Elsevier

Urban Climate

Volume 37, May 2021, 100824
Urban Climate

Microclimate characteristics in the famous dwellings: A case study of the Hakka Tulou in Hezhou, China

https://doi.org/10.1016/j.uclim.2021.100824Get rights and content

Highlights

  • Microclimate characteristics in the Hakka Tulou were comprehensively investigated.

  • Environments of thermal, wind, and light were considered into microclimate.

  • Hakka Tulou has ability to satisfy the purpose of warm in winter and cool in summer.

  • High wind speed appeared at Hakka Tulou center in summer and patio space in winter.

Abstract

Hakka Tulou is a famous local earth construction, which is included in the UNESCO list of World Heritage buildings. To the best of our knowledge, there is a lack of thorough research into the microclimate characteristics of Hakka Tulou. In this study, we investigated the microclimate characteristics in the Hezhou Hakka Tulou. The indoor thermal sensation of the enclosure in warm circumstances was approximately equal to that of cool circumstances. However, the indoor thermal environment of Hakka Tulou could be improved by outer guard structures. In summer, the corridor structure allows for cooling down of the indoor air temperature, while the patio structure has the advantage of dehumidification. However, in winter, the building envelope has the advantages of thermal insulation and moisture-proofing. The location of higher wind speed in summer was mainly orientated from the center of the Hakka Tulou; however, this center appeared in the patio space. Such special environmental factors may be useful for the purpose of warmth in winter and coolness in summer. Furthermore, the patios of the Hakka Tulou effectively improved the lighting coefficient and illumination in the courtyard. However, the daylighting capacities of the inner rooms were considerably lower than those in the outer rooms.

Graphical abstract

The authors systematically investigated the microclimate characteristics in the Hakka Tulou of Hezhou.

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Introduction

The Hakka Tulou is a classic type of massive traditional earth construction; some of these famous earth construction structures in China, such as Fujian Tulou, have been included in the UNESCO list of World Heritage Earthen Architecture Programmer (WHEAP) (Briseghella et al., 2019; UNESCO, 2008). These structures are also a popular attraction for tourists from around the world; however, there are few publications that cover the microclimate aspects of these very peculiar and massive earth buildings. Despite this dearth in specific research, there is a growing body of literature that recognizes the importance of the microclimate of buildings (including Hakka Tulou) (Briseghella et al., 2019). Recently, there has been renewed interest in earthen materials as low energy and environmentally friendly materials for the use in ecological and sustainable architecture (Minke, 2009). At the same time, earthen buildings have developed rapidly given the low cost of raw materials and the simplicity of production. More than one billion people still live in earthen buildings (Houben and Guillaud, 1994). The oldest Hakka Tulou was dominated by the circular rammed earthen wall; however, another type of Tulou (the square Tulou) was also built with a rigid adherence to the rules of fengshui, a Chinese geomantic art (Briseghella et al., 2019).

The square Hakka Tulou dominated the Hakka Tulous structures found in Hezhou city (Fig. 1). Hezhou has named as a China's longevity city by the vice chair of the International Expert Committee on Population Aging and Longevity and co-chair of the Commission on Environment and Health of the International Geographic Union in 2016 (Li, 2016). Therefore, the longevity of local people may be connected with the emergence of the square Hakka Tulou. One important feature of Hezhou is its abundant rainfall. According to statistics, the annual average precipitation of Hezhou reached as high as 1546.1 mm from 1957 to 2011 (Sun et al., 2012). The southerly wind prevails for half of the summer. During that season, the climate characteristics include high temperature, high humidity, sultry, and rainy (Wu et al., 2009; Weining et al., 2015). However, the northerly wind prevails for half of the winter and has the climatic characteristics of being the low temperature, cold damage, dry, and less rain (Wu et al., 2009; Weining et al., 2015). These special climatic characteristics may affect the microclimate characteristics of the Hakka Tulou in Hezhou.

At present, several representative methods of evaluation have been applied to the study of climatic characteristics of buildings, such as field measurements, wind tunnel tests, satellite remote sensing image inversion, a computational fluid dynamics (CFD) model, and meteorological models. The simulation has evident advantages compared with the field measurement and the satellite remote sensing image inversion. Firstly, the 3D numerical model can intuitively visualize the real building microenvironment. Secondly, simulation saves in substantial manpower and time. Among these simulation methods, CFD has served as the dominate simulation methods to explore the effects of the climate on a single building in great detail (Yang et al., 2012). However, these studies primarily investigated buildings with reinforced concrete (Kim and Jong, 2020; Shareef and Abu-Hijleh, 2020; Tsoka et al., 2018). There remains little published data on the microclimate characteristics of earthen buildings.

