Abstract
Cavity wall is one of the most common construction types in temperate maritime climates, including the UK. However, water penetration may lead to damp within the structure, freeze-thaw damage at the outer surface and a reduction in thermal resistance. The magnitude of wetting effects on the energy performance of cavity walls is still unclear, with potentially significant implications for climate-change-mitigation strategies. This paper investigates the thermophysical performance of uninsulated and insulated cavity walls and its degradation as the element is wettened. Experiments were performed in a hygrothermal laboratory where two cavity-wall specimens (one of which coated with external waterproofing treatment) were tested under a high wind-driven rain exposure. Changes in the thermophysical performance between dry and wet conditions were evaluated through U-value testing and Bayesian inference. Substantial U-value increase was observed for wet uninsulated specimens (compared to dry conditions); conversely, closer U-value ranges were obtained when insulated with EPS grey beads. Moreover, latent-heat effects through the external masonry leaf of the untreated specimen were predicted by the Bayesian framework. Results suggest a negligible efficacy of waterproofing surface treatments as strategies for the reduction of heat transfer within the element, and possible effects of these agents on the evaporative and drying process.
Highlights
Cavity wall is one of the most common construction types in the UK, and more generally in temperate maritime climates [1,2]
Experiments were performed in a hygrothermal laboratory where two cavity-wall specimens were tested under a high wind-driven rain exposure
When built in areas with high exposure to wind-driven rain (WDR), their thermophysical performance may be degraded as the resulting water penetration is considered the most important moisture source affecting the performance of the building fabric [3]
Summary
Cavity wall is one of the most common construction types in the UK, and more generally in temperate maritime climates [1,2]. When built in areas with high exposure to wind-driven rain (WDR), their thermophysical performance may be degraded as the resulting water penetration is considered the most important moisture source affecting the performance of the building fabric [3]. While the use of unfilled cavity walls in WDR exposed areas was based on the idea that the open cavity would have helped draining the wet external leaf, the water accumulated in the structure may lead to freeze-thaw damage of the external surface, damp within the structure and a consequent increase in thermal transmittance [3].
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