AA_Dissertation_Sustainable Retrofitting of Stilt Dwellings in Rural Southwest China by Anbo Hu

Sustainable Retrofitting of Stilt Dwellings in Rural Southwest China A Study on Affordable Strategy for Vernacular Building's Sustainability Potential

Anbo Hu MSc Sustainable Environmental Design Dissertation Paper (2022-2023) Graduate School Architectural Association School of Architecture September 2023

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AA SED ARCHITECTURAL ASSOCIATION GRADUATE SCHOOL PROGRAMME:

MSc SUSTAINABLE ENVIRONMENTAL DESIGN 2022-23

SUBMISSION:

Dissertation

TITLE:

Sustainable Retrofitting of Stilt Dwellings in Rural Southwest China

Acknowledgement NUMBER OF WORDS:

16,159

STUDENT NAME:

Anbo Hu

DECLARATION: “I certify that the contents of this document are entirely my own work and that any quotation or paraphrase from the published or unpublished work of others is duly acknowledged.”

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Date: 2023/09/29

The short but fulfilling experience at the AA-SED Programme will be an unforgettable period of my life. This dissertation will be a summary of my learning and outcomes in SED. Firstly, I would like to express my appreciation to all SED programme professors, including Simos, Paula and Joana and all other lecturers and technical tutors. Their guidance and suggestions enabled me to complete the dissertation and my postgraduate studies successfully. Secondly, I would like to thank my parents and my family. Their unconditional care and support enabled me to complete my graduate studies in a strange country. Finally, I would like to thank myself for the time and energy on studying for the professional skills in sustainability environmental design.

Abstract This dissertation delves into the potential for energy-saving retrofitting and outlines specific renovation measures for stilted houses, which are distinctive residential buildings with minor ethnic cultures in the rural areas of southwest China. To begin with, the dissertation provides essential background information covering aspects such as climate, geography, population, and energy usage in southwest China. It then proceeds to discuss the architectural features, settlement patterns, and materiality of stilted buildings based on existing literature and case studies. Two case studies are conducted to identify the challenges that stilted buildings face in terms of their thermal environment and offer initial directions for improvement. Subsequently, by establishing a fundamental thermal model which is calibrated with the data from cases, the research explores the lighting and energy performance of the building under varying conditions of various spatial layouts and material properties. Lastly, a guideline for stilt building retrofitting is summarized with the findings from simulation and case studies. Identifying specific measures that could be applied to various demands and building conditions under national regulation and affordability. By compositing these retrofitting measures, a comprehensive plan for the renovation of stilted buildings is proposed.

Content Introduction 8 1.Context 10

1.1 Geography 11 1.2 Climate 11 1.2.1 Temperature 11 1.2.2 Precipitation 12 1.3 Population 12 1.4 Energy Consumption 13 1.5 Adaptive Comfort Band 15 1.5.1 Winter Thermal Comfort 15 1.5.2 Summer Thermal Comfort 16

2. Vernacular Architecture in Southwest China

2.1 Building Typology 19 2.1.1 Plan Typology 19 2.1.2 Village Settlement 20 2.2 Construction 22 2.2.1 Building Components and Materials 23 2.2.2 Construction Process 25 2.3 Vernacular Passive Design 25

3. Case Study 28 3.1. Case Study 1: Sanjiang Dong Autonomous 29 3.1.1 Performance 31 3.1.2 Discussion 31 3.2 Case Study 2: A Stilt Dwelling in Tongren 34 3.2.1 Performance 35 3.2.2 Discussion 37 3.3 Conclusion 37

4. Retrofitting Approach 38 4.1. Simulation Focus and Principles 40 4.2. Methodology 41 4.3 Model Description 41 4.3.1 Materality 42 4.3.2 Parametre Calibration 43 4.3.3 Simulation Scenario and Schedule 43

5. Simulation 46 5.1 Base Case 47 5.2 Orientation Test 50 5.3 Daylighting 53 5.4 Window-Wall Ratio 54 5.5 Internal Gain 55 5.6 Envelope 56 5.6.1 Materiality and Structure 58 5.6.2 Estimated Cost and Conclustion 59 5.7 2050 Scenario 61

6. Scenario Variation 62 6.1 Scenario A: Additional Ceiling on the First Floor 6.2 Scenario B: Half Stilt Ground Floor 6.3 Scenario C: Fully Stilt Ground Floor

65 66 68

7. Retrofitting Guidance 70 7.1 Airtightness 71 7.2 Daylighting 71 7.3 Heating Pattern 72 7.4 Envelope 72 7.5 Conclusion 74

Conclusion 75 Bibliography 78

Introduction From 1978 to 2013, there was a significant increase in China's urban population from 170 million to 730 million, and the urbanization rate tripled from 17.9% to 53.7%, which resulted in the success of China's economic growth (CGPRC, 2014). It is estimated that the urban population will rise to about 1 billion in 2030, which occupies approximately 70% of the total population in China. This rapid urbanization process in China boosted economic development, accelerated Industrial upgrading, and led to massive migration from rural areas to cities. This population movement caused a huge demand for new residential housing in the town and massive abandoned housing in rural areas. During the rapid urbanization period from 2010-2011, the land for urban construction has increased by 3450 km² per year and raised around 76.4% compared with the initial land area. The urban population has only increased by 50.5%. (CGPRC, 2014) The urbanization process is far ahead of population growth. In this situation, developing existing building quality is more rational in the economy and environment than constructing new buildings. According to Liu et al. (2019), facilities' energy use accounted for about 30% of total energy consumption in the country. To reduce energy waste and achieve China's national target of becoming a carbonneutral country in 2060 (Jia & Lin, 2021). It is vital to reuse the building resources from the existing stock. In the case of urban overexpansion and the recession of rural areas, rural revitalization has become one of the most fundamental strategies of the Chinese government (Fan et al., 2023). Though rural revitalization is primarily related to economic development, talent training, ecological preservation, industrial upgrading, and cultural protection, building quality is the closest part to villager’s daily life. Living quality can not only reflect the economic level of a place but also have a deep connection with the ecological level and regional cultural conventions. Regarding the current rural construction and renovation situation, the Chinese government listed several existing issues 8

(CGPRC, 2014), mainly concerned with the financial and management field. The main problem regarding building construction is preserving the historical, natural, and cultural legacy. As a multi-ethnic country with a long history, different regions have distinctive and abundant regional characteristics. However, in the process of renewal and construction, some villages lack concern for the cultural environment and apply urban residential settlements and architectural forms to the countryside, destroying humanity and ecology. In the process of human habitat history, the vernacular rural architecture, due to the necessary demand of adapting to different landforms and climates, spontaneously developed a set of sustainable architectural forms. Therefore, considering today's pursuit of sustainable development, rural vernacular architecture has significant value to learn and utilize (Sun,2013). Regarding the regional characteristics of the urban development level, the eastconcentrated policy in China caused an imbalance in the urbanization level between the east and the West. As the later developed area, Southwest China has an urbanization rate of only 44.8%, approximately 20% lower than East China (CGPRC, 2014). According to Jiang et al. (2018), buildings consume nearly 40% of national energy use in China. The rural buildings accounted for 67% of energy consumption (NBSC,2021). As an area with a lower urbanization rate but a high population of 192 million (NBSC,2021), there is a massive market for sustainable retrofitting and design in southwest China to reduce energy waste. The southwest China region includes four provinces and a municipality in official definition: Guizhou, Yunnan, Sichuan, Tibet, and Chongqing Municipality. This is a large area that has distinctive altitude and climate differences. This research will focus on the part within the hot summer and cold winter climate zone, including details of Guizhou, Sichuan, Yunnan, and Chongqing City. In terms of the dwellings in this area, the timber multistoried building, which belongs to one of the three main types of vernacular building in China: multistorey timber building,

caves, and stone-made courtyards form (Shan, 2004), is commonly applied in this region as their residential housings with some slight differences between some villages due to their unique cultural or religious from various ethnic groups such as Miao and Dong. Due to the inconvenience of transportation, local natural resources such as wood and stone are commonly used as building construction materials (Zhang et al., 2022). The experienced local artisans and architects are their houses' primary designers and builders with the condensation of the understanding of their unique culture and knowledge. Although buildings have been entirely hand-made in the past few centuries due to the lack of advanced technology, they have sheltered the inhabitants and become part of their culture for centuries. The vernacular buildings in southwest China have abundant, sustainable features. For example, to adapt to the mountainous terrain and possible flood due to the high rainfall, some buildings that sit on the hillside will have stilt ground floor (Zhang et al., 2022), which could save building materials that are used to level the ground, allows more ventilation and drainage in hot and humid summer and could maximise the utilization of the space. However, China's rapid modernization process creates a higher desire for living quality and energy efficiency. Most of the traditional dwellings in this region are far from the modern living standard and have the problems of no electricity, no artificial illuminance and leaky envelope. Rural areas have massive possibilities and chances to improve under the national movement of low-carbon and carbon neutrality. This dissertation aims to summarize a methodology to improve vernacular dwellings' energy efficiency and living quality in rural southwest China by testing and simulating different scenarios regarding other thermal, daylighting and spatial layout possibilities. Before the simulation, this dissertation will discuss existing performance and issues for the building from cases, then, based on findings from the discussion, clarify the direction of the simulation. The literature review will

provide essential information to help establish the research questions regarding the climate, geography, population, and modernization process in rural southwest China. Some general issues can be found throughout this section. After the literature review, a more specific study on the context and cases would be needed to understand the family model, lifestyles, and traditions of those ethnic groups in this area and discuss the sustainability performance of existing topics. Based on the context and case studies findings, the simulation for a typical scenario first is a traditional rural family of 5 people. The simulation is expected to improve the building's performance on thermal daylighting aspects. Besides, this dissertation would improve their building quality in terms of spaces in the section of analytic works. The scenario study is expected to provide guidelines for building retrofitting in this area for residents with various living conditions and demands. The concept of cultural preservation would be the fundamental boundary of the research. Therefore, the retrofitting strategies would minimise the impacts on the building's unique cultural values and respect the local lifestyle. It is expected that the simulation would reduce the energy loads of the building, improving the comfort hours for inhabits, increasing the daylighting performance and finally provide a clear guideline for the design of wall, roof and glazing structure, which would be helpful as a universal model to be easily applied on different scenarios.

Figure 1. Southwest China Location

1. Context

1.1 Geography There are abundant landforms in southwest China, ranging from the Heng Duan Mountains, Qinghai-Tibet Plateau, and the Sichuan Basin to the Yunnan-Guizhou Plateau from west to east. As the research is concentrated on the area with similar vernacular residential buildings mainly located in part of the hot summer and cold winter and part of the temperate climate zone, Tibet is not considered in this research. This article's term 'southwest China' will only represent the research area. The research area involves four administrative regions in China: part of Sichuan, Yunnan province, Chongqing municipality and the entire Guizhou province. Take Guizhou province, the most representative province in southwest China, as an example; the latitude and longitude are 26° N 106° E. It is located in the Yunnan-Guizhou plateau, one of China's four plateaus (Long et al., 2016). Guizhou has an average elevation of around 1100m, and mountains and hills account for about 92.5% of the total area of Guizhou province (Government of China, 2014). Therefore, the rugged terrain resulted in the development difficulty and lack of communication with the outside in the past centuries. This landform also increased the difficulty of construction and resulted in the unique architectural style of stilt buildings. Although there are some differences in the topography of different parts of the study area, they are all in mountainous terrain and have similar altitudes.

1.2 Climate 1.2.1 Temperature For the part with stilt dwellings in southwest China, the climate is named a subtropical humid monsoon climate. It performs a hot summer and cold winter, with an average temperature of 24°C in the hottest month of July and 5.8°C in the coolest month of January (Weather and Climate,2023). The highest and lowest temperatures are 33°C and 2 °C for the average of the entire region, while some areas would have low temperatures of below 0°C in winter. The data demonstrated that the main issue for the thermal comfort for the residents would be the cold season, while most of the time, the average temperature is below 10°C from October to March. Therefore, the thermal performance of the building in the cold season is the main challenge in this region. Regarding summer, only a few days have higher temperatures than 30°C, and most of the time in summer in rural areas of southwest China, residents open their doors and windows to improve natural ventilation. Therefore, there is no additional cooling required for the countryside. Generally, there is no extreme temperature for this region, but the temperature during the cold season could be the main issue for the thermal comfort of the building. To understand the exact performance of the vernacular buildings here, more specific operative indoor temperatures will be discussed in the case study section.

