Exterior Envelope Renovation

The lightest scope is a siding refresh: take the old cladding off, inspect and repair the sheathing and any flashing failures, install a new rainscreen cavity and weather-resistive barrier (WRB) where they're missing, and re-clad in the chosen material. Cost varies widely by cladding choice. The middle scope adds continuous exterior insulation outboard of the sheathing — usually 1.5 to 4 inches of mineral wool or rigid foam — which markedly improves the wall's thermal performance and shifts the dew point outward where condensation is less consequential. The heaviest scope is a full envelope retrofit: re-cladding plus exterior insulation plus window replacement plus sometimes air-sealing rim joists and re-flashing transitions. The right scope depends on the age of the home, the condition of the existing walls, and how long the owner plans to stay.

A drained, vented rainscreen cavity behind the cladding is the single most consequential detail in a Lower Mainland envelope. It lets bulk water that gets past the cladding drain out, and it lets the wall dry between rain events. Homes built before the late 1990s often have no rainscreen — cladding is attached directly to building paper over sheathing, and any water that gets in stays in. Retrofitting a rainscreen during a re-clad is roughly the right answer for any Burnaby home being touched. We use furring strips (typically 19 mm) over the WRB, with insect screens top and bottom, and we detail the transitions at windows, doors, decks and the roof eaves carefully — the rainscreen only works if it's continuous.

The moment the cladding is off and the sheathing is exposed is the only practical window for adding continuous exterior insulation without breaking the bank twice. Mineral wool (Rockwool Comfortboard 80, for example) and rigid foam each have their use cases — mineral wool is vapour-open and fire-resistant, rigid foam delivers more R per inch. We size the exterior insulation based on the target Step Code or comfort goal and on what the existing wall assembly will tolerate from a dew-point perspective. There's real building science behind getting this stack right — the wrong combination of interior vapour retarder and exterior insulation can trap moisture in the wall. We design the assembly with that in mind, not as a feel-good upgrade.

Windows are the weakest performing piece of most older envelopes and the most visible upgrade. The current default for a competent retrofit is a modern double-glazed unit with low-e coating and argon fill in a thermally-broken frame. For Step 4 or Step 5 targets, or for owners who want serious winter comfort and silence, triple-glazed units with insulated frames are the right answer — heavier, more expensive, and a different conversation with the existing rough opening structure. On heritage and character homes the trade-off between visual continuity (wood sash, original sight-lines) and performance is real; we'll lay it out without pretending one answer fits every project. For deeper dives, see [Windows and glazing for Burnaby winter](/blog/windows-glazing-burnaby-winter) and our note on [heat pumps and HRVs in a BC custom home](/blog/heat-pump-hrv-bc-custom-home).

Envelope renovations in Burnaby usually need a building permit (and an electrical/plumbing permit if any mechanical is being touched as part of the work), but they don't normally trigger a development permit unless the cladding change crosses a heritage or character area design review threshold, or unless the work expands the building envelope. The permit process is straightforward enough when the documentation is in order — we submit assemblies, manufacturer specs for the windows and insulation, and the rainscreen detailing. The inspector will want to see the WRB and flashings before the cladding goes on, so the schedule is built around that inspection happening on time.