Chinese Residential Buildings Research Articles

Optimal HVAC Setpoints for Energy Efficiency and Thermal Comfort in Chinese Residential Buildings

The easiest way to improve energy efficiency and thermal comfort in existing buildings is to adjust setpoints. However, although Chinese standards regulated the heating and cooling setpoints for different climate zones in China, they lacked consideration for occupants’ thermal comfort and ignored the ventilation setpoints. Therefore, this study aimed to identify optimal heating, cooling, and ventilation setpoints at the design stage to enhance building energy performance and indoor thermal comfort in Chinese residential buildings. This study used DesignBuilder to simulate the energy usage and thermal comfort with different setpoints and judged which combination was the best. To conduct this study across the whole of China, the typical cities in different climate zones were selected by using machine learning. Results indicated that adjusting setpoints in Harbin, Beijing, and Shanghai could increase comfortable days by 43.95%, 54.23%, and 23.36% respectively, with minimal impact on energy usage. In Guangzhou, energy usage could be reduced by 7.56% with a 5.91% decrease in comfortable days, while Kunming could see an 11.11% increase in comfortable days with a 5.92% rise in energy consumption. Additionally, sensitivity analysis revealed that activity template variation was most critical for energy usage in Harbin, Beijing and equipment power density variation was most important for thermal comfort in Shanghai, Guangzhou, and Kunming. Furthermore, proposed setpoint combinations demonstrated resilience to future weather conditions in most typical cities, except for Guangzhou. These findings provide valuable insights for designers and researchers aiming to retrofit residential buildings, emphasizing the importance of considering both energy efficiency and occupant comfort. This study introduces innovative approaches like comprehensive setpoint optimization and machine learning for typical city selection, providing practical solutions to improve energy efficiency and thermal comfort in residential buildings.

Research on intelligent monitoring technology for roof damage of traditional Chinese residential buildings based on improved YOLOv8: taking ancient villages in southern Fujian as an example

In the process of preserving historical buildings in southern Fujian, China, it is crucial to provide timely and accurate statistical data to classify the damage of traditional buildings. In this study, a method based on the improved YOLOv8 neural network is proposed to select aerial photographs of six villages in Xiamen and Quanzhou cities in Fujian Province as the dataset, which contains a total of 3124 photographs. Based on the high-resolution orthophotographs obtained from UAV tilt photography, the YOLOv8 model was used to make predictions. The main task in the first stage is to select the buildings with historical value in the area, and the model's mAP (Mean Accuracy Rate) can reach 97.2% in the first stage task. The second stage uses the YOLOv8 model to segment the images selected in the first stage, detecting possible defects on the roofs, including collapses, missing tiles, unsuitable architectural additions, and vegetation encroachment. In the second stage of the segmentation task, the mAP reaches 89.4%, which is a 1.5% improvement in mAP50 (mean accuracy) compared to the original YOLOv8 model, and the number of parameters and GFLOPs are reduced by 22% and 15%, respectively. This method can effectively improve the disease detection efficiency of historical built heritage in southern Fujian under complex terrain and ground conditions.

Sustainable-Driven Renovation of Existing Residential Buildings in China: A Systematic Exploration Based on Review and Solution Approaches

Under the backdrop of China’s national strategy to achieve carbon neutrality by 2060, efforts are underway across governmental, corporate, societal, and individual sectors to actively explore energy-saving renovations in existing buildings. Given that residential buildings constitute a significant proportion of the total energy consumption throughout the lifecycle of buildings in China, sustainable renovation of residential structures can contribute significantly to implementing China’s carbon emission reduction policies. While there exists a plethora of technological means in the market aimed at improving the energy performance of residential buildings, there still needs to be a more systematic discussion on the framework for sustainable renovation of existing Chinese residential buildings, with knowledge dissemination still needing to be more cohesive. In this context, this paper provides a comprehensive review of the field, utilizing bibliometric methods. Through a systematic review of selected peer-reviewed literature from the Web of Science and Scopus databases, the study focuses on the sustainable renovation of existing Chinese residential buildings, categorizing the process into three main stages: sustainable renovation, building performance simulation and suitability assessment. The paper also reviews the research methods adopted by previous researchers in the renovation, simulation and assessment stages, considering various optimization algorithms, variables, objectives, and software tools. Subsequently, the paper synthesizes a research framework comprising these three stages combined for different research objectives, aiming to assist policymakers, designers, and researchers in gaining a comprehensive understanding of the implementation status of sustainable renovation in existing Chinese residential buildings, identifying barriers to implementation, and formulating more efficient renovation policies and strategies for the future.