Figure 2. China Elevation (Source: Solargis, 2023)

Figure 3. Guizhou Climate Chart (Source: Song et al., 2014)

Figure 4. Guizhou Climate Chart (Source: Weather and Climate, 2023)

1.2.2 Precipitation Apart from the temperature, this region has high precipitation and relative humidity. The average annual precipitation could reach around 1300mm, almost double the average annual precipitation in China of 672mm. The primary precipitation happened from June to August, with more than half of the days during these months being with rainfall. In terms of the relative humidity, as one of the wettest regions in China, it is higher than 80% for most days of the year. Besides, southwest China has limited annual sunshine hours of approximately 1400 hours, one of the areas with the least sunshine (Guizhou Meteorological Bureau,2023). In conclusion, the study area of southwest China is a humid, temperate area with limited sunlight and abundant precipitation. The expected main challenge for the dwellings in the rural area here would be to keep warm during winter, avoid floods, and gain enough sunlight and solar energy. 1.3 Population Generally, the population in southwest China is still migrating from the countryside to the city (Figure 7). In 2016, the urban population exceeded the rural population in SW China for the first time. In terms of the population structure, take Guizhou province as an example; around two-thirds population is between the ages of 15-64. However, about

12% of people are over 65 years old, which could be defined as an ageing society (NBSC, 2023). In addition, as more and more young generations move from rural to urban areas, the ageing problem of rural areas will be more severe. Regarding family size, in rural SW China, more than half of the households have a size of 3-5 people (Figure 6); a more significant family is common in rural China and typically includes three generations. Moreover, more than 20% of the population is ethnic minorities in southwest China (NBSC, 2022). As the stilt dwelling is one of the typical architectural styles of ethnic minorities in China, the research areas have a much higher rate of ethnic minorities. The ethnic groups that use stilt houses as their primary residences are mainly the Miao and Dong ethnic groups, with more population distribution in southwest China. In terms of the per capita disposable income in rural areas of southwest China, according to the data from the National Bureau of Statics of China (NBSC) in 2021, the daily income for rural residents is around 5.5 USD, which is almost equal to the poverty line for the upper middle-income countries proposed by World Bank in 2011 (FILMER et al., 2022). Therefore, the residents here cannot afford expensive

houses and materials. The affordability should be considered when designing the retrofitting strategies. 1.4 Energy Consumption There is a target proposed by the Ministry of Housing and Urban-Rural Development of China (MOHURD) that the average housing area in rural China should reach 45m² by 2030 (Shan et al., 2015). As around 0.5 billion people would live in rural areas at that time, the total building area in the countryside would be 22 billion m². As a result, improving energy efficiency in rural buildings will be an urgent challenge. According to the investigation by Shan et al.(2015), the annual energy use in rural China is 9.3 × 109 GJ, which accounts for around 40% of total building energy consumption in China. Among them, 43.6% was attributed to the southern region, while the northern region accounted for 56.4%. In total rural energy consumption breakdown, approximately 60% consisted of commercial energy sources such as coal, liquefied petroleum gas (LPG), and electricity. The remaining 40% comprised non-commercial biomass energy sources like firewood and straw. This ratio represents a significant shift from 1990, when non-commercial biomass

Figure 5. Population Age Structure in Guizhou. (Source: NBSC,2021)

Figure 6. Househole Types. (Source: NBSC,2021) Figure 7. Urban Populaion Rate in SW China (Source: NBSC, 2021)

Table 1. Annual Energy Consumption for Space Heating in Different Regions (Shan et al., 2015)

Table 2. Annual Energy Consumption for Cooking in Different Regions (Shan et al., 2015)

energy accounted for twice as much. The increased use of commercial energy sources is indicative of technological advancements. Heating and cooking constitute the primary sources of energy consumption in rural areas, accounting for nearly 75% of the total energy consumption. Heating accounts for around 40% of total energy consumption. Regarding heating methods, there are significant regional differences between the northern and southern areas due to climate variations. For example, nearly 60% of households use firewood for heating in the southern region where the research area is located. In contrast, in the northern region, the proportion of using coal as the heating source is as high as 74%. Cooking accounts for approximately 30% of energy consumption, with relatively minor differences between northern and southern regions. In the southern region, for instance, the primary cooking method still involves firewood use; in some areas, coal is also extensively used for cooking. Improving rural electrification systems is gradually replacing these outdated practices reliant on biomass energy sources. Changing the energy consumption patterns in rural buildings is crucial in achieving sustainable renovations, reducing building energy consumption, mitigating carbon emissions, and addressing air pollution. 1.5 Adaptive Comfort Band In the context of the energy crisis, thermal comfort is crucial for achieving energy efficiency (Sun et al., 2023). Residential buildings offer extensive opportunities for adaptive thermal comfort. In rural areas, due to harsher environmental and living co n d i t i o n s , re s i d e nt s h ave d eve l o p e d more flexibility to adapt to their thermal environment (Wei et al., 2022). Therefore, rural areas typically have a broader range of thermal comfort adaptability. According to the adaptive thermal comfort model proposed by Brager et al.(1998), environmental parameters are not the sole influencing factors on body thermal comfort. The human body can actively interact with the surrounding environment through three

primary ways: physiological adaptation, psychological adjustment, and behavioural regulation. In the rural areas of Southwest China, the population is dominated by ethnic minorities that have differences in housing layouts, lifestyle habits, and heating methods compared to the dominant ethnicity of Han in China. Consequently, their tolerance levels toward the thermal environment could be varied. 1.5.1 Winter Thermal Comfort To establish the adaptive thermal comfort for traditional rural dwellings in the southwestern region, Wu et al. (2019) conducted a study in Denglu Village, Taijiang County, Qiandongnan Miao and Dong Autonomous Prefecture, Guizhou Province. This village represents a typical Miao ethnic mountain settlement composed of wooden houses. Therefore, the findings of this study can be broadly applied to similar ethnic minority communities in rural southwestern areas. The study encompasses a comprehensive analysis that includes both objective and subjective factors. It involves statistical analysis of objective elements like temperature and humidity alongside an investigation and data collection concerning residents' physical sensations. The research is grounded in the comparison of indoor and outdoor temperature differences. Besides, it examines various building heating methods and residents' clothing indices. Additionally, it entails surveying villagers' feelings and observing their behaviour patterns. Mathematical equations are applied to model and establish correlations between these diverse factors and residents' perceptions of cold and heat. The research findings indicate that in this region, approximately 90% of residents have an acceptable range for environmental temperature during the winter months between 8.9-18.8 °C, and 80% of residents are within the range of 6.5- 21.2 °C. In contrast, about 80% of residents in Guizhou urban areas have an acceptable temperature range of 10- 23.6 °C (Sun et al., 2023). The results demonstrated that rural residents in Guizhou 15

have a higher level of adaptability to and acceptance of low temperatures compared to urban areas. The study also involved calculations of PMV (Predicted Mean Vote) and MTS (Manikin Thermal Sensation) for the residents of this village. PMV, as an objective indicator reflecting thermal comfort, eliminates regional factors such as residents' customs and their adaptation to the climate. In contrast, MTS is a thermal sensation index derived from statistical analysis of residents' subjective sensations under specific conditions. Due to the residents' long-term psychological and physiological adaptations to the local climate, their tolerance to low temperatures has increased. Therefore, the results reflected by MTS are more site-specific. When both PMV and MTS are equal to 0, the thermal comfort temperatures are 18.5°C and 14.3°C (Figure 8), respectively, with a difference of 4.2°C. The 18.5 °C is suitable as the optimal residential comfort temperature standard for urban residents relocating to this village from other areas, while the 14.3°C is applicable to the medium thermal comfort temperature standard for residents. The measured thermal comfort temperature of 14.3°C is around 3.6°C higher than the indoor operative temperature in this village during the measurement period. The village's buildings are typical Southwest rural stilt houses, so their temperature performance is representative. From this, it can be inferred that most stilt houses would

Figure 8. Linear Regression of Operative Temperature and MTS, PMV (Source: Wei et al.,2022)

have slightly lower indoor average operating temperatures than the thermal comfort temperature during winter. In summary, rural residents currently have a high tolerance to low temperatures of around 8°C. However, considering residents' tolerance to low temperatures may decrease with improving life quality, 14°C will be adopted as the heating point in this study. 1.5.2 Summer Thermal Comfort This study primarily focuses on exploring thermal comfort during the winter season. In rural areas of the southwestern region, active heating measures are typically required during this period. Therefore, the thermal comfort temperature during winter can serve as a reference standard for building retrofitting, envelope structure improvement, and reducing heating energy consumption. Regarding summer, residents in this region tend not to purchase active cooling equipment like air conditioning due to energy expenses. Instead, they generally employ passive cooling measures, such as opening windows for ventilation and sun shading. Furthermore, the average summer temperature in this region is around 25°C, occasionally reaching above 30°C on some days. From the perspective of energy and cost saving, there may not be a necessity for adopting active cooling measures. Wei et al. (2022) conducted a study regarding summer thermal comfort temperatures in rural areas of Linshui County, Sichuan Province, and the southwestern mountainous

region. According to their findings, when the TSV (Thermal Sensation Vote) = 0, the thermal comfort temperature during summer is 29.3°C, and when TSV ranges from -0.5 to +0.5, the comfortable temperature range is between 27.8°C to 30.9°C (Figure 9). These research results emphasize that residents in rural areas may adopt different thermal comfort strategies based on varying seasons and climatic conditions. During the summer, they tend to prioritize passive cooling methods overactive cooling devices, contributing to better understanding and fulfilling their thermal comfort needs. In general, rural residents have a tolerance to high temperatures of around 30°C in summer, and they commonly use passive ventilation, such as open windows or doors, to cool down the environment. As a result, considering the moderate temperature in rural southwest China in summer, the energy consumption for cooling will be ignored in this study.

Figure 9. Results of the Linear Regression Between TSV and Operative Temperature. (Source: Wu et al.,2019)

2. Vernacular Architecture in Southwest China This chapter aims to investigate the architectural form and resident's experience of vernacular stilted houses in Southwest China through the review of literature sources. It focuses on how the physical characteristics of these houses exist within the unique geographical, climate and cultural context. This includes the typology analysis of the space of stilted houses, the architectural features and manifestations based on passive design principles, the connection between housing types and the local residents' lifestyle, and the feedback from local residents regarding the use of these buildings. These information will provide effective directions for energy-efficient renovations of these buildings while preserving their distinctive cultural features and respecting the local way of life.

2.1 Building Typology Traditional rural dwellings in southwest China usually take the form of single-family houses, while enclosed courtyard houses are more common in the north (Ruan,2006). This area's geographical features are mostly steep mountains, so the residential buildings are usually in the form of stilted buildings. The stilted building could be divided into two main parts: the central part, which generally includes the living room, kitchen and other areas for daily activities, is built on a solid and flat foundation, parallel to the terrain; The flanks, which are perpendicular to the central part and supported by wooden columns on the hillside, are often used as bedrooms or storage rooms. In flat areas, buildings may fit entirely into the ground without the need to adopt the form of stilted buildings. However, this form of construction can also be regarded as a variant of stilted buildings.

2.1.1 Plan Typology According to the Technical code of practice for constructing the Tujia stilted house proposed by the Department of Housing and UrbanRural Development of Hubei Province in 2023, the floor plan layout should be simple and regular, minimizing eccentricities. The floor plan layout should be continuous without significant protrusions or openings. There are 4 stilted buildings: I, L, U-shaped and courtyard-type. The main difference between these types is the wing rooms (Guo,2015). I-shaped: This is the most common and basic type of building, consisting of a row of 3 to 7 rooms separated by walls and connected by a long veranda outside. Traditional rooms in the local area are generally odd in number, following the principle of 'one light, two dark, and three open rooms'.This means that the space is

Table 3. Four Types of Plans (Guo,2015)

arranged with a bright main functional area, like the living room in the middle, and two relatively darker spaces on either side, such as storage or bedrooms. This arrangement enhances daylighting and space rationality. The central space in the house is the most crucial part, symbolizing family unity and is typically used for displaying ancestral items and shrines. L-shaped: L-shaped space is also a common plan type, known as the 'Key Head'.It usually has a perpendicular extension on one side, typically provided as bedrooms for new family members or young members related by blood or marriage. The primary part of the bedroom is usually allocated to elderly members to reflect their status. Depending on the terrain, the structure of this extension can be the extended part of the original frame or an independently constructed new structure. The connection between the wings and the main body is usually a kitchen or dining room with a stove.

Figure10. Valley Settlement

As the result of limited usable land in the highdensity peak clusters, a village was dispersed in different depressions with small number of households of around a dozen or less. Due to the independence of settlements, the villages scattered all over the valley, the cultivated land and houses of each family are distributed in a relatively disorderly manner based on the terrain, forming a complex hierarchy. However, the complex landform resulted in the inconvenience of transportation and high risk of debris flow. -Hillside settlement As most of lands in SW China are mountains, many villages are built on the hillside to avoid floods and save farmlands. The number of families varies from a dozen to dozens depend

on the size of the mountain. The stilt buildings area commonly constructed in the hillside settlement to accommodate the landform. -Riverside settlement The riverside settlement is more extensive compared to the depression and mountain settlements, resulting in more fertile soil. These areas are typically traversed by rivers, which ensures abundant water resources and, consequently, higher agricultural yields. The greater environmental capacity in these regions dictates larger village sizes, with most households numbering in the hundreds.

Figure11. Hillside Settlement

U-shaped: This is a type of space based on the L-shape, and similar to the L-shape, the extended parts on both sides are used by new family members. The half-enclosed space in the middle can be used as a courtyard for drying grains or as an area for daily activities. Courtyard type: This is a rarer plan type, considered a symbol of wealth and status due to its large footprint and enclosed courtyard in the middle. 2.1.2 Village Settlement Based on Different landforms, and elevation, there are 6 main settlement types of research area in rural SW China: valley, hillside, riverside, hill-flatland, cave and Tunpu (a settlement evolved from the army settlement in Ming Dynasty) settlements (Zhao, 2010). Among them, cave and Tunpu are stone based building forms thus excluded from the discussion. -Valley settlement 20

Figure12. Riverside Settlement

Figure13. Hill-flatland Settlement

Figure14. Axonometric View of the Structure of Traditional I-shapoed Plan (Source: Department of Housing and Urban-Rural Development of Hubei Province, 2023)

Figure15. Axonometric View of the Structure of Traditional L-shapoed Plan (Source: Department of Housing and Urban-Rural Development of Hubei Province, 2023)

-Hill-flatland settlement The land in the hilly area is relatively flat and broad, with abundant water sources and large land carrying capacity, which creates proper conditions for settlement. The villages are densely distributed in lands with more population. The relatively open regional environment weakens the influence of blood ties, and the village is often not a single ethnic group, but a multi-ethnic mix. The settlements are spatially arranged along the main transportation roads. Due to the convenient transportation, more communication with the outside, immigration and marriage with the outside are more common, so that the village formed a multi-ethnic mix. Moreover, as a result of the flatlands, buildings could be built on a flat foundation, stilt dwellings are not common in this area. In conclusion, the complex landforms have resulted in varies settlements in different sizes and the difficulty of transportation which resulted in the isolation between villages. The study of vernacular southwest dwellings could mainly focus on the riverside and hill-flatland settlements because of their universality and more capacity of modernization.