Chen et al. developed a method for calculating the comfort levels of a microclimate of landscape architecture, combining objective physical parameters with subjective human thermal feelings of comfort (Ruizhi and Liang, 2013). Lv et al. investigated the effects of phase change wall room on an indoor thermal environment in the winter (Shilei et al., 2006). Other studies also proved that the control of bed microenvironments may allow for greater efficiency in thermal comfort energy (Lan et al., 2017). Cottus et al. explored the role of street trees in cooling the urban microclimate and improving human thermal comfort (Coutts et al., 2016). Abreu-Harbich et al. investigated the effect of tree planting design and tree species on human thermal comfort in the tropics (Abreu-Harbich et al., 2015). However, these studies have focused on the thermal environment and the effects of plants. There is little published data on the effects of the other important parameters on the microclimate analysis of buildings. Therefore, such parameters require further study to ascertain the microclimate analysis of buildings, such as the wind or light environment.

In this study, we selected a square Hakka Tulou in Hezhou as being representative of such earthen buildings. Some important boundary conditions of the Hakka Tulou were measured in the field. In addition to the thermal environment, other environmental conditions, such as the wind environment and the light environment, were also factored into the microclimate analysis of the Hakka Tulou. Therefore, this study will provide valuable information for understanding the microclimate characteristics in the Hakka Tulou and will also propose useful methods for improving such microclimate characteristics.

Section snippets

Description of the Hakka Tulou prototype

In this study, the selected Hakka Tulou is located in Hezhou, recognized as a world longevity city with an average life span of 78.01 years. Built in the late Qing dynasty over 200 years ago, this construction is typical of traditional Hakka residential architecture. It consists of south and north parts. We selected the north part of this Hakka Tulou as the measuring object, as shown in Fig. 1. The whole house looks quiet and elegant. This particular section is approximately 8800 square meters.

Microclimate characteristics of the Hakka Tulou

The evolutions of the solar radiation intensity in summer from 8:00 am to 6:00 pm are shown in Fig. S1. In the summer, the average solar radiation intensity was 682 W·m−2. The maximum value of the average solar radiation intensity was 1085 W·m−2 at 1:00 pm, while the minimum value was 102 W·m−2 at 6:00 pm. The maximum values of the indoor average wind speeds were reached between 12:00 pm to 1:00 pm (Fig. 3), which well-coordinated with the maximum value of the average solar radiation intensity

Discussion

The outdoor average temperature in the summer was higher than the indoor average temperature by approximately 2.0 °C; however, the outdoor average temperature in the winter was lower than the indoor average temperature by approximately 0.7 °C. The indoor average relative humidity in the summer increased 13.5% by comparing to the outdoor average relative humidity, while the indoor average relative humidity in winter decreased approximately 5.7% by comparing to the outdoor. All testing time in

Conclusions

Hezhou Hakka Tulou is both a local famous earth construction and on the UNESCO list of World Heritage buildings. Up to now, far too little attention has been paid to the microclimate characteristics of the Hakka Tulou.

In this study, we firstly investigated the microclimate characteristics of the Hakka Tulou in Hezhou by way of measuring and simulation. These microclimate characteristics included several key parameters, such as thermal, wind, humidity, and light environments.

Since little

Ethics approval

Not applicable.

Consent to participation

Not applicable.

Consent to publication

Not applicable.

Funding

This work was supported by the Natural Science Foundation of Guangxi Province, China [2018GXNSFAA138071, 2020GXNSFBA297075], the National Natural Science Foundation of China [52006096], and the Scientific Research and Technology Development Plan of Guilin, China [20180107–2].

Availability of data and materials

Supplementary data (Tables S1–S3 and Figs. S1–S6) associated with this article can be found, in the online version.

CRediT authorship contribution statement

Wenheng Zheng: Funding acquisition, Project administration. Beiyu Li: Data curation, Methodology, Software, Writing – original draft. Jianjun Cai: Formal analysis, Funding acquisition, Writing – review & editing. Yueming Li: Software. Lili Qian: Writing – review & editing.

Declaration of Competing Interest

The authors declare that they have no competing interests.

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