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The goal of this study is to bring out the efficiency of district landscaping on local urban heat island mitigation. Two cooling strategies at the district scale are evaluated through the coupled effect computation of microclimate and building energy demand: vegetation (trees, green walls and roofs) and high albedo values (cool roofs and façades). The study focus on an existing district, Part-Dieu, in Lyon (France). This district has a high urban density and is composed of buildings for which rehabilitation is expected to be difficult. The city is particularly sensitive to summer heatwaves that are supposed to be more regular with global warming. Two specific urban blocks, of about 10 building blocks each, are modeled: a 60,000 m 2 site where the urban fabric is a mix of historical buildings and 60s’ buildings, and a 70,000 m 2 new residential site under construction, more homogeneous compared to the first one. The simulation results are processed for a summer period (hourly time step) andcooling strategies are analyzed individually and combined. Two indexes, Energy Performance Index ( EPI ) and Ambient Temperature Mitigation Index ( ATMI ), are defined to evaluate strategy efficiencies. In our case studies, cooling energy demand is mitigated by around 3% with tree growth strategy, 35% with green roofs, and 76% with increased albedo of urban surfaces. Whereas detailed results of coupled simulation are useful here for engineers, global performance indicators defined in this study give useful hints for stakeholders and urban cooling strategy design. [ABSTRACT FROM AUTHOR]

Following development and validation of the SOLENE-microclimat tool, the underlying model was used to compare the impacts of various "greening strategies" on buildings' summer energy consumption and indoor comfort. This study distinguishes between direct and indirect impacts by successively implementing the test strategies on both the studied building and surrounding ones; it also considers insulated vs. non-insulated buildings. Findings indicate that green walls have a direct effect on indoor comfort throughout the entire building, whereas the effect of green roofs is apparently primarily confined to the upper floor. Moreover, the indirect effect of a green wall is greater, mainly due to the drop in infrared emissions resulting from a lower surface temperature. It has also been proven that the indirect effects of green walls and surrounding lawns can help reduce the loads acting on a non-insulated building. [ABSTRACT FROM AUTHOR]

Abstract: Covering a building envelope with vegetation provides a solution capable of mitigating the urban heat island phenomenon and its impact on the energy consumption of buildings. Simulation tools to assess the efficiency of such a solution are lacking, especially for green walls. The present research aims to offer a hydrothermal model of green walls and green roofs for implementation in the urban microclimate simulation software SOLENE-Microclimate. To this end, a fast, efficient coupled heat–mass transfer model has been developed. Simulation results are compared with experimental data obtained from the LEEA Laboratory in Geneva for three green wall samples. Aside from the level of uncertainty found for the evapotranspiration calculation, these results confirm that the model accurately characterizes the temperature evolution of all three prototypes. Results also show good correlation between measured and simulated temperatures. The model is indeed able to reproduce water stress and characterize various types of living walls. [Copyright &y& Elsevier]

Highlights • A new multiobjective optimization procedure for district energy performance is presented. • The optimization procedure is multi-level and integrates the NSGA-II algorithm. • Energy needs and consumption, economic cost and global warming potential were studied. • The case study concerns the design of an eco-district. • The optimization procedure gives accurate results with a low computational time. Abstract Increasing energy efficiency in the building sector is essential if we are to meet the objectives of sustainable development. The district scale offers significant potential for improving energy efficiency, particularly at the early stages of the design. Thus, a transversal approach to the optimization of the energy concept of districts was adopted. It was undertaken using the DIMOSIM (DIstrict MOdeller and SIMulator) simulation platform, which provides a detailed analysis of a configuration. The energy, economic and environmental aspects were combined to obtain the best overall performance. The multiobjective optimization procedure is multi-level and includes direct search and the NSGA-II evolutionary algorithm to deal with the specificities of this particular problem. Indeed, the search space contains continuous and discrete parameters, it is almost infinite and the objective functions are non-linear. This article describes the complete optimization procedure that was developed to solve this complex problem. A case study on the design of an eco-district illustrates the possibilities offered by this type of approach to obtain the best design solutions. [ABSTRACT FROM AUTHOR]

Since some years, dense cities and compact buildings are promoted as sustainable and energy efficient designs. Nevertheless, urban planning strategies should take into account the interactions between buildings and the microclimate because the Urban Heat Island (UHI) phenomenon can increase the cooling load of buildings and is strongly influenced by urban morphology, urban landscaping and the thermal properties of buildings and soil. The modification of these parameters, such as building density, can mitigate UHI, with direct and indirect improvement of building energy performances. The case study presented in this paper concerns a new district in La Rochelle (France) named Atlantech. Currently at the design stage, the goal is to transform this old military camp into a zero carbon district. This study was performed in parallel with urban planning using EnviBatE and SOLENE-Microclimate simulation. Two building densities are compared through the impacts on solar irradiance, wind airflows, building indoor temperatures and energy demand. Analysis of reference and densified district highlights various impacts such as the wind velocity decrease, up to 80%, and the effect on an existing nearby building solar irradiation, reduced by 7%. These results underline the potential usefulness of these simulation tools for urban planners at the design stage. [ABSTRACT FROM AUTHOR]