In Canada, residential buildings account for 16.7% of the total secondary energy end use and 12.7% of the total greenhouse gas emissions. Of these percentages, space heating and cooling account for about two-thirds of the total. As buildings are being built to higher standards, an air-tight, resilient, and thermally efficient building enclosure could be used to meet the targeted energy efficiency in new and retrofit construction. The research program was aimed at the use of vacuum insulation panels (VIPs) encapsulated within expanded polystyrene (EPS) board to form an exterior insulation system for use in new and retrofit construction nationwide. The program utilized experimental and numerical methods to evaluate the insulation system under steady-state thermal and transient hygrothermal conditions. The experimental study was split into two categories: steady-state thermal conductivity testing and in-situ hygrothermal monitoring. The steady-state testing, performed with a guarded hot-box at Carleton University, found that a 200 mm by 300 mm (8" x 12") VIP in the exterior insulation with a 1:1 VIP to EPS insulated area ratio on a code-built wood-frame wall would have an effective thermal resistance of R-5.1 to R-6.3 m2K/W. It was observed after the in-situ monitoring, performed at CanmetENERGY-Ottawa, that the backer material for the VIP-insulated system did not affect the long-term potential for mould growth or moisture-related damage in the assembly. The numerical study was performed using WUFI Pro 6.1 and WUFI 2D. The hygrothermal model was validated using the in-situ monitored data from 2016 to 2020 for Ottawa, CA. A methodology to model VIP insulated wall assemblies for building envelope retrofits was presented and performed in multiple cities across Canada. It was observed that masonry clad buildings (e.g., brick veneer) and wet climates (e.g., Vancouver and St. John's) had a higher potential to experience mould growth in new and retrofit buildings, for a similar envelope construction in a dryer climate. Finally, a screening study of eleven simulation inputs was performed using WUFI Pro 6.1 by following the Morris Method, a One-At-a-Time (OAT) screening procedure that compares the standard deviation and mean of the peak mould index.