## 1 Introduction  
Climate change has become a worldwide issue and buildings account for over 40% of global energy consumption, a figure which is still rising [1; 2]. Building sectors can potentially make significant reductions in greenhouse gas emissions compared with other sectors. Energy efficiency in the built environment can make great contributions to a sustainable economy [3]. In addition to minimizing energy requirements, sustainable buildings should also be designed and constructed to reduce water consumption, use low environmental impact materials, reduce wastage, protect the natural environment, and safeguard human health and wellbeing [4; 5]. In China, there are about 600 million people living in rural areas. With the economic development over the last several decades, people in these areas have been building new houses, and a great amount of energy consumption is expected as a consequence of the growing living standard [6]. A report of building energy efficiency in rural China by [PERSON] et al. [7] found that most of these buildings are very energy inefficient. [PERSON] et al. [8] and [PERSON] et al. [9] also reported energy and environmental situations, challenges, and intervention strategies in Chinese rural buildings. They found that the walls are typically built of solid bricks and single-layer glass windows with large window/wall ratios being commonly used in northern China. The energy consumption per household in northern China can be 10 times as much as that in southern China. Although a large amount of energy is consumed for space heating in northern China,the indoor thermal environment is still poor and does not meet the thermal comfort requirement of the occupants [10; 11]. Rural energy inefficient buildings, however, are not just a concern in China, which is a developing country; as reported by [PERSON] et al. [12] and [PERSON] et al. [13], the level of fuel poverty in the United Kingdom increased rapidly from 2003 to 2010 due to the dramatic increase in electricity and gas prices. Fuel poverty is when people are unable to adequately heat their homes due to a lack of resources and because of the inefficiency of house insulation and heating. Fuel poverty in China should be addressed because poor thermal comfort can lead to respiratory problems, circulatory problems, pneumonia, etc. [14]. To increase building energy efficiency, common measures such as the cavity wall, roof insulation, double glazing, low-emissivity glass, and draught proofing can be used [15]. [PERSON] et al. [16] reviewed many methods which can be used to improve the energy performance of residential buildings. These measures can potentially solve energy efficiency problems in buildings; however, they need to be adapted to the local environment, building types, and occupants' habits. To achieve an optimal building design, the overall concept of the construction needs to respond to the local environment and the intended use of the building. As pointed out by [PERSON] et al. [17] and [PERSON] et al. [18], a profound understanding of the reaction of a building to the specific climate and user's behavior is important in holistic building climate designs. Building form can affect energy consumption. [PERSON] and [PERSON] [19] highlighted that the vertical and horizontal geometric proportions are sensitive factors related to building energy use. Larger surface-to-volume ratios increase heat transfer through the building envelope by conduction and convection. [PERSON] et al. [20] conducted research on the effect of the ratio of building width to height on the convective heat transfer coefficient at the windward facades. They found that the convective heat transfer coefficient reduces when the building's width/height ratio increases. It was explained that the wind blocking effect is more pronounced for wider buildings, and the time that air is in contact with the upstream building facades increases, which therefore decreases the temperature difference between the air and the windward facades.