Research on the Indoor Thermal Environment of Several Traditional Chinese Residential Buildings

To study the indoor thermal environment characteristics and influencing factors of traditional Chinese residential buildings, the existing research studies on the indoor thermal environment of traditional residential buildings were collected and organized, and the relevant measured data was extracted using GetDate software. After data analysis, the construction characteristics of brick and wood structures, wood structures, and raw soil structures were summarized. The indoor and outdoor temperature changes of the residential buildings in summer and winter were revealed. Finally, the indoor thermal environment characteristics and influencing factors of three types of traditional residential buildings were summarized. The research results can provide a reference for the construction and low-carbon renovation of traditional residential buildings.

Effect of thermal bridges on the energy performance of Chinese residential buildings

Thermal bridges may represent up to 50 % of the building's envelope area and may increase the energy consumption of buildings by up to 30 %, however their impact is often not taken into account adequately in China. In this study, the energy performance of a typical two-story residential building under four different Chinese climate zones is investigated using WUFI Plus program in terms of annual heating and cooling energy demands. Several typical thermal bridges were taken into consideration. Two methods were used to evaluate the effect of thermal bridges on the building energy performance, the simplified method commonly used in China and the dynamic 3D modelling method, and were compared to do not consider thermal bridge. Also, two different types of building envelope, brick wall and aerated concrete wall, were used to evaluate the effect. The results show that by taking into account the thermal bridges, the annual heating energy demands of residential building increase 21.2 %, 24.8 %, 27.8 %, and 16.6 % under the four Chinese climate zones. Therefore, attention should be paid in the building envelope design to reduce thermal bridges. Compared to the dynamic 3D modelling method, the simplified method underestimates annual heating and cooling energy demands.

Equilibrating provincial carbon increments for residential buildings in China under carbon peaking constraints

The speedy raise of residential buildings' carbon emissions is a hindrance to achieving China's 2030 carbon peak goal. This study constructs an assessment framework for comprehensive consideration of 30 Chinese provinces' socioeconomic circumstances, energy demand, and emissions reduction technology to meet the consistent coupling degree of equity and efficiency (CDEE). This study is the first to propose an allocation scheme for equilibrating provincial carbon increments for rural and urban residential buildings in 2030 under carbon peaking constraints. The relevant results are fourfold. (1) Residential building's floor area per capita and energy carbon emissions coefficients are the soliddest drivers to facilitate and inhibit the raise of carbon emissions during 2010–2020. (2) Through dynamic Monte Carlo simulation from 2021 to 2030, we demonstrate that provinces with the most gamey carbon emissions in urban and rural areas include Shandong, at 121.52 (± 5.50) Mt. and Hebei, at 61.34 (± 3.08) Mt. in 2030, respectively. (3) A CDEE of 52.3% (biased equity) in urban areas and 34.5% (biased efficiency) in rural areas indicates equilibrated allocation of provincial carbon increment. (4) In the final 2030 allocation scheme, the greatest carbon mitigation pressures are in Beijing (11.34 Mt) and Heilongjiang (3.23 Mt), and the provinces with the largest carbon increment in urban areas include Hebei, Henan, and Guangdong, while the largest carbon increments in rural areas are in Hebei, Henan, and Guangdong. Overall, this study furnishes a targeted and valuable decision making reference for the government to determine provincial carbon peak goals for Chinese residential buildings.

