Should I insulate the floor above an unheated crawl space in Dieppe? | Insulation IQ?

Yes — insulating the floor above an unheated crawl space is one of the most impactful upgrades you can make to a Dieppe home, and it's a project where the return on investment is felt immediately every winter. Dieppe sits in Westmorland County, in the Greater Moncton area, where January average lows hover around -14°C to -16°C. An uninsulated floor above an unheated crawl space is essentially a giant cold radiator pulling heat out of your living area, making hardwood floors feel frigid, inflating heating bills, and stressing your HVAC system through what should be the most comfortable parts of your home.

What the code requires. New Brunswick has adopted the National Building Code of Canada (NBC), which places the greater Moncton/Dieppe area firmly in Climate Zone 6. Under NBC 9.36, a floor assembly over an unconditioned space — which includes an unheated, vented crawl space — must achieve at least RSI 5.46 (approximately R-31) in Climate Zone 6. Many older Dieppe homes, particularly those built before 2010, have either no insulation under the floor or outdated fibreglass batts well below this threshold. Upgrading to current code minimums alone can produce significant comfort and efficiency gains.

The preferred approach in NB. For an unheated vented crawl space, the standard method is to install mineral wool or fibreglass batts between the floor joists from below. Mineral wool (such as Rockwool Comfortbatt) is strongly recommended over fibreglass in damp Dieppe crawl spaces because it repels moisture, won't sag over time, and resists mould growth better than fibreglass. A common installation achieves R-31 to R-40 using two layers of batts — for example, a layer of R-22 mineral wool (approximately 5.5 inches) combined with a layer of R-14 in the joist cavity can get you to R-36, which exceeds code and provides measurable comfort improvement. The batts should be friction-fitted snugly between joists and held in place with netting, wire rods, or rigid supports — don't rely on gravity alone in a humid crawl space.

Vapour barrier on the ground is mandatory. Regardless of how well you insulate the floor joists, a 6-mil polyethylene ground cover must cover the crawl space floor. Ground moisture evaporation is substantial and continuous in the Dieppe–Moncton area, and without a ground vapour barrier, that moisture migrates upward into the floor framing, promoting mould, rot, and insulation degradation over time. The vapour barrier should lap up the perimeter foundation walls at least 300 mm and be taped at seams.

Watch for air leakage at the perimeter. The junction between the floor joists and the foundation (the rim joist and header area) is a major thermal bypass that defeats floor insulation if left unaddressed. Cold air infiltrates around the sill plate and travels along the underside of the subfloor. Sealing this area with a bead of acoustical sealant or low-expansion spray foam before installing floor batts ensures your insulation performs as intended. The rim joist area itself should be insulated separately — typically with cut-and-cobble rigid foam or two-component spray foam — to R-10 to R-20.

Comfort impact. Dieppe homeowners who upgrade floor insulation above unheated crawl spaces consistently report that the most noticeable change is tactile — floors that were previously uncomfortable to walk on in bare feet become noticeably warmer. Rooms that sat cold despite adequate HVAC output warm up faster and hold temperature better. For homes with in-floor radiant heat or baseboard heating, reduced heat loss through the floor also translates directly to lower energy consumption.

Cost and rebate picture. Floor joist insulation in a typical Dieppe bungalow or split-level with a 600–900 sq ft crawl space generally runs $1,200–$2,800 installed, depending on accessibility, existing conditions, and target R-value. The Canada Greener Homes Grant and NB Power Home Energy Savings Program both recognize below-floor insulation upgrades as eligible measures, with rebates calculated against the improvement in your home's energy model after a pre- and post-EnerGuide assessment. A well-documented upgrade can yield $500–$2,000 in combined grants depending on the overall project scope.

Don't underestimate the value of addressing your crawl space floor before another Dieppe winter. The professionals connected through the New Brunswick Insulation network can assess your specific crawl space conditions and deliver code-compliant results with the documentation needed to support rebate claims.

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• 3Tone Construction Ltd
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• Brunswick insulation & roofing