Vented crawl spaces are a known building science failure in Ontario’s climate. Encapsulation is the proven solution. Here’s the 2026 guide.
Why vented crawl spaces fail in Ontario:
Warm, humid summer air enters the vented crawl space and condenses on the cooler floor joists and subfloor – depositing moisture exactly where you don’t want it. Research established 20+ years ago that sealed, conditioned crawl spaces outperform vented ones in humid continental climates.
Full encapsulation process:
- Seal all foundation vents permanently
- Install heavy-duty poly liner (minimum 10 mil, preferably 20 mil) on ground and up walls
- Tape all seams and wall connections
- Rigid insulation on interior foundation walls
- Dehumidifier or conditioned air connection
- Seal access hatch to same standard
Critical: Remediate any existing mould before installing liner – encapsulation seals problems inside the structure. Surface mould on wood: treat with borate solution (Tim-bor, Boracare). Structurally compromised joists: sister or replace first.
GTA cost ranges (2026):
| Scope | Cost |
|---|---|
| Basic encapsulation, liner + vent sealing (600-800 sq ft) | $3,000-$6,000 |
| Full encapsulation with wall insulation and dehumidifier | $8,000-$16,000 |
| Mould remediation (if needed) | +$1,500-$5,000 |
Energy savings: typically $400-$800/year in reduced heating costs.
Crawl space and moisture questions at home.renovation.reviews