Thornhill homeowners can get professional spray foam installation for $2,600–$3,800 for a typical 1,200 sqft attic using open-cell foam to R-31. Closed-cell upgrades run $4,200–$5,400 for the same footprint. We serve all of Thornhill and the surrounding York Region communities with CUFCA-certified installation, $5M liability coverage, WSIB clearance, and full support for HRS and HER+ rebate applications.
Most Thornhill homes were built between 1970 and 1990 — a period before modern air-sealing standards. That means original fiberglass batt or blown-in insulation that has settled, compressed, or lost R-value over decades. A spray foam upgrade does two things at once: it raises the thermal resistance to current Ontario Building Code SB-12 requirements and seals every penetration, gap, and crack that lets conditioned air escape. Homeowners in Thornhill commonly report 25–35% reductions in heating costs after a full attic air-seal and spray foam installation.
Spray Foam Insulation Cost in Thornhill
Pricing in Thornhill follows GTA-standard rates, with minor adjustments for job complexity, access, and existing insulation removal. Here is the full cost range by foam type and application:
| Application | Foam Type | Price Range (CAD/sqft) | Typical Project Cost (CAD) |
|---|---|---|---|
| Attic (1,200 sqft) | Open-cell (R-31 to R-38) | $2.00–$2.50/sqft | $2,400–$3,000 |
| Attic (1,200 sqft) | Closed-cell (R-20 at 3½”) | $3.50–$4.50/sqft | $4,200–$5,400 |
| Basement rim joist | Closed-cell (2″ min, R-12) | $3.00–$4.00/sqft | $800–$1,600 (typical Thornhill semi) |
| Basement rim joist + walls | Closed-cell combo | $2.50–$4.00/sqft blended | $3,500–$5,500 |
| Crawl space (500 sqft) | Closed-cell (floor joists + walls) | $3.00–$5.00/sqft | $1,500–$2,500 |
| Wall cavities (new build / gut reno) | Open-cell | $1.50–$2.50/sqft | Quote by linear footage |
Note: Prices include material, labour, and equipment. Old insulation removal is priced separately ($0.50–$1.00/sqft blown-in removal). All prices are CAD; HST is additional. Use our spray foam cost calculator to estimate your project cost and applicable rebates before you call.
Open-Cell vs Closed-Cell Spray Foam for Thornhill Homes
The right foam type depends on where you’re insulating and what you need the foam to do. Thornhill’s 1970s–1980s housing stock typically presents three scenarios: an unfinished attic with joist bays, a poured-concrete or block basement, and occasionally a small crawl space. Here’s how open-cell and closed-cell perform in each context:
| Feature | Open-Cell Spray Foam | Closed-Cell Spray Foam |
|---|---|---|
| R-value per inch | R-3.7 | R-6.0–R-6.5 |
| Vapour barrier | No (semi-permeable) | Yes (≥2″ meets OBC Class II) |
| Air barrier | Yes (at ≥3″) | Yes (at ≥1.5″) |
| Cost (Thornhill range) | $2.00–$2.50/sqft | $3.50–$4.50/sqft |
| Ideal for | Attic floor, interior walls, sound control | Rim joists, basement walls, crawl space, below-grade |
| Moisture resistance | Low — not suitable below grade | High — resists bulk moisture intrusion |
| Structural contribution | Minimal | Adds racking strength (up to 300%) |
| OBC SB-12 compliance path | Prescriptive (attic R-31+) | Prescriptive + performance path |
Our recommendation for most Thornhill projects: Open-cell in the attic floor (cost-effective, achieves R-31 to R-38 at 8–10 inches), closed-cell on rim joists and any below-grade surfaces. Mixed-system installs are common and we handle both in one visit.
How Thornhill’s 1970s–1980s Housing Stock Changes the Calculation
Thornhill grew rapidly between 1965 and 1990, producing a large inventory of brick detached homes, semi-detached, and townhouses — most in the 1,100–1,600 sqft footprint. These homes share several characteristics that make spray foam particularly effective:
- Settling insulation: Original blown-in fiberglass or mineral wool in attics has typically settled from a nominal R-28 down to R-15 to R-20 effective by now. Every gap, wire penetration, and joist bay edge is an air-leak.
