Green roofs : thermal performance and noise reduction in a Mediterranean climate

Abstract

Green roofs are of various types and forms, the aim of this study was to identify the most thermally efficient roof from selected specimens of both traditional roofs and green roofs, whilst taking into consideration their acoustic performance, and the reduction in carbon footprint. The tests were carried out under laboratory conditions, with specimens for the traditional roof tested were: a black bare roof, a white roof, a roof with membrane and a roof with white membrane. The main focus of this study was the green roof system, which is an energy efficient measure for the Mediterrenean climate and especially for Malta. In these set of experiments 'torba' (chippings) which is usually regarded as construction waste, was used as a replacement to the organic material, and was mixed with compost to make up the growing medium. The experiments conducted were to test the effect of compost and 'torba' mix has on both the thermal and the acoustic performance on the roof. The 'torba' was added to the compost in 20% increments, so 5 mixes in all for the green roof tests. The tests were carried out in an isolated hot-box; this made it possible to determine the change in the thermal and sound insulation properties for the different roof typologies. The results have shown that green roofs act as a passive climate control by performing as an insulating material. This study may contribute to the inclusion of green roofs in Mediterranean climates, especially in Malta.