Impact of climate change on hygrothermal durability of exterior, non-load-bearing mass timber wall

This study investigates the impact of climate change on the hygrothermal performance and durability of Cross-Laminated Timber (CLT) wall assemblies in mass timber buildings. It focuses on moisture management under wind-driven rain (WDR) leakage and the role of drainage cavity ventilation in mitigating moisture accumulation and mold growth. The study also explores how future climate variability influences long-term moisture risks, providing insights for climate-resilient timber construction. Advanced hygrothermal simulations using WUFI Pro V6.7 were conducted on four wall configurations across five Canadian cities, representing diverse climate zones. The walls included a 19 mm ventilated drainage cavity to enhance drying performance, with two walls featuring an additional 10 mm interior air cavity. The study employs Moisture Reference Year (MRY) climate data, including projected warming scenarios of 1.5 °C and 3.5 °C above baseline to assess long-term moisture risks. The analysis assessed drying potential, mold susceptibility, and the effectiveness of ventilation rates (2–200 Air changes per hour) in reducing moisture-related risks. The findings indicate that higher ventilation rates improve drying performance, but moisture accumulation remains a concern in humid regions like Vancouver and St. John's, under futuristic climate scenarios. Cold and dry climate shows an inherent resistance against mold, requiring minimal ventilation. The results show that air cavities between the CLT and drywall, as well as adhesive layers, influence moisture retention, with cavities sometimes increasing mold risks in humid conditions. This study also highlights the limitations of rainscreen ventilation alone as a long-term solution. These findings contribute to advancing climate-adaptive design for mass timber buildings. • Evaluates CLT wall durability under past and future Canadian climate scenarios. • Studies climate, ventilation, and wall design impacts on hygrothermal performance. • More ventilation in cavities boosts drying and cuts moisture-related risks. • CLT adhesive layers reduce drying but don't raise mold risk if ventilated. • Promotes climate-adaptive designs with ventilation for CLT longevity.