Our 1972 Guelph ranch had a vented crawl space that we suspected was the source of musty odours on the main floor. After a professional assessment, we encapsulated it. Sharing the full process and results.
Assessment findings:
- Crawl space inspector found visible mould on 30% of the floor joists
- Existing 6-mil poly (installed maybe 15 years ago) was torn in multiple places
- Three of the four vents were open year-round
- Wood moisture content readings: 22 to 28% in the joists (anything above 19% supports mould growth)
What the encapsulation included:
- Mould remediation on floor joists (borate treatment + HEPA vacuuming): $1,800
- Remove old poly
- Install 20-mil reinforced poly barrier on floor, sealed to walls and piers with tape
- Spray foam all vents closed (sealed permanently)
- Closed-cell spray foam on foundation walls and rim joists (R-10 to R-12)
- Installed Aprilaire E100 dehumidifier (crawl-space rated) with drain line
Cost:
- Mould remediation: $1,800
- Encapsulation (poly, foam, sealing): $7,400
- Dehumidifier supply and installation: $1,900
- Total: $11,100
6-month results:
- Musty odour: completely gone from main floor
- Crawl space wood moisture content (re-tested): 11 to 13%
- Dehumidifier runs significantly less than expected — the encapsulation alone removed most of the moisture load
- Heating gas bill: down approximately $55/month (the crawl space was a major infiltration path)
Post-encapsulation, a different contractor confirmed the crawl was “one of the better jobs” they’d seen. The mould remediation before encapsulation is the step many companies skip — don’t let them.