A systematic review on thermal environment and thermal comfort studies in Chinese residential buildings

Amid the backdrop of the energy crisis, thermal comfort is crucial to achieve energy savings. Residential buildings are characterized by a wide range of adaptive comfort opportunities. However, there has been a lack of systematic refinement and review of residential thermal comfort field studies in China to provide valuable recommendations for energy conservation. We systematically reviewed studies on thermal environment and thermal comfort in Chinese residential buildings published in peer-reviewed journals up to 2020. A total of 34 studies were deemed to have provided sufficient information on both the thermal environment and thermal comfort. We found that in winter, there were obvious differences between urban and rural dwellings in Severe Cold (SC) and Cold (C) zones, with regard to their indoor air temperature (urban: 19.8 ∼ 25.0 °C v.s. rural: 11.3 ∼ 17.8 °C) and neutral temperature (urban: 17.6 ∼ 25.1 °C v.s. rural: 11.9 ∼ 23.45 °C). While in summer, the indoor air temperature in urban dwellings were slightly lower than those in rural areas due to their prevalent use of air conditioner (urban: 26.1 ∼ 28.9 °C v.s. rural: 29.5 ∼ 34.9 °C). Indoor air temperature and neutral temperature varied considerably in different climate zones in winter. In SC zones, the indoor environment was overheated, which could lead to energy wastage and overheating discomfort for residents. Residents in Hot-Summer and Cold-Winter (HSCW) zone were the most tolerant to the variation of thermal environment (the median coefficient of MTS or TSV equation: SC: 0.18; C: 0.20; HSCW: 0.13; HSWW: 0.23).

The Effect of Climate Factors on 400 Years of Traditional Chinese Residential Building Roof Design: A Study from Southwest China

Indigenous people have used architecture over millennia to adapt to climatic factors and achieve stable and comfortable living. These adaptations can still inform the design of contemporary regional architecture. In order to explore the relationship between traditional dwellings and climatic factors, we examine buildings in four provinces and cities in southwest China. A database was created using detailed data obtained from the literature on indicators of climatic factors (e.g., temperature, precipitation, temperature difference, wind speed, solar radiation) and architectural elements (e.g., roof slope and eave length). Thorough statistical analysis shows that (1) MPWM has the most significant correlation with the slope angle of traditional building roofs but is not recommended as a predictor in multivariate equations. (2) Temperature and wind speed were significant correlates of roof slope, and a multiple regression model dominated by AMT and AWS serves as a good predictor of roof slope. (3) Solar radiation was not correlated with roof slope but was the largest correlate of eaves length in traditional buildings. AMSR and AWS also dominantly affect eaves length in a regression relationship. These results serve not only as a reference to catalog the use of traditional passive technologies but can guide the design of green buildings. However, more research is needed to refine the use of passive technologies to adapt to climate change

The effectiveness of kitchen ventilation for organic gaseous compound control in Chinese residential buildings

The health hazards of cooking oil fume (COF) exposure underscore the importance of effectively controlling air pollution in kitchens, especially during cooking. The effectiveness of ventilation for gaseous pollutant control deserves more attention due to its toxicity, odor and strong diffusivity. In this study, field measurements of 23 carbonyl compounds before and during cooking in 120 Chinese residential kitchens were carried out to obtain carbonyls pollution status during cooking and to explore the effectiveness of kitchen ventilation for gaseous compounds. Carbonyls were actively sampled by dinitrophenylhydrazone adsorption tubes and analyzed by high performance liquid chromatography (HPLC) to accurately determine the concentrations. Overall, the mean concentration of total carbonyls was 496.2 μg/m3 during cooking with the range hood turned on, among which formaldehyde (153.6 μg/m3), acetaldehyde (121.3 μg/m3), and acrolein & methyl isobutyl ketone (92.8 μg/m3) had the highest mass concentration proportion (a total of 74%). Even with the range hood on, the carbonyls concentration could increase by approximately 200 μg/m3 under “Door Close, Window Close” conditions, indicating insufficient ventilation for diluting the pollutant. If Ccooking/Cnon-cooking = 1 was considered an acceptable gaseous pollutant control criterion, only 39%, 43%, 56%, and 65% of the kitchen with ventilation rates of <15 h−1, 15–25 h−1, 25–35 h−1, and >35 h−1 met the criteria, respectively. The effective exhaust air flow rate of the 25th–75th percentiles was distributed in the range of 4.3–8.9 m3/min, and the actual mean air flow rate was only 44% of the rated air flow rate stated by range hood manufacturers. Therefore, the effective ventilation rate was still not enough for gaseous pollutants in real residential kitchens, and the organized air supplement in the kitchen is crucial to control cooking pollution.

