Is spray foam insulation worth the higher cost compared to batts in NB? | Insulation IQ?

For most New Brunswick homeowners weighing spray foam against fibreglass or mineral wool batts, the honest answer is: it depends heavily on where in the building you're insulating. Spray foam is not universally worth the premium — but in specific locations and situations, it delivers performance that batts simply cannot match, and the long-term value is often clearly positive.

The core difference between the two comes down to air sealing. Batts insulate — they slow the conductive transfer of heat through a wall or ceiling cavity — but they do not air seal. They require a separate vapour retarder and careful attention to air barrier details to perform well. In New Brunswick's climate zone 6, where blower door tests on older Fredericton or Saint John homes regularly reveal air leakage rates of 5 to 10 air changes per hour or more, that distinction matters enormously. A poorly air-sealed attic with new R-50 batt insulation will still lose significant heat and risk moisture damage through air movement. Spray foam — particularly two-part closed-cell foam — simultaneously insulates and creates a robust air and vapour barrier in a single pass.

Closed-cell spray polyurethane foam (ccSPF) delivers approximately R-6 to R-7 per inch, compared to R-3.1 to R-4 per inch for fibreglass batts. At 3.5 inches in a 2x4 wall cavity, closed-cell foam achieves around R-21 to R-24, compared to R-13 to R-15 for a full batt. More importantly, it contributes structurally and adheres directly to framing and sheathing, eliminating virtually all convective looping within the wall assembly.

Open-cell spray foam (ocSPF) is softer, more vapour-permeable, and less expensive than closed-cell — roughly $1.00 to $1.80 per board foot versus $2.50 to $4.50 for closed-cell. It achieves about R-3.7 per inch and works well in interior wall cavities and interior-side attic slopes where air sealing is the priority but a vapour barrier is handled separately.

In dollar terms for a New Brunswick project, fibreglass batts for a typical 1,500 sq ft attic might cost $1,200 to $2,500 installed, while spray foam for the same area could run $4,000 to $9,000 depending on thickness and type. That is a real difference — and for many homeowners, the question is whether the performance gains justify it.

Where spray foam tends to be clearly worth the higher cost in NB:

Rim joists are arguably the best dollar-for-dollar spray foam application in a New Brunswick home. The rim joist area — where the floor framing meets the foundation wall — is notoriously leaky and difficult to batt-and-seal effectively. Two to three inches of closed-cell foam here costs relatively little (often $300 to $700 for a typical home) and eliminates a major air leakage path. Almost every energy advisor in New Brunswick recommends this as a high-priority measure.

Unvented cathedral ceilings and roof assemblies are situations where spray foam often makes the most structural sense. Without sufficient cold space above insulation to allow proper ventilation, batts create condensation risk. Closed-cell foam applied to the underside of the roof deck creates a hot roof assembly that manages moisture safely and is well-suited to New Brunswick's climate.

Basement walls in unfinished basements benefit from spray foam's moisture resistance, particularly if the wall sees any seasonal dampness — common in older masonry basements in Moncton or Saint John.

Where batts remain the practical choice is in standard framed wall cavities during new construction or gut renovations, open attic floors where the budget is the primary constraint, and any location where a continuous air barrier is being handled through other means (taped sheathing, membrane, etc.).

For most homeowners doing a targeted insulation upgrade, a hybrid approach is often the best value: spray foam on the rim joist, any cathedral or hard-to-seal areas, and tight transitions, combined with blown-in cellulose or fibreglass batts in the main attic floor. This approach satisfies NB Power's THES program requirements, can achieve the R-50 attic target in the NB Building Code, and keeps costs manageable.

The insulation professionals connected through newbrunswickinsulation.com can assess your home's specific conditions and help you decide where spray foam delivers the most value for your climate zone 6 property.

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