- Single-wall rim joists: Pre-1990 homes rarely had insulated rim joists. That 12-inch band running the perimeter of the basement ceiling is often the largest source of heat loss — and the cheapest single upgrade at $800–$1,600 for a typical Thornhill semi.
- Small-lot access: Many Thornhill properties have limited side-yard clearance. Our hose rigs are sized for tight access; we can reach attic hatches and basement windows without heavy equipment on the lot.
- Active renovation market: Thornhill’s renovation permit activity is among the highest in York Region. Spray foam is increasingly specified at permit stage — we can coordinate with your contractor for pre-drywall applications.
The payback on a Thornhill attic spray foam upgrade is typically 4–7 years at current natural gas rates, with a 25–35% reduction in annual heating costs. The air seal alone often eliminates ice damming on the eaves — a common complaint on 1980s Thornhill homes with low-slope rooflines.
Thornhill Attic Spray Foam: Full Cost Breakdown
The attic is the highest-priority application for most Thornhill homeowners — it accounts for 25–40% of total heat loss in a typical 1980s home. Here’s how a complete attic spray foam project breaks down:
- Step 1 — Existing insulation assessment: We measure current R-value and identify air-leak locations. If your existing blown-in is below R-20 or contaminated (mouse damage, moisture), removal is recommended ($0.50–$1.00/sqft).
- Step 2 — Air sealing: All penetrations (pot lights, top-plates, plumbing stacks, exhaust fans) are sealed with spray foam before the insulation layer goes in. This is the step most DIY and budget installers skip — it’s also where 60–70% of the heat-loss gain comes from.
- Step 3 — Spray foam application: Open-cell applied at 8–10 inches across joist bays achieves R-29.6 to R-37, meeting or exceeding Ontario Building Code SB-12 prescriptive R-31 requirement for Zone 6 (Thornhill falls in climate zone 6).
- Step 4 — Hatch insulation: The attic hatch is typically the weakest thermal point. We insulate the hatch cover to match surrounding R-value.
- Typical total (1,200 sqft attic, no removal needed): $2,600–$3,800 including air sealing, application, and cleanup.
For attic spray foam applications with complex geometry — cape-cod knee walls, cathedral ceilings, or rafter cavities — closed-cell is sometimes specified at the rafters (R-20 at 3½”) with open-cell filling remaining depth. We quote these custom configurations on-site.
Basement Spray Foam for Thornhill Homes
Basement spray foam in Thornhill addresses two distinct zones: the rim joist (above the foundation wall, where floor framing meets the foundation) and the basement walls themselves. Closed-cell is the right choice for both.
Rim joist (most common first upgrade): At 2 inches of closed-cell (R-12), the rim joist meets OBC minimum and qualifies for HRS rebates. A typical Thornhill detached home has 120–180 linear feet of rim joist; at $800–$1,600 all-in, this is the highest-ROI single upgrade we offer.
Full basement wall insulation: For homeowners finishing their basements or dealing with persistent cold floors and moisture on the walls, we apply closed-cell at 2–3 inches (R-12 to R-18) directly to the poured-concrete or block foundation wall. This creates a continuous vapour barrier without a separate poly sheet. A full Thornhill basement wall installation (800–1,000 sqft) runs $4,000–$6,500 depending on wall height and penetrations.
Crawl spaces are less common in Thornhill but do appear in older split-levels and raised-ranch homes near the Steeles Avenue corridor. We seal the crawl space floor joists and perimeter walls with closed-cell — typical job is $1,500–$2,500 for a 400–600 sqft crawl space.
Rebate Programs for Thornhill Homeowners
Thornhill addresses in York Region are eligible for multiple spray foam rebate programs in 2026. We handle all paperwork and energy-audit coordination. See our full rebate programs guide for eligibility rules and timelines.
