Regulation of outdoor thermal comfort by trees in Hong Kong

Kong, Ling; Lau, Kevin Ka-Lun; Yuan, Chao; Chen, Yang; Xu, Yong; Ren, Chao; Ng, Edward

doi:10.1016/j.scs.2017.01.018

Cited by 210 publications

(94 citation statements)

References 68 publications

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“…Through satellite imagery, Jonsson [139] discovered that at a larger scale, urban T amb varied between 2 • C and 4 • C as a result of the presence of vegetation; (ii) in the study conducted by Perini and Magliocco [140], it was also identified that at ground level and as a result of foliation, T amb , MRT, and PMV values were also considerably lower (≈−3.5 • C in T amb and −20.0 • C in MRT) in comparison to those identified in the rest of the city; and, finally, (iii) in an effort to determine influences of urban vegetation on local conditions within high density settings, Kong, Lau, et al [141] identified maximum reductions of 1.6 • C in T amb , 5.1 • C in MRT, and 2.9 • C in PET.…”

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confidence: 91%

Approaches to Outdoor Thermal Comfort Thresholds through Public Space Design: A Review

et al. 2018

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Based on the Köppen Geiger (KG) classification system, this review article examines existing studies and projects that have endeavoured to address local outdoor thermal comfort thresholds through Public Space Design (PSD). The review is divided into two sequential stages, whereby (1) overall existing approaches to pedestrian thermal comfort thresholds are reviewed within both quantitative and qualitative spectrums; and (2) the different techniques and measures are reviewed and framed into four Measure Review Frameworks (MRFs), in which each type of PSD measure is presented alongside its respective local scale urban specificities/conditions and their resulting thermal attenuation outcomes. The result of this review article is the assessment of how current practices of PSD within three specific subcategories of the KG 'Temperate' group have addressed microclimatic aggravations such as elevated urban temperatures and Urban Heat Island (UHI) effects. Based upon a bottom-up approach, the interdisciplinary practice of PSD is hence approached as a means to address existing and future thermal risk factors within the urban public realm in an era of potential climate change.

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confidence: 91%

Approaches to Outdoor Thermal Comfort Thresholds through Public Space Design: A Review

et al. 2018

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“…Urban green infrastructure is essential to reduce the warming magnitude in cities (Brown et al, 2015;Erell, 2017) as urban dwellers are more prone to heat-induced mortality (Gabriel and Endlicher, 2011). Reintroducing greenery into our cities is therefore widely recognized as an effective nature-based strategy to reduce outdoor air temperature and improve thermal comfort (Fung and Jim, 2017;Kong et al, 2017;Tan et al, 2017;Cheung and Jim, 2018b). The warming effects in cities can be attributed to the conversion of greenery to dark and heat-absorbing surfaces (Weng, 2001).…”

Section: Temperature Limit Of Thermal Neutralitymentioning

confidence: 99%

“…Reintroducing greenery into our cities is therefore widely recognized as an effective nature-based strategy to reduce outdoor air temperature and improve thermal comfort (Fung and Jim, 2017;Kong et al, 2017;Tan et al, 2017;Cheung and Jim, 2018b). Tree planting is most useful in reducing street-level air temperature (Armson et al, 2012;Norton et al, 2015) compared to other greening measures, such as green roofs (Santamouris et al, 2007) and green walls (Lee and Jim, 2017).…”

Section: Temperature Limit Of Thermal Neutralitymentioning

confidence: 99%

Global pattern of human thermal adaptation and limit of thermal neutrality: Systematic analysis of outdoor neutral temperature