2.2 Construction The selection of sites for Tujia stilted buildings serves two principles: meeting the practical needs of daily life and production while safeguarding against natural disasters. This site selection adheres to the principle of choosing a location where the house is nestled within a concave area (such as a valley) rather than perched on a prominent peak. Additionally, it should be situated on the leeward side to receive ample sunlight, avoiding areas with white rocks and maximizing the panoramic view. Preference is given to selecting a sunny and sheltered spot. Ideally, the house should be close to the mountains and distant from bodies of water. It should be positioned on a gentle slope between the mountains and the land, avoiding the occupation of fertile land suitable for farming. Construction should be near the rear peak or along its contours, with the auxiliary rooms elevated. This elevated design accommodates the uneven terrain, with the main house extending horizontally from the niche, creating an elevated structure characterized by independent columns. The stilt space can be utilized for purposes

Figure16. Structural Frame Specification (The Chinese words in the figure are the proper noun for each structural joint, therefore not translated) (Source: Department of Housing and Urban-Rural Development of Hubei Province, 2023)

like livestock breeding or storage, protecting against pests and allowing for proper ventilation. The upper part of the elevated structure typically serves as a daughter's bedroom (locally called the 'girl's room') or an embroidery room. The ground beneath the elevated section is often left untreated, and the pillars are directly placed on a stone foundation, offering flexibility in adapting to varying terrains. 2.2.1 Building Components and Materials The traditional stilted house could be divided into four parts: the foundation, the wooden frame, the roof, and the wall. From the space point of view, the size of the structural frame should follow the traditional principle: the width of the room between 4.27-6.27m, the depth between 4-6m, and the overhang could reach 1m. The aspect ratio should be between 0.6-0.7m.

Figure17. Drainage System on the Roof (Source: Guo,2015)

Figure18. Decration on the Doors (Source: Guo,2015)

Figure19. Section for Typical Stilt House (Source: Guo,2015)

-Timber Frame The primary framework of the building consists of a wooden column and beam system within a wood frame structure, following the traditional Chuan Dou architectural style from ancient Chinese architecture (Liu, 2004). The Han Chinese architectural tradition greatly influenced this architectural approach, with Han carpenters introducing specific guidelines for wood selection, dimensions, and construction techniques. This framework does not rely on joint structures; instead, it relies on precisely crafted mortise and tenon joints to tightly connect the elements, allowing for expandability and significant flexibility for future expansions or modifications (Guo, 2015). The structural framework is designed with a corresponding number of "frame walls", each aligning with the number of rooms in the building. These walls are interconnected through a beam configuration, and perpendicular purlins and rafters are interspersed at the upper end of each row of the frame. These elements serve the dual purpose of stabilizing the structure and bearing the roof's weight. -Coloumn Typically, the columns are crafted from whole

logs, serving the purpose of bearing the weight of the house. Consequently, the lower end of each column is thicker than the upper end. The bottom of each column is placed on top of a stone foundation rather than being directly connected to the ground. This design helps mitigate the corrosion of the structure caused by ground moisture (Guo, 2015). -Roof The roof of the stilted building typically has a slope of 25-30° (Department of Housing and Urban-Rural Development of Hubei Province, 2023), supported by columns and beams. Its composition includes purlins, rafters, ceilings, and the upper layer of tiles. Traditional stilted buildings do not have an additional waterproof layer beneath the tiles. Therefore, the tiles are responsible for providing shelter from wind and rain. These tiles are usually made of fired clay and interlock with each other to cover the roof. When it rains, water flows along the grooves between the tiles to the eaves and drips to the ground (Guo,2015). During windy days, the interlocking tiles prevent them from being lifted. Underneath the tiles is typically a ceiling made of wood panels or bamboo mats, creating a well-ventilated and moistureresistant space often used for storage.

Table 4. Most used materials in stilt house (Nguyen et al., 2011)

-Walls, Windows and Doors The walls, the doors and the windows are part of the same plane, with each end of the wall connected to load-bearing frames. Besides, the self-standing timber frame releases the walls from bearing the house's weight, allowing for more windows and carved decorations on the walls. Traditionally, the windows and the doors feature various ethnically characteristic carved decorations. With the development of industrialization and the pursuit of a higher quality of life, well-ventilated but less private carved doors and windows have gradually been replaced by tightly sealed wooden doors and glass windows. 2.2.2 Construction Process The construction process of traditional stilted buildings is highly intricate, with experienced master craftsmen responsible for site selection, design, and construction. Much of the expertise has been simplified into concise and practical experiential imagery in the minds of these craftsmen. They adapt the dimensions and practices of stilted buildings based on the current reality and any mistakes, making adjustments according to material variations. This iterative process of experiential accumulation is passed down through generations of master-apprentice relationships. In addition to craftsmen, many villagers also participate in the construction process, strengthening social connections within the community and fostering a spirit of mutual assistance in rural areas. According to Department of Housing and Urban-Rural Development of Hubei Province (2023), there are 28 steps in the construction process (Table 5), including date selection, building material preparation, rituals, construction, and repairs. The materials and labour used in construction primarily come from the local area, reinforcing the building's local character and unique cultural significance.

its passive design is reflected in its open floor plan and excellent ventilation performance. This design allows the stilts to maintain the comfort temperature in the summer while allowing fresh air to circulate through the building. Although the walls of the stilted house are made of wooden planks and lack air tightness, they are relatively well adapted to the characteristics of summer's hot and humid climate. The external structure of the house is relatively open which resulted in the lack of air tightness, but increased the passive ventilation frequency in the room, helps to eliminate indoor moisture and pollutants, and keeps the indoor relative humidity within the comfort range of the human body. As shown in the figure 16, as the wall elements of the stilted building do not bear the main structural load, each component could be easily disassembled. In the hot summer months, residents would remove the baffle in the attic during the day, so that the hot air inside the room can be exhausted from the top to keep the room cool. At night, they close the panel to retain the heat in the room to deal with the drop in nighttime temperatures. These baffles are usually kept closed throughout the winter to minimize heat loss and ensure the indoor thermal comfort. This passive and energy-saving design strategy could effectively manage indoor temperature in different seasons. However, in the cold winter, residents are unwilling to open windows for ventilation, and dur to the low air tightness, the indoor temperature could be lower. In addition, residents usually use firewood for heating and cooking in winter, which leads to a sharp increase in indoor carbon dioxide and pollutants, resulted in poor indoor air quality in winter. Nevertheless, in terms of thermal comfort and air quality in hot seasons, stilted buildings still have certain advantages in passive design.

2.3 Vernacular Passive Design The stilted building represents the wisdom and thinking of ethnic minorities in southwest China in adapting to the environment, and 25

Figure 20. Passive Strategy of Ventilation (Source: Guo,2015)

2. Date Selection

2. Site Selection

3.Ink Making

4.Felling

5. Transport Timber

6. Set up timber

7. Trim Timber

8. Draw Ink Lines

9. Make the Inventory

10. Mark Size

11. Error correction

12. Node Production

13. Dig Holes

14. Fix Holes

15. Connecting Joint

16. Trim

17. Erect

18. Mark Beam Joint

19. Trim Beams

20. Worship

21. Pillar Pier

22. Beams Connection

23. Install Purlins

24. Roof Fixing

25. Install Tiles

26. Balcony

27. Perfect the Roof

28. Install Walls

Table 5. Section for Typical Stilt House (Source: Guo,2015)

3. Case Study In this chapter, by reviewing the energy consumption analysis, questionnaire survey and related improvement strategies of other researchers on stilted buildings in southwest rural areas of China, the overall performance of stilted buildings in terms of temperature, daylighting and ventilation will be obtained, and the energy performance of buildings will be discussed. In addition, through the questionnaire survey made by other researchers, the residents' family size, house use mode, heating mode, and living behaviour mode would be understood, and these statistical results would be applied to the subsequent simulation. Meanwhile, reviewing the improvement strategies designed by other researchers and their research results could provide a direction for further strategy design. The subsequent simulation for building retrofitting would also be based on the previous research results, and the simulation parameters will also be based on the previous research.

Figure21. First Floor Plan of the Simulated Building (Source: Xiong,2022)

Figure22. Case 1 Thermal Model (Source: Xiong,2022)

3.1. Case Study 1: Sanjiang Dong Autonomous Through the investigation and data analysis by Xiong(2022), this case demonstrated the architectural style, thermal performance of the envelope structure, residential discomfort and building energy consumption of a stilt building in Baizhai, Chengyang, Guangxi province, and proposed several passive retrofitting strategies for its envelope structure, and analysed its effectiveness and feasibility based on the principles of economic, social and ecological sustainable development and respecting the local context. The building is located in the Dong ethnic area with timber stilt-featured dwellings. It

has a typical climate of hot summer and cold winter in southwest China, the relative humidity is around 80% all the year round. The stilt house of the research is a large threestory stilt house for 8 people with an area of 228m². Regarding building materials (Table 6), the load-bearing structure and enclosure structure are primarily made of locally grown fir, the roof is a combination of tile and wood panel, and the ground floor of the stilt is laid with stone. In terms of interior space design, the ground floor is used as an overhead layer for placing agricultural production tools and captive livestock, the first floor has a large hall for residents to talk, rest and do manual work, 29

and the second floor could be considered as an attic gives full play to the advantages of ventilation, and sets up some storage rooms for placing food and items that are easily spoiled.

Table 6. First Floor Plan of the Simulated Building (Source: Xiong,2022)

Table 7. 3 Types of Wall System (Source: Xiong,2022)

3.1.1 Performance In order to improve the thermal performance of the building, Xiong (2022) proposed a series of upgrading schemes for the envelope structure. He proposed three common envelope systems for wooden buildings (Table 7): XPS, EPS, and strawboard structures. These materials were simulated in the wall, floor and roof, respectively, and energy consumption and temperature results were obtained independently. In this simulation, Xiong (2022) set the heating and cooling points to 18°C and 26°C, a general urban thermal comfort temperature range. For the wall, the results show that the energy load of the original structure for maintaining thermal comfort is 79kWh/m². After using the three composite structures of XPS, EPS and straw wall, the energy consumption reduction is similar, about 30%, reduced to about 50kWh/m². The temperature performance of the three was close, with XPS performing slightly better than the other two. In terms of the roof, the three different retrofit schemes showed nearly identical results, showing a 23% reduction in energy consumption to 60kWh/m². For flooring, the three materials p e r fo r m e d s i m i l a r l y, re d u c i n g e n e rg y consumption by an average of 11% to 70kWh/ m². Overall, XPS performs relatively better out of the three. Apart from the wooden components, the envelope structure also includes glass, and the retrofit of glass is not only the improvement of its material but also the improvement of the air tightness of the gap between the window and the wall and the change of the window-floor ratio. The study here focuses on analysing the impact of materiality. 4 different glasses with different thicknesses, layer numbers and intermediate layer materials were proposed. According to the simulation results, the double-glazing coated with low-e layer and air gap can reduce

energy consumption by about 15%. The above is the analysis of a single variable in this case. The researcher then applied these materials to the building and added parameters about the residents' building usage mode, energy and lighting use pattern. In subsequent simulations, the initial energy consumption of the original building was adjusted to 32.5kWh/m², considering that the building would not turn on heating or cooling during moderate months and when the house is empty. After the combination, there are three optimization schemes: applying XPS, EPS and straw board to the entire building. According to the results, the combined retrofit option 1, the unified application of XPS as the envelope structure, could reduce energy consumption by about 72% to 9kWh/m². EPS and straw board could decrease to 10.1kWh/m² and 13.4kWh/m² (Table 8), respectively, which have no significant difference, and both meet the standards of passive residential buildings. According to Xiong (2022), the operative temperature chart of a typical summer and winter day demonstrated that in summer, compared with the base case, all three structures could drop the indoor air temperature significantly (Figure 23), which XPS decreases the most with the most stable temperature performance. In winter, XPS also has the best thermal performance, raising indoor temperatures by about 4-5 degrees compared to outdoors (Figure 24). Moreover, Xiong(2022) roughly calculated the cost and concluded that programmes one, two and three cost about 8530$,8040$ and 7200$. Given the annual per capita income of $2,000 in rural southwest China (NBSC,2021), the renovation is slightly pricey, though it is usually affordable for large stilted houses with eight occupants. 3.1.2 Discussion Xiong (2022) pointed out the characteristics of traditional stilted buildings' relatively thin envelope structure, and verified through simulation. Afterwards, Ecotect was used to simulate three common structural upgrades for timber structures. This study provides 31

Figure 23. Typical Summer Day Temperature (Source: Xiong,2022)

Figure 24. Typical Winter Day Temperature (Source: Xiong,2022) Figure 25. Case 2 Building with Plans and Measurement Spots (Source: Zhao et al., 2022)

Table 8. Energy Load of Different Retrofitting System (Source: Xiong,2022)

Table 10. Case 2 Building Structure Properties (Source: Zhao et al., 2022)

Table 9. XPS Wall System Compoments (Source: Xiong,2022)

economically feasible passive building retrofit solutions to improve stilted buildings' thermal comfort and energy efficiency, including a rough estimate of the cost to provide feasible recommendations for the retrofit of stilted buildings in low-income rural areas. However, the study did not fully consider the differences in thermal comfort requirements in different regions. According to the study in Chapter 1.5, the rural residents in southwest China have a higher acceptance of thermal comfort of about 14.3-29.3°C. Therefore, the comfortable temperature range of 1826°C proposed in this case study might have limitations, and the actual energy consumption of the building could be lower. In addition, in terms of thermal comfort analysis, specific space usage scenarios are not discussed in this study. For example, the

heat source of the stilted building generally comes from the stove in the kitchen or living hall. The bedroom is usually not equipped with heating facilities, so there would be a significant difference between rooms. As a result of the varied usage frequencies of spaces, the temperature demands are also varied. Moreover, due to residents' lifestyles and income levels, air-conditioning would generally not be equipped in stilt dwellings, so the actual cooling energy load should not be included. Finally, the study ignored the impact on daylighting and ventilation, the discussion was limited to thermal but not openings. Changing the window size according to the daylighting n e e d s w i l l a l s o i nte ra c t w i t h t h e r m a l performance.

