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Opinions and Proposals on Energy Conservation in Buildings
2006-12-13
By Zhou Hongchun
Research Report No 221, 2006
Along with the rapid development of industrialization and urbanization, the total energy consumed is increasing quickly in China, so energy conservation has become one important task for our construction of resource-saving and environmental-friendly society. The Outline of the 11th Five-Year Plan takes the 20% reduction of energy consumption per unit GDP as an important constrained index and embodiesthe determination of the central government to push forward energy conservation work. However, to reduce energy consumption per unit of production value really needs great efforts. This paper puts forward some opinions and proposals on energy conservation in buildings, which is an important field that cannot be neglected in energy conservation work.
I.Connotative Meaning of Constructional Energy Consumption and the Gap between China and Other Countries
Connotative meaning of constructional energy consumption is interpreted by its narrow sense and broad sense. Constructional energy consumption in a narrow sense refers to the energy consumption in the use of buildings, mainly in heating, air-conditioning, elevator, hot water supply, household appliances and office equipment. Constructional energy consumption in a broad sense refers to the energy consumption during the material production and construction process in addition to the constructional energy consumption in a narrow sense. Accordingly, the connotative meaning of constructional energy conservation also can be divided in this way. This paper mainly discusses energy consumption and constructional energy conservation in a narrow sense, and extends it to the broad sense when necessary.
Developed countries often calculate energy consumption in terms of four sectors: industry (material production and construction are included), transportation, commerce (office building, hotel, shopping mall, hospital and school), and civil use (residential building). Both commercial and civil energy consumption are commonly called as constructional energy consumption, that is to say, constructional energy consumption in Western countries mainly refers to its narrow sense.
Amongst all aspects of constructional energy consumption, heating and refrigerating account for a considerable proportion. Let’s look at the energy consumed for heating firstly. According to the research conducted by Academician Jiang Yi of Tsinghua University, the energy consumed for heating accounts for over 50% of theconstructional energy consumption in north China; As for those buildings built before the relevant standard of constructional energy conservation was implemented,the winter average heating index is 30-50W/m2. With regard to energy consumed for refrigerating, some experts estimate that China’s refrigerating load of air conditioners is 45 million KW in 2002, equivalent to 2.5 times’ the generating capacity of the Three Gorges Power Stations. With the fast increasing quantity of household air conditioners, the energy consumed for refrigerating in China will be increased continuously.
With regard to building type, energy consumed in public building is much more than residential building. According to relevant study, the public buildings in Beijing, which occupy 41.5% of the total buildings, consume 78.2% electricity of the city’s total.
From the facts above, most constructional energy consumed is for heating and refrigerating in the use of buildings, especially public buildings. Therefore, constructional energy conservation should focus on heating and refrigerating especially in public buildings.
Compared with developed countries, China has made few improvements in constructional energy conservation. For example, in Germany (which has similar weather conditions to Beijing in winter), the energy consumed for heating per square meter in buildings has decreased from 24.0-30.8 kg of coal equivalent (kgce) before 1984 to 3.7-8.6kgce in 2001, with a decrease of over 2/3; while that in Beijing is always 22.45kgce. The energy consumed for heating in buildings in north China is 2-3 times than that in the Northern Europe under same weather conditions. The heat- preservation function of building enclosure of most domestic buildings is far inferior to that in the developed countries with similar weather: Heat Conductivity Coefficient (HCC) of exterior wall is 3.5-4.5 times of overseas levels, HCC of exterior window is 2-3 times of overseas levels, HCC of roofing is 3-6 times of overseas levels, and air permeability of door and window is 3-6 times of overseas levels. These also show the great potential of constructional energy conservation in China.
II. Significance of Constructional Energy Conservation
Constructional energy consumption plays a significant role in the total energy consumption of a country. Take USA for example. In 2000, its constructional energy consumption occupies 38.9% of the total energy consumption and becomes the largest sector of energy consumption superior to industry (33.3%) and transportation (27.9%). China has not unified the statistics scope of constructional energy consumption. From the statistical yearbook of energy consumption by industry (See following table), in 2004, the energy consumed for wholesale, retail trading and catering trade, living consumption and other purposes accounts for 16.8%, and exceeds 20% if in addition to warehousing & post and telecommunication and construction industries.
Energy Consumption Total and Proportion by Industry in China
Based on the historical experience of developed countries, the proportion of constructionalenergy consumption in total energy consumption was increased along with the increase of income per capita. For example, Japan’s energy consumption proportion for industry, transportation and construction in the total are 62.5%, 16.4%, and 18.1% respectively in 1973 and change to 46.3%, 24.3%, and 26.8% respectively in 2003.[1] The reason is obvious: in a certain period of economic development, along with the increase of income per capita, per capita living space will be increased, so people will require more comfortable indoor environment, including appropriate day lighting, temperature, humidity and ventilation conditions. Consequently, it is unavoidable for China to increase the proportion of constructional energy consumption greatly in the future, and constructional energy conservation will show its significance gradually.
Because China is in the rapid progress of urbanization, the construction of urban housing has entered into a peak stage. Take residential building for example. During the 5 years from 1998 to 2002, the annual average completed residential buildings reached 680 million m2, while during the 29 years from 1950 to 1978; accumulated residential buildings were 530 million m[2] only. Namely, the annual completed residential buildings of today are the total of past 30 years. Under such circumstances, if the proportion of energy effective buildings could not be increased as soon as possible, energy resources would certainly be wasted greatly.
To save the constructional energy consumption will ease the pressure on energy supply, transportation and environmental protection in China. The energy reserves such as coal, petroleum, and natural gas on earth are limited and non-renewable. They are reduced as much as they are exploited. To save the constructional energy consumption can prolong the service life of energy resources and support sustainable development of economy with sustainable utilization of resources. Fossil energy resources such as coal produce a large amount of CO2, SO2 and suspended substances in the process of combustion, and these harmful gases and dusts harm human health. Using air-conditioner largely not only increases power consumption but releases a large amount of heat to intensify the heat island effect in city. So to save the constructional energy consumption is to protect environment.
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[1]MakitoTakami: Energy Conservation Management and Countermeasures in Japan, International Symposium for Energy Conservation and Legislation.
[2]It is calculated based upon the following data in the report made by Chen Jinhua on behalf of Housing System Reform Leading Group of the State Council: "In the 12 years from 1979 to 1990, nationwide urban newly-built housings are 1.5 billion m2…74% of the total from 1950 to 1990". See Chen Jinhua’s "Summarize experience earnestly and push ahead reform of the urban housing system in an active and steady manner", Reform of Housing System in China, Beijing: Reform Press, Dec.1996.