Cheung

Jim

2018

Intl Journal of Climatology

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Neutral temperature is the temperature at which people feel neither cool nor warm. Previous regional studies have found that neutral temperature can change with season, which can be attributed to the psychological adaptation effect of people. However, few studies have examined whether the adaptation pattern can be observed across wide geographical and climatic regions. In some cases, outdoor comfort surveys cannot determine neutral temperatures because thermal sensation votes obtained do not reach neutrality. It reflects that thermal adaptation has a temperature limit, and thermal neutrality can hardly be achieved outside the limit. This study aims to establish linear models between neutral temperature and background temperature (survey‐period and climate normal) using neutral temperature data reported in international studies. The limit of thermal neutrality will also be determined in the best‐fit model. The neutral temperature data in 19 empirical outdoor thermal comfort studies published between 2009 and 2017 were used in the linear regression models. Survey‐period mean air temperature was found to be the best predictor of neutral temperature (R2 = 0.539, p = 0.007). The effect of long‐term acclimatization may be less important than it was previously thought because survey‐period temperature can explain over a half of the variability in neutral temperature. The temperature limit of thermal neutrality was defined by the lowest and the highest neutral temperatures in the best‐fit model; the limit was between 12.9 and 32.3 °C in air temperature. The findings indicate that the adaptation effect has a worldwide pattern as neutral temperature always lies closely to background air temperature.

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“…Outdoor spaces are considered vital constituents of urban environments because they can host entertainment activities that are fundamental to the character of a city and the quality of life of city residents (Chen & Ng, 2012). In particular, outdoor human comfort is extremely important in city planning because it can not only improve the physical and mental health of city residents, but also can help reduce power consumption in residential buildings (Amindeldar, Heidari, & Khalili, 2017;Chatzidimitriou & Yannas, 2016;Elnabawi, Hamza, & Dudek, 2016;Kong et al, 2017;Li, Huang, Wu, & Xu, 2018). Actually, an enjoyable outdoor thermal comfort can encourage city residents to spend more time in outdoor spaces (Chen & Ng, 2012;Du, Mak, Huang, & Niu, 2017).…”

Section: Introductionmentioning

confidence: 99%

“…However, congested airflow at the pedestrian level has become a major concern in the high-density cities because it is the driving force for the transfer of pollutant, heat, and water vapour (Ai & Mak, 2015;Chatzidimitriou & Yannas, 2017;Ignatius, Wong, & Jusuf, 2015). This problem is more serious in densely built cities at low or mid latitudes, such as Hong Kong and Singapore, which suffer from urban heat island and global warming Kong et al, 2017;Ng, 2009;O'Malley, Piroozfar, Farr, & Pomponi, 2015;Yang, Wong, & Jusuf, 2013). Therefore, improving pedestrian level wind environment in high-density cities has become a pressing issue for the establishment of comfortable, healthy, and sustainable cities.…”

Section: Introductionmentioning

confidence: 99%

Improving pedestrian level low wind velocity environment in high-density cities: A general framework and case study

Mak

2018

Sustainable Cities and Society

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A B S T R A C TAn acceptable pedestrian level wind environment is essential to maintain an enjoyable outdoor space for city residents. Low wind velocity environment can lead to uncomfortable outdoor thermal experience in hot and humid summer, and it is unable to remove the pollutants out of city canyons. However, the average wind velocity at pedestrian level is significantly lowered by closely spaced tall buildings in modern megacities. To improve the low wind velocity environment at pedestrian level in high-density cities, a general framework and detailed guidelines are needed. This study is the first time to develop such a framework, and provide detailed guidelines for improving pedestrian level low wind velocity environment in high-density cities. Additionally, a detailed review and summarisation of evaluation criteria and improvement measures are presented in this paper, which provide additional options for urban planners. To investigate the performance of the framework, the Hong Kong Polytechnic University campus was utilised as a case study. Results showed that pedestrian level wind comfort was greatly improved with the developed framework. The outcomes of this study can assist city planners to improve the low wind velocity environment, and can help policy makers to establish sustainable urban planning policies.

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Regulation of outdoor thermal comfort by trees in Hong Kong

Cited by 210 publications

References 68 publications

Approaches to Outdoor Thermal Comfort Thresholds through Public Space Design: A Review

Approaches to Outdoor Thermal Comfort Thresholds through Public Space Design: A Review

Global pattern of human thermal adaptation and limit of thermal neutrality: Systematic analysis of outdoor neutral temperature

Improving pedestrian level low wind velocity environment in high-density cities: A general framework and case study

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