Spray Foam vs Blown Cellulose vs Batt: Toronto Attic Comparison 2026

# Spray Foam vs Blown Cellulose vs Batt: Toronto Attic Comparison 2026

Quick answer. The three primary attic insulation materials behave very differently in Toronto's freeze-thaw climate, and the wrong choice for your specific attic geometry can cost you 30–50% of theoretical R-value within five years.

The three primary attic insulation materials behave very differently in Toronto's freeze-thaw climate, and the wrong choice for your specific attic geometry can cost you 30–50% of theoretical R-value within five years. This guide compares spray foam, blown cellulose, and fiberglass/mineral wool batt across every variable that matters: thermal performance, air sealing, moisture, settling, fire, environmental impact, cost, and lifespan.

For the broader pillar guide, see Attic Insulation Toronto: Complete 2026 Upgrade Guide. For the cost angle specifically, see Attic Insulation Cost Toronto: R-Value Tier-by-Tier Pricing.

The 60-Second Decision Framework

Standard rectangular attic with adequate ventilation: Blown cellulose. Best $/R, good air-blocking, recycled content.
Cathedral ceilings, complex framing, or air-leakage problems: Closed-cell spray foam at roof deck (hot-roof) or hybrid.
Rim joists, knee walls, fire-rated assemblies: Mineral wool batt (Rockwool/Roxul).
Standard attic when fiberglass is preferred: Loose-fill fiberglass (Owens Corning, Knauf, CertainTeed).
Almost never in attic floors: Fiberglass batts. They don't fill irregular cavities and air-leak heavily.

R-Value per Inch

Material	R-Value per Inch	Inches Needed for R60
Closed-cell spray foam	R6.0–R7.0	9"–10"
Open-cell spray foam	R3.5–R4.0	15"–17"
Blown cellulose	R3.2–R3.8	16"–19"
Loose-fill fiberglass	R2.2–R2.7	22"–27" (settled) or R2.5 dense-pack
Fiberglass batt	R3.0–R3.7	16"–20"
Mineral wool batt	R3.7–R4.3	14"–16"

Spray Foam vs Blown Cellulose vs Batt — tools and materials staged in a Greater Toronto Area home

R-value per inch matters when ceiling height in the attic is limited. In a typical Toronto bungalow with truss-framed attic, you have 18"–30" of clearance — plenty for any material. In a 1920s East York attic with shallow rafter bays, closed-cell spray foam may be the only way to hit R60 without losing usable space.

Air-Sealing Performance

Air sealing is where the materials diverge most dramatically. Air leakage causes 30–50% of total heat loss in poorly sealed homes — sometimes more than conduction.

Material	Air-Sealing Rating	Notes
Closed-cell spray foam	Excellent	Air barrier built-in, no separate sealing needed
Open-cell spray foam	Good	Air barrier built-in but lower density
Blown cellulose (dense-pack)	Good	At 3.5+ lb/cuft density, near-air-barrier performance
Blown cellulose (loose-fill)	Fair	Reduces convection but not an air barrier
Loose-fill fiberglass	Poor	Air passes through readily
Fiberglass batt	Poor	Air passes through, edges leak
Mineral wool batt	Poor	Same as fiberglass

The takeaway: only spray foam is itself an air barrier. Every other material requires separate air sealing of penetrations before installation.

Moisture Behavior

Toronto's climate creates two moisture stresses on attic insulation: winter condensation (warm interior moisture meets cold roof deck) and summer humidity (hot humid attic air meets cool ceiling).

Material	Moisture Performance	Risk
Closed-cell spray foam	Excellent — vapor retarder	Can trap moisture if installed over wet substrate
Open-cell spray foam	Fair — vapor permeable	Can hold moisture; not recommended for cold climates without vapor control
Blown cellulose	Good — manages moisture	Borate-treated, dries slowly but doesn't lose R-value when damp
Loose-fill fiberglass	Fair — water passes through	Loses R-value when wet, recovers when dry
Fiberglass batt	Same as loose-fill	Same
Mineral wool batt	Excellent — hydrophobic	Sheds water, doesn't lose R-value when damp

For a Toronto-specific issue: many old homes have intermittent ice dam leaks that wet the attic insulation. Cellulose and mineral wool tolerate this best. Closed-cell spray foam tolerates it but masks the leak (you don't see water staining). Open-cell spray foam can hold moisture and grow mold.

