Bought a 1960s bungalow in East York last year with a partial crawl space under the addition. The home inspector flagged moisture concerns but was vague. Sharing what we found and what we did.
The Inspection Results
Crawl space had:
- Original fiberglass batts hanging between joists (half fallen down)
- Visible mold on joists in the wet corner
- No vapor barrier on dirt floor
- Relative humidity measured at 78% RH in October
- Radon test: 185 Bq/m3 (below 200 threshold but close)
Decision: Full Encapsulation
With mold present and radon close to the action level, we went full encapsulation rather than a basic vapor barrier only.
Scope of Work
- Mold remediation: HEPA vacuum, antimicrobial treatment, encapsulate affected joists
- Remove fallen insulation, dispose
- Install 20-mil reinforced poly vapor barrier on floor and walls, taped to foundation
- Seal all foundation vents (4 total) with insulated plugs
- Spray foam insulation on crawl space walls (2 inches closed-cell)
- Install Santa Fe Compact dehumidifier with drain line to sump
- Install passive sub-slab depressurization pipe (radon precaution, not active yet)
Cost
Mold remediation: $2,100
Encapsulation (liner, vent sealing, insulation): $8,400
Dehumidifier: $1,200
Radon pipe installation: $450
Total: $12,150
6-Month Results
Crawl space RH now holds at 48-52% year-round. Main floor feels noticeably less drafty. Will do a follow-up radon test at the 12-month mark.
Is anyone else on this forum dealing with encapsulation projects? Particularly curious about experiences in clay-heavy soil areas.