An Investigation into the Hygrothermal Performance of a Mineral Wool Based Externally Insulated Enclosure in a Cold Climate

A high RSI enclosure has been developed for use in low energy buildings in cold climates and utilizes high density mineral wool outboard of typical wood frame construction. This study investigated both the in-situ thermal resistance and hygrothermal performance of the proposed enclosure approach. The in-situ data has been used to calibrate 3d thermal models and 1d transient hygrothermal models. The in-situ testing indicated a clear-wall RSI value of 8.96 m2K/W for the north wall and 10.97 m2K/W for the south wall, a change of -3.4% and +17.5% from expected nominal. Thermal modelling indicated the metal fasteners reduced the thermal resistance by 7% to 24% depending on the fastener and stud configuration. The calibrated hygrothermal simulations assessed the performance of the proposed enclosure, and a split-insulation variant, in several cold climates. The results indicate acceptable performance in all locations except for the split-insulation case located in an extremely cold climate.