Thermal performance of different configurations of a roof pond-based system for subtropical conditions

• Contributions of different components of a roof pond-based indirect evaporative cooling system.
• Thermal benefits from increase in thermal mass due to the water body and shading of the roof pond.
• The study contributes with findings for subtropical locations with Cfb climate type.
• Evaporative component of the roof pond corresponds to an indoor temperature drop up to about 2 °C.
• Shading effect corresponds to a temperature reduction which may peak at about 10 °C during cloudless daytime periods.

Indirect Evaporative Cooling Systems (IECS), characterized by the use of wetted roof or wall surfaces for structural cooling without increasing indoor air humidity, consist of an interesting bioclimatic strategy still not quite explored in Brazil. This study aims to evaluate the thermal performance of an IECS by means of experiments with test cells in a subtropical location. Experiments were carried out for Curitiba, Brazil (25.5ºS, 49ºW, 910 a.m.s.l.) with two equal-sized small test cells, first with a control cell without the roof pond and with each test cell fitted with roof ponds, for testing different modes of operation of the IECS. Configurations of the system encompassed: a) conventional roof pond-based IECS; b) roof pond with sealed water reservoir, naturally ventilated and fully shaded (for testing the effect of thermal mass without the evaporative function); c) IECS with an unshaded roof pond. The relative contributions of evaporation and shading have been assessed. The year-round evaluation showed a high cooling performance of the IECS for the subtropical location tested.