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Ever since the first public buildings were erected thousands of years ago, their spaces, surfaces and sounds have been designed to influence human behaviour inside and out. This ranges from the quietness of libraries, to the music in religious buildings and the ‘buzz’ of shops.
In light of climate change, perhaps the biggest challenge facing designers today - especially in the developing world - is that buildings are the largest users of energy for heating and cooling, accounting for around some 40 percent of energy consumption.
Yet most surveys show conventional modern designs, with steady temperatures and mechanical ventilation, are considered uncomfortable by around 80-90 percent of occupants. These were among the key issues discussed last month at a major summit in Hong Kong.
The International Conference on Indoor Air Quality and Climate was attended by more than 1,000 researchers from 50 countries, including Brazil, Cameroon, China, India, Indonesia, Malaysia, Nigeria, the Philippines, South Africa and Thailand.
The challenges facing designers are particularly great in developing countries because they are home to around 6 billion of the approximately 7 billion people in the world today. As the economy develops in these countries, construction of buildings will grow more rapidly.
In China alone, for instance, 10 or more new cities spring up each year. Nearly all the buildings are equipped with modern air conditioning systems, built to consume more energy.
Another key reason for high energy consumption in the developed world is that building spaces - whether homes or offices - have become increasingly divided up for privacy with personal entertainment and communications systems, and for the immediate environment to be adjusted temperature-wise according to individual requirements. This impacts the free movement of air and other environmental processes that have to be balanced in the overall design.
As a result, politicians and professional bodies are now advocating more comprehensive and flexible regulations for the varied and often conflicting requirements of modern buildings.
For example, economising on heating or cooling to reduce carbon and particulate emissions from power stations is often achieved by reducing ventilation, which causes increasing humidity and dangers from indoor pollutants, including malfunctioning heating boilers.
New designs to answer these concerns also have to consider the accumulation of microscopic particles on surfaces, and in a building’s air and water systems. New materials and controls are reducing infection risks, and at the same time, intensive research is being directed towards identifying new microbes and their possible health effects.
The health impacts of indoor pollutants depend on how they circulate and disperse in hospitals, hotels and other environmentally controlled buildings. There are serious concerns that with air conditioning and ventilation systems, levels of air flow are often insufficient to minimise the risks of cross infection or to keep humidity low enough to prevent growth of mould and long-term damage to internal walls and even the structure of houses.
Buildings must not only function safely and efficiently, but also aim to satisfy their occupants. In offices and residential accommodation, people like irregular changes of air flow in a room - one reason why many like their own fans, or open windows in warmer weather. This casts doubt on the rationale of designs based on unchanging indoor environments.
The variability of the environment clearly needs to be related to the activities taking place in the space. In hospital rooms, for instance, different types and levels of heating and ventilation are needed for patients in their beds and medical staff around them, which is becoming possible with better understanding of complex, often unpredictable air movements in confined spaces.
The developing techniques of computational fluid dynamics applied to confined spaces, together with new mechanical systems enable architects to specify a building’s environment ‘on the drawing board’. But designers and engineers have yet to master methodologies to introduce the necessary and pleasurable elements of randomness across indoor spaces.
Better insulation and mechanical systems are reducing office energy consumption by slow circulation of cooled water under floors, rather than higher speed and more noisy air flow. Yet energy use in housing is not decreasing as fast as was expected with new technology.
One reason is that family members, especially in the developed world, are increasingly separated in their own heated/cooled/ventilated rooms with personal entertainment and communications systems.
This is a long way from families huddled under a blanket or around a fireplace burning wood, which is still the main fuel for about three quarters of the world’s population. In many developing countries, women in particular suffer from poor indoor air quality due to continued use of solid fuels.
The way in which the outdoor and indoor environments of buildings are related depends on the wider urban area, especially variations in wind, temperature and air pollution. Recent studies have shown that many small green spaces in city centres have greater cooling effects for buildings than a few large parks.
As air pollution drifts across large cities, the concentrations of different gases vary greatly from one district to another and with elevation. So pollution experienced by occupants in a building can change according to where the ventilation system takes in air, for example.
These external factors affect the interior via the transition space between the immediate surroundings and interior. This zone may be geometrically as simple as a wall with windows, or it can be quite complex with the openings, blinds, colonnades and verandahs found in sunny climates, or dynamic with air jets at doorways as in modern shopping malls.
Taken overall, it is clear that a revolution is needed in building design and construction, and the challenge is greatest in the developing world. The solution must centre not only on reducing energy consumption in the context of global warming, but also on making those living and working inside buildings happier.
Julian Hunt is a visiting professor at Delft University of Technology, a member of the UK House of Lords, and also former Director General of the UK Met Office. Yuguo Li is a professor and head of the Department of Mechanical Engineering at the University of Hong Kong.