??Residential construction in China has been experiencing continuous rapid development and has achieved remarkable accomplishments. Together with this development, numerous issues have emerged. Residential housing, in general, exhibits shortcomings such as short lifespan, high energy consumption, subpar living experiences, and difficulties in maintenance. The concept of sustainable development has not been effectively implemented in housing construction. With the progress of economy and society, and the improvement of living standards, people's housing demands have shifted from simply “having a house” to “living in a good house”. Contradiction between extensive housing construction and demand for high-quality living environments has become increasingly prominent. The emergence and application of long-life sustainable housing technology system provide a new path for addressing the contradictions of China in housing construction and promoting sustainable development in the field of architecture.
??This paper briefly discusses the main issues in China's housing construction in the new era, elucidates the design theory and implementation strategies of long-life sustainable housing technology system, analyzes specific implementation processes through case studies, and introduces new ideas and innovative approaches that Baoye Group has adopted in implementing the concept of sustainable development in housing.
??Main issues in China's housing construction in the new era
??2.1. Residential comfort and livability
??In 2020, China Real Estate Association and China Construction Technology Consulting Group conducted a comprehensive survey on satisfaction of the people with their housing over the past 40 years. The survey examined the quality of housing from both community level and individual dwelling level. Table 1 presents the top 10 issues of dissatisfaction at individual dwelling level since the year 2000. Common quality issues such as poor sound insulation of floors and partition walls, cracks and hollow areas in wall plaster, inadequate control of indoor noise, bathroom leaks, window leakage, and external thermal insulation cracks continue to be the major pain points raised by the people. Additionally, in the new era, there is a growing demand among the people for smart homes. People aspire to have access to smart entrance guard, intelligent alarms, smart maintenance, intelligent lighting, smart furniture, and other smart home features.
??Table 1: Top 10 issues of dissatisfaction at individual dwelling level since the year 2000
??The issue of residential comfort and livability directly reflects various problems in housing construction: insufficient attention to the actual needs and living experiences of residents in architectural planning and design, inadequate functional layout of houses, and incomplete public facilities and community amenities. The rapid turnover and cost-driven development models have reduced the emphasis on construction quality. The use of cheap materials and simplified construction processes has resulted in a decline in building quality and increased various quality issues and safety hazards. Constructing high-quality housing is an inevitable requirement to meet the growing aspirations of the people for healthy living and a better life.
??2.2. High energy consumption during building operation
??According to “2022 Research Report of China Building Energy Consumption and Carbon Emissions” released by China Association of Building Energy Efficiency, in 2020, carbon emissions in the life cycle of buildings in China amounted to 5.08 billion tons of CO2, accounting for 50.9% of the country's total carbon emissions. Among them, carbon emissions from the production of building materials were 2.82 billion tons of CO2, carbon emissions during construction were 0.1 billion tons of CO2, and carbon emissions during building operation were 2.16 billion tons of CO2, accounting for 28.2%, 1.0%, and 21.7% of the total national carbon emissions, respectively. Comparing with the research data from China Association of Building Energy Efficiency in recent years (Figure 1), carbon emissions during building operation are still slowly increasing, with an annual average growth rate of 4.7%. It has not yet reached its peak, indicating that there is still a long way to go to achieve the goals of emission peak and carbon neutrality in building industry.
??Production of building materials is a significant aspect that involves various industries, and it requires collective efforts from whole society to reduce its carbon emissions. However, carbon emissions during construction and building operation can be effectively controlled through appropriate measures. Prefabricated building technology has been widely applied in housing construction and has proven to be effective in reducing carbon emissions during construction. The use of high-quality insulation methods and exterior products with high thermal insulation performance are objective conditions for reducing carbon emissions during building operation.
1: Energy consumption and carbon emissions during building operation
??2.3. Quality issues in full decoration
??In 2002, Housing Industrialization Promotion Center of the Ministry of Construction of China issued “Implementation Rules for Decorating Commercial Housing Once and for All”, which defined full decoration for the first time. It stipulated that before delivery, all fixed surfaces in functional spaces should be fully laid or painted, and basic equipment in kitchen and bathroom should be installed. However, due to the lack of national top-level design and comprehensive policy support in areas such as land, finance, and taxation, full decoration had not received sufficient attention at that time. Since 2012, both national and local policies promoting full decoration have been frequently introduced, and more than ten provinces (municipalities) across the country have joined the full decoration movement. For instance, in 2016, Zhejiang Province mandated that all new residential buildings in the central urban areas of each city and county throughout the province, which are developed on land transferred or allocated, must implement full decoration and finished product delivery. There is also encouragement for residential buildings under construction to actively implement full decoration.
