Home Air Sealing Ontario

Why air sealing often delivers better payback than insulation alone

Insulation slows heat flow through materials. It does almost nothing to stop heat carried by moving air. A 2-inch gap around a pot light penetration in your ceiling can negate the thermal value of several square feet of insulation above it. Air sealing and insulation are complementary measures — but sealing must come first.

The only way to accurately quantify your home's air leakage is a certified energy audit with a blower door test. The resulting ACH50 number tells you how leaky your home is relative to both code requirements and your specific upgrade targets. Combined with thermal imaging, it pinpoints exactly where leakage is occurring.

Where does air leakage happen in Ontario homes?

The most common sources of air leakage in Ontario homes, roughly in order of impact:

• Ceiling penetrations: pot lights, electrical boxes, plumbing stacks, attic hatches
• Top plates: the gap between exterior walls and attic floor
• Rim joists: where floor framing meets the foundation
• Basement band joists and around windows and doors
• Fireplace and chimney surrounds
• Plumbing and mechanical penetrations through walls and ceilings

Older brick homes common in Toronto, Hamilton, and inner GTA communities often have particularly severe leakage at the ceiling-wall interface — a structural feature of the construction that requires specific sealing techniques.

Air sealing vs insulation — which should you do first?

Always air seal before adding insulation. Here's why: adding insulation over a leaky ceiling pushes the dew point into the insulation layer, creating conditions for moisture accumulation and eventual mould. It also reduces the effective R-value of the new insulation by allowing warm air bypass. See our full explainer on air sealing vs insulation.

Air sealing rebates in Ontario

Air sealing is a qualifying measure under the Home Renovation Savings Program and the Enbridge Home Efficiency Rebate. Most programs require a pre-work EnerGuide audit to establish the baseline, and a post-work blower door test to confirm improvement. We handle the documentation and submissions as part of our advisory service.