Experimental investigation of cavity air gap depth for enhanced thermal performance of ventilated rain-screen walls

Abstract

To mitigate the overheating problem of high-performance buildings in the summertime, a ventilative cooling method behind the cladding has been widely employed. The commonly used airspace behind cladding ranges between 9.5 mm (3/8″) to 19 mm (3/4″) and it is set solely considering moisture performance in North America. Although the literature indicates that higher thermal performance can be achieved by implementing bigger airspaces, the advantage of higher air gaps in comparison to the current way of construction is not clear. Therefore, in this study, an experimental investigation is carried out by comparing cavity depths of 19 mm (3/4″), 51 mm (2″), 102 mm (4″), and 152 mm (6”) under a mild marine climate of Burnaby, British Columbia, Canada. The test walls are instrumented for temperature, heat flux, and cavity airflow. The results indicate that the commonly used 19 mm cavity depth has the lowest airflow rate and therefore gets warm and results in the highest heat-gain to the building. Compared to the 19 mm cavity, the 50 mm cavity has 5x more total airflow and 25% lower heat-gain, while the 152 mm cavity has the biggest heat-gain drop of 40%.