Hygrothermal Performance of Exterior Walls in Cold Climate: A Field Study

The durability of the building envelope is closely related to how exterior walls handle various moisture flows over time. Many tools exist that allow to simulate hygrothermal transfers through the building envelope. However, for these many uncertainties are inherent to using these tools, particularly linked to assessing and predicting human behavior, local weather conditions and building material properties. Field data is therefore extremely valuable for performing hygrothermal assessments of buildings. This contribution is part of the HYG research project which aim to gain insight and provide guidance on how to build long-lasting building envelopes with low risk of humidity and mold problems. To achieve this more, than 40 buildings in Denmark, Canada and Greenland have been instrumented with temperature/humidity sensors and have undergone airtightness and mold testing. This contribution presents the methodology of the project as well as preliminary results of three case buildings located in Quebec, Canada. One is a conventional building and the other two are insulated with hemp batts and have different smart vapour retarders. The conventional building with mechanical ventilation shows good RH levels indoor and in the wall construction but has a tendency for low indoor RH levels during winter. The two alternative buildings show that even in humid outside and inside conditions, natural hygroscopic building materials had a satisfactory hygrothermal performance. Results show that mechanical ventilation reduces the levels of moisture both in the interior environment and in the wall assembly.