Observational studies of mean radiant temperature across different outdoor spaces under shaded conditions in densely built environment

Lai, Anita; Maing, Minjung; Ng, Edward

doi:10.1016/j.buildenv.2016.12.034

Cited by 73 publications

(37 citation statements)

References 25 publications

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“…This is different from the study by Allegrini, Dorer, and Carmiliet in 2015 for the climate of Zürich (Switzerland), in which they stated that wind flow can remove the heat within the urban morphology. Somehow, this study is linear with the study in Singapore (Lai, Maing and Ng, 2017) that densely built form restricts the sky view factor then affects the mean radiant temperature across different outdoor spaces. This study is similar because it is done in a hot and humid climatic region.…”

Section: Discussionmentioning

confidence: 94%

“…The densely built environment creates an very-restricted sky view factor, which then impacts the mean radiant temperature across different outdoor spaces. In hot and humid regions, a large sky-view factor is preferable for cooling open spaces (Lai et al, 2017). The distance between building significantly impacts the building façade's surface temperatures.…”

Section: Density and Livabilitymentioning

confidence: 99%

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Urban morphology aspects on microclimate in a hot and humid climate

Paramita¹,

Matzarakis²

2019

Geographica Pannonica

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Bandung, the capital of West Java province, Indonesia has experienced rapid urbanization, which has affected the urban environment, including its building density, land use, and the quality of urban living. This specific urban morphology has had a significant effect on the urban microclimate. This study was aimed at describing the urban microclimate of three different overcrowded settlements, i.e., Linggawastu (overcrowded settlement), Gerlong Girang (moderately crowded), and Pasir Impun (least crowded). The discussion will detail aspects of the masses and buildings, the distance between buildings, the height of buildings, and the availability of green open spaces to give the perspective of urban morphology toward the microclimate. Fixed weather logger in those three locations were collected over one month, meanwhile the mobile measurements to find the micro-meteorological values of air temperature (Ta), globe temperature (Tg), humidity (RH), and wind speed (v) to define the mean radiant temperature (Tmrt). The measurements provided evidence of the trend of heat trapped in densely populated settlements shown in the diurnal temperature range from Tamax and Tamin (∆Ta) as only 3.2 °C. Meanwhile in Pasirimpun, which is least populated, ∆Ta = 9.5 °C. Linggawastu with building coverage ratio (BCR) > 96% gave the contribution of low Tg=28.3 °C, as there is less insolation penetration to the area. Thus, the PET for two densely populated areas, Linggawastu and Gerlong Girang, tends to be neutral to slightly cool. Nevertheless, this study points out the high humidity in the morning and afternoon, as well as the low air velocity, is a strong affecting factor.

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Section: Discussionmentioning

confidence: 94%

Section: Density and Livabilitymentioning

confidence: 99%

Urban morphology aspects on microclimate in a hot and humid climate

Paramita¹,

Matzarakis²

2019

Geographica Pannonica

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“…This index affects the mobility of air and is of great significance to the urban microclimate (e.g., thermal comfort) [39]. Within the near surface spatial range, the degree of openness has the following two meanings: (1) the degree of opening to space and (2) the degree of opening to surrounding areas (usually referred to as the degree of enclosure) [40]. A high degree of opening to the space mitigates the heat island effect and reduces the air temperature effectively [15].…”

Section: Degree Of Openness Versus Thermal Environment In Near Surfacmentioning

confidence: 99%

Impacts of Urban Form on Thermal Environment Near the Surface Region at Pedestrian Height: A Case Study Based on High-Density Built-Up Areas of Nanjing City in China

et al. 2020

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The continuous worsening of urban thermal environments poses a severe threat to human health and is among the main problems associated with urban climate change and sustainable development. This issue is particularly severe in high-density built-up areas. Existing studies on the thermal environments (temperature data extracted from satellite remote sensing images) are mainly focused on urban canopy areas (airspace below the average height of trees or buildings) rather than the near surface region (at pedestrian height). However, the main outdoor activity space of urban residents is the area near surface region. Hence, this study aims to investigate the influence of urban form (i.e., building density, height, and openness) on thermal environment near the surface region. The high-density built-up areas of a typical megacity (i.e., Nanjing) in China were selected, and the thermal environments of 26 typical blocks were simulated using ENVI-met software. Temperature field measurements were carried out for simulation validation. On this basis, a classified and comparative study was conducted by selecting the key spatial form elements that affect thermal environments. The results showed that in actual high-density built-up areas, single urban form parameter does not determine the thermal environments near the urban surface but mainly affected by the use (function) of space. For this study, the overall thermal environment of a street block is optimal when the building density is between 40% and 50% and the average building height is between 8 and 17 stories. Nonetheless, the urban form can be improved to optimize the overall effects on building functions and thermal environments. Furthermore, function-specific urban form optimization strategies were proposed to optimize thermal environments according to specific functional needs.

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“…The sky view factor (SVF) describes the impact of canopy density on air circulation [8] and the irradiance reduction of plant canopies [9,10,21]. Because SVF can be measured conveniently, some studies have used SVF to discuss variations in shading levels and air temperature [22][23][24][25]. Areas with relatively dense broadleaf trees tend to have low SVF values [26].…”

Section: Introductionmentioning

confidence: 99%

Screening of Tree Species for Improving Outdoor Human Thermal Comfort in a Taiwanese City

Lin

Tsai

2017

Sustainability

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Tropical cities can use urban greening designs featuring trees that provide shade and cooling in hot outdoor environments. The cooling effect involves numerous tree characteristics that are not easy to control during planting design, such as the canopy size and the optical properties of leaves. Planting the appropriate tree species dominates the cooling effects and the human thermal environment. Based on environmental and plant data, including the tree species, crown diameter of trees, physiologically equivalent temperature (PET), and sky view factor (SVF) in an outdoor space, a series of hierarchical cluster analysis (HCA) procedures was implemented to identify the tree species that are appropriate for improving thermal comfort. The results indicated strong correlations between SVF, average crown diameter, and PET. SVF decreased as the average crown diameter increased. For the average crown diameter of trees in an area wider than 1.5 m, the cooling effect was especially dominated by the tree species. Therefore, 15 species were screened by HCA procedures, based on a similar cooling effect. These species had various cooling effects, and were divided into four categories. Tree species, such as Spathodea campanulata and Cinnamomum camphora, had the appropriate crown diameter and cooling effect for the most comfortable thermal environment.

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Observational studies of mean radiant temperature across different outdoor spaces under shaded conditions in densely built environment

Cited by 73 publications

References 25 publications

Urban morphology aspects on microclimate in a hot and humid climate

Urban morphology aspects on microclimate in a hot and humid climate

Impacts of Urban Form on Thermal Environment Near the Surface Region at Pedestrian Height: A Case Study Based on High-Density Built-Up Areas of Nanjing City in China

Screening of Tree Species for Improving Outdoor Human Thermal Comfort in a Taiwanese City

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