Quantifying tree canopy coverage threshold of typical residential quarters considering human thermal comfort and heat dynamics under extreme heat

Li, Yingnan; Lin, Dongli; Zhang, Yuhan; Song, Zipeng; Sha, Xiaohan; Zhou, Siqi; Chen, Cen; Yu, Zhaowu

doi:10.1016/j.buildenv.2023.110100

Cited by 37 publications

(13 citation statements)

References 70 publications

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“…This may be due to larger simulated regions having more modeling elements and significant differences from the actual environment. Although there are differences between the simulation and measurement results, their consistency is relatively high (d > 0.8), well above 0.6, and the error is within an acceptable range compared to previous studies [18,50]. Therefore, ENVI-met can reasonably and accurately predict the research area's microclimate and thermal comfort conditions.…”

Section: Model Validation Resultsmentioning

confidence: 59%

“…They observed that umbrella-shaped and cuboidal tree forms had the most pronounced effect on outdoor thermal comfort and that there was a positive correlation between tree planting density and thermal comfort. Yingnan Li et al [18] related vegetation cover to building height and found that the benefits of trees for human thermal comfort were more evident in relatively low-rise residential communities. In contrast, trees had difficulty alleviating heat discomfort in high-rise residential areas.…”

Section: Introductionmentioning

confidence: 99%

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Study on Microclimate and Thermal Comfort in Small Urban Green Spaces in Tokyo, Japan—A Case Study of Chuo Ward

Sun,

Zhang,

Yang

et al. 2023

Sustainability

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Small urban green spaces are abundant in densely populated urban areas, but little is known about their impact on the urban heat island effect and thermal comfort. Therefore, this study selected as research sites four small urban green spaces in a typical high-density built-up area, Chuo Ward in Tokyo, Japan. The ENVI-met software 5.1.1 simulation method was used to analyze these sites’ microclimate and thermal comfort conditions. The following are the results: (1) Small urban green spaces significantly reduce urban air temperatures, particularly during hot weather, with temperature reductions ranging from 2.40 °C to 2.67 °C, consistently lower than the highest temperatures in Tokyo’s Chuo Ward, mainly between 1:00 and 2:00 p.m. (2) Thermal comfort analysis indicates that small urban green spaces can significantly improve urban thermal comfort during the day, particularly around noon, by reducing one or two thermal comfort levels compared to typical urban street blocks. However, these differences gradually diminish throughout the evening and night, and thermal comfort inside and outside green spaces becomes more uniform. (3) Green space size is not the only factor influencing thermal comfort; the layout of plants within the green space and the layout of the surrounding buildings also have an impact. Despite their small size, even small green spaces can significantly enhance comfort. This study highlights the need to promote urban sustainability through the extensive integration of small green spaces in dense urban environments. Small green spaces can serve as a high-frequency, low-cost solution for environmental sustainability by addressing the increasingly severe urban heat island effect as well as environmental challenges that in the urbanization process.

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Section: Model Validation Resultsmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Study on Microclimate and Thermal Comfort in Small Urban Green Spaces in Tokyo, Japan—A Case Study of Chuo Ward

Sun,

Zhang,

Yang

et al. 2023

Sustainability

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“…Planting trees can significantly reduce the T a and T mrt . A study conducted in Shanghai suggested that there may be a threshold for adding trees to improve the thermal environment in residential areas [57]. An excessive number of trees can lead to overcrowding, potentially decreasing V a and disrupting the circulation of cold air, thereby causing an increase in T a in residential areas [58].…”

Section: Discussionmentioning

confidence: 99%

Comprehensive analysis on the thermal comfort of various greening forms: a study in hot-humid areas

Lin,

Wu,

et al. 2024

Environ. Res. Commun.

