Impact of the substrate thermal inertia on the thermal behaviour of an extensive vegetative roof in a semiarid climate

Abstract

The aim of this paper is to evaluate the impact of thermal inertia of the substrate of a vegetative roof on its thermal behaviour. Thermal inertia of the substrate was incorporated in two existing thermal models of vegetative (green) roof systems, the Sailor (2008) and Tabares and Srebric (2012) models. The predicted temperatures across the substrate, with and without inertia, were compared with experimental data obtained on a real vegetated roof located in a semiarid climate. The study shows the absolute need to consider the thermal inertia of the substrate to accurately predict the temperatures within the substrate and thus the heat flux through the roof. When taking into consideration the thermal mass, substrate temperatures predicted by both models agree well with experimental data, with a Root-Mean-Square Deviation of about 1°C at a depth of 10 cm. For the analysed period and investigated vegetative roof, the Tabares and Srebric model outperforms the Sailor model.