High performance enclosures reduce building energy consumption, however, may vary from expected RSI values and be at risk of moisture damage. This research investigated the hygrothermal performance of a high performance enclosure for use in Toronto and other cold climates. The proposed enclosure utilized 228mm of exterior mineral wool attached to a typical wood frame structure. The in-situ thermal resistance was compared with the nominal thermal
resistance and found to differ by up to 14.4%. Three-dimensional thermal modelling determined a range (-4.2% to -24.4%) of potential RSI reductions caused by metal-screw fasteners. In-situ measurements and calibrated one-dimensional WUFI-Pro models determined that the enclosure is not at risk of moisture damage in Toronto and other cold climates. A parametric analysis identified several climatic and materialistic variables that had an influence on the hygrothermal performance of the enclosure. The combined use of collected in-situ data and calibrated modelling allowed for a comprehensive hygrothermal analysis of the proposed enclosure.