Spray Foam vs Blown-In Cellulose: An Ontario Contractor’s 18-Year Verdict

The question I get asked most often by families booking an attic insulation assessment is some version of: “Should I go with spray foam or the blown-in stuff?” It is a reasonable question because the marketing behind both materials can be persuasive, and the choice genuinely matters for how well your home performs and what you pay in the long run.

After 18 years of insulating attics across Toronto, Mississauga, Brampton, Oakville, Hamilton, Vaughan, Burlington, and the rest of the GTA, I have a clear answer — one that is not “it depends” in the frustrating, non-committal way. It does depend on certain factors, but the decision tree is simpler than most people think.

Here is my honest, material-by-material breakdown.

Blown-in cellulose installation in a Mississauga home — a full 1,600 sqft attic upgraded to R-60 in a single day.

Understanding the Two Materials

Blown-In Cellulose

Cellulose is made from recycled paper — primarily old newsprint — treated with borate compounds for fire and pest resistance. It is a loose-fill material that is blown into place using a machine, filling cavities and settling around obstructions naturally. It has been used in North American homes since the 1970s and has a well-established performance record.

Key characteristics:

• R-value: approximately R-3.7 per inch
• Air resistance: moderate to good, especially when properly air sealed beneath
• Moisture behaviour: absorbs and releases moisture without structural damage in most situations
• Environmental profile: high recycled content, low embodied carbon
• Cost: starting at $0.99/sqft for a standard installation

Spray Foam

Spray foam is a two-component chemical product that expands when applied. It comes in two main types — open-cell and closed-cell — with different performance profiles. When applied correctly, it bonds to surfaces and creates both an insulating layer and an air barrier simultaneously.

Key characteristics:

• R-value: R-3.7 per inch (open-cell) to R-6.5 per inch (closed-cell)
• Air sealing: excellent — superior to any loose-fill product
• Moisture behaviour: closed-cell resists moisture; open-cell is permeable
• Cost: $3.00–$7.00/sqft depending on type and thickness
• Application: requires licensed, trained applicators and safety precautions during curing

Head-to-Head: The Key Performance Categories

Thermal Performance

For a standard vented attic — which is what the majority of GTA homes have — both materials can achieve the same R-value if sufficient depth is installed. Ontario Building Code requires a minimum of R-50; we recommend upgrading to R-60 for optimal performance. With blown-in cellulose, achieving R-60 requires approximately 16 inches of material. With open-cell spray foam, you would need around 16 inches as well. Closed-cell achieves R-60 in approximately 9 inches — relevant in shallow attic spaces.

Winner: Tied for most vented attics; closed-cell foam has an advantage in constrained spaces.

Air Sealing

This is the category where spray foam has a genuine edge — and it is an important one. Spray foam expands into every gap and crack, creating an essentially continuous air barrier. Cellulose relies on proper pre-installation air sealing using foam and caulk, which when done well is effective, but requires an additional step.

However, here is the nuance that most comparison articles miss: a properly air-sealed attic with blown-in cellulose on top performs nearly as well as spray foam from an air leakage standpoint. The key phrase is “properly air-sealed.” When a contractor skips or rushes the air sealing step — which happens more often than it should — cellulose suffers relative to spray foam.

When we install blown-in cellulose, air sealing is always part of the job. We seal every penetration before the first bag of cellulose goes in.

Winner: Spray foam has a slight structural advantage; properly-executed cellulose with air sealing is nearly equivalent.

Cost and Rebate Eligibility

This is where the decision becomes clear for most Ontario families. A 1,400-square-foot attic insulated with blown-in cellulose to R-60 might cost $1,400–$2,000 installed. The same attic done with spray foam would typically run $4,200–$9,800, depending on type and depth.

Both materials are eligible for the Ontario Home Renovation Savings (HRS) program (subject to eligibility and program availability), which offers up to $1,250 for standalone attic insulation upgrades. However, because spray foam costs significantly more, the rebate offsets a smaller percentage of the total investment.

For full rebate details, visit homerenovationsavings.ca. The energy audit requirement applies regardless of which material you choose.

Winner: Cellulose, by a significant margin, for standard vented attics.

Material comparison: blown-in cellulose (left) versus spray foam application. Each has its place depending on attic type and project scope.

