Wall cavity ventilation has been studied and investigated by numerous researchers both numerically using computer tools and experimentally using laboratory and field investigations. Results have not always been conclusive and recommendations in which cladding types, and under what climatic conditions the air cavity provides benefits, are not well understood. This paper first discusses the functions of an air cavity behind various cladding types and its effect on the thermal and moisture performance. Benefits and drawbacks of an air cavity applied to various types of clad walls in various US climates are examined. Numerical simulations of various degrees of complexities were critically evaluated in terms of what is actually modeled and how these results relate to real field performance. Laboratory and field tests are compared to the simulation results. Conclusions from past and currently ongoing research projects are discussed with a perspective on the knowledge acquired that could aid in optimizing the design of air cavity ventilation with respect to thermal and moisture performance. Guidelines for selection and proper design of vented or ventilated cavities are highlighted. A thorough review of the needed research, and the critical information still missing, is discussed in order to highlight the correct application of ventilated cladding systems for future building envelope construction.

Presented at Thermal Performance of Exterior Envelopes of Whole Buildings X – December 2007

Units: SI