Developing a calibrated in-situ hygrothermal model of a community center to assess panelized exterior retrofit design suitability.

Over 70% of buildings in Canada were constructed prior to the implementation of the Ontario Building Code of 1975, the first code in Canada to include energy requirements. Many of these buildings are reaching the end of their useful life and require building envelope repairs where the alternative is to demolish and rebuild, which is less sustainable. Performing a retrofit on the building envelope can improve the buildings air tightness and thermal resistance. While these improvements increase the energy efficiency of the building, it also creates potential for the building envelope to accumulate moisture if the design is not carefully selected.

This paper describes the development of a calibrated hygrothermal model utilizing in-situ data. The model can then be used to assess the performance and suitability of two different retrofit panel designs for a community centre, which has a corrugated steel siding envelope, located in Ile Bizard, an island in Montreal, Quebec, Canada. In-situ data from two, 3 m by 3 m test walls, with sensors installed throughout, is utilized to calibrate the hygrothermal WUFI model leveraging differential evolution methods. To minimize the residual error between the measured and simulated data, an objective function utilizing the Huber loss function was generated for the relative humidity in the layers of each wall assembly.

The calibration process adjusts the air exchange rates, locations, and direction within the assembly. This calibration process was shown to improve agreement for relative humidity with the measured data by 30% when compared to the average simulation results from five different engineers. The calibration process was successful and through the calibrated models it was determined neither retrofit panel poses a mould risk.