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Pocket parks, the green infrastructures with small sizes and flexible layouts, are suitable for thermal environment improvement in the urban built-up block with limited green space. To quantify the relationship between pocket parks and the thermal environment in western China, two parks in the built-up block of Xi'an were selected. By field measurement, the cooling effect could be extended 100 m from the park boundary, connecting two parks. Furthermore, the road and greening within the block demonstrate significant influence on the cooling diffusion by regression analysis. Based on ENVI-met simulation, the ratio of the tree and the grass, the layout of the tree and the grass, and the layout of the paving were analyzed at different proportions of greening and paving of the park. Finally, a combination of the daytime physiological equivalent temperature (PET) and nighttime air temperature (AT) was proposed to choose the optimum layouts: the trees concentrated in the center and the pavement with more roads. Results can provide insights for designing pocket parks based on the thermal environment improvement. [ABSTRACT FROM AUTHOR]

During the process of the high-speed urbanization in Chinese cities, the social, economic, and political status and the interaction between each factor have been more focused on urban traditional district renewal. However, the effects on urban microclimate and the residential living conditions in traditional districts are not well discussed, which is strongly related to the living comfort and citizens' well-being. In this study, two typical traditional districts in Xi'an are selected. According to the original situation of building functions and the community characteristics, two renewal plans are proposed by adding vegetation in open spaces (V), and adding vegetation combined with building redevelopment (V&B), in order to balance the living convenience and thermal environment. Via ENVI-met simulation, the effects of the district renewal plans on thermal environment including wind speed, air temperature, and mean radiant temperature are evaluated. This study provides method of environmental evaluation for traditional district renewal, which contributes to sustainable urban planning in historical districts, and provides recommendations for related policy development. [ABSTRACT FROM AUTHOR]

Increased artificial constructions due to urbanization absorb more solar radiation, making urban surface and air temperatures rise and affecting the energy performance of urban buildings and the human health. Many studies have reported that green facades and roofs, materials with high albedos can noticeably reduce building surface temperatures and cool the air in summer. However, little is known about the cooling effects and assessment of different mitigation strategies when they are adopted in a block scale. This study focuses on assessing and comparing the effects in the high-rise communities in Xi'an, China, which are a good representation of the city because they are composed of a high density of buildings, and they cover the majority of the current urban sprawl land. Simulations of three community prototypes through ENVI-met software were carried out in order to assess the mitigation techniques in terms of the ground surface, building surface, and vertical canopy air temperature decrease. The main techniques adopted were cool pavements, cool coating facades and roofs, green facades with ivy and green roofs with funkia and 15 cm substrates, and combinations of those. The statistical analysis results revealed that green roof can cool the roof more than the cool roof, while cool facade can cool the facade more than green facade. As to single mitigation strategy, the cool pavement have the most significant potential to decrease canopy air temperature. In general, the combination of different strategies had much more positive effects than single solution. These positive results indicate that the cooling strategies are urgently needed in the current urban construction to alleviate the urban heat island effect. Image 1 • The cooling potentials of various strategies and their combinations were compared in three high-rise community. • The performance of computational simulation software ENVI-met were tested by comparing measured data. • Decrease of land surface temperature, building surface temperature and canopy air temperature were achieved and evaluated. • The community characteristics affect the cooling effects. [ABSTRACT FROM AUTHOR]

• Economy of various vegetation-planting options are analyzed. • The improvement and cost of PET for different vegetation are analyzed quantitatively. • Continuous planting is the most effective layout to improve the thermal comfort. • We prove that dispersed planting of trees is the most economical layout for improving thermal comfort. Global climate change and urbanization have generated increased attention to thermal comfort in urban residential areas. The use of vegetation to improve thermal comfort has been confirmed by many previous studies. However, in actual construction projects, we not only need to know the positive benefits of different greening patterns on outdoor thermal comfort but we also need to consider the cost. In this paper, the main research intent is to analyze the economics of the improvement of outdoor thermal comfort through different greening patterns to provide a theoretical basis for the selection of efficient greening patterns for actual construction projects. All vegetation species, include tree, shrub and ground-cover plant, could reduce the PET difference for whole daytime. To reduce the PET mean value by 1°C, the expenses of tree is 1/31.2 to 1/320.7 of the ground-cover plants or 1/2.9 to 1/18.2 of shrubs. We propose that trees should be planted in areas where improving outdoor thermal comfort is necessary. The dispersed planting of trees can make the improvement of outdoor thermal comfort more economical. Ground-cover plants and shrubs could be planted on a large scale in areas that have a low demand for outdoor thermal comfort. [ABSTRACT FROM AUTHOR]