Search

The increase in urban population worldwide has led to a significant increase in anthropogenic activities, and the replacement of vegetation with impervious pavements that have a dark surface and high thermal inertia which has contributed to the development of urban heat islands (UHIs). Since pavements represent an important fraction of urban areas, the use of cool pavements is considered an important strategy for reducing the effects of UHIs. This article offers an overview of recent research advances related to the use of several types of cool pavements to mitigate UHIs. The thermal behavior and the main factors that influence the cooling effect of these pavements were analyzed. The cooling performances of these pavements were compared with each other. Limitations and factors that affect their durability were identified. Further efforts are needed to address these limitations, which will be essential to effectively address the negative impacts of UHIs. The results show that the cooling performance of cool pavements can help reduce the temperature in urban environments. This study will serve as a basis for future developments in cool pavements and targets issues that need to be worked – especially for new technologies in this field. • A complete review of the different cool pavement technologies was carried out. • Factors influencing the cooling performance of cool pavements were identified. • Recent developments to improve the performance of cool pavements were presented. • Limitations and opportunities for future developments in cool pavements were discussed. [ABSTRACT FROM AUTHOR]

Green roofs are known for their beneficial aspects on the buildings energy consumption and the environment quality. However, the lack of precise knowledge of thermal, water, botanic characteristics is an obstacle to predict theirs efficiencies in the case of construction projects. In this study, three of the main physical properties of green roofs were experimentally investigated to determine some of the key green roof modeling parameters. First, the thermo-physical properties of green roofs were characterized by correlating the thermal conductivity of the substrate with the water content for different maximum water capacities. Also, the thermal resistance of green roof was evaluated in controlled weather conditions using a low speed wind tunnel. Next, the moisture storage was characterized using the dynamic vapor sorption technique to determine both of sorption and desorption isotherms as well as the moisture buffer capacity. Third, the microstructural properties of green roof substrate were characterized using mercury intrusion porosimetry to measure the porosity range of green roof substrate. The experimental results were used to estimate the parameters used as input data in the developed green roof model to evaluate the energy performance of a building. [ABSTRACT FROM AUTHOR]

Abstract: In this study, three of the main physical properties of green roofs were experimentally investigated to determine some of the key green roof modeling parameters. First, the thermo-physical properties of green roofs were characterized by correlating the thermal conductivity of the substrate with the water content for different substrates and maximum water capacities. Next, the moisture storage was characterized using the dynamic vapor sorption technique to determine both the sorption and desorption isotherms for three different temperatures as well as the moisture buffer capacity. Third, the micro-structural properties of green roof substrate were characterized using mercury intrusion porosimetry to measure the porosity range of the substrate and to compare this porosity range with different concrete porosities. In addition to these characterizations, the evapotranspiration term, which is very important in the water balance, was measured. The few studies found in literature provide the expression of the evapotranspiration term for a watered grass and vegetated areas on a large scale. In this study, this term is expressed for the experimentally studied green roof complex (substrate + vegetation). The ultimate objective of these experiments is to estimate the parameters used as input data in the developed green roof model to evaluate the energy performance of a building. [Copyright &y& Elsevier]

Abstract: Green roofs have a positive effect on the energy performance of buildings, providing a cooling effect in summer, along with a more efficient harnessing of the solar radiation due to the reflective properties found inside the foliage. For assessing these effects, the thermodynamic model was developed as well as the thermo-physical properties of the green roof components were characterized. Its typologies and vegetation styles should also be studied. The proposed model is based on energy balance equations expressed for foliage and soil media. In this study, the influence of the mass transfer in the thermal properties and evapotranspiration were taken into account. We then added the water balance equation into our model and performed a numerical simulation. By assuming the outdoor conditions, the roof support temperature and the drainage water as inputs, the model evaluates the temperatures evolution at foliage and soil ground levels. A parametric study was performed using the proposed model to classify green roofs depending on the considered climate condition. Comparisons were undertaken with a roof slab concrete model; a significant difference (of up to 30 °C) in temperature between the outer surfaces of the two roofs was noticed in summer. The model was experimentally validated according to green roof platform, which was elaborated. The mass transfer effect in the subtract was very effective in reducing the model errors. Simulation results show that the use of vegetation in the roof building improves not only thermal comfort conditions, but the energy performance of a building. [Copyright &y& Elsevier]