The Battle of the Panes – Triple-Pane Windows vs. Double-Pane WindowsPatrick
When it comes to replacing their windows, our customers often ask; “ok, so what’s better triple pane windows or double pane windows?” The difference between double pane and triple pane windows is more than a pane of glass. To understand how they compare, let’s look at the pros and cons for each window type and break down the factors that affect cost, energy efficiency and overall performance of these two rivals.
1. Increased energy efficiency
Triple pane windows can save 2-3% more on your heating bill than double paned windows, so they’re most commonly used in homes in colder climates.
2. Increased R value
Triple pane windows have three individual pieces of glass separated by two sealed airspaces. The additional glass and airspace improves insulation as gas (usually argon gas or Krypton gas) are injected into both air fill spaces between the panes of glass, significantly increasing the thermal performance.
3. Increased condensation resistance
Triple pane windows can improve your relative humidity levels (the point before surface condensation occurs) by almost double due to warmer window surface temperatures. It will allow you to maintain a higher indoor relative humidity in cold weather.
4. Additional Low E coating equals better performance
Think of Low-emissivity (Low-E) coating as invisible insulation. Low-E coated glass helps keep your home warm and cozy by blocking heat loss through windows while allowing the sun’s heat in. Low-E coating also blocks the sun’s harmful UV rays in the summer, keeping your furniture from fading, while keeping temperatures balanced. In triple pane windows, two of three layers of a Low-E film can be added on the non-exposed surfaces of the glass (one per chamber).
5. Cuts down sound transmission
In today’s housing market, neighbours and distractions are often in close proximity. Triple pane windows trap sound waves in the first chamber; therefore, are effective at blocking unwanted noises.
1. Higher cost
With more glazing and extra coating of Low E, on average triple-pane windows cost 10-15% more than double-pane units
2. More weight so therefore larger sized windows may need to be smaller
With three panes of glass and two spacers instead of one, triple pane windows become much heavier than double pane windows, so depending on your home’s structure, window sizes may need to be reduced.
3. Lower VT rating
The visible transmittance (VT) is an optical property that indicates the fraction of visible light transmitted through the window. Triple pane options will reduce the VT rating as the light needs to pass through 3 panes of glass and typically 2 low-e coatings resulting in less daylight coming through.
1. Lower cost than triple pane windows
The main benefit of double pane windows is the cost factor. The cost difference between double pane and triple pane windows is approximately 10-15%.
2. Lighter to handle
Double pane windows weigh less than triple-glazed windows, do not have to be as strong and are easier to lift for installation.
3. Current standard for Canadian homes
Canadian building codes require new homes to be outfitted with at least double pane windows due to the harsher climate during the winter.
4. Higher VT
A product with a higher VT transmits more visible light. Double pane windows have a higher visible transmittance (VT) than triple pane windows; therefore, are easier to see through and admit more natural daylight. Besides giving you a nice view, high-VT windows can save energy because you need less artificial light.
1. Less efficiency than triple
When comparing factors such as the SHGC (solar heat gain coefficient), or U-values (heat loss through frames, spacer and glass (R factor), there is an approximate improvement of 20-30% in a triple pane window’s energy ratings over the double pane units.
2. Lower condensation resistance than triple pane
Triple-glazed windows have a warmer inside-the-home glass surface temperature in the winter which can improve relative humidity levels in the home and decrease the potential for condensation.
3. If a 4th surface Low E is added it lowers the condensation resistance
Although using a 4th surface (inside surface) low E coating makes the glass more efficient raising the R value, it also lowers the condensation resistance. On extreme cold days some condensation on the glass may occur depending on interior humidity levels. The humidity in the home should be lowered as the outside temperature drops.
4. Can’t combine different Low E coating to change performance
With only two panes of glass, you only have one opportunity to add a coating of Low E film as there is only one non-exposed glass surface (one chamber).