is not a window type, it is a high-performance coating on double and triple pane windows that alters the glass’ behavior in all four seasons.
How Low-E Works
Low-E (Low Emissivity) Coating reflects long-wave infrared radiation which is the form of infrared energy that carries heat. It will help keep your home warm during the winter months instead of letting it out through the window panes. During the summer it reflects the sun’s radiative heat before it penetrates your home. This leads to reduced fuel consumption during winter and reduced cooling costs during summer.
Hard Coat vs Soft Coat Low-E
| Type | Application Method | Performance Level |
|---|---|---|
| Hard coat (pyrolytic) | Embedded in the glass as part of the glassmaking process. Incorporated in the glass as it is being formed | Durable and less efficient |
| Soft coat (sputtered) | The post-manufacturing application in vacuum | More efficient — has been used in high quality Canadian windows |
Today the Canadian window industry, particularly in high performance, uses “soft coat” Low-E exclusively, and all installations in Climate Zone 6 use the “soft coat” version.
The Gold Standard Combination
The highest-performing window configuration available for Canadian winters is Soft coat Low-E + Argon fill + Triple pane glazing. This combination achieves:
- U factors down to 0.12
- No condensation at all within the enclosure even at -30°C
- The most efficient use of energy for heating and cooling
- Excellent Energy Star Canada ratings
Double Pane vs Triple Pane vs Low-E: Side-by-Side
| Feature | Double Pane | Triple Pane | Low-E Glass |
|---|---|---|---|
| U-factor | 0.30–0.45 | 0.15–0.25 | Enhances either |
| Frost Prevention | Partial | Strong | Strong |
| Energy Savings | Good | Best | Best |
| Noise Reduction | Moderate | High | Moderate–High |
| Condensation Risk | Higher | Very Low | Very Low |
| Cost | $ | $$ | $$ |
| Ideal for Canadian Winter Weather Conditions! | Mild zones | All zones | All zones |
| Energy Star Canada | Eligible | Top-rated | Top-rated |
What GTA Homeowners Actually Need
Best Choice: Triple Pane + Low-E + Argon
This is the best advice for almost all people who own homes in the GTA and Toronto. It offers the lowest U factor, no condensation, high energy savings and the best noise reduction – all important for urban life in Ontario.
Acceptable Alternative: Double Pane + Low-E + Argon
If cost is truly an issue, a quality double pane window with Low-E coating and Argon fill can also qualify for the Energy Star Canada. It will be as effective as triple pane in the coldest months, but a great improvement over old windows.
What to Avoid
- Single pane glass, don’t ever get this unit outside for the Canadian winters
- Aluminum frames that don’t have thermal breaks – conduct cold right into your home
- Install windows with Argon fill and/or Low-E coating that are within budget.
- Any window that is not Energy Star Canada certified.
Window style is important as well. When closed, casement windows create a compression seal making them more airtight than sliding windows. Casement and awning styles always perform better than single and double sliders in cold climates and provide maximum winter performance.
Frame Material: Don’t Overlook It
Keeping the glass half the picture is. The window frame material plays a major role in the overall window thermal performance, durability (particularly the repeated freeze-thaw cycles in Canada) and maintenance requirements.
- Vinyl frames – It’s the ideal solution for the Canadian winters. Vinyl has no thermal conductivity, is maintenance free, will not absorb water and won’t warp, and will not fail over decades of hot and cold. The most common frame type for top quality Canadian window products.
- Wood frames – Natural insulation is excellent, and they have a classic look, but need to be inspected, sealed, and painted on a regular basis to avoid moisture intrusion and rotting in time. Properly maintained, wood windows can serve for 30+ years.
- Aluminum frames – are strong, require minimum maintenance for surface care but are not very good at insulating, unless they are fitted with a thermal break, which is a non-conductive material placed between the frame profiles. As a result, aluminum frames are responsible for a great amount of heat loss and continuous condensation during Canadian winter.
Cost, Government Rebates & ROI
Government Grants & Incentives
Energy Star windows could be eligible for significant financial assistance from federal and provincial energy efficiency programs to Canadian homeowners upgrading their windows:
- Up to $10,600 in Government Grants.
- Interest free loans available for $40,000
These incentives can significantly lower the net cost of switching to higher quality, triple pane Low-E windows, which can make the upgrade easy and cost-effective.
Energy Savings Payback
Older homes that have single or early double pane windows lose 20-30% of their heating and cooling energy use each year when they are replaced with triple pane Low-E glass. When you have a larger home, such as a home in the GTA that has a lot of windows, that saving soon adds up. Energy savings can pay for the initial investment over 10 years — and the windows will last many decades after.
If the government grants are used at the time of purchase, the payback period is further shortened.
Professional Installation: Non-Negotiable
The worst case scenario is that even the best triple pane Low-E window performs poorly if it isn’t installed correctly. A significant portion of the window’s insulating value can be lost if air gaps are left around the frame, or it is not sealed properly or the glazing is not installed correctly, which results in buying a high-quality window for budget performance.
With certified professional installation, you can count on:
- Tight fit around all edges of the frame (no drafts)
- Waterproofing and sealing all joints around the building to ensure no infiltration and damage from water
- Correct fitment (no frame or surrounding wall distortion)
- The manufacturer’s warranty for protection — most manufacturers will need certified installation to cover the warranty
- Clean, undamaged work, no damage to adjacent walls, trim or exterior siding
FAQs: Best windows for Canadian Winters
Are triple pane windows worth it in Canada?
Yes (for the majority of Ontarians). Triple pane windows offer real measurable insulating performance and reduce heating costs, and condensation, much more than double pane. The ROI period is much shorter due to government window rebates and energy savings.
What is the best window for extreme cold in Canada?
Thermally insulated vinyl frame with triple pane glass, and Low-E soft coating and Argon or Krypton gas fill. This configuration can provide U-values as low as 0.12-0.15, and help virtually prevent frost and condensation inside.
Do double pane windows work in Canadian winters?
When combined with Low-E and Argon fill, they work well, but at their maximum performance level in prolonged sub-zero conditions in Climate Zone 6. GTA householders are encouraged to consider upgrading to triple pane windows as a long-term solution.
What does frost on the inside of windows mean?
If you have frost inside your windows it means they are not insulating well. The cold surface inside can freeze water from the interior air (most often in older double pane windows or single pane windows). The inner surface is kept warmer by a triple pane Low-E that takes care of that.
How do I know if my windows are losing heat?
Indications of key problems include drafts around the frame or glass; condensation or frost on the inside of windows; cold air coming through closed windows; higher heating bills; and cracks or gaps in caulking or weatherstripping around the frame.