3.2 Case Study 2: A Stilt Dwelling in Tongren The study of Zhao et al.(2022) investigated the energy-saving potential of deep renovation of the traditional courtyard stilted building envelope in a historical conservation area located in Tongren City, Guizhou Province. The climate here is characterised as the typical southwest region with a hot summer and cold winter. The difference is that this case is located in an urban area. Therefore, the architectural form would be slightly different from the rural area. In addition, the range of thermal comfort will also be more limited. The heating temperature proposed in this case is 15.4°C with the heating period from Dec to March. For the rest time, according to the 'Energy-saving Design Standards for Residential Buildings in Hot Summer and Cold Winter Zone' proposed by the Ministry of Housing and Urban-Rural Development in 2010, the upper limit of thermal comfort is

26°C. This is a two-story enclosed wooden building of an area of 232m² and with five inhabitants. Unlike freestanding stilts in rural areas, the two sides of the building are enclosed by stone walls. As a result, predictably, the thermal performance of the building would be higher than that of freestanding stilt buildings in rural areas. It is important to note that this historic preservation building has been renovated to maintain regular use. The renovation did not affect the integrity of the building and the original layout. The doors, Windows, walls, ceilings and other components were replaced by timber board similar to the original structure, and air conditioning and heating equipment were added in some rooms. The research mainly includes the humidity and temperature simulation of the target building and its improvement plan.

Figure 26. Heat Transfer Detail (Source: Zhao et al., 2022)

Figure 27. Air Temperature and Reletive Humidity of Measured House (Source: Zhao et al., 2022)

3.2.1 Performance Before the simulation, the building was measured using tools to calibrate the results. Short-term monitoring (two weeks) from 15th Dec to 29th Dec was carried out using measuring instruments to measure air temperature, relative humidity and heating energy consumption. As the building is a courtyard house, and the space facing the atrium has a semi-open, movable facade, the air temperature in most interior spaces is the same as outside. During the measurement period, the heating equipment was used in Bedroom 1 (A7 in Figure 27), making the room air temperature significantly higher than others. As the chart shows (Figure 27), of the three indoor spaces measured, A3, A7, and A9, only the A7 temperature with the heating on is significantly higher than the outdoor temperature, and there is a noticeable fluctuation during the day. It is worth mentioning that although A15 and A16 are outdoor areas, their measured temperatures are slightly higher than the outdoor temperatures outside the building. This might be due to the dense building envelope and the heat generated by indoor activities. In addition, during the measurement period, the humidity of A7 was lower than that outside, which may be caused by the evaporation of indoor moisture and then ventilated through the window. For the software simulation, the defined building materials are shown in Table 10. Different from Case 1, since this case has been renovated once, and since the building is not entirely wooden and part of the external wall is stone, the thermal performance could be better than that of traditional stilt buildings. However, the building's walls and roof are still single-layer timber panels without additional insulation. As a result, there is still a great potential for the thermal envelope improvement. According to the energy balance diagram of Bedroom 1, the opaque structure is the main route of heat loss. Including Windows, about 93% of energy is lost through opaque structures, and only 7% is lost through natural ventilation. Therefore, upgrading the opaque network could significantly enhance

the thermal performance of the room. Regarding the heat gain, as there is a heater in the room, nearly 99% of the heat gain comes from internal activities. This study's retrofitting scheme of the envelope structure is primarily based on the building renovation guidelines for cold winter and hot summer areas proposed by the Ministry of Housing and Urban-Rural Development of China in 2010. This standard mainly regulated the U-values of different opaque structures. Therefore, the simulation just changed the U-value to the provided number. Table 9 compares building energy consumption before and after the renovation. T h e o r i g i n a l b u i l d i n g ' s a n n u a l e n e rg y consumption for maintaining thermal comfort was 2496.7kWh, and after the renovation, the energy consumption was reduced to 1092.9kWh, a significant decrease of 56%. This study applies XPS material, commonly used in China (Huang et al., 2020), for insulation. It calculates that the total material cost is about 2000 Yuan (around 700 US dollars), and only three years of payback time. Therefore, this renovation could be considered a low-cost, high-return initiative. 3.2.2 Discussion This case combines the field measurement with the calibrated simulation results of the residential timber building in Tongren. For buildings that have been renovated and renovated once, the cost of energy efficiency is lower but still effective. According to the Ministry of Housing and Urban-Rural Development of China, the energy use reduction for heating and cooling could be as high as 56% after upgrading. In this study, the opaque structure was not listed in detail in the simulation, with only the U-value of the material listed. In retrofitting, with the increase in the number of layers of opaque materials, the increasing thickness would also affect the structure and the indoor space. In addition, the activities of indoor personnel were also ignored, such as the kitchen, which could be the primary heat source space and affect the indoor air temperature as much as the heater in the house. What 35

Table 11. Existing U-value and Proposed U-value of th Building (Source: Zhao et al., 2022)

Case 0: Measured Period Case 1: One Year Simulation for Exsiting Envelope Case 2: One Year Simulation for Changed Envelope Table 12. Comparison of energy consumption before and after renovation of envelope structure (Source: Zhao et al., 2022)

Table 13. Estimated Cost and Payback Time (Source: Zhao et al., 2022)

could be referred to is that this study defined multi-zone in the simulation, which could demonstrate temperature changes caused by different heat sources in multiple spaces. At last, the study referenced a vital point (Zhao,2022, as cited in Künzel, 1979): when a heater is installed in a residential building, occupants' tolerance to low temperatures decreases over time. Therefore, the thermal comfort range could change with the changing of living habits. For buildings designed for the future, taking into account the changes in the tolerance of thermal comfort and changes in the global climate could be considered of the same importance. Although this building is located in an urban area, and not a completely stilt house, as it has a similar structure and materials to the vernacular stilt dwellings, the retrofitting methods here could provide great value and research direction to the topic.

in China, as a thermal insulation material for building envelopes. In addition, the first case provided the specific structural details of each opaque structure for vernacular stilt dwelling. The parameters provided in both cases could be referenced in subsequent studies.

3.3 Conclusion Both cases provide ideas for sustainable retrofitting of traditional timber houses in southwest China though the first case is for rural areas, while the second is for urban. However, both show consistency in the renovation direction and energy-saving results, reflected in the similar energy-saving result of more than 50% after retrofitting. This indicates the great potential for improving the sustainability of timber dwellings in southwest China. Regarding building scale, both are the primary types with a single-family size and a building area of about 200-300m². However, they only focus on the simulation of building energy consumption and ignore the discussion of specific scenarios. Since the essence of the building is to serve humans, it is worth discussing the thermal comfort of particular scenarios and times. It is worth mentioning that the second case indicated that thermal comfort changes dynamically with living habits and adaptation. According to this point of view, the thermal comfort range in subsequent simulations can be dynamically adjusted based on the specific use. From the results, both studies verified the effectiveness of XPS, a widely used material 37

4. Retrofitting Approach This study will explore the possibility of sustainable renovation of stilted buildings in a broader scope. Apart from exploring different building materials, based on the principle of reducing the building's energy consumption, this study will also discuss the impact of window size, building orientation, indoor activities and spatial layout on building thermal performance. Analyzing more extensive factors affecting sustainability, a more applicable guideline for retrofitting stilted buildings in southwest China is expected to be summarized.

4.1. Simulation Focus and Principles F ro m t h e c a s e s t u d i e s a n d l i t e ra t u re review, it can be observed that traditional stilted houses, due to their long history and interaction with local residents, have evolved into forms that are more suitable for the local climate and lifestyle. However, some aspects could still be improved when viewed through modern standards. The main issues of vernacular stilted dwellings in terms of sustainability and thermal comfort can be summarized as follows: 1. Cold winter. Lack of insulation resulted in poor thermal performance, as low indoor temperatures were far below the comfort band in winter. 2. Daylighting. Due to certain traditions of ethnic minority residents (Ma et al., 2015), most buildings have small windows, resulting in dark indoor space. 3. Airtightness. Traditional manual construction methods and building materials lead to a leaky building environment. The poor airtightness and frequent indoor-outdoor heat exchange can be seen as advantages in the summer but could lead to rapid indoor heat loss in the winter.

The retrofitting will focus on addressing these issues, particularly on the thermal envelope, which has the most impact on the building energy consumption. For passive building research, discussions should be conducted in actual living scenarios while considering both energy conservation and living comfort. Focusing solely on technical improvements w h i l e n e g l e c t i n g h u m a n n e e d s wo u l d contradict the original intention. Hence, the following principles should be followed: 1. Vernacularity. Local culture should be respected, and efforts should be made to preserve the building's traditional architectural style and facade, retaining the regional characteristics of the architecture. 2. Practicality. Renovation should be integrated with specific living needs, and energy use should be tailored to particular scenarios and living patterns. 3. Affordability. Affordability should be considered in the renovation, avoiding expensive strategies and materials to ensure that low-income rural populations can afford them.

Figure 28. Axonometric Drawing for the Base Case Model (Source: Zhang et al., 2022. Illustrated by Author)

4. Sustainability. The primary goal should be to enhance the building's sustainability, using low-carbon, environmentally friendly, and renewable materials within allowable limits. 4.2. Methodology First of all, to ensure the accuracy of the simulation results, a stilted building in rural southwest China with operative air temperature measured by Jin and Zhang in 2021 would be selected. A thermal model in Ladybug with a given scenario of a typical rural family in rural southwest China would be studied and calibrated with the measured data. The model will be simplified to a more flexible form for subsequent single-variable testing of the model. Before changing the original parameters of the building, the single variable test would be conducted on the model. The optimal orientation and window-floor ratio of the building will be obtained by changing the orientation and window-floor ratio first. Following these two results, the simulation will propose different thermal envelope components for opaque structures, including walls, floors, roofs and windows. In addition, since the traditional stilted building structure is manually constructed and lacks airtightness. Before the opaque retrofitting , the method of improving

the airtightness of the building would be discussed. The test for the thermal envelope structure of the building would be based on a specific living scenario and occupancy pattern. Specific internal heat gain and loss in different zones would be considered in the form of the multi-zone simulation. Finally, the model's energy consumption is expected to reach the average annual heating energy consumption of less than 8kWh/m² regulated in the "Near Zero Energy Building Index" proposed by the Ministry of Housing and Urban-Rural Development of China in 2019. On the basis of achieving the national standard of 'Near Zero Energy Building', different layouts of the building, heating methods, and household sizes would be tested afterwards to summarize a more applicable guideline for sustainable renovation of stilted buildings in this region. 4.3 Model Description The base case for the simulation in this study is a traditional stilted house located in a rural area of southwest China, which has the tested period of temperature by Zhang et al. in 2022. The south-facing building, built between 1970 and 1980, has two levels, the ground floor serving as the main living area, including the living room in the centre, and three bedrooms, as well as a kitchen and a bathroom. The entire upper floor is for storage use. The

Figure 29. Plans for the Base Case Model (Source: Zhang et al., 2022. Illustrated by Author)

space between the storage floor and the pitched roof on the gable wall is open to allow natural ventilation. In terms of the material of the building, the entire structure of the building is made of wood and built in a traditional method, including walls, floors and timber frames. The windows are singleglazed with wooden frames, and the floors are concrete. As the building's plan and structure are common and representative in rural southwest China, this case could be flexible for further study. Subsequent studies on different materials, orientation, window size and space layout will be based on this base model. 4.3.1 Materality The specific structure of this building is shown in Table 14. The wall is a single layer of 30mm thick wood, with a calculated U-value of about 2.8 W/m²K. The windows are single-

Table 16. Original Tested Operative Temperature (Source: Zhang et al., 2022)

Figure 25. Scenario Description

glazed with a K-value of 4.7W/m²K. The roof is a typical tiled timber roof structure with a calculated U value of about 2.2 W/m²K. As a result, the building's basic parameters in the envelope are far from the passive building standards in China. The infiltration rate of 5ach for the base building in this study is based on the value

Table 14. Comparison of Base Case Values with Chinese Standard (Source: MHURD, 2010)

Table 17. Operative Temperature of Base Model (Source: Ladybug)

adopted by Jimin et al., (2020) for another traditional stilt building in southwest China. In order to obtain more distinctive differences in temperature between different strategies in the subsequent simulation, the infiltration rate will be improved to 0.6ach specified for passive dwellings by MHURD in GB/T 513502019. Regarding specific methods to improve air tightness, Bucklin et al., (2022) pointed out that sealing materials such as special joint sealant of expanding polyurethane foam can be used for the envelope of wooden buildings to achieve better airtightness. In addition, adding insulation to the envelope can also enhance the airtightness of the house. 4.3.2 Parametre Calibration Due to the different outdoor temperatures in the calibration period, this calibration will not use the method of directly comparing the indoor operating temperature with the case, but based on statistical measurement results of temperature data measured by Zhang et al. Before the calibration, the thermal model has set the material and the parameters to be consistent with the case. According to the data from Zhang et al. (Table 16), the measured period was winter, and the average outdoor temperature was 8.3°C, while the average indoor operating temperature of the bedroom and living room in winter was 1-2°C higher than that of the outdoor.

The meteorological documents used in this simulation show that the average outdoor temperature in winter is 6.5°C, which is slightly lower than the case, but after simulation, the average indoor operating temperature in the living room and bedroom is also shown to be 1-2°C higher than the outdoor (Table 17), which shows consistency with the results in the case. At this point, calibration can be considered complete. 4.3.3 Simulation Scenario and Schedule A typical model of a rural family in southern China of 5 people is adopted in the simulation. The scenario includes three generations: two elderly people, a young couple and a child. The young husband is considered to go out to work and returns home only for festivals. Therefore, this model can be regarded as having only 4 people. The setting of the scenario and schedule is based on the common way of life in rural areas. In rural areas, it is common for aged people to do farm work. Farm work usually starts early in the morning, so after breakfast at 8 a.m., the child will go to school while the adults will out for farming. At noon, adults will return home for lunch and lunch break, and in the afternoon there will be a second farm work. Around 5 p.m., all family members will return home for dinner and then gather in the living room for leisure activities. Then return

Table 15. Materials for the Base Model (Source: Zhang et al., 2022)

to their bedrooms around 11 p.m. For the heating Settings, it is estimated that the bedroom and living room of the model are equipped with an electric heater. This heating point of 14°C is based on the chapter 1.5 of this paper. When the indoor air temperature is below 14°C, the heater will be turned on. Considering that the heating is only turned on when the space is occupied by people, the heating in the bedroom is only turned on from 9 p.m. for 3 hours. For the living room, as this is the most frequently used space, maintaining a stable and comfortable temperature helps to improve the quality of life. As a result, during the cold season, the heating will be on from 9 a.m. to 10 p.m (Figure 30).

