Improving thermal performance of a ventilated tiled roof by using phase change materials

Abstract

The adoption of ventilated roofs and facades, as well as the integration of phase change materials (PCMs) in the building envelope, has proved to be effective as a passive cooling technique in reducing the solar heat gain through the building envelope during the summer period, therefore reducing the energy requirement for cooling. Even though much research focused on each of these strategies individually, their combination has not been deeply studied yet. Preliminary numerical studies were carried out on the application of PCMs on a pitched ventilated tiled roof, and the most effective position turned out to be the one suspended in the middle of the above sheathing ventilation (ASV) channel. Based on this conclusion and exploiting an existing mock-up facility, two equivalent pitched ventilated roofs with an air gap of 4 cm were built as coverage of two identical rooms, each one equipped with a fan coil, one with a 0.007-m PCM layer suspended in the middle of the ASV and the other one without. They were then tested under real conditions at the TekneHub Laboratory at the University of Ferrara. The behaviour of the two configurations were compared in terms of temperature, velocity of the air in the ASV, heat flux and energy requirement for cooling, which were monitored through T-type thermocouples, heat flow metre, anemometers and energy metres, respectively. The aim of the research was to validate the numerical results and confirm that the combination of the two strategies allows further improvement of roof performance.