PhD Oral Exam - Sahar Sahyoun, Building Engineering

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Canada has taken significant steps to address climate change and protect its federal heritage buildings by setting targets for reducing energy use whilst ensuring the thermal comfort of building occupants. Whereas internal insulation systems have emerged as a potential strategy to address these challenges, the use of such systems may also increase the risk to freeze-thaw (FT) damage of the exterior wall assembly and thereby lead to long-term deterioration of historic brick walls due to reduced drying capacity. The information provided in current standards and guidelines simply includes general suggestions for heritage preservation. There is, however, a need for scientific and technical advice focused specifically on enhancing thermal performance, ensuring durability of the walls with the use of interior insulation, and addressing the effects of climate change on the masonry system. The information provided in this study is to contribute to the existing body of knowledge related to the long-term performance of historic masonry walls, by examining the FT damage of internally insulated historic brick masonry walls under a changing climate. In this study, recommendations are provided for optimal selection of types and thicknesses of insulation, whilst minimizing the risk to FT damage. To assess the building envelope performance over the long term, a 30-year period is typically recommended to evaluate the effects of climate change on the wall assembly. However, to reduce the computation time and costs associated with undertaking simulations using multiple climate parameters, an alternative approach is to select a single moisture reference year (MRY) that allows a correct evaluation of the moisture stress over time.

In this study the reliability of presently used climate-based indices for selecting a MRY to permit accurately evaluating the risk of FT damage of internally insulated solid brick walls was first assessed. Given, however, that the use of such methods failed to represent the actual performance of the walls, this subsequent research undertaken, and described in this study, suggested an alternative method to select a MRY based on hygrothermal simulations of brick masonry constructions. A parametric analysis was thereafter conducted to identify the most influential parameters to the formation of FT damage in brick masonry wall structures. Simulations were conducted over a continuous 31-year period, as well as for each separate year, demonstrating no cumulative impact on annual FT cycles. The study determined that MRYs at the 93rd percentile severity could be employed for evaluating FT in retrofitting design decision-making. By examining potential FT damage under different future climatic conditions and considering various factors, this research offers a decision-making process for internal insulation retrofit projects and proposes solutions when significant risk of FT deterioration is expected.