??Some real estate companies have launched menu-based fine decoration services, but the quality is poor with numerous decoration issues. The promised “move-in ready” experience during marketing turns out to be empty words. Full decoration has turned into superficial work done just to pass the final acceptance, without truly focusing on the actual needs of homeowners and carefully crafting the details. Quality issues such as uneven and dusty floors, uneven walls, hollow tiles, cracked and damaged wallpaper, and damaged gypsum ceilings force homeowners to dismantle and re-decorate, resulting in waste of resources, energy, and economic loss. High-quality fine-decorated residential buildings have become an urgent demand in the housing market.
??Residential secondary decoration can indeed pose safety hazards. Accidents have occurred where homeowners indiscriminately remove load-bearing walls, leading to the entire building becoming structurally compromised and unsafe. In 2023, in Harbin, China, a homeowner removed a load-bearing wall during renovation, causing cracks in the upper part of the building and endangering the lives and property of over 240 households. The total losses amounted to over one hundred million yuan. To prevent the recurrence of such accidents, it is necessary to extensively promote knowledge about interior decoration and strengthen decoration management. Additionally, developers and design institutes should optimize the arrangement of load-bearing walls, effectively isolating the possibility of accidents caused by the removal of load-bearing walls from the structure level.
??Concept and strategy of long-life sustainable housing
??The introduction and application of long-life sustainable housing technology system provide a new approach to address the housing issues mentioned above.
??The literal meaning of long-life sustainable housing in Chinese refers to residential buildings with a design service life of 100 years. Specifically, long-life sustainable housing refers to residential buildings that are designed and constructed based on the principles of sustainable development. They involve integrated planning, design, production, construction and maintenance throughout entire lifespan of buildings. These buildings are characterized by long-lasting performance, excellent quality, and green sustainability, ensuring a high-quality living environment and long-term asset value for the residents. In 2010, China Real Estate Association proposed “Initiative for Constructing Long-Life Sustainable Housing” during the Sino-Japanese Century Housing System International Summit. In May 2012, the association initiated international cooperation with the Japan-China Building and Housing Industry Association to commence the construction and promotion of long-life sustainable housing in China.
??It should be pointed out that the concept of long-life sustainable housing not only refers to the physical lifespan of a building reaching 100 years but also emphasizes the functional lifespan, which means the ability to maintain functional relevance for 100 years. This involves the flexibility to adapt and update the internal space layout according to changes in the age and number of family members and the evolving needs of living functions. From this perspective, long-life sustainable housing is a residential system characterized by robust vitality and dynamic functional changes.
??The core technology of long-life sustainable housing is SI system (a residential construction system with completely separated Skeleton and Infill). The SI system achieves three main purposes: enhancing the durability of structure and major components, improving the maintainability and upgradability of equipment and components, and increasing the flexibility for interior layout changes and renovations.
??As of now, total area of long-life sustainable housing demonstration projects has exceeded one million square meters. The advanced concept has gained recognition from an increasing number of provinces. Beijing, Shandong, and Hebei have respectively issued local standards, and group standard “Design and assessment standard for long-life sustainable housing” was officially published in 2018.
??Requirements of “construction industrialization, building longevity, quality excellence and green low-carbon” for long-life sustainable housing are achieved through Longevity Integration Technology, Adaptability Integration Technology, SI Industrialization Integration System and Technology and INFILL Assembly Integration System and Technology, as shown in Figure 2.
??Figure 2: Implementation strategy of long-life sustainable housing
??Practice and innovation of long-life sustainable housing by Baoye Group
??As implementing enterprise of the first batch of demonstration projects for long-life sustainable housing, Baoye Group actively participates in application and promotion of long-life sustainable housing system. Leveraging its own whole industry chain model and building energy-saving and emission reduction technologies, Baoye Group has developed Xinqiao Fengqing project based on long-life sustainable housing system. During the construction of this project, the company has applied decades of practical experience and research achievements in the field of building industrialization, making innovative explorations in promoting sustainable housing construction and building energy-saving and carbon reduction in China.