Figure 30. Timetable for different rooms of the Simulation Model

Annual Comfort Hours (14-30°C): 5841 (67%)

Figure 31. Base Case Operative Temperature in Winter (EPW: Guiyang, Guizhou. 2020)

5. Simulation

Figure 32. Base Case Operative Temperature in Summer (EPW: Guiyang, Guizhou. 2020)

5.1 Base Case -Temperature After completing all parameter configurations and calibrations with the case study, the study utilizes the initial simulation model as the base case. Based on the simulation outcomes, this research selects the period from January 1 to January 7 as a representative week for winter conditions to evaluate the overall building performance under low-temperature conditions. Similarly, for the summer season, the period from July 18 to July 24 is chosen as a typical summer week. As shown in Figure 31, during the winter weeks, in the absence of any improvement measures such as enhancements to the building envelope, air tightness, or indoor heating strategies, the temperature in each area of the base model is only marginally 46

higher than the outdoor temperature, typically by 2-4°C. Most of the time, the temperature in these areas remains below the specified comfort point of 14°C. However, due to the substantial heat generated from cooking, the kitchen experiences significantly higher temperatures compared to other spaces. The temperature in bedroom 3 is relatively similar to that of the living room. In contrast, the upper storage space, owing to large openings on both sides of the gable walls, experiences noticeable indoor-outdoor air exchange, resulting in temperatures significantly lower than other areas. In terms of temperature fluctuation trends, the absence of an insulation layer leads to considerable temperature variations indoors and high rates of heat exchange. In the summer, as indicated in Figure 32, 47

Figure 35. Heating Load for 4 Orientation (EPW: Guiyang, Guizhou. 2020) Figure 33. Wind Rose Chart for the Site (EPW: Guiyang, Guizhou. 2020)

Figure 34. Energy Balance for Base Case (Source: Ladybug)

Figure 36. Heating Load for 4 Orientation (EPW: Guiyang, Guizhou. 2020)

Figure 37. Layout and Facade Changes Figure 38. Natural Ventilation Schedule

outdoor temperatures primarily remain below 30°C during a typical summer week. However, the kitchen experiences significantly higher temperatures, typically 2-7°C higher than outdoor temperatures, due to the substantial internal heat gain from cooking. Bedroom 3 and the living room, being adjacent to the kitchen, also experience temperature fluctuations in response to changes in the kitchen's temperature. This observation underscores the low thermal inertia of the original building envelope. It's important to note that natural ventilation is not considered in this simulation. Therefore, enhancing building thermal performance can commence with increased insulation and improved natural ventilation strategies. -Energy According to the energy balance diagram (Figure 34), without heating equipment, the primary internal heat gain is from people, equipment and followed by solar energy. In terms of heat loss, it primarily occurs through air exchange due to the high infiltration rate of 5 ACH (Air Changes per Hour) and the thin opaque structure. Improving the building's airtightness can be seen as the first step in enhancing its performance. Additionally, increasing the thermal resistance of the building envelope can significantly reduce heat loss as well.

5.2 Orientation Test To determine the optimal orientation for the building, simulations were conducted for four different orientations: north-south, eastwest, southeast-northwest, and southwestnortheast. To simplify the testing, with a primary focus on energy consumption, only the heating load was compared. In order to highlight performance differences, the building's airtightness was first improved to 0.6 ACH. The results showed that different orientations had almost no impact on the building's energy consumption (Figure 35), 4 orientations share similar heating loads of around 11-12 kWh/m². Simultaneously, based on the Daylight Factor (DF) test for various orientations, there are no substantial variations in DF performance among the four different orientations. With the exception of the lower-level living room, the DF values for the remaining spaces fall within an acceptable range for residential buildings. Considering the dominant wind direction in the region is southwest-northeast (Figure 33), and aiming for better ventilation performance combined with the relatively lowest energy consumption, the southwestnortheast orientation was chosen as the optimal orientation for the building.

Annual Comfort Hours (14-30°C): 6180 (71%)

Figure 39. Operative Temperature in Winter for Changed Layout (EPW: Guiyang, Guizhou. 2020)

Figure 40. Operative Temperature in Summer for Changed Layout (EPW: Guiyang, Guizhou. 2020)

Figure 41. UDI for 4 Types of Window-Wall Ratio (EPW: Guiyang, Guizhou. 2020)

5.3 Daylighting Following the adjustment of the model's orientation to the southwest, a daylight illuminance level simulation was conducted for the ground floor of the model using the Ladybug tool. The simulation encompassed three different times of the year on four dates: 8 a.m. (morning activities, cooking), noon (noon break), and 6 p.m. (evening activities, dinner preparation) of March, June, September and December 21st, respectively. The results revealed that at 8 a.m., except during the summer, indoor spaces were relatively dark. However, areas near the windows received around 500-1000 lux, which was sufficient for morning activities. At noon, various areas enjoyed abundant natural light on different days. At 6 p.m., the lighting was dimmer compared to 8 a.m., but artificial lighting was typically used during this time to meet daily activity needs. Nevertheless, the living room, being the most frequently used space, consistently had lower Lux and Daylight Factor (DF) values throughout the year due to limited openings, with natural light only

coming in from the open door. To enhance the living room's daylighting performance, the model's entrance was relocated from its original inward concave position to align with the bedroom walls on both sides. Additionally, to address kitchen overheating issues, a natural ventilation schedule was introduced in the simulation. The kitchen was set to keep its windows open from 7 a.m. to 8 p.m. whenever the temperature exceeded 14°C. For the bedroom, the windows were set to remain open all day if the temperature exceeded 22°C (Figure 38). After implementing the natural ventilation schedule and adjusting the building's layout and orientation, the thermal performance of different areas was evaluated, as depicted in Figures 39 and 40. In a typical winter week, the temperature performance of each area did not significantly differ from the base case, with a slight decrease in the living room and bedroom 3 temperature, making it more stable. The temperature variation in the kitchen during winter is more noticeable, and

Power Density in Kitchen: 110W/m² Wood Burning Stove Figure 42. Winter Operative Temperature for 4 Types of Window-Wall Ratio (EPW: Guiyang, Guizhou. 2020)

28kWh

Figure 43. Summer Operative Temperature for 4 Types of Window-Wall Ratio (EPW: Guiyang, Guizhou. 2020) Figure 44. Operative Temperature for the Changed Layout Model in March 21st (EPW: Guiyang, Guizhou. 2020)

due to improved natural ventilation, the temperature curve becomes smoother, with peak temperatures slightly decreasing by 1-2°C. The total Comfort Hours (temperature between 14°C-30°C) for the entire building also increased from 5841 to 6180. 5.4 Window-Wall Ratio After adjusting the natural ventilation and the layout of the model, the study examined d i f fe re n t w i n d o w- w a l l ra t i o s ( W W R ) . According to the national code JGJ-134-2010, in regions with cold winters and hot summers, the WWR for south-facing buildings should not exceed 40%. Therefore, four WWR scenarios were tested: 10%, 20% (original model size), 30%, and 40%. Initially, UDI (Useful Daylight Illuminance) simulations were conducted for these scenarios. T h e re s u l t s s h o we d t h at t h e U D I wa s significantly lower for the 10% WWR scenario compared to the other three, so it was excluded from further consideration. Among the remaining three window sizes, the performance in the living room

was similar. However, for the bedroom, t h e 4 0 % W W R s h o w e d o v e ra l l b e tt e r performance than the 20% and 30% WWR scenarios. Nevertheless, in the areas near the window, the UDI for the 40% and 30% WWR scenarios was lower than that for the 20% WWR scenario due to excessive light. To make a more informed decision, a thermal modeling test was conducted for these three window sizes in Bedroom 3 and the kitchen. Based on Figure 42 and Figure 43, there was no significant difference in temperature performance between the three different window proportions. This lack of difference may be attributed to good ventilation in these two areas. Considering the high cost and extensive construction required for changing window sizes, and recognizing that a 20% WWR was sufficient to meet daily activity needs, the study decided to continue using the 20% WWR for further research.

5.5 Internal Gain Before making adjustments to the building envelope, it is crucial to determine the direction of strategies. Based on previous results, it was evident that the original building experienced significant temperature fluctuations during winter due to a lack of insulation. Therefore, the first step was to increase the insulation layer to stabilize temperature variations and prevent heat loss. In contrast, during the summer, the kitchen generated substantial internal heat gain, resulting in significantly higher indoor temperatures even with natural ventilation. Hence, adjusting the kitchen's heat source was considered the initial step to improve energy efficiency. As traditional stilt houses typically used woodfired stoves for cooking, the power density

Figure 46. XPS Insulation (Top) & Strawboard Insulation (Bottom) (Source: Website)

Table 18. U-Value Comparison Between XPS and Strawboard with CN Strandard (Source: Ladybug)

Power Density in Kitchen: 24W/m² Modern Natural Gas Stove

14kWh

Figure 45. Operative Temperature for the Changed Layout Model- Decreased Power Density in Kitchen (EPW: Guiyang, Guizhou. 2020)

Table 19. Detailed Structure for XPS Envelope (Source of Data: Xiong, 2022. Configured by Author)

Table 20. Detailed Structure for Strawboard Envelope (Sourceof Data: Xiong, 2022. Configured by Author)

was initially considered to be 110W/m². However, when modern equipment such as natural gas or induction cooktops is used, the Chinese national standard GB∕T 51350-2019 allows for a reduction in kitchen power density to 24W/m². It was anticipated that changing the cooking method would significantly reduce the internal gains generated by wood burning, resulting in a more stable indoor thermal environment. March 21st was chosen as the date to observe kitchen energy consumption and temperature changes. According to Figure 45, the original model had an internal heat gain of approximately 28 kWh from equipment on March 21st. After reducing the kitchen's power density to 24W/m², the equipment heat gain decreased to 14 kWh, which is about half of the original value. This demonstrates that the kitchen's heat generation is the

primary contributor to equipment heat gain, and the adjustment led to an overall reduction in kitchen temperature. 5.6 Envelope Regarding the choice of building envelope materials, based on discussions in Chapter 3 and analysis of two case studies, both cases ultimately opted for XPS (Extruded Polystyrene), a commonly used insulation material in China. Additionally, Xiong (2022) provided a case study involving the testing of insulation envelope structures with XPS on the roofs, walls, and floors of traditional wooden structures. These tests resulted in a significant 72% reduction in energy consumption for the original buildings. However, in the first case study, the use o f s t ra w b o a r d a s i n s u l a t i o n m a t e r i a l also achieved a substantial reduction of

Strawboard Total Cost: 3260.9 £

XPS Total Cost: 3967.3 £

Table 21. Cost Evaluation for Two Structure (Source: Xiong, 2022)

kWh

Total Heating Load: 211kWh (1.5kWh/m²)

Total Heating Load: 386kWh (2.8kWh/m²)

Figure 49. Heating Load of XPS and Strawboard System (EPW: Guiyang, Guizhou. 2020)

XPS

Annual Comfort Hours (14-30°C): 8134 (93%)

Strawboard

Annual Comfort Hours (14-30°C): 7564 (86%)

Figure 47. Typical Winter Week Operative Temperature for XPS Structure (EPW: Guiyang, Guizhou. 2020)

Figure 50. Typical Winter Week Operative Temperature for Strawboard Structure (EPW: Guiyang, Guizhou. 2020)

Figure 48. Typical Summer Week Operative Temperature for XPS Structure (EPW: Guiyang, Guizhou. 2020)

Figure 51. Typical Summer Week Operative Temperature for Strawboard Structure (EPW: Guiyang, Guizhou. 2020)

approximately 60% in building energy consumption. Comparing the material costs between XPS and strawboard in the first case study, it was found that XPS structures were, on average, 20% more expensive than strawboard. Therefore, considering affordability, this study will conduct separate tests to evaluate the performance of both XPS and strawboard as insulation materials. 5.6.1 Materiality and Structure In terms of specific structural arrangements, in the consideration of culture preservation, insulation materials and envelope structures should be installed within the building's interior without affecting the overall exterior facade. Which could preserve the original architectural aesthetics while enhancing the internal thermal performance. Specific structural layers for XPS and strawboard are detailed in Tables 18 and 19. For the walls, insulation layers and air gaps are added in between the wooden panels, which are applied to the floor as well. The roof, due to its complex structure, had a richer layering system, but still primarily relied on insulation to enhance its thermal performance. The windows are replaced with double-glazed

units with a U-value of 2.3 W/m²K. Both retrofit measures shared similar layering and thickness. Following the retrofit, the walls and floors extended downward by 150 mm, while the roof extended by 80 mm. From a floor plan perspective, the floor area was reduced from 139 m² to 134 m², approximately 96% of the original size. The net floor height decreased from 3.3 m to 3.15 m. Overall, the retrofitting of envelope structures had a minimal impact on the use of indoor spaces. In terms of thermal performance, for XPS structures, the U-values for walls, roofs, and floors improved from the original values of 2.8 W/m²K, 2.2 W/m²K, and 2.2 W/m²K (Table 14) to 0.47 W/m²K, 0.25 W/m²K, and 0.41 W/m²K, respectively. Strawboard structures achieved U-values of 0.82 W/m²K, 0.5 W/m²K, and 0.72 W/m²K (Table 20). Both retrofit measures demonstrated significant improvements in U-values, all of which were lower than the values recommended in the Chinese building standard GB∕T 51350-2019. Furthermore, based on the thermal model simulation, the XPS retrofit maintained indoor operating temperatures close to or above 14°C during a Typical Winter Week when outdoor temperatures were mostly below 14°C

(Figure 47). In summer, it kept the operating temperatures of various areas mostly below 30°C. Compared to the previous results, XPS greatly improved the building's passive performance, with annual comfort hours increasing by 22% to 8,134 hours. For strawboard, its winter thermal performance was slightly lower than XPS, but all indoor areas could maintain temperatures around 14°C, with the lowest point reaching approximately 10°C. Summer performance showed no significant differences from XPS, with indoor temperatures mostly staying below 30°C. Its annual comfort hours also increased by 14% to 7,564 hours (Figure 50). I n s u m m a r y, b o t h r e t r o f i t m e a s u r e s significantly improved the indoor operating temperatures and stabilised the temperature fluctuations by adding thermal envelope structures. Therefore, if the primary goal is to achieve better thermal insulation

