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This paper presents the design and the results of a reduced-scale experimental bench to study the effect of green roofs and green facades on local urban microclimate. An analysis of experimental data was carried out on three street canyons: one reference street, one street between two buildings with green roofs and one with a green wall to the west. The results show a hygrothermal effect of green envelopes on buildings on urban heat island mitigation. In the detailed analysis of these green coating techniques, we highlighted that green facades modify strongly the radiative balance of the street and improve the hygrothermal comfort in urban canyons through reducing the overheating in the street in hot summer days. [ABSTRACT FROM PUBLISHER]

We developed and studied key performance indexes and representations of energy simulation heat fluxes to evaluate the performance of the evaporative cooling process as a passive cooling technique for a commercial building typology. These performance indexes, related to indoor thermal comfort, energy consumption and their interactions with their surrounding environments, contribute to understanding the interactions between the urban climate and building for passive cooling integration. We compare the performance indexes for current and future climates (2080), according to the highest emission scenario A2 of the Special Report on Emission Scenario (SRES). Specific building models were adapted with both green roof and wetted roof techniques. The results show that summer thermal discomfort will increase due to climate change and could become as problematic as winter thermal discomfort in a temperate climate. Thanks to evapotranspiration phenomena, the sensible heat contribution of the building to the urban heat island (UHI) is reduced for both current and future climates with a green roof. The performance of the vegetative roof is related to the water content of the substrate. For wetted roofs, the impacts on heat transferred to the surrounding environment are higher for a Mediterranean climate (Marseille), which is warmer and drier than the Paris climate studied (current and future climates). The impact on indoor thermal comfort depends on building insulation, as demonstrated by parametric studies, with higher effects for wetted roofs. [ABSTRACT FROM AUTHOR]

In this paper, we propose a practical approach for decision-making regarding passive cooling design for buildings in dense urban contexts. For non-cooled buildings under temperate climates, assessment of summer thermal discomfort determines the usual passive cooling design together with fossil energy and GHG savings at earth scale. However, passive cooling techniques for indoor climate can be also valuable for local environment impacts, especially urban heat islands’ mitigation. Lack of simple representative criteria and complexity of simulation outputs constitute a barrier for the development of passive cooling. Based on a study of a generic commercial building, we analyzed several designs with Sankey diagram and we developed two performance indexes. This chart synthesis of complex output data allows a direct comparison of design solutions. This analysis gives hints for better designer understanding of urban climate and building interactions for the studied passive cooling solutions: cool roofing, nocturnal natural ventilation and rooftop PV system as shading device. Our results show that nocturnal natural ventilation is efficient to moderate indoor overheating compared to the "cool roof". In addition, cool roofs reduce anthropogenic heat transferred to urban environment. PV panels as shading device mitigate summer discomfort and produce energy that increase building energy efficiency through the year. We defined two Key Performance Indexes (KPIs) to define cooling potential of both indoor and urban environment. These KPIs obtained for different temperate climates highlight new prospects for the design of efficient urban designs with controlled environmental impacts and decision process of stakeholders. [ABSTRACT FROM AUTHOR]