It is important to consider reducing energy use while improving occupants’ indoor thermal comfort. The actual thermal comfort needs and demands should be considered to determine the indoor thermal environment design. In previous studies, research has not been carried out on thermal comfort in karst areas. Thus, a long-term field investigation was carried out on multi-storey residential buildings in the karst area of Guilin city centre during summer (from August 2019 to September 2019) and winter (from December 2019 to January 2020). In this study, the indoor thermal environments of three categories of dwellings were analysed. A total of 77 residential buildings with 144 households were randomly selected, and 223 occupants from 18 to 80 years old participated. A total of 414 effective questionnaires were collected from the subjects. The results show that there was an obvious conflict between the predicted mean vote (PMV) and the thermal sensation vote (TSV). The neutrality temperatures calculated by the regression method were 24.2 °C in summer and 16.2 °C in winter. The thermal comfort range was observed at operative temperatures of 20.9–27.5 °C in summer and 12.2–20.1 °C in winter. The desired thermal sensation for people in the Guilin karst area was not always reflected in the thermal neutrality range. A preference for warmness was identified in the survey.

Human thermal comfort presents noticeable variation across urban and rural areas. Among previous studies, only a few field investigations focus on thermal comfort experienced by rural houses within hot summer and warm winter (HSWW) zones, especially across the north area. The existing thermal environment and energy-saving standards in China make it difficult to provide accurate guidance for building performance design in this area due to the lack of thermal comfort information for humans. This study undertook a field-based survey in rural houses in Hezhou, located in the northern part of an HSWW zone in China. Both on-site environmental data collection and subjective surveys were performed at the same time. Subsequently, this study examined the correlation of operative temperatures with subjects’ perceptions of the thermal environment. Our findings indicate that the actual neutral temperature in summer was 25.34 °C, whereas the predicted value was 25.17 °C. Temperatures within the range of 21.69~30.55 °C were considered acceptable during the operation. The elderly had a higher thermal tolerance than the adults. There was no significant statistical difference between males and females. Our findings contribute to the ongoing development of thermal comfort research for rural housing.

Considering the perovskite-based building-integrated photovoltaics, we use the single box model of 4 × 4 × 3 m³ to illustrate a promising solution for the zero-energy residential building and the distributed power generators in the Wuhan urban area in China (N30° E114°), where we have the high ratio of façades on the tall buildings. According to our estimation, the energy gains from the solar cells on the façades could be competitive with the ones on the rooftops. In comparison with the perovskite/silicon tandem solar cells, the perovskite-based single-junction solar cells could boost the annual energy gains more than 1.5 times on the façades. It is because of the perovskite-based single-junction solar cells being less angle-dependent, even if their efficiencies under the vertical illumination are lower than that of the perovskite/silicon tandem solar cells. Within the same single box, the energy demands caused by the air-conditioning system are simulated by the program THERB with 100 and 65% solar irradiation; the previous one is the standard case, and the later one assumes that 35% of solar irradiation is converted to the electricity. To control the indoor temperature above 18°C in winter and below 26°C in summer, the single box could achieve zero-energy demand except for January and December. And the annual surplus photovoltaic energy gains of 3071 kW h could be used as the distributed generator for the resident downstairs.

The energy consumed in residential buildings has become a key factor in China. An energy-efficient and low-emission fuel cell co-generation system (FC-CGS) is a promising electric and thermal energy generation technology to enhance the energy-saving effects for residential application. SOFC-CGSs and PEFC-CGSs are the two major types of residential FC-CGSs. This paper aims to analyze the energy-saving effects of FC-CGSs for residential buildings in Chinese hot summer and cold winter areas. Changsha city is selected as an example. This study at first outlines SOFC-CGSs and PEFC-CGSs, introduces the simulation methods and develops a standard family model for simulation, then calculates domestic demands of the system, and finally compares the primary energy consumption and CO2 emissions of FC-CGSs with those of a traditional power and heat generation system based on gas and electricity. The results show that residential PEFC-CGSs offered primary energy reduction of 8.8% in winter. However, the average reductions of primary energy and CO2 emissions of SOFC-CGSs were 15.1% and 9.9%, respectively.

Passive design, which includes several passive design strategies like shading devices and insulated envelop, is the most economical effective strategy for reducing energy consumption inside residential buildings. To investigate the impact of passive design on building thermal performance, a representative city Wuhan in Chinese hot summer and cold winter areas was selected for optimum analysis. The design parameters required for the climate of Wuhan using the Climate Consultant Software and passive strategies were analysed through the DesignBuilder Software in this paper. The results show that the optimization of passive design could reduce the annual primary energy by 52.2%. It will guide the architect in his choice of appropriate passive measures directly for the hot summer and cold winter region in China.