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The potential impact of greening on improving thermal environments is widely recognized. However, few studies have comprehensively evaluated the influence of different forms of greening, such as various tree crown widths, green facades, green roofs, and their combinations, on both outdoor and indoor environments. In this study, we conducted an extensive investigation within a residential precinct at Guangzhou University by combining on-site measurements and numerical simulations with the ENVI-met model. Physiologically Equivalent Temperature (PET) and Temperature Humidity Index (THI) were used to assess outdoor thermal comfort. The results indicated that planting trees had a greater impact on improving the outdoor thermal environment than green facades and green roofs, and this effect increased with the crown width of the trees, with a maximum potential reduction of 4.8 °C (0.2 °C) in PET (THI). Green facades can bring a change of up to 101.9 W/m2 in sensible heat flux, resulting in a reduction of up to 1.8 °C in indoor Ta (air temperature). Conversely, green roofs composed of grass exhibit minimal effects in both outdoor and indoor environments. Finally, we provide recommendations for the construction and renovation of projects in residential areas, with a focus on hot-humid areas.

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“…A study in Nigeria showed that outdoor air temperature could be reduced by up to 3.38 • C and mean radiant temperature by up to 24.24 • C when 45 percent of the canopy was covered with trees [24]. Based on the consideration of thermal dynamics and human thermal comfort, the study quantified the maximum effective canopy cover thresholds of 45 percent, 30 percent, and 25 percent for residential areas of 33 m (11 floors), Forests 2024, 15, 518 3 of 23 54 m (18 floors), and 100 m (33 floors) in height, respectively [25]. Additionally, increased plant canopy density can intercept more solar radiation, reducing outdoor air temperature in residential areas and improving thermal comfort [26].…”

Section: Current Research Perspectives On Greenery In Residential Areasmentioning

confidence: 99%

A Study on the Effect of Green Plot Ratio (GPR) on Urban Heat Island Intensity and Outdoor Thermal Comfort in Residential Areas

Zheng,

Li,

Zheng

2024

Forests

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Greenery impacts the urban thermal environment, but the benefits of the three-dimensional green volume of space have not been effectively evaluated. In this paper, we analyzed the impact of 3D greenery on urban heat island intensity and thermal comfort in residential areas from the perspective of the green plot ratio (GPR). We selected a typical residential area, set up simulation models, and then analyzed the effect of different GPR values on the outdoor thermal environment using the validated ENVI-MET simulation. The results showed that increasing GPR in residential areas can effectively reduce the intensity of urban heat island and improve thermal comfort. When the GPR reaches 0.5 and 1.5, the thermal comfort level of the building overhead space and the north–south street space decreases from “very strong thermal stress” to “strong thermal stress”. When the GPR reaches 2.5, the outdoor thermal comfort of the east–west street space and courtyard space is reduced to “hot”. When the GPR is higher than 0.5, the urban heat island intensity in the north–south street space decreases by one level, from “very strong” to “strong”. When the GPR reaches 3.5, all four types of spaces have “moderate” urban heat island intensity. Increased GPR exacerbates urban heat island intensity to some extent and worsens outdoor thermal comfort due to the nocturnal insulating effect of plants. Based on the results, the study proposes the bottom-line control of the GPR index from the perspective of urban heat island mitigation and thermal comfort improvement. This paper points out the benefits of GPR in residential areas in improving the human environment, which is of great practical value for developing urban residential environment from “increasing quantity” to “improving quality”.

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Quantifying tree canopy coverage threshold of typical residential quarters considering human thermal comfort and heat dynamics under extreme heat

Cited by 37 publications

References 70 publications

Study on Microclimate and Thermal Comfort in Small Urban Green Spaces in Tokyo, Japan—A Case Study of Chuo Ward

Study on Microclimate and Thermal Comfort in Small Urban Green Spaces in Tokyo, Japan—A Case Study of Chuo Ward

Comprehensive analysis on the thermal comfort of various greening forms: a study in hot-humid areas

A Study on the Effect of Green Plot Ratio (GPR) on Urban Heat Island Intensity and Outdoor Thermal Comfort in Residential Areas

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