What is the minimum R-value required by the NB Building Code for exterior walls in a new Fredericton home?

The NB Building Code requires R-22 to R-28 effective thermal resistance for above-grade exterior walls in new construction, depending on the specific wall assembly and whether continuous insulation is used to address thermal bridging.

For a new home in Fredericton, the most common approach to meet code is a 2x6 stud wall with R-22 batt insulation between the studs, plus R-5 continuous exterior insulation (typically rigid foam) over the sheathing. This combination achieves the required effective R-value while eliminating thermal bridging through the wood framing.

Why the "effective" R-value matters more than the batt R-value: A standard 2x6 wall filled with R-22 batts doesn't actually perform at R-22 because the wood studs create thermal bridges. Wood studs are only about R-6, and they occupy roughly 25% of the wall area in a typical 16-inch on-center framing system. This thermal bridging reduces the whole-wall performance to approximately R-16, even with R-22 batts. The continuous exterior insulation breaks these thermal bridges and allows the wall to perform closer to its rated R-value.

Alternative code-compliant assemblies include advanced framing techniques (2x6 studs at 24 inches on center with R-22+ batts), double-wall construction, or insulated concrete forms (ICF). Some builders use mineral wool batts, which perform slightly better than fibreglass in thermal bridging scenarios due to their higher density and thermal resistance.

Fredericton's Climate Zone 6 requirements are driven by the city's 4,800+ heating degree days and winter temperatures that regularly reach -20 to -30°C. These code minimums represent the baseline for energy efficiency — many builders exceed the minimum to achieve better comfort and lower heating costs. High-performance homes in the Fredericton area often target R-30+ effective wall performance through thicker continuous insulation or advanced wall systems.

Important note about vapour barriers: Regardless of the insulation type or R-value, all exterior walls in NB require a continuous 6-mil polyethylene vapour barrier on the warm (interior) side of the insulation assembly. This prevents moisture-laden interior air from reaching cold surfaces within the wall cavity, where it would condense and cause mould or rot.

For new construction in Fredericton, work with your builder to ensure the wall assembly meets both the thermal and moisture management requirements of the NB Building Code. The insulation system must work together with proper air sealing and vapour management to perform effectively in New Brunswick's cold Maritime climate.