Assessment of Moisture Response and Expected Durability of a Heritage Masonry Building Subjected to Projected Future Climate Loads of Ottawa, Canada

Abstract

As part of the Canadian government's recent drive to the "on Greening Government initiative, heritage buildings forming part of the parliamentary precinct in Ottawa, Canada are to be retrofitted in the coming years to help reduce energy usage and decrease greenhouse gas emissions associated with heating and cooling. Increasing levels of GHG concentrations over time has the potential to raise the mean global temperature by +3.5 degrees. The predicted impact on Ottawa's climate will be significant, increasing precipitation annually by 14.4% and decreasing the January winter design temperature from - 25o C to -11.7o C or 53%. In this paper, the moisture response of a heritage building located in Ottawa, Canada is determined from results of numerical simulations when subjected to both historical and projected future climate loads. Various insulation strategies for masonry wall systems were assessed. The objective was to decrease the energy demand associated with heating and cooling by applying insulation on the interior face of the masonry. Using future climate loads, results from hygrothermal modeling showed that although the climate change model produces higher volumes of annual precipitation, no deleterious levels of moisture build-up were observed in the wall system. In fact, moisture levels remained relatively consistent, irrespective of the insulation type applied to the interior face of the walls. Moisture content for all scenarios was well below critical saturation of the masonry materials. The warming climate has a dramatic effect by reducing the number of hours below freezing experienced by the interior brick wythe when interior insulation is applied. From the hygrothermal analysis, it was concluded that the warming temperatures will substantially reduce the number of hours the interior wythe of masonry experiences freezing temperatures which in turn, reduces the potential for freeze-thaw damage to the masonry. The interior application of moderate levels of insulation should therefore be considered for retrofit measures for this heritage building, located in Ottawa, Canada, without increasing the risk of damage to the wall.