Moisture Management

Ontario’s climate means attics need to handle moisture carefully. Cellulose is hygroscopic — it absorbs moisture and releases it, acting somewhat like a buffer. In most residential applications with proper ventilation, this is not a problem. In fact, some building scientists consider this property beneficial in certain assemblies.

Closed-cell spray foam is vapour-impermeable, which means it locks moisture out — ideal for locations where bulk water is a risk (rim joists, crawlspaces) but can trap moisture in assemblies that need to dry in one direction.

Open-cell spray foam is vapour-permeable and handles moisture similarly to cellulose in many respects.

Winner: Context-dependent. For standard vented attics, both perform well. Closed-cell foam is preferred for rim joists and unconditioned crawlspaces.

Environmental Impact

Cellulose is made from 80–85% recycled content and has among the lowest embodied carbon of any insulation material. It is the most environmentally conscious choice in this comparison by a notable margin.

Spray foam uses petrochemical blowing agents and has higher embodied carbon. Some newer foam formulations use lower-GWP blowing agents, but cellulose remains the better environmental option.

As Natural Resources Canada notes in its insulation guide, cellulose insulation is one of the most environmentally responsible choices available to families.

Winner: Cellulose, clearly.

When Spray Foam Is Actually the Right Answer

After all that, I want to be clear: spray foam has its place. After 18 years, here are the situations where I genuinely recommend it over cellulose:

• Cathedral ceilings: Where there is no attic cavity and insulation must be applied directly to the roof deck, closed-cell spray foam is often the only practical option for achieving adequate R-values.
• Rim joists: The transition between foundation wall and floor frame is a major air leakage point. A 2-inch layer of closed-cell foam here outperforms any blown-in product.
• Unvented attic assemblies: Some modern construction uses “hot roof” assemblies where insulation is applied to the underside of the roof deck. This requires spray foam.
• Severe air leakage situations: In older homes with extensive penetrations and complex framing, spray foam on the attic floor can be a more efficient way to achieve air tightness than labour-intensive manual sealing.

For the standard vented attic in a typical GTA detached or semi-detached home — which is most of what we see — blown-in cellulose with proper air sealing is the better choice in almost every dimension that matters to families: cost, environmental profile, rebate eligibility, and long-term performance.

What We Install at Canada Energy Solution

Blown-in cellulose is our primary recommendation and our most-requested service, starting at $0.99/sqft. We also install spray foam (open-cell and closed-cell) in applications where it is genuinely the better product, and fiberglass batt insulation where specified. Our approach is to recommend what is right for the home, not what is most profitable for us.

Learn more about our blown-in cellulose attic insulation service.

As the Energy Star program emphasizes, sealing air leaks combined with proper insulation delivers the best overall energy performance — regardless of material choice, the fundamentals remain the same.

The 18-Year Verdict

For standard vented attics in Ontario homes: blown-in cellulose with thorough air sealing, upgraded to R-60, is the best value and the most practical choice for the vast majority of families.

Spray foam earns its premium price in specific applications — cathedral ceilings, rim joists, hot roof assemblies — where it provides advantages that cellulose genuinely cannot match.

That is the honest answer after 18 years. The material you choose matters less than the quality of the installation and the competence of the contractor.

Frequently Asked Questions

Can I mix spray foam and cellulose in the same attic?

Yes, and it is often the optimal approach. We commonly use closed-cell spray foam to seal critical penetrations and rim joist areas, then blow cellulose over the attic floor for cost-effective thermal mass.

Does cellulose settle over time and lose R-value?

Cellulose does settle slightly after installation — typically 10–15% — which is factored into the installed depth to achieve the target R-value. Once settled, it is stable and does not continue to degrade.

Is spray foam worth it for old Ontario homes?

For the attic floor of a typical detached home, no — the cost premium is not justified by the performance difference when cellulose is properly air-sealed. For the rim joist and other specific areas, yes.

Canada Energy Solution holds a BBB A+ rating, 4.9-star Google rating (438+ reviews), and is TSSA certified. We serve all GTA communities including Toronto, Mississauga, Brampton, Oakville, Hamilton, Vaughan, Burlington, Scarborough, North York, and Etobicoke. Call (647) 812-5200 for a free assessment or to discuss which insulation material is right for your home. Actual cost depends on your home — book a free assessment for an exact quote.