Abstract
A green roof is composed of a substrate and drainage layers which are fixed on insulation material and roof structure. The global heat resistance (Rc) within a green roof is affected by the humidity content of the substrate layer in which the coarse recycled materials can be used. Moreover, the utilization of recycled coarse aggregates such as incinerated municipal solid waste aggregate (IMSWA) for the drainage layer would be a promising solution, increasing the recycling of secondary resources and saving natural resources. Therefore, this paper aims to investigate the heat transfer across green roof systems with a drainage layer of IMSWA and a substrate layer including recycled tiles and bricks in wet and dry states according to ISO-conversion method. Based on the results, water easily flows through the IMSWAs with a size of 7 mm. Meanwhile, the Rc-value of the green roof system with the dry substrate (1.26 m2 K/W) was 1.7 times more than that of the green roof system with the unsaturated substrate (0.735 m2 K/W). This means that the presence of air-spaces in the dry substrate provided more heat resistance, positively contributing to heat transfer decrease, which is also dependent on the drainage effect of IMSWA. In addition, the Rc-value of the dry substrate layer was about twice that of IMSWA as the drainage layer. No significant difference was observed between the Rc-values of the unsaturated substrate layer and the IMSWA layer.
Highlights
Over the past few decades, the rapid increase in urban areas has exerted pressure on the environment owing to the high consumption of natural resources in the construction sector and low energy performance of building envelope components such as walls and roofs
The drainage layer of green roofs should be made using coarse aggregates to pass the water through the roofing systems [30,54]
The thinness of the incinerated municipal solid waste aggregate (IMSWA) layer (5 cm) caused us to avoid using a big size for the drainage layer
Summary
Over the past few decades, the rapid increase in urban areas has exerted pressure on the environment owing to the high consumption of natural resources in the construction sector and low energy performance of building envelope components such as walls and roofs. Since the greatest amount of urban spaces has been covered by roofing systems [6], the use of green roofs as one of the building envelope components has been proposed, and it has been frequently installed in rooftops to broaden the green infrastructure with high energy efficiency in the construction process [7,8,9,10]. The green roofs can promote the heating and cooling energy performance of dwelling houses in an urban area. Rainwater runoff can be reduced and delayed when a green roof is used for the rooftops [9,11,12,13,14]
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