Over the last 20 years, statistics show, the winter temperature of Japanese homes has risen by between 5° to 10º centigrade. This reflects the rising living standards that have accompanied economic growth in Japan, and shows how domestic energy consumption grows with the increasing comfort of the home. The same process has already taken place in the United States and the developed countries of western Europe.
China is currently going through a period of continued rapid economic development. People’s living standards are rising continuously, and with them, the amount of energy consumed by buildings.
Figure 1 (below) shows the change in energy consumption per square metre (excluding energy for heating) of urban public buildings over recent years:
Fig. 1. Building energy consumption per square metre for urban public buildings (excluding energy used in heating)
Recently, many builders have begun to construct luxury homes that use central air-conditioning systems to provide constant temperatures and levels of humidity the whole year round. Although some of these residences make use of advanced energy-efficiency technology, their air-conditioning systems still consume – for a number of reasons -- far more energy than those in standard home. These systems work over the whole home, rather than in selected areas; they operate continuously, rather than intermittently as needed; and the windows are sealed shut, so are unable to provide natural ventilation.
In southern China, residential compounds have appeared which have a central air-conditioning system for the whole compound. This has led to a huge rise in energy consumption. Patterns of use of domestic appliances also have started to change, leading to further increases in households’ energy consumption. Detached houses, which are becoming popular, especially in the north, not only take up more land per household, but also increase the building-surface area per home. This means that they consume far more energy than normal urban flats.
Meanwhile, ordinary office blocks are increasingly being replaced by “modern” office buildings and various kinds of “landmark” buildings. Such buildings are slowly becoming the norm in non-residential urban construction. Although they usually consume many times more energy than ordinary office blocks, all kinds of new buildings – whether offices, schools or university dormitories – are trying to keep up with demands to “attain international standards” and “stay advanced for thirty years”. They are large in size and use central air-conditioning systems, and most of them also use mechanised ventilation systems that make them reliant on large amounts of energy. At the same time, many of the older ordinary public buildings are being renovated and fitted with central air conditioning and sealed windows, turning them from low- to high-energy consumers.
So, we have to ask ourselves a question: in what direction will building energy consumption in China develop? Will we follow the path taken by the US, western Europe and Japan, whereby as the economies grew, people gradually moved into energy-intensive homes and offices? Or will we persist with our current standards of less energy-intensive homes and offices, and even lower our per-square-metre energy consumption through increased social awareness and the use of new energy-efficient technologies?
The question needs to be answered, and the solutions have to be put into practice. If energy-intensive homes and offices become the norm, then with urban construction increasing at a rate of 7% to 8% a year as it currently is, we will follow in the footsteps of the US, western Europe and Japan. And by then it already will be too late to start thinking about the problem.
Our urban development is taking place under completely different conditions to urban development in the US, Europe and Japan. Levels of natural resources to which we have access -- especially sources of energy -- are far lower than those enjoyed by the developed countries in their periods of development. The pressure on us to protect the environment is far greater than it was for the developed countries.
1· What are the limits placed on urban construction by the volume of natural resources to which we have access? While satisfying the demands of society and the economy, we have to restrict the scale of urban construction as far as possible.
2 · Homes and offices built in the future can never be allowed to “attain international standards” in terms of energy consumption. This means that we must find a path to development that is different from the developed countries – an energy-efficiency plan with “Chinese characteristics” which allows us to maintain building-energy consumption at today’s low levels.
In reality, does the model pursued by the developed countries – expending huge amounts of energy for the interior environment – actually provide people with comfortable and healthy surroundings? According to wide-ranging research carried out in luxury offices in developed countries, and recently in China, the answer is no.
In the mid-1980s, “sick building syndrome” (SBS) was first identified in luxury offices abroad. People working in these offices reported deterioration in health, a tendency to develop allergies, difficulty concentrating and tiredness. Of the large office blocks surveyed in Europe and North America, almost 50% were found to have problems. Also, “the higher the initial investment in the building, and the higher the running costs, the more serious was SBS”.
Twenty years of multi-disciplinary research has identified many causes of the problem. It is commonly agreed that interior spaces that are too sealed-off from the outside do not provide enough air circulation, which causes accumulation of various pollutants and a drop in air quality. Researchers also believe that constantly maintained temperatures and rigid air-circulation systems are another cause of problems.
Two different solutions to the problem are proposed. One is to mechanise even further, and increase the number of mechanical ventilation systems in order to guarantee enough air circulation. This would lead to further increases in energy consumption. The other is to totally rethink the interior environment – to use various methods to increase natural ventilation, and go back to a more traditional style of building with a focus on natural adjustment. When all else fails, mechanical systems can be used in a supplementary fashion. In some respects, this represents a return to the energy-efficient office buildings that we are advocating.
Similar trends have occurred in residential buildings. With the rise in quality of homes and the emergence of new decorating materials, there have been many cases of people’s health being threatened by poor indoor air quality. The main problem with new buildings and newly refurbished homes is bad odours. Apart from strict controls on materials used for furniture and decoration to reduce the amount of indoor pollution created, the most effective method of improving indoor air quality is guaranteeing sufficient levels of ventilation and air renewal.
Again, there are two different ways of thinking about the problem, which lead to different solutions. One is to guarantee a large enough surface area of windows that can be opened to provide sufficient natural ventilation. A similar approach can be taken when controlling indoor humidity levels; natural methods should be given priority in moderating the indoor environment, and supplementary mechanical systems can be used in certain spaces at certain times, as and when they are needed. The second, “mechanist”, solution is to provide specialised air-renewal systems that require windows to be shut and which moderate temperature and humidity over the whole area, 24 hours a day, 365 days a year.
The former solution brings us closer to nature by working in harmony with nature, and reduces the amount of energy consumed in the operation of buildings. The latter goes a step further in cutting off our relationship with nature, and increases energy consumption. One also has to wonder whether these totally artificial indoor spaces might create more health problems.
The two different ways of thinking produce different kinds of buildings, and different systems for the moderation of the indoor environment. They also represent a fork in the road towards different levels of building-energy consumption. A modernising, urbanising China, with limited energy sources and natural resources, has to promote energy efficiency in architecture. This is an issue which deserves the close attention of government, industry and, indeed, all urban residents.
Jiang Yi, professor at Tsinghua University and an academician of the Chinese Academy of Engineering, is an expert on building and environmental engineering. He is noted for his research on power-saving buildings and ecological construction.