Future projected changes in moisture index over Canada

As a consequence of global warming, buildings in Canada and around the globe are expected to face unprecedented climate over their design lives. The Moisture Index (MI) is a climate-based indicator currently used in the National Building Code of Canada (NBCC) to guide the design of wall assemblies for acceptable durability performance. In this study, future changes in MI are calculated across Canada under 2 and 3.5 degrees C of future global warming. Results indicate that the coastal and great lakes regions of Canada will have increased MI, whereas prairies and northern regions will in the future have decreased values of MI. Furthermore, it is demonstrated that drastically different projected future MI changes can be obtained with different values of drying potential normalization factor, and it is suggested that this value is chosen by carefully analyzing the historical and future projected drying potential values. Finally, our analysis shows that wall assemblies at an increased number of reference locations given in the NBCC, importantly those falling in the densely populated south-western Ontario region, will need to be designed with additional safety measures such as a capillary break in the future for them to achieve satisfactory moisture performance over their design lives.

Automated summary

The study shows that with global warming, the Moisture Index (MI) in different regions of Canada will change, requiring different design measures. Further analysis demonstrates the significant impact of choosing the normalization factor for drying potential on future MI change predictions. It is suggested that additional safety measures, such as capillary breaks, should be implemented in the future when designing wall assemblies.