Thermal conductivity of an unplanted sustainable green roof system

Abstract

Finding a balance between green open spaces and urban areas is important. In places where the density of buildings is high greening of roofs can significantly improve the area. One of the main benefits of green roof systems, especially in warm climate countries, is the improved thermal performance of the building's envelope. The main purpose of this study was to evaluate the thermal performance of unplanted local growth media and a drainage layer used in green roof systems. Unplanted growth media consists of soil and other in/organic material without planted vegetation, Laboratory tests were carried in a hotbox to study the energy performance of an unplanted green roof specimen at different moisture contents and soil surface temperatures. Results showed that the thermal conductivity of the specimen increased with both an increase in surface temperature as well as with an increase in the moisture content. It also resulted that a typical U-value of an unplanted soil layer is about 2.25W/m2k in winter, while in summer it would be about 1.30 W/m2k. This study gives an indication of the thermal performance of the soil layer of a green roof system had the up-keeping of the vegetation been ignored ending up with bare and unplanted media.