Impact of Vegetation, Substrate, and Irrigation on the Energy Performance of Green Roofs in a Mediterranean Climate

Abstract

Green roof energy performance is still a challenging topic, namely in a Mediterranean climate since it depends on building characteristics, roof type, and also on climatic conditions. This paper evaluates green roof buildings’ energy needs and use in a Mediterranean climate. An experimentally calibrated numerical model was used to perform a parametric analysis and identify the influence of key parameters in heating and cooling energy needs, as well as annual energy use. The vegetation height, the soil depth, and LAI (leaf area index) were identified as the key parameters. The irrigation levels were also crucial for the energy performance of green roofs, particularly during the summer period and in a Mediterranean climate. Heating energy needs were mainly associated with soil depth due to higher thermal resistance, whereas cooling energy needs depended mostly on LAI, which influenced evapotranspiration and shading effects. A reduction of soil depth from 1.0 m to 0.1 m increased winter energy needs by up to 140%, while low values of LAI increased cooling energy needs up to 365%. Annual energy use in a Mediterranean climate showed a higher dependence on soil depth, with oscillations of up to 115%, followed by LAI and vegetation height. Finally, irrigation levels impacted the annual energy use more significantly for lower watering flow rates. Reductions of about 500% were obtained when changing watering flowrates from 0 mm/day to 6 mm/day in intensive green roofs. Since green roofs with native species expect low values of watering, this may increase their cooling energy needs.

Effects of Extensive Green Roofs on Energy Performance of School Buildings in Four North American Climates

“…In this study, parameters were selected for an extensive green roof and consisted of different growing media, leaf area index (LAI), plant height, plant albedo, soil thickness and thermal insulation thickness, as shown in Table 3. Substrate and vegetation plant properties were selected based on previous studies [1,17,33,[57][58][59]. Light-weight and heavy-weight substrates were not input parameters in EnergyPlus; however, their properties were considered as inputs in the software.…”

“…The EUI in Los Angeles was affected by the leaf area index. Gomes et al [33] conducted a parametric analysis to analyze the impact of design parameters such as plant height and LAI on cooling and heating loads in a Mediterranean climate. The results showed that the cooling load increased up to 365% with a LAI of 1 compared to the LAI of 5.…”

Addressing the Water–Energy–Food Nexus through Enhanced Green Roof Performance

“…Irrigation systems can also affect building energy consumption, as shown through thermal analysis of GRs [26,27]. As soil depth decreases, energy consumption during winter increases up to 140%.…”

The Impact of Green Roofs on the Parameters of the Environment in Urban Areas—Review

“…The conducted research shows very divergent results of the influence of particular plant species on the parameters of the environment inside the building as well as in its surroundings. This is very closely related to the climatic conditions and the leaf surface characteristic of a given plant species [86,87].…”