# Building Energy Retrofit Measures in Hot-Summer-Cold-Winter Climates: A Case Study in Shanghai
## 3 Background Study: Building Energy Consumption and the Climatic Context in Shanghai
### Building Energy Consumption in Shanghai and Beyond  
By way of their function, buildings consume much energy, particularly for occupant activities, facilities, comfort and lighting. Building energy consumption primarily depends on building typology among other factors [37]. According to the US Energy Information, residential buildings are more dominant in terms of energy use [38]. However, commercial buildings have a significant share and will probably increase their energy use tremendously in coming decades when compared with the  
Figure 4: Impact of climate change in the city of Shanghai (**a**) annual average temperature change [32] (Presented temperatures are the annual average temperatures for the entire year) and (**b**) hourly temperature variation in summer for different periods [34]. 2003 baseline. A comparison of building energy usage with building typology in a different urbanising country is presented in Figure 5. In the US, commercial buildings consumed about one-third of the country's primary energy consumption in 2003 [39; 40] and were estimated to rise to about 45% by 2030. In China, energy consumed by commercial buildings is expected to increase from 400 TWh (in 2003) to about 1000 TWh (in 2030). Major reported consumers of building energy are HVAC systems--lighting and heat exchange systems. In the US, HVAC systems account for about 35% of building energy consumption [41]. In Canada, 54% of whole-building energy consumption is for heating and 6% for cooling; while equipment, lighting and hot water systems account for 20%, 13% and 7%, respectively [42]. In Europe, [PERSON] et al. presented that 52% and 4% of building energy usage was accounted for by heating and cooling, respectively [42]. In Greece, [PERSON], [PERSON] discerned that building energy consumption depends primarily on the immediate climate condition. Due to increasing global temperature, building heating load was found to have decreased by approximately 50%, while the cooling load increased by approximately 248% [43]. Therefore, HVAC and lighting systems are considered essential parameters in designing energy and emissions savings measures for existing buildings [41; 44]. In China, annual energy consumption similarly peaked from 571 million to 4.64 billion tons of coal equivalent (TCE) from 1978 to 2018. Carbon emissions increased from 400 million to 7.95 billion tons representing an increase from 6% to 20.3% of the world's total, making China the world's largest emitter [45]. Buildings are critical consumers of energy accounting for 30% of total national energy consumption, which is projected to rise to 35% by 2020 [46; 47]. Energy consumed by heating and cooling contributes a significant share (approximately 65%) to the total building energy consumption [47]. As a result, China has devised various policies to economically transform and sustain environment development by reducing the energy demand across all sectors, particularly architecture and built environment [48]. Hence, the proposal on energy-efficient buildings as a means of carbon mitigation poses not only a challenge to China's economic development, but also creates crucial economic transformation opportunities for achieving sustainable environment development. As the economic centre of China, carbon emissions associated with high energy consumption has posed immense pressure on Shanghai. Data from Shanghai Municipal Statistics Bureau [36; 49] shows that electricity, coal gas, liquefied petroleum gas (LPG) and natural gas, which are significant generators of CO\({}_{2}\), are the primary sources of building energy in Shanghai. Electricity is considered the primary source of energy with 3253.6 kWh/household [50]. Figure 5(a) shows the total energy consumption over the past 46 years. Figure 5(a) depicts a slow growth rate in annual energy consumption from 1970 to 2000. After this year, energy consumption grew faster than ever until 2013 when it gradually slowed down. Figure 5: Building energy projection by region 2003–2030 [38].