2050 Scenario

performance, XPS structures should be chosen as the optimal retrofit measure. However, co n s i d e r i n g t h e ge n era l l y l ow- i n com e population in rural areas, more cost-effective measures are often preferred. 5.6.2 Estimated Cost and Conclustion As a result, based on the cost data provided by Xiong (2022), the specific costs of the two retrofit options are shown in Table 21. For this building, the XPS retrofit is approximately 20% more expensive than the strawboard retrofit, costing 3,967.3£ and 3,260.9£, respectively. Additionally, based on the annual heating loads for both options and the electricity tariff standards regulated by the Chinese government in 2021 (the electricity tariff for the Guizhou region is 0.05£/kWh), it is calculated that the XPS retrofit would only save approximately 8£ per year in electricity Annual Comfort Hours (14-30°C): 7611 (87%)

Figure 52. Typical Winter Week Operative Temperature for Strawboard Structure (EPW: Guiyang, Guizhou. 2050)

Figure 51. Retrofitted Area and Dimension

Figure 53. Typical Summer Week Operative Temperature for Strawboard Structure (EPW: Guiyang, Guizhou. 2050)

Total Energy Load: 2.83 kWh/m²

Total Energy Load: 7.82 kWh/m²

Figure 54. Energy Load for 2020 EPW (EPW: Guiyang, Guizhou. 2020)

Figure 55. Energy Load for 2050 EPW (EPW: Guiyang, Guizhou. 2050)

Figure 56. Energy Balance for 2050 EPW (EPW: Guiyang, Guizhou. 2050)

costs compared to strawboard structures. However, the expenses are 700£ higher. Therefore, considering affordability, using strawboard as the insulation material is recommended. Furthermore, as a common material in rural areas, straw is easily accessible to farmers, potentially resulting in lower costs in practice. Additionally, straw is more environmentally friendly and has a lower carbon footprint than XPS, as it consumes minimal energy and produces minimal carbon emissions during processing and transportation. From an environmental perspective, the strawboard should be a more reasonable choice.

higher than heating, reaching around 350 kWh in the peak month of June. The total energy load (heating + cooling) reached 7.82 kWh/ m², nearly three times higher than in 2020. Nevertheless, considering that the Chinese building standard GB/T 51350-2019 defines passive buildings in hot summers and cold winters regions as those with heating/cooling energy consumption below 8 kWh/m², this retrofit measure still satisfies the category of passive energy-efficient buildings in 2050.

5.7 2050 Scenario To prepare for potential climate change in the future, the strawboard envelope structure was tested using the 2050 EPW (EnergyPlus Weather) file. This test only altered the EPW file while keeping other parameters unchanged. Based on temperature results, it was observed that the outdoor temperatures during the typical winter and summer weeks in 2050 showed a slight increase, likely due to global warming. However, the indoor temperature performance in the kitchen and bedroom 3 followed a similar trend to the simulation under the 2020 EPW file. Nevertheless, during the typical summer week, the increased frequency of outdoor temperatures exceeding 30°C reduced the percentage of time when indoor temperatures in various areas fell within the thermal comfort range (Figure 53). Overall, the total annual comfort hours remained consistent at approximately 7610 hours, similar to the 2020 results. C o n s i d e r i n g e n e rg y co n s u m pt i o n , t h e potential rise in temperatures in 2050 led to adjusting the simulation to include cooling equipment energy consumption as a proactive cooling measure that residents might adopt in hot conditions. The cooling was set to activate when room temperatures exceeded 30°C. Results indicated that in 2020, there was minimal demand for cooling energy consumption (Figure 54). However, in 2050, cooling energy consumption was significantly 61

6. Scenario Variation In previous research, an analysis of the ground-level living spaces for fully attached buildings to the ground was completed. Since the layout of this stilted building model is common in rural southwest China, the outcomes of this study have already provided valuable guidance. In most cases with similar spatial layouts, retrofits can be based on the results of completed results. However, a related comfort study has not been conducted for the upper-level storage spaces and the attic formed by the roof. Although attic spaces are typically used for storage in rural China, in this model, it is rare that the entire floor be used as storage. Mostly, part of the space would be used as bedrooms. Therefore, this research will focus on the comfort analysis of the rooms on the first floor to explore their potential use as bedrooms. Additionally, to provide more general retrofit guides for different forms of stilted buildings, additional research will be dedicated to investigating the temperature and energy performance of the indoor spaces when the building is constructed on uneven terrain, with the floors raised on stilts.

Figure 57. Scenario Variations

Figure 58. A1: Open Gable Wall Figure 59. Re-arranged First Floor Plan

Annual Comfort Hours (14-30°C): 6305 (72%) Annual Comfort Hours (8-30°C): 8212 (94%)

Figure 60. Typical Winter Week Operative Temperature for Upper Floor-A1 (EPW: Guiyang, Guizhou. 2020)

Figure 61. Typical Summer Week Operative Temperature for Upper Floor-A1 (EPW: Guiyang, Guizhou. 2020)

6.1 Scenario A: Additional Ceiling on the First Floor Firstly, based on the previous temperature simulation results, it can be observed that the storage space, when unceiled and with open sidewalls, maintains a temperature nearly the same as the outdoors. However, during a typical winter week, the thermal inertia effect due to its volumetric heat capacity results in more stable temperature changes than outdoors. Regarding the thermal retrofit of the first floor, the primary measure is to reduce indoor airflow to mitigate the significant heat loss caused by excessive air exchange. Since the research focuses on bedroom comfort in this scenario, privacy issues necessitate an enclosed space. Therefore, an additional ceiling is installed between the attic and the first floor. One of the original storage rooms is converted into Bedroom 4, equipped with windows of the same size and property as those in the ground floor bedroom and an operating program of occupants and lighting to provide it with the same internal heat gain. As local farmers typically require storage space with airflow, the initial analysis condition involves adding a floor that is identical in structure to the ground level but does not enclose the gable wall on the top to allow airflow in the attic. According to the results presented in Figure 60 and 61, during winter, the operating temperature of Bedroom 4 is lower compared to Bedroom 3 when the attic is open (as shown in Figure 50). However, it is generally close to 14°C most of the time. In summer, the temperature in Bedroom 4 is generally around 30°C, with occasional daytime temperature spikes above 30°C. The summer performance is satisfactory because bedrooms are typically used at night when temperatures are usually lower than 30°C. Furthermore, Bedroom 4 exhibits higher thermal stability than Bedroom 3, possibly due to the lack of heat gain in other zones of the first floor. If a comfort range of 14°C-30°C is considered, Bedroom 4 has 72% hours of the year within this range, approximately 14% less than

Bedroom 3. However, considering the study by Wu et al. (2019) referenced in Chapter 1.5.1, residents in rural southwest China can tolerate lower temperatures, with around 80% accepting temperatures as low as 6.5°C and 90% tolerating temperatures as low as 8.9°C. Therefore, if the comfort range is set to 8°C-30°C, Bedroom 4 remains within this range for 94% hours of the year. Consequently, converting one of the first-floor rooms into a bedroom in a thermal comfortable condition would only require the addition of a ceiling with a structure identical to the ground level. To further investigate the possibilities of increasing the temperature in Bedroom 4, simulation A2 was tested to obtain the temperature performance of Bedroom 4 when the gable walls are closed. According to the results presented in Figures 63 and 64, the temperature in Bedroom 4 remained almost the same whether in winter or summer, compared to the previous scenario. The annual comfort hours also remained nearly the same. Therefore, closing the attic did not have a significant effect on increasing the temperature in Bedroom 4. If there is a desire to raise the operative temperature in Bedroom 4, the primary method is to increase internal heat gain. However, after closing the attic, the attic's temperature remains much more stable, staying close to the average of the outdoor temperature curve. Therefore, if specific temperature requirements exist for the attic storage space, such as a temperature-stable storage area, closing the attic might be a viable option.

Figure 62. Closed Gable Wall

Annual Comfort Hours (14-30°C): 6469 (74%) Annual Comfort Hours (8-30°C): 8215 (94%)

Figure 63. Typical Winter Week Operative Temperature for Upper Floor-A2 (EPW: Guiyang, Guizhou. 2020)

Figure 65. Half Stilt Scenario

Annual Comfort Hours (14-30°C): 7107 (81%)

Figure 64. Typical Summer Week Operative Temperature for Upper Floor-A2 (EPW: Guiyang, Guizhou. 2020)

6.2 Scenario B: Half Stilt Ground Floor Although stilt houses are named as it, in most real cases, the floor is in complete contact with the ground. However, the stilted type may be prevalent in areas with exceptionally rugged terrain. Typical stilt houses are L-shaped buildings located on hillsides, with part extending vertically from the central part of the building and raised to adapt to the terrain. Due to considerations of structural stability and the complexity of construction, most stilt houses have only a small portion raised above the ground. Therefore, this study will analyze the 'partly stilt' type. Considering that L-shaped and I-shaped floor plans have consistent spatial coherence and to ensure parameter accuracy, the original floor plan will be directly used to study the impact of "Half-stilt" on thermal performance. The model starts with the 66

section beginning with the stilt bedroom, while the living room section remains attached to the ground. The simulation results show that for Bedroom 3 (Figure 66), compared to the situation where it is not stilt, suspending its floor results in a maximum decrease in overall temperature of about 2 °C during both the typical winter and summer weeks. However, since the modified construction set of the strawboard system is applied, the floor still exhibits relatively good temperature performance. Throughout the year, around 81% of the time, remain in the adaptive comfort zone, which is only a 3% reduction compared to the situation where the floor is fully attached to the ground. In conclusion, using a strawboard envelope system for the floor is still feasible in the case where the underside of the floor is exposed to the air.

Figure 66. Typical Winter Week Operative Temperature-Scenario B (EPW: Guiyang, Guizhou. 2020)

Figure 67. Typical Summer Week Operative Temperature-Scenario B (EPW: Guiyang, Guizhou. 2020)

6.3 Scenario C: Fully Stilt Ground Floor The entire building is rarely raised above the ground. This situation is mainly to prevent floods and insects and to improve ventilation. It is more common in tropical areas such as Southeast Asia (Rashid & Ara, 2015). Since the entire floor slab is exposed to the air, more heat will lost through the opaque structure. However, since this type of building is usually located in a hot climate region, there is minimum demand for improving thermal insulation performance, and the requirements for building heat dissipation are high, so insulation layers are usually not installed on the floor slabs in those areas. However, in southwest China, located in a zone with cold winters and hot summers, it is necessary to install an insulation layer on the floor for this type of building. According to the simulation results (Figure 70), the overall temperature of each area is almost consistent with the halfstilt situation (Scenario B), and the operating temperature of bedroom 3 is still slightly lower than that of the unexposed floor. It can be seen that the difference in indoor operating temperature when part or all of the floor slab is exposed is almost negligible. If there is no accessibility requirement, the full stilt type generally has better ventilation performance and can reserve more storage space on the ground.

Figure 69. Full Stilt Scenario

Annual Comfort Hours (14-30°C): 7104 (81%)

Figure 68. Full Stilt Building Photo (Source: Website)

Figure 70. Typical Winter Week Operative Temperature-Scenario C (EPW: Guiyang, Guizhou. 2020)

Figure 71. Typical Summer Week Operative Temperature-Scenario C (EPW: Guiyang, Guizhou. 2020)

7. Retrofitting Guidance Stilt houses' primary sustainability performance and retrofit potential have been explored by studying typical stilt house prototypes and their variations. Simulations have been modelled to the directions for improving the sustainability performance of stilt houses, including their airtightness, daylighting performance, envelope structure and its performance, retrofit costs, energy usage patterns, different spatial layouts, and the comfort of multiple zones within the floor plan. Through simulation adjustments, all of the above scenarios have ultimately obtained retrofit measures that place them within the comfort zone. These scenarios have encompassed most issues that stilt houses face in rural areas. Therefore, this chapter will consolidate these measures and their performance to provide a universally applicable passive energy retrofit guide for stilt houses from multiple perspectives.

7.1 Airtightness Air tightness is one of the essential factors in building energy efficiency. Usually, because the construction process of stilted buildings is manual and lacks precise seam infiltration prevention, their air tightness is poor, such as the gaps between walls, floors, roofs and windows. According to the measurement of a stilted building by Zhao et al. (2022), even after preliminary renovation, the building still has many tiny holes or seams, and the width of the seam can reach about 5mm. As a result, the internal heat gain in the room could escape quickly through those gaps. Although generally, there are different air tightness for various stilted buildings, according to the study of a typical stilt structure by Jimin et al. (2020), it can be roughly determined that the infiltration rate of a traditional stilted building is 5 ACH. Commonly, two aspects should be considered to improve the airtightness of a stilted building: the envelope structure and the seams. For the envelope structure, the most direct method is to increase the layer and thickness of the envelope structure and improve its air tightness by enhancing its ability to isolate airflow. In terms of the seams, it should be more meticulous. Professional sealing materials such as expanding polyurethane foam and sealant can enhance the timber structure's airtightness (Bucklin et al., 2022). The seams require regular maintenance and checks due to the possible instability of the sealing material. In addition, replacing doors and windows with higher quality is critical. On the one hand, the doors and windows of the original stilted building have wider joints; on the other hand, they generally have unqualified thermal resistance. After replacement, it could be expected that better prevention of air penetration could be achieved. In conclusion, after taking a series of measures and measuring the air infiltration rate of the building with professional instruments and means below 0.6ach, the air tightness of the building can be deemed to be qualified under the passive building standard GB∕T 513502019.

