Urban form and density as indicators for summertime outdoor ventilation potential: A case study on high-rise housing in Shanghai

Yang, Feng; Qian, Feng; Lau, Ssy

doi:10.1016/j.buildenv.2013.08.019

Cited by 156 publications

(77 citation statements)

References 18 publications

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“…As a result, larger SVF with higher levels of air circulation leads to a decrease in air temperature. Meanwhile, according to Yang et al, wind velocity decreases as the FAR increases [36]. Therefore, we conclude that the effect of SVF for enhancing air circulation decreases in urban areas where FAR is high.…”

Section: Discussionsupporting

confidence: 53%

Temporal Effects of Environmental Characteristics on Urban Air Temperature: The Influence of the Sky View Factor

Lee

Park

2016

Sustainability

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This study examines the relationship between air temperature and urban environment indices, mainly focusing on sky view factor (SVF) in Seoul, Korea. We use air temperature data observed from 295 automatic weather stations (AWS) during the day and night in Seoul. We conduct a spatial regression analysis to capture the effect of spatial autocorrelation in our data and identify changes in the effects of SVF on air temperature, while conducting the regression model for each dataset according to the floor area ratio (FAR). The findings of our study indicate that SVF negatively affects air temperature during both day and night when other effects are controlled through spatial regression models. Moreover, we address the environmental indices associated with day-time and night-time air temperatures and identify the changing effects of SVF on air temperature according to the areal floor area ratio of the analysis datasets. This study contributes to the literature on the relationship between SVF and air temperature in high-density cities and suggests policy implications for improving urban thermal environments with regard to urban design and planning.

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Section: Discussionsupporting

confidence: 53%

Temporal Effects of Environmental Characteristics on Urban Air Temperature: The Influence of the Sky View Factor

Lee

Park

2016

Sustainability

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“…A possible reason can be that the horizontal convection on the ground level was enhanced due to thermal buoyancy between shaded (directly under LEW) and un-shaded places, i.e., thermal buoyancy causes uplift of warmer air at sun-lit spaces, and they were supplied by cooler air from surrounding shaded spaces (Figure 14). Under hot and calm weather conditions, thermal buoyancy could be the major forces behind measured air movement at the pedestrian level [25]. However, more data are to be collected before any solid conclusions can be made on this observation.…”

Section: Discussionmentioning

confidence: 99%

Towards a Climate-Responsive Vertical Pedestrian System: An Empirical Study on an Elevated Walkway in Shanghai China

2016

Self Cite

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Elevated walkways can bring pedestrian-friendly urban space back to high-density urban centers that are planned largely for vehicle traffic-for instance, the Lujiazui CBD in Shanghai. Most studies on elevated walkways have focused on transportation planning, structural safety as well as urban form and design. Few have paid attention to thermal conditions and pedestrian comfort issues on elevated levels. Considering all of the environmental factors that influence human thermal comfort, one could claim that there will be more breezes on elevated levels compared to sidewalks at the ground levels, but they can be exposed to increased solar radiation and thus higher radiant temperatures, if not properly shaded. The overall effect of the change in elevation on human thermal comfort is thus unknown. This study attempts to investigate the microclimate and human thermal comfort of a recently completed Lujiazui Elevated Walkway (LEW) system in the Lujiazui CBD, Shanghai, under a hot-humid sub-tropical climate. Micrometeorological measurements and a guided questionnaire survey were carried out on peak summer days. The data analysis indicates that the LEW is thermally more uncomfortable than its ground level counterpart. Air temperature was higher, whereas wind velocity is lower on the skywalk level than on the ground level, which is counter-intuitive. The resultant physiological equivalent temperature (PET) indicates warm conditions on the ground level (with good shading) while there are hot conditions on the skywalk. Based on the empirical findings, design strategies are proposed to improve the thermal comfort conditions on the LEW, and to better support pedestrian activities in this typical high-rise high-density urban area.

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“…and the urban micro-climate. They, with a special focus on wind velocity, concluded that by a decrease of 10% in the tree view factor, the wind velocity increased by a factor of 3-4 % both during the day and at night (Yang et al 2013). A study in Athens, Greece, found a significant correlation between the tree view factor and PET.…”

Section: Tree Canopy Cover(tcc)mentioning

confidence: 99%

“…In addition, canopy cover can reduce the wind speed in urban space. Another study concluded that by a 10% increase of canopy cover the wind speed increased by 8% (Yang et al 2013). There are different ways to calculate canopy cover: the normalized difference vegetation index (NDVI), green coverage ratio (GCR), leaf area index (LAI), vegetated sky view factor and the partially shaded area (PSA) are the common ones.…”

Section: Tree Canopy Cover(tcc)mentioning

confidence: 99%

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Heat mitigation by greening the cities, a review study

Venhari¹,

Tenpierik²,

Hakak³

2017

Environ. Earth Ecol.

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In the past decades, many studies have proposed urban greening as a method to mitigate the rising temperatures in cities and urban heat islands. The cooling effect of urban green spaces can be divided into two components; cooling intensity and cooling extension. These two components are affected by different factors. This paper provides a review of research on the impact of urban greening on temperature and on the parameters that have an effect on that. Based on this review, two categories that have an effect on cooling intensity and cooling extension were identified: internal factors and external factors. These play an important role in the effectiveness of urban green spaces. As internal factors or indexes, the following were extracted; Size index, Shape index, Vegetation species and Tree canopy coverage are the most common indexes in most of the studies. The external factors can be divided into climate and surrounding properties. A discussion of the reviewed studies reflects the impact of each index on the cooling intensity and cooling extension. The existing methods and techniques for determining these indexes have also been considered in this paper. As such, this study is helpful for designers and planners for decision-making during the design phase.

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Urban form and density as indicators for summertime outdoor ventilation potential: A case study on high-rise housing in Shanghai

Cited by 156 publications

References 18 publications

Temporal Effects of Environmental Characteristics on Urban Air Temperature: The Influence of the Sky View Factor

Temporal Effects of Environmental Characteristics on Urban Air Temperature: The Influence of the Sky View Factor

Towards a Climate-Responsive Vertical Pedestrian System: An Empirical Study on an Elevated Walkway in Shanghai China

Heat mitigation by greening the cities, a review study

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