| Program | Max Rebate (CAD) | Audit Required? | Eligibility for Thornhill |
|---|---|---|---|
| HRS Attic (Home Renovation Savings) | $1,250 | No | Yes — attic must reach R-31+ |
| HRS Multi-Measure | $5,000–$10,000 | Yes (pre + post) | Yes — combine attic + basement + air sealing |
| HER+ (Enbridge Home Efficiency Rebate Plus) | Up to $10,000 | Yes | Yes — Enbridge gas customers in York Region |
| Canada Greener Homes Loan | Up to $40,000 (0% interest) | Yes (EnerGuide) | Yes — loan (not grant); application open |
Stacking strategy for Thornhill homeowners: The highest-value combination for a typical Thornhill upgrade (attic + rim joist) is HRS Attic ($1,250) stacked with HER+ (up to $10,000 for Enbridge customers). A full attic + basement wall job costing $7,500–$9,000 can net $3,500–$6,000 in rebates with proper audit coordination. We pre-screen every Thornhill quote for rebate eligibility and include the audit-coordination steps in our project plan at no extra charge.
Spray Foam vs Other Insulation Options for Thornhill Homes
Many Thornhill homeowners ask how spray foam compares to blown-in cellulose or fiberglass batts. The comparison is straightforward on the metrics that matter most for 1970s–1980s homes:
| Factor | Spray Foam (Open-Cell) | Blown-In Fiberglass | Blown-In Cellulose |
|---|---|---|---|
| Air barrier | Yes — eliminates convective loops | No — air moves freely through batts | Partial — dense-pack only |
| R-value at 10″ | R-37 | R-30 (nominal, R-20 with air movement) | R-38 (settled over time) |
| Moisture management | Vapour-open, no condensation risk in attic | Can trap moisture if air-sealed incorrectly | Absorbs moisture; mould risk if wet |
| Air sealing included | Yes — intrinsic | No — separate step, often skipped | No — separate step required |
| OBC SB-12 compliance | Prescriptive + performance path | Prescriptive path only (with separate air barrier) | Prescriptive path only |
| Rebate eligibility | Full HRS + HER+ eligible | HRS eligible (lower rebate tier) | HRS eligible (lower rebate tier) |
| Typical 15-year performance | No settling, R-value maintained | Settles 20–30%, R-value drops | Settles 15–25%, R-value drops |
The key differentiator for Thornhill’s older housing stock is the air seal. Spray foam is the only insulation type that simultaneously insulates and air-seals in a single pass. For a home that has been losing heat through decades of air infiltration, that dual function is what drives the 25–35% heating-cost reduction — not just the R-value number.
Thornhill Neighborhoods We Serve
Thornhill straddles the boundary between York Region (Vaughan and Markham) and sits just north of Toronto along the Yonge Street corridor. We serve every neighborhood within this geography:
- Old Thornhill — Heritage homes along Yonge Street and John Street; mix of 1950s–1970s detached homes, many with original plaster walls and knob-and-tube concerns (we coordinate with your electrician).
- Thornhill-Markham border — Higher density of 1980s–1990s brick detached homes along Bayview Avenue and Woodbine Avenue. We also serve adjacent Markham area properties.
- Yonge/Clark/Centre Street corridor — Mix of townhomes and semis; attic access is typically through a hatch; rim joist work is straightforward.
- Steeles Avenue corridor — Closer to the Toronto boundary; some homes in this area have already been converted to legal second suites. We handle fire-code-compliant spray foam for suite separations.
- Thornhill-Vaughan (west of Yonge) — Newer subdivisions (1990s–2000s) with larger footprints; basement finishing projects are common in this area.
We also serve neighbouring communities including North York directly to the south, Richmond Hill to the north, and all points across the GTA. Our service fleet operates out of Toronto with no travel surcharge for Thornhill jobs.
Why Choose Spray Foam Kings for Thornhill Insulation
- CUFCA Certified: We meet the Canadian Urethane Foam Contractors Association’s training and safety standards — not all Ontario installers do.
- $5M General Liability + WSIB: Full coverage, certificates on request before any Thornhill job starts.
- 15+ years GTA experience: We’ve insulated thousands of homes in the GTA, including hundreds in York Region with the same 1970s–1980s housing stock as Thornhill.
- OBC SB-12 compliant installs: Every project is spec’d to meet Ontario Building Code Section 12 requirements. No guesswork, no re-inspection failures.
- Rebate coordination included: We pre-screen your property, coordinate the energy audit, and complete all HRS and HER+ paperwork. You don’t deal with the bureaucracy.