??4.1. Project overview
??Xinqiao Fengqing block is located in Shaoxing, Zhejiang Province. It covers an area of 41,000 m2, with a total construction area of 135,000 m2 and a plot ratio of 2.3. The project consists of 14 buildings, including 10 high-rise residential buildings and 4 demonstration buildings for long-life sustainable housing.
??This project fully implements the comprehensive solution of long-life sustainable housing, achieving a high-quality residential environment, durable housing structures, and high-standard housing performance. It provides residents with a high level of comfort and has received zero complaints since its fine-decorated delivery in October 2019.
??Figure 3: Aerial view of Xinqiao Fengqing Block
??This project has fully utilized long-life sustainable housing technology system, effectively addressing common concerns of residents regarding typical housing issues. By adhering to high-quality standards of fine-decorated delivery, it has prevented homeowners from secondary renovations, thus eliminating the possibility of various decoration-related incidents from the very beginning.
??4.2.1. Large space integration technology
??By appropriate structure selection and design optimization, the number of load-bearing walls inside the building is minimized and large space is realized. This enhances flexibility of indoor spaces, catering to practical needs of a family throughout its entire lifecycle. Meanwhile, this technology effectively reduces the likelihood of removing load-bearing walls inside the building.
??4.2.2. Internal insulation of external wall integration technology
??The adoption of internal insulation method avoids the historical problem of external wall insulation layer detachment. This project utilizes a polyurethane foam interior insulation system, which occupies minimal space, provides excellent insulation performance, and also has waterproofing capabilities. It effectively addresses common issues such as thermal bridges and condensation.
??4.2.3. Light steel keel partition wall integration technology
??This project adopts light steel keel walls for internal partition wall. Light steel keel partition walls have the characteristics of high strength, good fire resistance, excellent sound insulation performance, dry construction and fast construction speed. This technology enhances the flexibility and adaptability of inner spaces, creating favorable conditions for future residential function renovations and updates.
??4.2.4. Integrated kitchen technology
??This project adopts integrated kitchen technology, where kitchen components are integrated into the cabinets. Gas appliances, electrical appliances, utensils, and cabinet accessories are scientifically and reasonably integrated according to relevant standards. Integrated kitchen has the characteristics of optimal space layout, minimal labor intensity, intelligent operation, and enhanced comfort.
??4.2.5. Integrated Pipeline Technology
??All the pipelines are installed within the inner space of interior finishing, allowing for complete separation of structural body as the supporting skeleton (S) and various system pipelines as the infill (I). This fully achieves the construction system of SI, making it convenient for future maintenance and replacement.
??4.2.6. Same floor drainage integration technology
??Same floor drainage integration technology is adopted in the bathroom, where sewage horizontal pipes and water supply pipes are both laid within the same floor. This arrangement prevents the impact of drainage issues from upper floors, avoiding the problem of “upper floor leakage contaminating lower floors” This technology allows for easy troubleshooting and maintenance of bathroom issues within the unit, while also reducing the noise generated by drainage from upper floors.
??4.2.7. Unit bathroom technology
??Unit bathroom technology is used for the integration of sanitary fixtures in bathrooms. This technology utilizes a waterproof base, wall panels, and a top cover to form an integrated framework. Within this framework, various functional sanitary fixtures are installed, creating independent sanitary units. Assembly process of the unit bathroom's drainage pan, and integrated wall panels ensures a waterproof seal, guaranteeing no leakage. Compared to traditional wet construction methods, unit bathroom offers faster construction speed, noise-free installation, minimal construction waste, and energy efficiency, resulting in an environmentally friendly solution.
??4.2.8. Dry floor heating integration technology
??This project adopts dry floor heating integration technology to provide comfortable winter living environment for homeowners in regions with hot summers and cold winters. Dry floor heating offers advantages such as space-saving, fast heating, and high comfort. It effectively addresses common quality issues of wet floor heating, such as maintenance difficulties and poor leakage control.
