Windows, insulation, and air sealing
Everything separating conditioned space from outside: windows and doors, insulation in walls and attic, and the air barrier. The 2024 Ontario Building Code raised minimum performance expectations here, which affects renovations as well as new construction.
Can you do your own windows, insulation, and air sealing work in Ontario?
Largely yes for air sealing and attic top-ups. Window replacement is usually a contractor job, and structural changes to openings need a permit.
Authority: Your municipal building department · Source: 2024 Ontario Building Code (O. Reg. 332/12 (2024 edition)) · Reviewed 2026-09-10
Can you work on it yourself?
Largely yes for air sealing and attic top-ups. Window replacement is usually a contractor job, and structural changes to openings need a permit.
Air sealing is consistently the highest return per dollar in this category and is almost always cheaper than window replacement. A contractor who leads with windows before addressing air sealing is selling the expensive answer first.
Authority Your municipal building department
How long it lasts
Windows commonly 20–30 years, with seal failure showing first. Insulation does not wear out but settles, gets disturbed, and is frequently inadequate by current standards in older homes.
What failure looks like
- Condensation or fogging between panes, indicating a failed seal
- Drafts at outlets, baseboards, and window trim
- Uneven snow melt on the roof, indicating heat escaping into the attic
- Cold interior wall surfaces in winter
- Rooms that are persistently harder to heat than the rest of the house
Worth knowing about your own house
- Where is this house actually losing air, and has anyone tested rather than guessed?
- What is the attic insulation depth now?
- Are the windows failed, or just old?
Sources and review
Reviewed Reviewed 2026-09-10 Next review 2027-09-10 Tier C · 365-day SLA Reviewer: Justin Challenger