Investigation of VRF system cooling operation and performance in residential buildings based on large-scale dataset

With the increase in the energy consumption of air-conditioning (AC) systems in Chinese residential buildings, the realization of energy savings in AC systems has attracted increasing attention. The variable refrigerant flow (VRF) system is a common AC system for residential buildings in China. In most previous studies on VRF systems, onsite measurements or surveys were conducted to collect operational data. These traditional methods may face various data issues, such as limited sample sizes and invalid data, making them unable to capture the spatial and temporal performance features of VRF systems in residential buildings on a large scale. To fill this gap, with advances in data storage and transmission technology, Big Data methods have been widely used for data collection. In the present study, researchers adopted 16,985 sets of VRF system operation data from China as the database and conducted data analysis for both the spatial and temporal dimensions. Several key indicators were proposed from the two perspectives (spatial and temporal), including the part-space index (PSI), load ratio (LR), use duration (UD), and cooling energy consumption. The main findings were as follows: (1) The “part-time part-space” operation mode of residential VRF systems can be analyzed according to the statistical results of the UD and PSI. (2) An LR of <30% is the main operating condition for VRF systems in residential buildings. (3) Extracted typical LR patterns can reflect different user behavior. The statistical results obtained in this study provide a basis for VRF engineering projects.

Gravity center change of carbon emissions in Chinese residential building sector: Differences between urban and rural area

In China, dynamic spatial–temporal evolution and urban–rural gap in carbon emissions of residential building sector are crucial for understanding the current state, which is faced with great challenges related to emission mitigation. To overcome the challenge, this study employed the gravity center model to explore spatial–temporal evolution of carbon emissions and analyzed the driving factories leading the differences between urban residential buildings and rural residential buildings via decomposition analysis. Meanwhile, Tapio decoupling index is used to predict the future movement of the gravity center. Our results indicated that: (i) the carbon emissions gravity center of both residential building types tends to move south; (ii) the northeast and northwest regions play the largest role in driving the gravity center movement of urban residential buildings and rural residential buildings, respectively; (iii) per capita disposable income is the primary factors affecting the gravity center movement. (iv) the gravity center of both residential building types might tend to move westward in the future. Overall, this study attempts to remedy the current lack of research pertaining to spatial–temporal evolution laws governing carbon emissions in the Chinese residential building sector and provides a reference point for the implementation of targeted urban and rural emission reduction policies.

Carbon Mitigation in the Operation of Chinese Residential Buildings: An Empirical Analysis at the Provincial Scale

The rapidly growing carbon emissions of residential building operations have become an obstacle to China’s commitment to achieving its carbon-neutral goals by 2060, but they also demonstrate great carbon mitigation potential. To help buildings reach carbon neutrality targets, this study decomposes the drivers of carbon emissions and evaluates the changes in carbon mitigation of residential buildings across 30 Chinese provinces from 2000 to 2018. The results indicate that (1) the operational carbon intensity increased in most provinces and the average annual growth rate across the 30 provinces was 4.2%; (2) from 2001 to 2018, North China and Northeast China had the highest average annual carbon mitigation intensity, at 602.7 and 376.9 kg of carbon dioxide per household, respectively. However, Northwest China had the highest carbon mitigation efficiency, with a carbon mitigation rate of 23.5%; and (3) in most cases, the total carbon mitigations of the operational residential buildings assessed at the provincial scale higher than those assessed nationwide, with a difference of 14.4 million tons of carbon dioxide on average. In addition, this study reviewed the energy efficiency codes for residential buildings and summarized effective energy efficiency measures. Overall, this study fills a gap in our understanding of carbon mitigation tools and provides a reference for the evaluation of historical carbon mitigation effects in the operation of residential buildings.

