Mitigating Urban Heat Island Through Green Roofs

Abstract

One of the key measures to fight urban heat island (UHI) phenomenon is by increasing the use of green approaches including green technologies and vegetation. However, there is a shortage of available space for establishing greening elements due to high density of urban development and high cost of urban land. By using green roofs, the hottest spots of a city can be mitigated. Further advantages of green roofs include mitigating air pollution, improving management of run-off water, improving public health and enhancing the aesthetic value of the urban environment. This paper reviewed, analyzed, and discussed previous literature on green roofs and their role in alleviating UHI. Previous researches acknowledged the ability of green roofs in UHI mitigation. This paper recommends using green roofs as a main strategy for decreasing the harmful impacts of UHI especially the high air temperatures as well as their ability to add to the greening of cities.

Green Roof Technology- Mitigate Urban Heat Island (UHI) Effect

“…Furthermore, the soils also acted to protect the underlying layers from UV radiation and strong wind [11]. However, amount of sunlight transmitted under the canopy of plants depends on plant species [12]. Secondly, green roof helps to reduce surface urban heat island through evapotranspiration.…”

Seasonal and Diurnal Thermal Performance of a Subtropical Extensive Green Roof: The Impacts of Background Weather Parameters

“…The literature has generated extensive studies on green-roof thermal effects in various climatic contexts. These studies roughly fall into three categories in terms of study approaches and objectives, including: (1) on-site monitoring to investigate green-roof impacts on summer temperature parameters and building heat flux patterns [9][10][11][12][13][14][15][16][17][18][19][20][21][22]; (2) dynamic energy modeling to analyze the heat and moisture processes within the green-roof layers and identify key influential factors [23][24][25][26][27][28]; and (3) building energy simulation or meso-scale climatic modeling to predict the cooling and energy effects of individual or multiple green-roof installations [29][30][31][32][33][34]. The studies have reported that green roofs can reduce summer daily peak surface temperature by 15 °C-45 °C and peak air temperature by up to 5 °C.…”

The Energy Impact in Buildings of Vegetative Solutions for Extensive Green Roofs in Temperate Climates

“…hairiness and silver staining. Cerastium biebersteinii offers a better ornamental aspect and a stronger resistance to drought [20]: the habitat to which it belongs is, in fact, the arid Caucasian mountains environment. Even though it has a creeping growth habit, it is more erect than Sedum album and creates large niches under the cover.…”

“…• reduction of summer thermal loads: during the summer season, the shading induced by plant species [18,20] causes a reduction of surface temperatures [20,21], and a resulting reduction of both indoor temperatures [2,21], and energy consumptions related to the cooling of indoor rooms located below the roofing system [2,21]; • reduction of building materials surface temperature peaks caused by direct solar radiation and concomitant reduction of surface thermal fluctuations [21][22][23]: this corresponds to an increased durability of roofing system materials (such as waterproof roofing membranes); • reduction of surface temperatures and consequent reduction of radiation phenomena as the basis of the urban heat island effect (UHI) [24,25]; • evaluation of the energy behavior in winter [26], during which the reduction of solar heat gains could cause an increase in heating loads as a function of the reference climatic zone [1]. This implies that the design of the roofing system should be carefully studied in order to correctly size the thickness of both the growing medium and the insulating layer in order to obtain a positive balance even during the winter season.…”