Our basement in North Vancouver has a partially below-grade wall — one side is fully underground and the other is exposed. Do we need different insulation strategies for each section?

Yes, absolutely — a partially below-grade basement with mixed wall exposure requires two distinct insulation strategies, and getting this wrong in North Vancouver's climate is one of the fastest ways to end up with mould behind your drywall.

North Vancouver sits in one of the wettest microclimates in all of Metro Vancouver. The North Shore mountains create orographic lift that pushes annual rainfall well above 2,000mm in many areas, and that moisture presses against your below-grade foundation wall continuously from October through April. The exposed above-grade section faces a completely different set of physics — wind-driven rain, outdoor temperature swings, and direct cold-air exposure. Each section needs an insulation strategy matched to its actual moisture and thermal conditions.

The Fully Below-Grade Section

For the wall section that's fully underground, your primary concern is hydrostatic pressure and condensation. Cool concrete in contact with moist soil will wick moisture, and if you place fibreglass batt directly against that wall, you're creating a perfect mould incubator. Never use fibreglass batt directly against a below-grade concrete wall in Metro Vancouver — it absorbs moisture and holds it against the concrete indefinitely.

The right approach here is to start with a moisture-resistant rigid layer directly against the concrete. Closed-cell spray foam at 2 inches (R-13) is the premium choice — it adheres directly to the concrete, acts as its own vapour barrier, and provides a capillary break between the concrete and any subsequent framing. XPS rigid foam board (2 inches, R-10) adhered to the wall is a more budget-friendly alternative that performs well in this application. After either of those, you can frame a 2x4 stud wall 25mm off the foundation and fill the cavity with Rockwool (mineral wool) batt — R-15 for a 3.5-inch cavity — to reach the R-20 target that BC Building Code and the BC Energy Step Code set for below-grade walls. Rockwool is moisture-resistant and dimensionally stable, making it far better suited to North Vancouver conditions than fibreglass.

The Exposed Above-Grade Section

The exposed section of your wall behaves more like an above-grade exterior wall — it faces outdoor air temperatures, wind, and rain — but it still connects to the concrete foundation below, so you can't treat it exactly like a standard above-grade wall either. The thermal bridging through the concrete or block at the transition point is a real concern.

For this section, the same closed-cell spray foam or XPS approach on the interior face is still a good starting point to manage any residual moisture from the concrete mass. From there, you can build out a standard insulated stud wall with Rockwool or fibreglass batt (fibreglass is acceptable here since the wall is exposed and drying potential exists on the exterior side). Make sure your vapour barrier is continuous across both sections — the transition point between below-grade and above-grade is where many contractors get sloppy, and that gap becomes a moisture pathway.

The Transition Zone

The junction where the wall transitions from below-grade to above-grade is the most critical detail in your project. This is where temperature differentials are sharpest and condensation risk is highest. Your contractor should treat this zone with particular care — typically by running the spray foam or rigid foam continuously through the transition rather than stopping it at grade level. A thermal break at that point defeats much of the insulation value you've built up on either side.

Practically speaking, get your waterproofing assessed before any insulation goes in. If the below-grade section shows any signs of efflorescence (white mineral deposits), staining, or dampness, address that first. North Vancouver hillside homes often have significant hydrostatic pressure from uphill runoff, and no insulation strategy compensates for active water infiltration.

For a project with this level of complexity — mixed exposure, high-rainfall climate, and a critical transition detail — this is firmly in professional territory. The insulation strategy needs to be coordinated with your framing, vapour barrier, and any waterproofing work. Vancouver Basement Finishing can match you with a local basement contractor experienced with North Shore conditions for a free estimate on your project.