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Settling and Long-Term R-Value

Material	Settling	R-Value at 5 Years
Closed-cell spray foam	None	100%
Open-cell spray foam	None	100%
Blown cellulose	10–15%	R52–R54 (from R60 install)
Loose-fill fiberglass	2–5%	R57–R58 (from R60 install)
Fiberglass batt	None (but compresses if walked on)	100% if undisturbed
Mineral wool batt	None	100%

The settling number is the strongest argument for fiberglass over cellulose in Toronto attics where you want sustained R-value 10+ years. The counter-argument: cellulose is cheaper per inch of install, so over-installing to R65 to settle to R55 is roughly cost-equivalent to installing R60 fiberglass.

Fire Performance

Material	Fire Behavior
Closed-cell spray foam	Combustible — requires thermal barrier (drywall) below in conditioned attics
Open-cell spray foam	Combustible — same
Blown cellulose	Class A fire rating — borate-treated to resist ignition
Loose-fill fiberglass	Non-combustible (glass) but binders can burn
Fiberglass batt	Same as loose-fill
Mineral wool batt	Non-combustible — melts at 1,000°C+

For Toronto attics, fire performance matters most around recessed lights, chimneys, and attic-floor penetrations. Mineral wool batts are often used as a fire-rated transition between insulation and chimney cleanouts.

Environmental Impact

Material	Recycled Content	GWP (CO2 Equivalent)
Closed-cell spray foam (HFO blowing agent)	0–10%	Low (HFO replaces high-GWP HFC)
Closed-cell spray foam (HFC blowing agent — older formulations)	0–10%	Very High — being phased out
Open-cell spray foam	0–5%	Low — water-blown
Blown cellulose	80–85% (recycled newsprint)	Very Low
Loose-fill fiberglass	30–60% recycled glass	Low-Medium
Fiberglass batt	30–60% recycled glass	Low-Medium
Mineral wool batt	40–75% recycled slag	Medium

For homeowners pursuing LEED or Passive House certification, blown cellulose is typically the lowest-impact choice. For homes pursuing Net Zero retrofit, low-GWP closed-cell spray foam (Demilec Heatlok HFO) provides the best thermal performance with acceptable carbon footprint.

Cost per Square Foot (1,500 sqft Toronto attic, install only, no removal)

Material	Cost per SqFt	Total
Blown cellulose	$1.20–$1.60	$1,800–$2,400
Loose-fill fiberglass	$1.40–$1.80	$2,100–$2,700
Fiberglass batt R60	$1.80–$2.40	$2,700–$3,600
Mineral wool batt R60	$2.20–$3.00	$3,300–$4,500
Open-cell spray foam (10")	$3.50–$4.50	$5,250–$6,750
Closed-cell spray foam (3" floor)	$2.80–$3.70	$4,200–$5,500
Closed-cell spray foam (full hot-roof)	$4.50–$7.00	$6,750–$10,500

Lifespan

Material	Functional Lifespan
Closed-cell spray foam	50+ years
Open-cell spray foam	40+ years
Blown cellulose	30+ years (with periodic top-up to maintain R-value)
Loose-fill fiberglass	50+ years
Fiberglass batt	50+ years
Mineral wool batt	75+ years

Spray Foam vs Blown Cellulose vs Batt — close-up of professional workmanship in a Toronto-area home

In practice, all materials outlast the homeowner's tenure if installed correctly and not damaged.

