Crawl Space Insulation R-Value Toronto: Foam Board, Spray Foam, and Code

# Crawl Space Insulation R-Value Toronto: Foam Board, Spray Foam, and Code

In a conditioned (encapsulated) Toronto crawl space, the insulation goes on the foundation walls and at the rim joist, not on the floor above. This post covers the R-value targets, the products we use most often (DOW Insulpink and Owens Corning Foamular for foam board, closed-cell spray foam at the rim), Ontario Building Code 9.10.17 thermal barrier requirements, and how the assembly performs in older Toronto homes.

For the full project context, see the pillar [Crawl Space Encapsulation Toronto Complete Guide](/blog/crawl-space-encapsulation-toronto-2026-complete-guide). For costs, see [Crawl Space Encapsulation Cost Toronto](/blog/crawl-space-encapsulation-cost-toronto). For the vapor barrier behind the foam, see [Crawl Space Vapor Barrier Toronto Comparison](/blog/crawl-space-vapor-barrier-toronto-comparison).

Why Walls, Not Floor Above

The encapsulated assembly treats the crawl as part of the conditioned envelope. The thermal boundary moves from the floor (where it sits in a vented crawl) down to the foundation wall. Two reasons:

• Air tightness. A sealed wall and rim joist is far easier to make airtight than a floor with plumbing, electrical, and ductwork penetrations.
• Plumbing protection. Pipes in the crawl stay above freezing because the space is now part of the conditioned envelope.

Insulating the floor above (the old vented-crawl approach) leaves the rim joist as a giant thermal bridge and does nothing for the pipes.

R-Value Targets for Toronto

Ontario Building Code 9.36 effective values for foundation walls in climate zone 6 (Toronto):

• Foundation wall above grade: R-17 effective.
• Foundation wall below grade: R-10 effective.

In practice we install:

• Foundation wall: 1.5-inch DOW Insulpink (R-7.5) or 2-inch Owens Corning Foamular 150 (R-10) minimum. For pre-1930 stone-foundation homes in East York, the Beaches, or Cabbagetown we step up to 2.5-inch Foamular 250 (R-12.5) because the stone wall itself contributes near zero R-value.
• Rim joist: 2-inch closed-cell spray foam (R-12 to R-14) minimum. The rim is the single highest-leverage thermal upgrade in any older Toronto home.

Foam Board: DOW Insulpink vs Owens Corning Foamular

Both are extruded polystyrene (XPS) and both work. Differences:

• DOW Insulpink: R-5 per inch. Tongue-and-groove edges available. Slightly tighter cell structure.
• Owens Corning Foamular 150: R-5 per inch. Square edges. Standard in most Toronto box stores.
• Owens Corning Foamular 250: R-5 per inch but higher compressive strength. Used in below-grade applications and where a smoother substrate is needed.

We default to 2-inch Foamular 150 on suburban poured-concrete foundations and 2.5-inch Foamular 250 on stone or rubble foundations.

Installation:

• 1. Vapor barrier on the wall first (terminated with bar at top of foundation).
• 2. Foam board over the barrier, mechanically fastened with concrete anchors and 2-inch washers at 16 inch spacing.
• 3. Tape all seams with foil-faced or manufacturer's seam tape.
• 4. Air-seal the top edge to the rim joist or sill plate with a bead of polyurethane sealant.

Closed-Cell Spray Foam at the Rim Joist

The rim joist (band joist) is the band of wood that sits on top of the foundation wall and supports the floor joists. In a vented crawl, this is the worst air leak in the house. Closed-cell spray foam at 2 inches solves it:

• R-value: R-12 to R-14 at 2 inches.
• Air sealing: full air seal including small gaps and irregular surfaces.
• Vapor: closed-cell spray foam is its own vapor barrier.
• Code: must be covered with a thermal barrier per OBC 9.10.17 if the space is accessible.

Toronto sprayers we work with: Polar Foam, Demilec Heatlok, BASF Walltite. All are HFO-blown low-GWP formulations as of 2024-2026.

OBC 9.10.17 Thermal Barrier Requirements

Foam plastic insulation in an unprotected installation is a fire risk. OBC 9.10.17 requires a thermal barrier between foam plastic and the interior of the building when the space is accessible.

Acceptable thermal barriers:

• 1/2-inch drywall (most common).
• Intumescent coating (DC315, FireFree FX or similar) at the manufacturer-specified thickness.
• Cementitious coating.

In a true crawl space (under 5 ft clear, used only for utility access, not living space), the thermal barrier is sometimes waived under the "service space" interpretation, but Toronto building inspectors increasingly require an intumescent coating even on service-only crawls. We confirm with the local inspector on every project.

Avoid Fiberglass Batts

Fiberglass insulation in a Toronto crawl is a problem regardless of how much you put down:

• Holds moisture instead of repelling it.
• Becomes rodent nesting material.
• Compresses and falls out of joist bays over years.
• Loses R-value when wet.

If we find existing fiberglass in a crawl during a Tier 2 or Tier 3 encapsulation, we remove and dispose of it before installing foam.

Honest Positioning

Foam board and rim-joist spray foam are standard renovation work for us. We self-perform the foam board; we partner with a licensed spray foam crew (Polar Foam or local equivalent) for the closed-cell rim work because the equipment, ventilation, and certification are specialty. The seam taping, mechanical fastening, and thermal barrier are all RenoHouse scope.

If pre-encapsulation testing reveals vermiculite (Zonolite) in floor cavities or asbestos pipe wrap, abatement (Pinchin, EHS) precedes any foam work. See [Crawl Space Asbestos Vermiculite Toronto](/blog/crawl-space-asbestos-vermiculite-toronto).

Energy Impact

Field measurements on Toronto encapsulation projects with Tier 2 spec (R-10 walls plus R-12 rim) typically show:

• 15% to 25% reduction in heating energy on natural gas bills.
• 5% to 10% reduction in summer cooling.
• Floor surface temperatures 3 to 6 degrees Celsius higher in winter (the kitchen above the crawl stops feeling cold).

The rim-joist treatment alone is responsible for roughly half of the total energy benefit. Skipping it to save $1,500 leaves most of the savings on the table.

For the resale and ROI math, see [Crawl Space Encapsulation ROI Toronto Resale](/blog/crawl-space-encapsulation-roi-toronto-resale).

Get a Spec for Your Crawl

Free crawl space inspection with R-value recommendations at [/services/home-renovation/crawl-space-encapsulation](/services/home-renovation/crawl-space-encapsulation). We give you the foam type, thickness, manufacturer, and thermal-barrier plan in writing before any deposit.