ABSTRACT
Many wall systems in North America incorporate a drained and vented air cavity behind the cladding. The purpose of this air cavity is to help control the flow of moisture through the wall system. Providing ventilation airflow through this wall cavity, often referred to as cladding ventilation, can help reduce interstitial condensation during winter by allowing exfiltrating water vapor to bypass the diffusive resistance of the cladding. There are also studies that show that cladding ventilation can help reduce or prevent sun-driven inward moisture; when rain wets an absorptive exterior surface in the summer and the sun subsequently drives this moisture toward the interior. However, the mechanisms by which cladding ventilation reduces the potential for sun-driven condensation, as well as modeling this effect, are not well documented in the literature. This paper provides insight into the two-dimensional phenomena of the mechanisms by which cladding ventilation reduces sun-driven condensation, compares experimental results to theoretical calculations, and discusses the challenges faced by enclosure designers in modeling the effect of cladding ventilation in a sun-driven condensation scenario.