??4.2.9. Overall ventilation integration technology
??This project utilizes separate exhaust systems for bathroom waste gas and kitchen fumes to prevent cross-contamination in the shared ventilation ducts. Additionally, negative pressure fresh air technology is employed, creating a negative pressure environment indoors using exhaust devices. This allows each room to naturally receive fresh air through individual air inlets.
??4.2.10. Systematization of doors and windows
??This project adopts independently developed systematization of doors and windows, which have significantly improved performance compared to ordinary doors and windows in terms of wind pressure resistance, water tightness, air tightness, energy efficiency, and sound insulation. The heat transfer coefficient of the windows can reach 1.0 W/m2?K, and the handle can be opened and closed over 120,000 times or more.
??Figure 4: Integration technologies of long-life sustainable housing applied in Xinqiao Fengqing Block
??4.3.1. Double-superimposed shear wall system
??The long-life sustainable housing system does not impose mandatory requirements for load-bearing walls to be constructed using prefabricated or cast-in-place wall panels, but they must meet the durability requirements of a 100-year lifespan. This project adopts double-superimposed shear wall system, which is imported from Germany. After years of technical accumulation and practical engineering projects testing, double-superimposed shear wall system has been proven to enhance safety, durability, and seismic performance of residential structures, with a design service life exceeding 100 years.
??Double-superimposed shear wall system offers fast construction speed and high precision, with excellent waterproofing performance. Since the components are prefabricated in factory, it avoids common quality issues such as honeycombing, rough surfaces, and air voids that can occur during concrete pouring. This system reduces maintenance costs throughout the lifespan of residential building and fulfills the requirement for “longevity of construction” of long-life sustainable housing system.
??Figure 5: Double-superimposed shear wall system
??4.3.2. Quick-mix decoration plaster system
??The problem of external insulation detachment has been a historical challenge affecting the living experience of residents. It is also one of the most common complaints regarding housing quality. To address this issue, internal insulation of external wall is adopted, which fundamentally solves the durability problem of insulation detachment. In addition, external wall surface is covered by quick-mix decoration plaster system imported from Germany. This system has a clear process, is environmentally friendly, and free from pollution. It offers excellent weather resistance, self-cleaning properties, and prevents issues such as detachment and cracking, thereby extending the lifespan of external walls.
??Figure 6: Layered diagram of quick-mix decoration plaster system
??4.3.3. Evaluation of building energy consumption
??The current building energy consumption measurement standards implemented in China still use the K-value system, which has been in use since the 1980s. According to this system, as long as the K-value of different parts of the building envelope, such as doors, windows, walls, roofs, floors, and ground, meet the relevant specifications, the entire building is considered to meet energy efficiency requirements. However, there is no unified measurement indicator for comprehensive energy efficiency of buildings, and there is a lack of actual measurement data on the overall thermal insulation performance of buildings. Building energy consumption indicator Q-value refers to the heat loss per unit area per hour with a temperature difference of 1°C between the interior and exterior of the building. It is measured in W/m2?K, and a lower Q-value indicates better thermal insulation performance. The Q-value is a measurement index for the building overall thermal insulation performance, which is more comprehensive and accurate than the K-value.
??After the completion of this project, an identical two-story long-life sustainable housing was constructed in Baoye Group's full-scale environmental laboratory. Comprehensive energy consumption testing was conducted to measure the Q-value of the test building. Results revealed that long-life sustainable housing achieved an energy saving rate of 53.9% compared to traditional buildings in China, which demonstrates the effectiveness of long-life sustainable housing technology system in reducing energy consumption during building operation.
??Satisfying the transition from “having a house” to “living in a good house”, addressing common quality issues that affect residential comfort, and reducing energy consumption over the entire lifespan of buildings are significant challenges for the sustainable development of housing in China. The long-life sustainable housing technology system offers a solution to these problems. As the first demonstration project in Zhejiang province, Xinqiao Fengqing block fully utilizes mature research achievements of long-life sustainable housing technology in four major systems: structure system, external protection, equipment pipelines, and inner decoration, creating a safe, healthy, long-lasting and comfortable living environment. During the implementation of this project, innovative technology developed by Baoye Group, which has been deeply cultivated for many years on the path of building industrialization, was also fully utilized, injecting new blood into the development of long-life sustainable housing technology system.
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