Twenty years ago there was great alarm that energy supplies would be exhausted and chaos would result. Now we are equally alarmed that energy supplies are so plentiful that we can render the planet, if not totally uninhabitable, at least a most uncomfortable place to live. It is curious that the remedies for both problems are the same.
It would be foolish, however, to assume that because the previous crisis proved illusory, the present one can be treated in the same way. In effect, we are being given a second chance. To meet either case, rigorous economy in the use of energy is required.
In this country some 45 per cent of delivered energy is used in existing buildings. The construction of new buildings and the maintenance of existing ones absorbs yet more. It is very apparent that achieving energy conservation in buildings is critical for the future.
We must ensure we have appropriate design skills and know which factors in the form, construction and operation of buildings affect energy consumption and can be modified to achieve savings. We also need a comprehensive appreciation of the energy flows during the whole life cycle of the building. And to achieve and sustain high levels of energy efficiency, accurate and reliable feedback from buildings is essential.
We need special design skills to achieve high levels of energy performance in contemporary buildings. When the building professions became formalised in the middle of the last century, architects did not have to address thermal problems. Heating engineers estimated heat losses from the form and materials, but, in design, were concerned with boiler, pipe and radiator sizing. It was a simple, sequential design procedure which worked well for a very long time. However, changes in materials, fenestration and heating systems present a new design situation. The nature of the building fabric and the size and location of windows can have a major influence on the dynamic thermal environment.
A few buildings have been able to exploit building form and materials to provide acceptable comfort in the face of changing external conditions without the assistance of heating installations. This is not something which can be universally applied, but it does demonstrate that the old pattern of sequential thermal design no longer covers all modern needs. The fabric of the building can play an active part in thermal performance. For effective design, the fabric must be as much part of the thermal design process as of the architectural one.
Individual members of the architectural and services professions do cross the old boundaries, and extremely successful schemes can result. The professions will say that they fully support this. However, if one looks at the structure of education or the types of design given special recognition, the picture is somewhat different. The anomaly is most apparent in the fee structure, which essentially rewards large buildings and complex plant. To achieve energy conservation, small and simple is beautiful.
The aim must be the smallest building possible to meet the need and the simplest possible plant. Control systems, in particular, should be as straightforward as possible and readily understandable to occupants. Complex computer control systems seem to be a badge of virility for larger buildings. They may give brilliant service where the responsible staff are well-qualified, able to control the system, interpret the results and take appropriate action. Otherwise, a simpler system related to the capabilities of the staff will probably give better service.
Building life cycle
It is very easy to regard energy consumption as taking place only when the building is in occupation. This is far from being the case. All the main elements in the building life cycle have energy implications - materials, construction, operation, demolition and disposal (see box).
Twenty-odd years ago the bre and other organisations made studies of the energy content of building materials in dwellings and the heat losses. They found that the energy content of the materials was equivalent to about two years of heat losses from the building, and concluded that materials did not represent a very significant element in overall building energy requirements. Current Building Regulations require U-values for walls and roofs less than half those in 1976. Many heating appliances have also made comparable increases in efficiency. The heat input required to maintain comfort is very much reduced. There seems no reason to suppose that there has been a similar change in the energy content of materials. The current situation seems very different to that of 1976. The relative energy importance of materials in the overall balance has increased.
In the studies of life-cycle energy use, no account appears to have been taken of the energy requirements to sustain the building workforce. When assessing the cost of buildings, the cost of the workforce is included without question. There seems no reason not to apply the same rules to energy assessment.
Efficient building use
No matter how potentially energy-efficient a building is, real savings will not be achieved if the use of the building is not equally efficient. The density of occupation should be as high as possible. It is interesting to wonder whether a floor-space tax would not have been as successful at energy saving as thermal Building Regulations. It could apply to all buildings rather than just new ones.
Similar space-use considerations apply to dwellings. Many of the energy- saving houses which appear in technical journals seem quite large, and one wonders what their density of occupancy will be.
Information on energy performance is usually expressed in terms of consumption or cost per square metre. As a result it does not indicate whether the building is less than fully occupied. In an office building, the loads are likely to be the same whether it is fully occupied or not, so increasing the designed building size would apparently improve the energy performance figures.
Efficient use of space is a prerequisite of efficient use of energy.
Feedback on the appearance of a building is automatically available by inspection, as well as in glossy magazines. Feedback on the functional performance is usually very difficult to obtain and, when it is available, it is often very difficult to interpret. If robust data can be obtained on a building it is clearly useful, but the usefulness is severely limited unless it can be compared with data from other buildings. The Energy Efficiency Office's best practice programme provides an excellent series of booklets which set out objectives and methods for monitoring. It also provides comparative data on the performance of buildings.
Except in the case of highly energy-intensive processes, the cost of energy is a very small fraction indeed of the turnover of the occupant's business. It may well be of the order of 1-1.5 per cent. The Energy Efficiency Office points out that energy saving might be regarded as profit, in which case it will be a more significant percentage. Some particularly efficient organisations will automatically keep close control of all aspects of expenditure, but many others may not regard it as worthwhile. While this may be true in immediate financial terms, the situation may be different in the national energy picture.
In dwellings, performance data are unlikely to be collected. In many cases the operation of the system may not be understood. Occupiers of new or existing dwellings may find they have an instruction manual for lighting the boiler but little else. The main feedback will be the fuel bill.
In many cases the solution to a high fuel bill might be to move to a dwelling of more appropriate size. At present this is an expensive and complicated process. Simplification of this might have an unexpected bonus in energy saving.
Since living in dwellings is virtually universal, it might be expected that basic school education would provide everyone with a working understanding of how heating systems operate and how to check performance. This may happen in some schools, but more generally school physics seems to operate either at a high, abstract level, or at a simple one. A serious attempt to bridge this gap in the thermal field might have very useful results.
The energy implications of buildings cannot be fully explored without consideration of location. Sites which are subject to high levels of noise or atmospheric pollution may make air-conditioning inevitable. Sites chosen in rural locations with a high quality of environment may generate a great deal of car travel. Individual sites which offer a good solution may be found. But if development over many years has tocontribute an ultimately environmentally-sensible layout, what planning structure is required?
One thing does seem clear. The concept of the large, concentrated city surrounded by its green belt is a pattern which may well be the worst from the environmental viewpoint. It was conceived before present population and transportation trends were apparent. At present it seems to be breaking down with progressive urban sprawl. The linear system of city development, although conceived long before the scale of current problems could be appreciated, may offer a possible solution. Proposals for this type of development have been made in this country. Perhaps they should be considered again.
The existing building stock
Some simple measures such as providing insulation in roofspaces and replacing heating plant at the end of its useful life can be carried out extremely effectively. Most other modifications to the building fabric or plant are likely to be much less cost- and energy-effective than in new buildings. However, there are two measures that can be just as effective in existing buildings as in new ones. These are ensuring the maximum efficiency in the use of space, and ensuring that occupants know how to control the building and plant.
Perhaps we should adapt William Morris's principle and allow only buildings which we think we understand, know to be economical and energy conserving, and believe to be beautiful. Building Regulations, please take note.
Peter Burberry is emeritus professor of building engineering at umist
LIFECYCLE STAGES WITH ENERGY
MATERIALS AND COMPONENTS
Manufacture and processing
Movement on site
Heating and cooling
Breaking and dismantling
Movement on site
Recycling or tipping