Crawl Space Encapsulation in Ajax

Small crawl space (300–500 sqft, dry, no major remediation): $4,000–$7,000. Standard (500–800 sqft, vapour barrier + insulation + dehumidifier): $6,500–$9,500. Larger or wetter (800–1,200 sqft, sump pit, mold remediation, full encapsulation): $9,000–$12,000. Coordinated abatement (asbestos pipe-wrap, mold over 100 sqft Type 2): +$2,000–$5,000. Bundled with foundation repair or basement waterproofing: 10–15% discount typical.

20-mil reinforced polyethylene — the residential durable-vapour-barrier standard. 6-mil and 10-mil products are construction-grade poly and not durable enough for crawl spaces with foot traffic, storage, or mechanical equipment access. 20-mil reinforced poly is overlapped 12 inches at seams, taped with butyl tape, mechanically fastened to walls and rim joists, and sealed at all penetrations. For commercial or extreme conditions some installers go to 30–60 mil; 20-mil is the residential right answer for Ajax.

A vented crawl space in Ajax's climate is wrong for two reasons. (1) Summer: humid air entering at 25°C / 75% RH cools when it contacts cool soil and joist surfaces (~15°C), raising relative humidity to 85–95% — perfect mold conditions. (2) Winter: cold air entering pulls moisture out of the basement plenum and into the soil, creating a vapour drive that degrades insulation and rots joists. Encapsulation closes the air boundary — the crawl space becomes a dehumidified interior space at 50% RH, with no exchange to outside. Energy bills drop 5–15% and mold/pest pressures collapse.

Aprilaire E080 (80 pints/day, ENERGY STAR rated, ducted condensate, automatic humidistat) or Santa Fe Ultra-Aire 70H (70 pints/day, premium build, MERV 11 filter). Both target 50–55% RH year-round, condensate is ducted to the sump pit or exterior. Smaller crawl spaces (under 600 sqft, dry) sometimes use the Aprilaire E060 (60 pints). Plug-in stand-alone basement dehumidifiers (Frigidaire, GE) are NOT recommended for encapsulation — they cycle on/off too aggressively and pump bucket overflows are a problem.

2 inches of XPS rigid foam board (R-10) or 3 inches (R-15) on the perimeter walls and rim joists, taped seams (Tuck Tape or Tyvek tape), mechanically fastened to the foundation and joists. Some installs add R-19 mineral wool batts above for total R-29 — particularly when the floor above is uninsulated. We do NOT install fibreglass batts directly against the vapour barrier (they trap moisture). XPS is preferred over EPS for moisture-resistance and over polyiso for low-temperature R-value retention.

RenoHouse self-performs encapsulation work but coordinates with HCRA-licensed specialty contractors for: (1) Mold over Type-1 quantity thresholds (>10 sqft to >100 sqft depending on Ministry of Labour Reg. 278/05 designation) — abatement before encapsulation begins. (2) Asbestos pipe-wrap, vermiculite (Zonolite) attic insulation that has filtered into the crawl space, asbestos-containing flooring or mastic — Type 1, 2, or 3 abatement per OHSA and Reg. 278/05. (3) Active rodent infestation — pest-control coordination before encapsulation. We scope and budget for these on the inspection visit.

No — encapsulation is the wrong solution for active groundwater intrusion. If standing water is present from groundwater, the fix is exterior weeping tile, foundation membrane, downspout extensions, and sometimes interior sub-floor drainage tied to a sump pit. Encapsulating over an active groundwater problem traps moisture rather than solving it. We may install a sump pit and pump as part of encapsulation when seasonal moisture is present, but persistent standing water requires waterproofing remediation FIRST. Inspection visit determines the correct sequence.

Modestly, yes. Ajax homes with vented crawl spaces typically see a 5–15% heating-bill reduction after encapsulation, depending on how much heat was being lost through the floor above. The bigger benefits are comfort (warmer floors above), durability (no more rot, no more rusting plumbing), indoor air quality (no more musty smell, no more mold spores rising through floor cracks), and pest control (sealed envelope eliminates rodent entry). Pair with attic insulation top-up and air sealing for compounding effects.

Small crawl space (300–500 sqft, dry): 2–3 days. Standard (500–800 sqft, light cleanup): 3–5 days. Larger or wetter (800–1,200 sqft, sump pit, mold/asbestos remediation): 5–10 days plus 2–5 days for the abatement scope. Mold or asbestos abatement adds permit and Ministry of Labour notification lead time (5–10 business days) before encapsulation can begin. Scope is finalized at the inspection visit.

Often yes — even partial encapsulation of a problem crawl space (mold smell, dampness, pest activity) can transform indoor air quality and basement-above usability. Partial-basement homes (typical Ajax bungalow with full-basement under main floor and crawl space under addition or kitchen extension) commonly have moisture problems concentrated in the crawl space portion. Encapsulating just that section while leaving the full basement as-is is a valid scope at $3,000–$5,000 typical. The boundary between encapsulated and non-encapsulated must be sealed — we engineer the transition.