Simulation on air temperature and particle distribution under natural make-up air in indoor environment with a Chinese-style residential kitchen

Kitchen is an important place in Chinese residential building. However, unfavourable thermal environment and unsatisfied air quality occur during cooking. Studies on kitchen environment are experimentally investigated with enough make-up airflow. But mostly normal kitchens are merely installed with a exhaust hood and have not installed air supply system. This work carried out numerical simulation to investigate kitchen indoor environment under natural air make-ups. Air inflow under window fully open, insufficient air inflow from window crack and well-controlled constant inflow volume from window opening are included. Results show that there was a uniform temperature distribution in occupant’s working zone under window open condition. Vertical temperature differences were 4.0 °C under insufficient air make-up. In breathing zone, temperature difference was 6.0 °C and 4.7 °C under uncontrolled and well-controlled airflow, respectively. Mean particle concentration could be largely reduced under controlled and well-organized enough make-up air in kitchen.

Interstitial condensation in Chinese residential buildings: cliché or challenge?

In this paper, we compare the predictions of interstitial condensation by the steady-state method and the transient method under different climate conditions in China. Simulations reveal significant differences between the two methods, and the wind-driven rain also plays an important role. As a result, the transient hygrothermal simulation considering wind-driven rain should be recommended instead of the steady-state method for predicting interstitial condensation under complicated climate conditions.

A Preliminary Study on Green Building 3D Modelling Energy-saving Design Combined with Traditional Ecological Concepts

By combining the green ecological wisdom on traditional Chinese residential buildings, this paper summarized the ideas that can be used for references and applications in modern green energy-saving design. In addition, in view of the inherent shortcomings of traditional residential buildings, this paper proposed a green energy-saving design method for traditional residential buildings based on 3D modelling technology, which is complementary to the traditional ecological construction concept. Based on the establishment of a 3D building information model of traditional residential buildings, the optimal solution for the energy-saving design of green buildings is found through energy-saving adjustments to the building space structure and building spacing parameters.

Thermal comfort diversity in Chinese urban residential buildings across various climates

China has a vast territory with a variety of climates. Residents living in different climate zones are exposed to different indoor thermal environments in their homes and thus may have various thermal comfort levels. This study conducted a one-year campaign in 157 residential apartments in 12 cities across five climate zones in China by means of indoor thermal environment monitoring and online questionnaires in bedrooms. The study found that the severe cold (SC) and cold (C) climate regions had a warm and dry winter with median air temperature and relative humidity of around 23 °C and 25%, respectively. In summer, the cold climate region had the highest indoor air temperature among all regions. In terms of thermal sensation, more than 85% of residents voted in the middle three categories (slightly cool, neutral, and slightly warm), indicating an overall satisfactory thermal environment in Chinese residential buildings. However, residents in the hot summer and cold winter (HSCW) region reported the highest percentage of “cold” votes (18%) in winter, while those in the cold climate region reported the highest percentage of “hot” votes (18%) in summer. A “seasonal effect” was observed, by which the thermal sensation and clothing insulation in a particular season followed the general air temperature level of that season. The findings of this study are expected to contribute to the design and control of a thermally comfortable environment in residential buildings.

Evaluation of thermal imbalance of ground source heat pump systems in residential buildings in China

