Impact of solar reflectivity and infrared emissivity on the thermal performance of metal and concrete roofs in cloudy warm-humid climate

Abstract

Regions near latitude 0° are characterized by warm-humid climate and also by high cloudiness. In these regions, metal roofs has been the most widely used typology. However, in the last decades, the use of heavy concrete roofs has increased significantly. Given its material characteristics, this roof typology offers a higher thermal resistance and thermal mass than a metal roof. Most strategies focus on the use of these characteristics, as well as the use of high reflectivity and emissivity. However, the impact of cloudiness on the effectiveness of these strategies has been little addressed. This research focuses on the impact of reflectivity and emissivity change on the thermal performance of these two roofs in a cloudy warm-humid climate. To achieve this objective, simulations validated with measurements were used. The results show that the efficiency of reflectivity and emissivity is lower in this region compared to other regions. The impact of these properties is further reduced with increasing thermal mass or decreasing thermal transmittance, so the effectiveness of reflectivity and emissivity is minimal on the concrete roof. Finally, this study supports that a metal roof with a reflectivity and emissivity above 0.70 can offer lower daily average temperatures than a concrete roof.