How thick should the glass be for good insulation?

Glass thickness alone isn't the key factor for insulation - it's actually the number of panes and the air or gas spaces between them that provide the thermal performance you need in Ottawa's climate.

For optimal insulation in Ottawa's Climate Zone 6, you'll want triple-pane windows with two insulating air spaces rather than focusing on glass thickness. Standard window glass is typically 3mm to 6mm thick per pane, but the real insulation comes from the 16mm to 20mm air or gas-filled spaces between the panes. These spaces, when filled with argon or krypton gas, create the thermal barrier that keeps your home comfortable and energy bills manageable.

Triple-pane windows are the gold standard for Ottawa homes, offering U-factors of 0.8 to 1.2 (lower is better), compared to older single-pane windows with U-factors around 5.0. The middle pane in a triple-pane unit is often slightly thinner (3mm) while the outer panes are typically 4-6mm, but this configuration provides exceptional thermal performance. Quality triple-pane windows also include Low-E coatings on specific glass surfaces to reflect heat back into your home during winter.

In Ottawa's harsh winters, proper window selection can save you $200-400 annually on heating costs compared to older double-pane units. Look for windows that meet ENERGY STAR requirements with U-factors of 1.22 or lower - these qualify for Canada's Greener Homes Grant, potentially saving you up to $5,000 on your window replacement project.

For recommendations on your own windows, request a free quote through Ottawa Window Pros and go through pane count, gas fills and coatings with an installer.

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