What R-value does 2 inches of closed-cell spray foam provide in New Brunswick? | Insulation IQ?

Two inches of closed-cell spray foam provides approximately R-12 to R-14 in New Brunswick — typically landing around R-13 when installed under standard conditions. Closed-cell spray foam has a per-inch R-value of roughly R-6 to R-7, making it the highest-density, highest-performing insulation material available by thickness. That's a significant distinction from open-cell spray foam, which runs closer to R-3.5 to R-4 per inch and requires nearly double the thickness to reach the same thermal resistance.

In Climate Zone 6, which covers all of New Brunswick including Moncton, Fredericton, Saint John, and Miramichi, that R-12 to R-14 from 2 inches of closed-cell foam is often used as a continuous air barrier and vapour barrier layer rather than the sole source of insulation. The NB Building Code (aligned with the National Building Code of Canada) requires R-20 for above-grade walls and R-31 effective for foundation walls depending on the assembly. Two inches of closed-cell foam is typically the first layer in a hybrid assembly, paired with fibreglass batts or rigid board to achieve full code compliance.

For example, a common wall assembly in New Brunswick new construction or deep retrofits uses 2 inches of closed-cell spray foam applied directly to the sheathing or concrete wall, followed by R-14 fibreglass batts in the stud cavity. This gets you to roughly R-26 to R-27 effective — comfortably above the NBC minimum and well-suited to our cold winters.

Closed-cell foam at 2 inches also delivers an air permeance of less than 0.02 L/(s·m²) at 75 Pa, which qualifies it as an air barrier material under the NBC. This is one of its most underrated qualities in the New Brunswick climate: even a perfectly insulated wall with air leakage will feel cold and can accumulate moisture. The foam essentially seals and insulates in a single step.

The vapour control class of 2-inch closed-cell foam is typically Class II (semi-impermeable), with a permeance rating below 60 ng/(Pa·s·m²). This satisfies the vapour barrier requirement on the warm side of the insulation for most New Brunswick wall assemblies, eliminating the need for a separate 6-mil poly sheet in many applications. That's particularly valuable in basement walls and rim joists where installing poly behind drywall is awkward.

From a cost perspective, 2 inches of closed-cell spray foam in New Brunswick typically runs .50 to .00 per square foot installed, depending on the area, substrate complexity, and access. That's higher upfront than fibreglass or blown-in products, but when you factor in the air sealing value and vapour control it provides — functions that would otherwise require separate materials and labour — the total installed cost of the building assembly is often comparable.

If you're renovating in Fredericton or Moncton and considering closed-cell foam for your basement walls, rim joists, or crawlspace, it's worth consulting with an insulation professional about whether 2 inches as a hybrid base coat or a full fill to 3–4 inches is the right strategy for your specific assembly. The New Brunswick Construction Network connects homeowners with qualified insulation contractors across the province who can assess your building and recommend the right thickness for your goals and budget.

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Looking for experienced contractors? The New Brunswick Construction Network connects homeowners with qualified professionals:

• 3Tone Construction Ltd
• Brunswick insulation & roofing
• Gionetterenovations
• Thirty Four Renovations
• Arctic Fox Construction Inc.