An investigation of sensible heat fluxes at a green roof in a laboratory setup

During the last few years, several models have been proposed for the calculation of green roof thermal behavior, but the validation studies of such models are lacking a comprehensive set of highly accurate data. In this study, an experimental laboratory setup was used to create different environmental conditions and to measure sensible heat fluxes to/from a vegetated roof assembly. This experimental setup has been successfully used for different wind velocities (0-3 m/s) to create free and forced convection conditions around green roof tested samples. Furthermore, our study proposed a basic model for calculations of the convective heat transfer at green roof assemblies, which is a modified version of the Newton's cooling law, calibrated and then validated with different sets of data. For forced convection flow regimes, the proposed basic model resulted in RMSE (Root Mean Square Error) of 11 W/m(2) and R-2 value of 0.81. Similarly, the model provided RMSE of 6.6 W/m(2) and R-2 of 0.90 for sensible heat fluxes with free convection conditions. In the future, this model will be used in on-site experimental studies to understand its performance under wind conditions that exhibit a much wider range than the studied velocity range near the leaf canopy. (C) 2011 Elsevier Ltd. All rights reserved.