Abstract

Canada has taken steps to address climate change and protect heritage buildings by setting energy reduction targets and ensuring occupant comfort. 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. Current standards provide general heritage preservation advice, but more specific technical guidance is needed to enhance thermal performance, ensure wall durability with interior insulation, and address climate change impacts 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 insulation selection to minimize freeze-thaw damage.
Typically, a 30-year period is recommended to evaluate the long-term effects of climate change on building envelopes. However, an alternative approach is to select a single moisture reference year (MRY) that can accurately assess moisture stress over time, reducing the time and costs of simulations with multiple climate parameters. This study assessed the reliability of of presently used climate-based indices for selecting an MRY to evaluate the risk to FT damage in internally insulated brick walls. Finding the existing methods inadequate, the study proposed an alternative approach based on hygrothermal simulations.
A parametric analysis was thereafter conducted to identify the key factors influencing FT damage in brick masonry walls. 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.