Thermal and economic performance of extensive green roof during typical Lebanese winter and summer days

Abstract

The main objective of this research is to determine and compare, using real-time monitoring, the thermal performance of a Traditional Gravel Ballasted Roof (TGBR) mockup and an Extensive Green Roof (EGR) mockup during typical Lebanese winter and summer days. For this purpose, temperature profile of a TGBR mockup was experimentally assessed and compared to the one of an EGR mockup using a 70 cm x 70 cm roof mockups installed on the rooftop of the Chemical Engineering Department at the University of Balamand in Lebanon. The internal temperature was measured for the different roof layers using a total of 7 cross-calibrated thermocouples while air temperature was monitored at 110 cm height using a waterproof temperature sensor. Temperature measurements were recorded every minute. Findings revealed that EGR protect the roof membrane from high temperature fluctuations due to thermal phenomena such as evapotranspiration and solar shading. Moreover, results confirmed that EGR mitigate the temperature fluctuations by 7.61% and 22.66% during typical Lebanese winter and summer days respectively. Outcomes of this study also verify the passive cooling effect of EGRs during hot summer days and during cold winter days. Therefore, EGRs are very efficient in countries with short winter season and long warm/sunny days such as Lebanon. From an economical perspective, EGRs are more cost effective than TGBRs (contributing to an approximate money saving of 73.72 USD during the winter season and 75.52 USD during the summer season).