Figure 72. Seams for traditional Timber Building (Source: Zhao et al. ,2022 )

Table 22. Regulated Max WWR for Hot Summer and Cold Winter Zone (Source: MHURD, JGJ134-2010 )

7.2 Daylighting Regarding the natural lighting of stilted buildings, first of all, due to the customs of ethnic minorities in rural areas of southwest China, traditional stilted buildings usually have smaller windows (Ma et al., 2015). In addition, due to the mountainous terrain with complex natural environments, occasionally, there are obstacles such as trees or mountains outside the window to block sunlight to the room. Moreover, there is no uniform standard for window sizes in stilted buildings, so the daylighting of different traditional stilted buildings is also different. According to the simulation results, different orientations have little impact on the indoor Daylight Factor. For a typical 5m×6m room, when the window-wall ratio is 20%, within the range of 2m close to the window, DF would be around 5-20%. From the illuminance chart, it could be observed that the natural lighting performance of the entire space is acceptable during the main usage times of the day: early morning, noon and dinner time. According to the WWR range stipulated in the specification JGJ134-2010, through testing, rooms with less than 20% WWR have relatively low indoor Useful Daylight Illuminance (UDI). In contrast, lighting performance in the range of 20%40% is similar and can be considered more reasonable. 71

In conclusion, when operating a natural daylight renovation in a building, adjusting the window size will affect the opening size of the wall at the same time. Therefore, within an economical range, corresponding measures can be taken within the range of 20%-40% WWR according to the actual situation. 7.3 Heating Pattern Regarding the traditional cooking and heating methods of residents living in stilt houses in rural areas, firewood is usually used for cooking and heating. On the one hand, it results in a large amount of carbon emissions and indoor air pollution (Figure 78). On the other hand, burning firewood will cause the indoor temperature to rise sharply. In winter, the large amount of heat generated by firewood can raise the indoor temperature quickly. However, since the frequency of opening windows for ventilation is reduced in most cases in winter, indoor air quality would be a serious issue during cooking (Ma et al., 2015). In summer, the heat generated by cooking can cause indoor overheating. Therefore, within the scope that the budget allows, replacing traditional wood stoves with modern electromagnetic power or gas stoves can significantly improve indoor air quality and enhance the stability of the indoor thermal environment. 7.4 Envelope The building envelope structure is considered a crucial part of the passive renovation of stilted buildings. Thermal structures of traditional stilted buildings are typically

Figure 73. Two Types of facade openings on the Top (Guo, 2015)

simple, mainly using single-layer materials without thermal insulation and waterproofing measures. Although the thin timber wall and floor structure provide good heat dissipation in summer, it is the main issue affecting winter's indoor thermal comfort. Envelope upgrading can be divided into two main parts: 1. Walls, floors and windows. 2. Roof and attic Firstly, stilted buildings usually include 1 to 3 floors (Guo, 2015). The attic and living space are usually connected without obstacles in single-storey buildings only. Single-story houses can be further divided into two types,

Figure 74. Three Types of Single Floor Section

Figure 75. Open Gable Wall (Source: Website)

Figure 76. Closed Gable Wall (Source: Website)

one with openings on the top of both facades and the other not (Figure 74). Considering that openings may lead to higher air exchange rates, in the case of a single-story house with openings on both sides, the openings need to be closed if the living space is not isolated from the attic to form an enclosure to reduce heat loss. Otherwise, even after improving the envelope, the temperature of the indoor space will still fluctuate dramatically as the outdoor temperature changes. After closing the openings, ventilation can still be enhanced by opening windows. Therefore, the primary task of renovating the envelope structure of a single-story stilt building is to reduce indoor and outdoor air exchange, then the envelope materials. The large openings on the original facade need to be closed or isolated from the living space. For stilted buildings with 2 to 3 floors, thermal insulation measures need to be set according to specific needs (Figure 77). Depending on the level of the main living spaces, such as bedrooms, living rooms, and kitchens, the facades, windows and ceilings of this level will need to be modified. If these spaces are located on the ground floor, and the top floor is abandoned for daily use, then only the ground floor envelope requires retrofit. The same retrofit measures will be required if the top floor includes living space. Multi-story stilted buildings can be divided into two types, one with openings on both sides of the top of the gables and the other with closed gables on both sides. No measures

Figure 77. Different Types of the Upper Floor Space

Figure 78. Inddor CO2 Condition of Stilt Building (Source: Ma et al., 2015)

are required for the type with openings if the top floor is only used for storage. The openings on both sides can ensure natural ventilation of the storage space, which is beneficial for storing grains. However, if the upper floor includes living space, such as bedrooms, an additional floor slab is required between the attic and the living space. In this case, retaining the original opening in the gable is still possible and recommended. For types with no openings on both sides of the gable, the same strategy can be adopted by setting up floors to separate the living space level and the attic to avoid the waste of space and enhance the thermal comfort of the living space. Regarding specific retrofit measures, after testing the commonly used insulation materials XPS and strawboards on walls, floors and roofs, XPS performed best as an insulation material regardless of budget. By installing an XPS system and double glazing with a U-Value of 2.3W/m²K on the building envelope, the heating load of the indoor space can be reduced by approximately 72%. If strawboards are used instead of XPS for the same structure, the heating load can only be reduced by 60%. Therefore, if optimal thermal performance is pursued, using the XPS system provided in the 74

Conclusion

simulation is recommended. In terms of the cost, in the simulated case, the total material cost for a typical-sized doublestorey stilt building after being renovated with the XPS system and double-glazed structure was approximately £3,900. The strawboard structure can save about 20% of the cost compared to the XPS structure. Considering the prevalence of low-income groups in rural areas and the high availability of straw materials in rural areas, the actual cost may be even lower. Given that straw is a renewable and environmentally friendly material that is abundant in the natural environment, strawboards are recommended as wall insulation in rural areas. 7.5 Conclusion This chapter provides flexible retrofit measures for stilted buildings with different structures and needs. This guideline covers the issues faced in energy-saving renovation of stilt buildings in most cases, including air tightness, lighting, air quality, indoor thermal stability, and affordability. The actual needs can be split and matched with the guidelines for specific renovation measures for specific buildings to achieve a combined and targeted renovation plan. 75

Conclusion This article discusses the potential of energysaving retrofitting and specific measures for stilted houses, the characteristic residential buildings of ethnic minorities in southwest China's rural areas. First, background information such as climate, geography, population, and energy use in southwest China is discussed. The stilted building's structural form, settlement form, and material composition were summarized based on literature and cases. Case studies determined the primary issues of stilted buildings in the thermal environment and the possible improvement measures. After that, by modifying the basic thermal model, the building's lighting and energy consumption performance under different circumstances was explored by changing the model and various parameters. Finally, after applying specific envelope structures, the building energy consumption has achieved the national passive building standards in various scenarios. A universal retrofitting guideline for stilted buildings was proposed by summarising these renovation measures. In the beginning, In the essential public information on geography, population, energy, etc., severe ageing, population loss, poverty and other issues on the social level in the southwest rural areas were discovered. Although those issues may not be caused by low building quality, as the slow down of population migrates to cities, there is still a large amount of population in rural areas. Improving the quality of dwellings in an affordable way is urgent. Secondly, by analyzing the energy usage in the region, it was found that rural areas still use coal and firewood for cooking or heating, which is relatively backward in technology and produces massive pollution and energy consumption. Based on this, the research has determined the direction of reducing building energy consumption in the area as much as possible. Subsequently, based on the long-term high environmental tolerance of residents in rural areas, a specific adaptive comfort band for rural areas was formulated and used as the benchmark for subsequent 76

simulations. The subsequent research on vernacular architecture determined that the stilted building is a single-family traditional timber frame building with a relatively open plan and with unique ethnic minority cultural characteristics. Therefore, due to its unique cultural value, it was determined that the renovation should be carried out without disturbing the main ethnic architectural features. After wards, through the study of two re n o vat i o n ca s e s o f st i l te d b u i l d i n g s , the building materials and various basic p a ra m e te rs u s e d fo r s i m u l at i o n we re determined. It was also found that the main problem of stilted buildings in thermal comfort is the cold indoor temperature in winter. Lack of airtightness and the thin envelope structure are the main reasons. Two cases provide specific retrofitting schemes and corresponding construction costs for the envelope upgrading. XPS material was selected as the most effective thermal insulation material in both cases, and the energy consumption of both cases decreased by about 50-70% after the envelope structure renovation. Based on the case studies, the direction of the simulation was determined to increase winter temperatures, air tightness of the stilted building, and determine window sizes to meet daylight requirements. A typical double-story stilt building is adopted as the thermal model, and the scenario is set to a typical rural family of five. The simulation parameters are determined according to two case studies. Through the simulation, it was found that different orientations and window sizes have little impact on building energy efficiency. Therefore, the building orientation of the stilted building can follow the dominant wind direction of the area from southwest to northeast to achieve the best natural ventilation. Meanwhile, in the test of different window sizes, it was found that a window size of 20% window-wall ratio is sufficient to satisfy daily natural light needs. If the WWR is less than 20%, it will lead to a relatively dark indoor space, while 20%-40% will cause

glare on the space close to the window. In addition, the heating method in the kitchen of using wood-burning stoves was changed to modern equipment such as gas stoves, which significantly reduced the internal heat gain of the kitchen. At the same time, the problem of indoor temperature overheating in summer was solved by increasing the window opening time for natural ventilation. In the building envelope section, the expensive XPS system and the cheap and easily accessible strawboards were tested in the model. According to test results, they can reduce building energy consumption by 72% and 60%, respectively. The overall cost of materials for the two is 3960 pounds and 3260 pounds, respectively. By comparing the energy consumption saved by the two, it is found that XPS only saves 7 pounds in electricity bills a year compared to straw boards. Therefore, after comprehensive consideration, the straw board is the most cost-effective, low-carbon and environmentally friendly insulation material. F i n a l l y, b a s e d o n t h e m e t e o ro l o g i c a l documents in 2050, the envelope's performance in the context of future climate warming was tested. The study found that the renovation plan can still reduce the building's energy consumption for heating/cooling to less than 8 kWh/m² in 2050, which could still meet the standards of passive buildings in China. Moreover, based on the possible different structural forms of the stilted building, the possibility of using the first floor as a bedroom space under the strawboard structure, and the indoor temperature performance when the ground was partially or entirely suspended. The study found that after installing the strawboard structure, on the premise of improving indoor air tightness, the indoor operating temperature can be stabilized above 8°C under different circumstances. In most cases, the temperature can still be between the range of 14°C-30°C in more than 70% of the hours of the year. The research findings are summarized in the guideline chapter, which summarizes the results demonstrated in the research

for different scenarios. On the premise of affordability and protecting the ethnic elements of the building and the use of indoor space, it provides universal guidance for improving the air tightness, envelope performance, lighting, and energy saving of the stilt building.

Bibliography Brager, G.S. and de Dear, R.J. (1998) ‘Thermal adaptation in the built environment: A literature review’, Energy and Buildings, 27(1), pp. 83–96. doi:10.1016/s03787788(97)00053-4. Bucklin, O. et al. (2022) ‘Mono-material wood wall: Novel building envelope using subtractive m a n u fa c t u r i n g o f t i m b e r p ro f i l e s to i m p ro ve thermal performance and airtightness of solid wood construction’, Energy and Buildings, 254, p. 111597. doi:10.1016/j.enbuild.2021.111597. Chinese Government (2021) Guizhou Electricity Price Standard. Available at: https://www.gov.cn/ xinwen/2021-10/22/content_5644314.htm. CGPRC, 2014. Central Government of People’s Republic of China – China’s New Urbanization Plan (2014–2020) https://www.gov.cn/zhengce/2014-03/16/ content_2640075.htm. Department of Housing and Urban-Rural Development of Hubei Province [DHURDHP] (2023) Hubei provincial standard. Technical code of practice for the construction of Tujia stilted house. Fan, S. et al. (2023) ‘Does financial development matter the accomplishment of rural revitalization? evidence from China’, International Review of Economics & Finance, 88, pp. 620–633. doi:10.1016/ j.iref.2023.06.041. FILMER, D., FU, H. and PÁRAMO, C.S. (2022) An adjustment to global poverty lines. Wolrd Bank, 2 May. Available at: https://blogs.worldbank.org/ voices/adjustment-global-poverty-lines (Accessed: 04 September 2023). Government of China (2014) Guizhou Province Information https://www.gov.cn/guoqing/2013-04/08/ content_5046168.htm. Guizhou Meteorological Bureau (2023) Climate impact assessment for 2022 in Guizhou Province. Available at: http://gz.cma.gov.cn/qxfw/qhjcpg/qhpj/202303/ t20230331_5413152.html (Accessed: September 2, 2023). Guo, C. (2015) Sustaining the traditional stilt house of Tujia ethnicity in southeast Chongqing, China [Preprint]. Available at: https://doi.org/10.14264/uql.2016.272. Huang, H. et al. (2020) ‘Optimum insulation thicknesses and energy conservation of building thermal insulation materials in Chinese zone of humid subtropical climate’, Sustainable Cities and Society, 52, p. 101840. doi:10.1016/j.scs.2019.101840.

Jiang, Y. (2012) China building energy efficiency annual development report 2012. Beijing: China Building Industry Press.

Ministry of Housing and Urban-Rural Development [MHURD], PRC. (2013) Energy Saving Design Standards for Rural Residential Buildings. GB/T50824-2013.

Wei, D. et al. (2022) ‘Indoor thermal comfort in a rural dwelling in Southwest China’, Frontiers in Public Health, 10. doi:10.3389/fpubh.2022.1029390.

Jiang, Y. et al. (2018) China Building Energy Use 2018, ResearchGate. Available at: https://www.researchgate. net/publication/337160052_China_Building_Energy_ Use_2018 (Accessed: 29 August 2023).

Ministry of Housing and Urban-Rural Development [MHURD], PRC. (2019) Technical Standard for Near Zero Energy Buildings. GB/T 51350-2019.

Wu, C., Shan, J. and Kong, D. (2019) ‘Field study on winter indoor thermal comfort of stilted buildings of Miao nationality in Guizhou’, Heating Ventilating & Air Conditioning, (9), pp. 135–141. ISSN:1002-8501.

