Modelling hygrothermal conditions of unsaturated substrate and drainage layers for the thermal resistance assessment of green roof: Effect of coarse recycled materials

Abstract

Alternative materials exist for green roof layers: secondary resources like coarse or fine recycled aggregates may be used as a substitute to natural materials. For using these new types of materials, it is needed to assess their heat resistance which is performed according to ISO 9869-1 standard. Moreover, the initial hygrothermal conditions of unsaturated substrate and drainage layers have also to be modelled and assessed for optimizing the layers' thickness. In this study, the green roofs with unsaturated substrate and drainage layers incorporating coarse recycled materials were tested and assessed. The hygrothermal conditions of unsaturated substrate and drainage layers were simulated using WUFI software. A small difference (4.2%) was observed between the Rc-value of the green roofs with and without coarse recycled materials, confirming that these materials provided a sufficient thermal resistance, similar to soil particles for the substrate layer. Considering a constant thickness for the substrate layer (15 cm), a 6-cm drainage layer with coarse aggregates was considered as the optimum design for green roof systems. Besides, 18-cm unsaturated substrate layer was the optimum design when the drainage layer' thickness was considered constant (5 cm). The 6-cm drainage layer and 18-cm unsaturated substrate layer were definitely the best design for the roofing systems with the simultaneous change in the substrate and drainage layers' thickness.

Water permeability, water retention capacity, and thermal resistance of green roof layers made with recycled and artificial aggregates

“…The findings showed that the increment of the substrate and drainage layers' thickness improved the roofing system's thermal efficiency, despite the effects of thicker layers being the same. In 2021 and 2022, Kazemi et al [22,60] assessed how the green roof with a 15 cm-substrate of coarse recycled materials and a 5-cm drainage layer of recycled coarse aggregates was able to resist the heat-flow in which the R-value as a heat resistance indicator was measured for green roof layers in accordance to ISO 9869-1 standard [61]. As per the results, the Rc-value of green roof layers with and without coarse recycled materials was near to each other.…”

“…As a sustainable ecosystem system, the green roof is known for its ability to provide thermal resistance for rooftops in some cases and buffer the surface stormwater runoff in urban areas [11][12][13][14][15][16][17][18]. The shape and type of materials used in green roof drainage and substrate layers significantly impact energy efficiency and rooftop water evacuation [19][20][21][22].…”

“…Natural mineral and energy resources are heavily utilized to construct building envelope components (such as roofing systems) and provide adequate indoor thermal comfort [22,[44][45][46][47][48][49][50][51][52][53]. For instance, consuming an estimated 40% of primary energy for construction sectors has produced a series of insoluble environmental concerns [54,55].…”

Mechanical Properties of Recycled Aggregate Concretes Containing Silica Fume and Steel Fibres

“…Concrete is considered the most widely used construction material in the world [1][2][3][4][5][6][7][8][9][10][11][12][13]. Rapid urbanisation due to population growth results in the redevelopment of housing sectors and infrastructures in many cities around the world [14][15][16][17][18].…”

Coarse recycled materials for the drainage and substrate layers of green roof system in dry condition: Parametric study and thermal heat transfer

“…Moreover, European standards have never reported the optimum thickness for green roof layers [13,47]. Even though recycled coarse materials seem to be a suitable insulation material for green roof systems thanks to their great porosity [48][49][50], very little information is available on their thermal and insulating performances. So, in the present study, the thermal resistance of green roofs with a recycled coarse aggregates layer (drainage layer) and a substrate layer produced with coarse recycled materials was measured and evaluated in accordance with ISO 9869-1 [51].…”