Common Toronto Use Cases

Case 1: 1960s Leaside bungalow, 1,500 sqft attic, truss framing, R30 existing. Tier 2 with blown cellulose to R60. Cost: $5,500. Reasoning: standard scope, best $/R, no geometric complications. Case 2: 1920s East York 1.5-storey, complex framing with knee walls, R20 existing, ice dam history. Hybrid: closed-cell spray foam at knee walls and roof deck transitions, blown cellulose at flat attic floor. Cost: $8,500. Reasoning: spray foam handles the geometry that cellulose can't fill cleanly. Case 3: 1990s High Park two-storey, 1,200 sqft attic, R40 existing, no ice dams. Top-up only with blown cellulose to R60. Cost: $2,800. Reasoning: existing insulation is already adequate; just need a refresh. Case 4: 2010 Leslieville townhouse with cathedral ceilings (no attic). Closed-cell spray foam at the underside of the roof deck. Cost: $7,000. Reasoning: only material that fits the assembly. Case 5: 1955 Beaches detached, suspected vermiculite. Vermiculite testing first; if positive, abatement, then blown cellulose. Cost: $9,000–$13,000. Reasoning: standard cellulose scope after the abatement, since the geometry isn't complex.

When to Avoid Each Material

Avoid closed-cell spray foam if: The roof deck has a known leak (foam masks the leak; water rots the deck under the foam). Or if the home is being sold within 5 years to a buyer who values "natural" materials (some buyers see spray foam as a negative). Avoid open-cell spray foam in Toronto attics: Toronto's climate has too much moisture stress. Open-cell holds moisture and can grow mold. Use only with explicit vapor control. Avoid blown cellulose if: Attic has chronic moisture issues that haven't been resolved (cellulose holds moisture and dries slowly). Avoid fiberglass batt if: You're insulating an attic floor (it doesn't fill irregular geometry). Use loose-fill fiberglass or cellulose instead. Avoid mineral wool batt as primary attic floor insulation: Cost is too high vs cellulose for equivalent R-value. Use mineral wool for fire-rated transitions, rim joists, or knee walls.

Brand Notes

Closed-cell spray foam: Demilec Heatlok HFO is the dominant Toronto product (low-GWP, ULC-listed). Icynene ProSeal HFO is the runner-up. Huntsman Building Solutions and BASF Walltite are also available. Blown cellulose: GreenFiber Cocoon is the most common in Toronto. Applegate is regional but available. Both are borate-treated for fire and pest resistance. Loose-fill fiberglass: Owens Corning ProPink is the most-installed loose-fill in Toronto. Knauf Jet Stream Ultra is a higher-density premium option. CertainTeed InsulSafe SP rounds out the top three. Mineral wool: Rockwool (formerly Roxul) is the dominant brand. Comfortbatt for residential, Comfortboard for exterior continuous insulation.

For brand-specific R-value certificates and warranty terms, see Attic Insulation Toronto: Complete 2026 Upgrade Guide.

What to Specify in Your Scope of Work

When asking for quotes, specify:

1. R-value target (R60 minimum for OBC compliance)
2. Material (or "any of cellulose/loose-fill fiberglass — please quote both")
3. Density (for cellulose, request 1.2–1.5 lb/cuft minimum for blown attic floors)
4. Settled R-value, not installed R-value (cellulose settles 10–15% — install R65–R68 to settle to R60)
5. Air sealing scope (comprehensive, not just attic hatch)
6. Baffles (every rafter bay, not just visible ones)
7. Pot light covers (specify quantity)
8. Documentation (photo, R-value certificate, depth markers)

Bottom Line for Toronto Material Choice

For 80% of Toronto attics: blown cellulose at R65 (settles to R60) with comprehensive air sealing. Cheapest, environmentally best, performs well in Toronto climate.

For attics with complex geometry, ice dam history, or cathedral elements: hybrid with closed-cell spray foam at problem areas + cellulose at flat floor.

For attics where settling is a major concern (you don't plan another insulation top-up for 20+ years): loose-fill fiberglass (Owens Corning ProPink or Knauf Jet Stream Ultra) at R62.

For specialty applications (knee walls, rim joists, fire transitions): Rockwool batts.

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Choosing materials for your Toronto attic insulation? RenoHouse installs all four primary attic materials and will recommend based on your home's specific geometry, age, and rebate strategy. Visit our attic insulation upgrade service page or schedule an insulation thermal audit to scope materials precisely for your home.