The thermal comfort level of Chinese residents in the hot-summer and cold-winter zone is increasing with economic development in recent years. More district heating and cooling systems were installed in these areas. Supported by the government, ground source heat pump (GSHP) is used as a common environmentally friendly district heating and cooling system in many residential communities. However, the evaluation of the real performance of GSHP is limited, especially limited understanding of the common issue of thermal imbalance of GSHP systems over several years—the mismatch between heat extraction from and rejection to the ground. Performance of GSHP systems can deteriorate over years if the thermal imbalance is significant and not addressed. For GSHP in the hot-summer and cold-winter climate zone, there are few thermal imbalance studies based on real field data and modeling. To address this gap, this paper proposes an integrated simulation model to evaluate thermal imbalance of GSHP systems considering key influencing factors including occupant behavior and heat pump performance. A case study was conducted to simulate and analyze the actual operation of GSHP in Chinese residential buildings. The indoor comfort temperature setting and flexibility of residents’ control on indoor terminal air-conditioning units determine the actual heating and cooling demand in residential buildings, which resulted in differences in thermal imbalance for GSHP systems. It was found that GSHP systems with radiant floor only for heating lead to the most severe thermal imbalance, while GSHP systems with fan coil units or radiant ceiling for cooling and/or heating achieved much better thermal balance. The proposed thermal imbalance ratio is an important indicator that can be used to evaluate thermal imbalance of GSHP systems and thus inform their design and operation for energy efficiency.

Operating behavior and corresponding performance of mechanical ventilation systems in Chinese residential buildings

The purpose of this field study was to evaluate the ventilation practices of occupants, the performance of ventilation systems and the indoor air quality in mechanically ventilated apartments by means of mechanical ventilation and indoor air quality data collection. A one-year measurement study was conducted in 36 apartments in 5 cities across three different climate zones in China. The average daily open-system operation duration in Chinese apartments was 9.1 h. Approximately 11.1% of residents tended to operate the mechanical ventilation system nearly all day. Most residents operated the system intermittently. The duration of operation increased from summer to winter as the outdoor air particulate matter (PM) 2.5 concentration increased. The average efficiency of mechanical ventilation systems was approximately 50%, and the median air change per hour (ACH) was approximately 0.56, which is much lower than the nominal value. Most mechanical ventilation systems can possibly maintain the indoor air quality of residential buildings at a moderate level. This study is expected to contribute accurate field data for mechanical ventilation system evaluation and design in Chinese residential buildings.

Concentration Levels and Impact Factors of Benzene Series in Chinese Residential Building

From December 2016 to December 2017, the concentrations of the benzene series (benzene, toluene, xylene, and ethyl-benzene) in air were analyzed in 223 residential buildings in five climatic regions of China during different seasons. The arithmetic average concentrations of benzene, toluene, xylene, and ethyl-benzene were 6.78, 17.4, 17.68, and 9.87 μg·m-3, respectively. Indoor benzene series concentrations in China were slightly higher than that in other countries; the standard limits for indoor benzene series concentrations in China are much higher than those of other countries and organizations. Among the many factors affecting the concentration of the benzene series in the rooms, the relationship between the completion time of decoration, smoking, and cooking frequency and the concentration of benzene homologues was studied. The results showed that the concentration of toluene decreased with the prolongation of decoration time, the concentration of benzene in smoking households was higher than that in non-smoking families, and there was no direct correlation between cooking frequency and indoor concentration of the benzene series. The study provides statistical data on exposure to the benzene series in decorated homes and a discussion of setting values of relevant standards.

Large-scale and long-term monitoring of the thermal environments and adaptive behaviors in Chinese urban residential buildings

Indoor thermal environments in residential buildings vary due to differences in the outdoor climates, the envelope thermal properties of the buildings, the types of heating and cooling systems, and adaptive behaviors such as the operation of air conditioners and windows by dwellers. This study comprehensively investigated the thermal environments in 46 apartments in nine cities across five climate zones in China via on-site monitoring of the indoor air temperature, the relative humidity, and the air conditioner and window use for one year. The results demonstrate large variations in the thermal environments among the cities. During the heating period, the interior air in Urumqi and Shenyang was overheated (>24 °C) 43% and 59% of the time, respectively, while the indoor air temperature in Chongqing can be lower than 10 °C. As the outdoor climate became warmer, the temperature difference between indoors and outdoors decreased due to the increased window-opening duration. In summer, the indoor humidity ratio was higher than 12 g/kg for a long time in all cities except Urumqi. A clear linear positive correlation between the indoor and outdoor humidity ratios was identified until the indoor humidity reached 18 g/kg, which was due to the increased use of air conditioners. The results of this study provide an updated overall picture of the thermal environments in Chinese residential buildings.