Jimin, Z., Jiang, H. and Xiang, L. (2020) ‘Ecological building design based on the optimization of thermal performance of stilt houses in Guangxi Province’, IOP Conference Series: Earth and Environmental Science, 531(1), p. 012004. doi:10.1088/17551315/531/1/012004. Jin, Y. and Zhang, N. (2021) ‘Comprehensive assessment of thermal comfort and indoor environment of traditional historic stilt house, a case of Dong minority dwelling, China’, Sustainability, 13(17), p. 9966. doi:10.3390/su13179966.

National Bureau of Statics of China (2021) Proportion of urban population at year-end by region. Available at: http://www.stats.gov.cn/sj/ndsj/2021/indexch.htm (Accessed: September 2, 2023). National Bureau of Statics of China (2023) What is population aging and how it is determined? Available at: http://www.stats.gov.cn/zs/tjws/tjbz/202301/ t20230101_1903949.html (Accessed: September 2, 2023). National Bureau of Statistics of China [NBSC]. China statistical yearbook. Beijing: CSY press; 2010.

Künzel, H. (1979) 'Reprasentativeumfrage über das Heizen und Lüften in Wohnungen (engl.: Representative survey on heating and ventilation in dwellings)', Fraunhofer Institute for Building Physics IBP, IBPMitteilung, 47, as cited in Huang, H. et al. (2020).

Nguyen, A.-T. et al. (2011) “An investigation on climate responsive design strategies of vernacular housing in Vietnam,” Building and Environment, 46(10), pp. 2088–2106. Available at: https://doi.org/10.1016/ j.buildenv.2011.04.019.

Liu, D. (2004) Introduction to Chinese Dwellings. Tianjin: Baihua wenyi.

Rashid, M. and Ara, D.R. (2015) ‘Modernity in tradition: Reflections on building design and technology in the Asian vernacular’, Frontiers of Architectural Research, 4(1), pp. 46–55. doi:10.1016/j.foar.2014.11.001.

Liu, Z. et al. (2019) “Application and suitability analysis of the key technologies in nearly zero energy buildings in China,” Renewable and Sustainable Energy Reviews, 101, pp. 329–345. Available at: https://doi.org/10.1016/ j.rser.2018.11.023. Long, D. et al. (2016) ‘Drought and flood monitoring for a large karst plateau in southwest China using extended Grace Data’, Hydrologic Remote Sensing, pp. 73–102. doi:10.1201/9781315370392-6. Ma, H. et al. (2015) “Physical environment of stilted buildings in rural area of Southwest China,” Procedia Engineering, 121, pp. 341–348. Available at: https://doi. org/10.1016/j.proeng.2015.08.1077. Meng, X. et al. (2015) ‘Survey research on living environment and energy consumption in the west rural areas of China’, Procedia Engineering, 121, pp. 1044– 1050. doi:10.1016/j.proeng.2015.09.101. Ministry of Housing and Urban-Rural Development [MHURD], PRC. (2010) Design standard for energy efficiency of residential buildings in hot summer and cold winter zone. JGJ-134-2010.

Xiong, H. (2022) Research on passive renewal design of traditional stilted buildings in northwestern Guangxi (Taking Chengyang Bazhai in Sanjiang Dong Autonomous County as an example). dissertation. (In Chinese). Zhang, F. et al. (2022) ‘Climate adaptability based on indoor physical environment of traditional dwelling in North Dong areas, China’, Sustainability, 14(2), p. 850. doi:10.3390/su14020850. Zhao, M., Mehra, S.-R. and Künzel, H.M. (2022) ‘Energy-saving potential of deeply retrofitting building enclosures of traditional courtyard houses – A case study in the Chinese Hot-Summer-Cold-Winter zone’, Building and Environment, 217, p. 109106. doi:10.1016/ j.buildenv.2022.109106. Zhao, X. (2010). Research on settlement culture type and the characteristics in Guizhou Karst Area. Carsologica Sinica, (4), 457-462. doi:10.3969/ j.issn.1001-4810.2010.04.018.

Ruan, X. (2006) Allegorical architecture: Living myth and architectonics in Southern China. Honolulu: University of Hawai'i Press. Shan, D. (2004) Chinese vernacular dwelling. Beijing: China Intercontinental Press. Shan, M. et al. (2015) ‘Energy and environment in Chinese rural buildings: Situations, challenges, and intervention strategies’, Building and Environment, 91, pp. 271–282. doi:10.1016/j.buildenv.2015.03.016. Sun, F. (2013) “Chinese climate and vernacular dwellings,” Buildings, 3(1), pp. 143–172. Available at: https://doi.org/10.3390/buildings3010143. Sun, Y. et al. (2023) ‘A systematic review on thermal environment and Thermal Comfort Studies in Chinese residential buildings’, Energy and Buildings, 291, p. 113134. doi:10.1016/j.enbuild.2023.113134. Wa n , L . ( 2 0 1 3 ) S t u d y o f b u i l t e nv i ro n m e nta l sustainability assessment of poor rural areas of Southwest China. dissertation. Chinese University of Hong Kong.

Figures

Figure 1. Southwest China Location Figure 2. Solargis (2023) China Elevation. Available at: https://apps.solargis.com/prospect/map?s=51.584171,0.10889&c=17.245744,106.12793,5 Figure 3. Song, Yehao et al. (2014) ‘The energy-related impacts of social factors of rural houses in Southwest China’, Energy Procedia, 57, pp. 1555–1564. doi:10.1016/ j.egypro.2014.10.147. Figure 4. Weather and Climate (2023) Guizhou, China climate, Guizhou, CN Climate Zone, Monthly Weather Averages and Historical Data. Available at: https://tcktcktck.org/china/ guizhou. Figure 5. National Bureau of Statics of China (2023) What is population aging and how it is determined? Available at : h tt p : / / w w w. stat s . g o v. c n / zs / t j w s / t j bz / 2 0 2 3 0 1 / t20230101_1903949.html Figure 6. National Bureau of Statics of China (2023) What is population aging and how it is determined? Available at: http://www.stats.gov.cn/zs/tjws/tjbz/202301/ t20230101_1903949.html Figure 7. Urban Populaion Rate in SW China (Source: NBSC, 2021) Figure 8. Linear Regression of Operative Temperature and MTS, PMV (Source: Wei et al.,2022) Figure 9. Results of the Linear Regression Between TSV and Operative Temperature. (Source: Wu et al.,2019) Figure10. Valley Settlement Figure11. Hillside Settlement Figure12. Riverside Settlement Figure13. Hill-flatland Settlement Figure14. Axonometric View of the Structure of Traditional I-shapoed Plan (Source: DHURDHP, 2023) Figure15. Axonometric View of the Structure of Traditional L-shapoed Plan (Source: DHUPDHP, 2023) Figure16. Structural Frame Specification (The Chinese words in the figure are the proper noun for each structural joint, therefore not translated) (Source: Department of Housing and Urban-Rural Development of Hubei Province, 2023) Figure17. Drainage System on the Roof (Source: Guo,2015) Figure18. Decration on the Doors (Source: Guo,2015) Figure19. Section for Typical Stilt House (Source: Guo,2015) Figure 20. Passive Strategy of Ventilation (Source: Guo,2015) Figure21. First Floor Plan of the Simulated Building (Source: Xiong,2022) Figure22. Case 1 Thermal Model (Source: Xiong,2022) Figure 23. Typical Summer Day Temperature (Source: Xiong,2022) Figure 24. Typical Winter Day Temperature (Source: Xiong,2022) Figure 25. Case 2 Building with Plans and Measurement Spots (Source: Zhao et al., 2022) Figure 26. Heat Transfer Detail (Source: Zhao et al., 2022) Figure 27. Air Temperature and Reletive Humidity of Measured House (Source: Zhao et al., 2022) Figure 28. Axonometric Drawing for the Base Case Model (Source: Zhang et al., 2022. Illustrated by Author) Figure 29. Plans for the Base Case Model (Source: Zhang et al., 2022. Illustrated by Author) Figure 30. Timetable for different rooms of the Simulation Model Figure 31. Base Case Operative Temperature in Winter (EPW: Guiyang, Guizhou. 2020) Figure 32. Base Case Operative Temperature in Summer (EPW: Guiyang, Guizhou. 2020) Figure 33. Wind Rose Chart for the Site (EPW: Guiyang,

Guizhou. 2020) Figure 34. Energy Balance for Base Case (Source: Ladybug) Figure 35. Heating Load for 4 Orientation (EPW: Guiyang, Guizhou. 2020) Figure 36. Heating Load for 4 Orientation (EPW: Guiyang, Guizhou. 2020) Figure 37. Layout and Facade Changes Figure 38. Natural Ventilation Schedule Figure 39. Operative Temperature in Winter for Changed Layout (EPW: Guiyang, Guizhou. 2020) Figure 40. Operative Temperature in Summer for Changed Layout (EPW: Guiyang, Guizhou. 2020) Figure 41. UDI for 4 Types of Window-Wall Ratio (EPW: Guiyang, Guizhou. 2020) Figure 42. Winter Operative Temperature for 4 Types of Window-Wall Ratio (EPW: Guiyang, Guizhou. 2020) Figure 43. Summer Operative Temperature for 4 Types of Window-Wall Ratio (EPW: Guiyang, Guizhou. 2020) Figure 44. Operative Temperature for the Changed Layout Model in March 21st (EPW: Guiyang, Guizhou. 2020) Figure 45. Operative Temperature for the Changed Layout Model- Decreased Power Density in Kitchen (EPW: Guiyang, Guizhou. 2020) Figure 46. XPS Insulation (Top) & Strawboard Insulation (Bottom) (Source: Website) Figure 47. Typical Winter Week Operative Temperature for XPS Structure (EPW: Guiyang, Guizhou. 2020) Figure 48. Typical Summer Week Operative Temperature for XPS Structure (EPW: Guiyang, Guizhou. 2020) Figure 49. Heating Load of XPS and Strawboard System (EPW: Guiyang, Guizhou. 2020) Figure 50. Typical Winter Week Operative Temperature for Strawboard Structure (EPW: Guiyang, Guizhou. 2020) Figure 51. Typical Summer Week Operative Temperature for Strawboard Structure (EPW: Guiyang, Guizhou. 2020) Figure 51. Retrofitted Area and Dimension Figure 52. Typical Winter Week Operative Temperature for Strawboard Structure (EPW: Guiyang, Guizhou. 2050) Figure 53. Typical Summer Week Operative Temperature for Strawboard Structure (EPW: Guiyang, Guizhou. 2050) Figure 54. Energy Load for 2020 EPW (EPW: Guiyang, Guizhou. 2020) Figure 55. Energy Load for 2050 EPW (EPW: Guiyang, Guizhou. 2050) Figure 56. Energy Balance for 2050 EPW (EPW: Guiyang, Guizhou. 2050) Figure 57. Scenario Variations Figure 58. A1: Open Gable Wall Figure 59. Re-arranged First Floor Plan Figure 60. Typical Winter Week Operative Temperature for Upper Floor-A1 (EPW: Guiyang, Guizhou. 2020) Figure 61. Typical Summer Week Operative Temperature for Upper Floor-A1 (EPW: Guiyang, Guizhou. 2020) Figure 62. Closed Gable Wall Figure 63. Typical Winter Week Operative Temperature for Upper Floor-A2 (EPW: Guiyang, Guizhou. 2020)

Figure 70. Typical Winter Week Operative TemperatureScenario C (EPW: Guiyang, Guizhou. 2020) Figure 71. Typical Summer Week Operative TemperatureScenario C (EPW: Guiyang, Guizhou. 2020) Figure 73. Two Types of facade openings on the Top (Guo, 2015) Figure 74. Three Types of Single Floor Section Figure 75. Open Gable Wall (Source: Website) Figure 76. Closed Gable Wall (Source: Website) Figure 77. Different Types of the Upper Floor Space Figure 78. Inddor CO2 Condition of Stilt Building (Source: Ma et al., 2015)

Tables

Table 1. Annual Energy Consumption for Space Heating in Different Regions (Shan et al., 2015) Table 2. Annual Energy Consumption for Cooking in Different Regions (Shan et al., 2015) Table 3. Four Types of Plans (Guo,2015) Table 4. Most used materials in stilt house (Nguyen et al., 2011) Table 5. Section for Typical Stilt House (Source: Guo,2015) Table 6. First Floor Plan of the Simulated Building (Source: Xiong,2022) Table 7. 3 Types of Wall System (Source: Xiong,2022) Table 8. Energy Load of Different Retrofitting System (Source: Xiong,2022) Table 9. XPS Wall System Compoments (Source: Xiong,2022) Table 10. Case 2 Building Structure Properties (Source: Zhao et al., 2022) Table 11. Existing U-value and Proposed U-value of th Building (Source: Zhao et al., 2022) Table 12. Comparison of energy consumption before and after renovation of envelope structure (Source: Zhao et al., 2022) Table 13. Estimated Cost and Payback Time (Source: Zhao et al., 2022) Table 14. Comparison of Base Case Values with Chinese Standard (Source: MHURD, 2010) Table 15. Materials for the Base Model (Source: Zhang et al., 2022) Table 16. Original Tested Operative Temperature (Source: Zhang et al., 2022) Table 17. Operative Temperature of Base Model (Source: Ladybug) Table 18. U-Value Comparison Between XPS and Strawboard with CN Strandard (Source: Ladybug) Table 19. Detailed Structure for XPS Envelope (Source of Data: Xiong, 2022. Configured by Author) Table 20. Detailed Structure for Strawboard Envelope (Sourceof Data: Xiong, 2022. Configured by Author) Table 21. Cost Evaluation for Two Structure (Source: Xiong, 2022) Table 22. Regulated WWR for Hot Summer and Cold Winter Zone (Source: MHURD, JGJ134-2010)

Figure 64. Typical Summer Week Operative Temperature for Upper Floor-A2 (EPW: Guiyang, Guizhou. 2020) Figure 65. Half Stilt Scenario Figure 66. Typical Winter Week Operative TemperatureScenario B (EPW: Guiyang, Guizhou. 2020) Figure 67. Typical Summer Week Operative TemperatureScenario B (EPW: Guiyang, Guizhou. 2020) Figure 68. Full Stilt Building Photo (Source: Website) Figure 69. Full Stilt Scenario