- HFO blowing agents: Our closed-cell foam uses next-generation HFO blowing agents with a global warming potential of less than 1 — the lowest available in Ontario.
- One-day installs for most Thornhill attics: Standard attic jobs are in and out in 4–6 hours. We ventilate the space and provide re-occupancy guidance before we leave.
“We’d been losing heat through our 1982 Thornhill attic for years — three quotes, and Spray Foam Kings was the only company that did an actual air-seal walkthrough before touching the foam. Heating bill dropped $180/month the first winter. Worth every dollar.” — David R., Thornhill homeowner, verified Google review
Get Your Free Quote Today
Call: 647-641-6881
Book a free on-site assessment through our free Thornhill quote form — we typically respond within 2 business hours and can schedule a site visit within the week. Every quote includes a rebate pre-screening at no charge.
FAQ — Spray Foam Insulation in Thornhill
How much does spray foam insulation cost in Thornhill?
A typical Thornhill attic (1,200 sqft) costs $2,600–$3,800 CAD for open-cell spray foam to R-31. Closed-cell for the same attic runs $4,200–$5,400. Rim joist insulation alone — the highest-ROI single upgrade — costs $800–$1,600 for a standard Thornhill detached home. All prices are CAD; HST is additional.
Do you service Thornhill, Ontario?
Yes — we serve all of Thornhill including Old Thornhill, the Yonge Street corridor, Thornhill-Markham border areas, and Thornhill-Vaughan neighborhoods west of Yonge. No travel surcharge applies. We also serve adjacent Richmond Hill, Markham, Vaughan, and North York as part of our core GTA service area.
What is the best spray foam type for a Thornhill home?
For most 1970s–1980s Thornhill homes: open-cell in the attic floor (R-31 to R-38 at 8–10 inches, $2.00–$2.50/sqft) and closed-cell on rim joists and basement walls (R-12 minimum at 2 inches, $3.00–$4.00/sqft). Open-cell achieves the air seal and R-value at lower cost for attics; closed-cell is required anywhere below grade or where a vapour barrier is needed.
Can I get a rebate for spray foam insulation in Thornhill?
Yes. Thornhill homeowners are eligible for the HRS Attic rebate ($1,250, no audit required) and HRS Multi-Measure ($5,000–$10,000, pre/post audit). Enbridge natural gas customers in York Region also qualify for HER+ (up to $10,000). Stacking HRS Attic + HER+ on a combined attic and rim joist project can return $2,500–$4,000 in rebates. We handle all rebate paperwork at no extra charge.
How long does spray foam installation take in Thornhill?
Most Thornhill attic spray foam jobs complete in 4–6 hours. A combined attic + rim joist project runs 6–8 hours. Full basement wall insulation is typically a separate day. We schedule the energy audit (if required for your rebate program) in advance and sequence the work to minimize site visits.
Does spray foam meet the Ontario Building Code for Thornhill homes?
Yes. Open-cell spray foam at 8–10 inches in the attic achieves R-29.6 to R-37, meeting the OBC SB-12 prescriptive requirement of R-31 for climate zone 6 (which includes Thornhill). Closed-cell at 2 inches on rim joists (R-12) meets the minimum wall insulation requirement. All our Thornhill installs are spec’d to OBC SB-12 — we provide documentation for permit files on request.
Will spray foam help with ice damming on my Thornhill roof?
Yes — ice dams form when warm air from the living space heats the roof deck and melts snow, which then refreezes at the cold eaves. A proper spray foam air seal in the attic eliminates the warm-air pathway to the roof deck. Most Thornhill homeowners with chronic ice-dam problems see them eliminated in the first winter after attic spray foam installation. The air seal — not just the R-value — is the key step.
How do I know if my Thornhill attic needs spray foam or just a top-up?
If your current attic insulation is below R-20 effective (roughly 6 inches of settled blown-in), the existing insulation has not been air-sealed, you have pot lights or plumbing stacks punching through the attic floor, or you’ve had ice dams in the past two winters — spray foam is the correct solution, not a top-up. A blown-in top-up over existing insulation without air sealing captures only 15–20% of the available heat-loss reduction. We include a free attic assessment with every Thornhill quote to confirm which approach is right for your specific home.
