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When sufficient is best

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A research study planned by the Building Services Research and Information Association (bsria) aims to develop an entirely different approach to the specification of services in buildings, writes Ruth Slavid. Called 'Design for 'Just Sufficient' Performance' it aims to deal with the problem that in most buildings the services are hope- lessly over-specified.

'Just sufficient design,' said Gay Lawrence Race, the researcher at bsria who is leading the project, 'is that you start from normal conditions and treat the extremes as exceptions, not vice versa.' Although this may seem rational, projects are very rarely designed this way. There is concern about the building failing in the most extreme conditions, and very little thought given to the fact that oversized equipment may be performing inefficiently in day to day conditions. One of the PROBE studies, for example, found that a building with 32 refrigeration compressors was, on a warm June day, using only two of them.

'Oversizing can lead to poor performance and control at normal operating conditions,' said Race. Even properly specified equipment will often operate at only 20 per cent of its capacity. If it has been over-specified this may drop to only 5 per cent, at which level there are often operating problems.

And often decisions are not taken on engineering grounds, even misguided engineering grounds. 'One of the many factors influencing the margins people use for design is the fear of under-performance and the fear of litigation,' Race said.

The difficulty of designing for the normal condition is that, in extreme circumstances, the system may under-perform for a few days a year. But it may be more efficient to compensate with portable heaters or chillers, inefficient in themselves but only used infrequently. The important thing, said Race, is to make an informed decision.

The research project will start in November 1999 and will run until April 2002. Its output will comprise:

guidance on the performance, whole-life costs and risks associated with 'just sufficient' design solutions

information on plant, equipment and control strategies available to maximise efficiency at low loads and to cope with occasional peak requirements.

The project has support from bodies including detr and the Chartered Institute of Building Services Engineers, but bsria is currently seeking sponsors to join a 'research' club.

The benefits to consultants of joining will, it says, include:

the ability to offer added value to clients by advising them of alternative, innovative design approaches and the associated risks and benefits

the opportunity to formulate framework agreements clearly setting out the risks inherent in design options, that can be agreed and adopted at the start of the design process.

This is one of three new research projects which bsria is launching. The others are entitled 'Development of an automated productivity measurement tool' and 'Commissioning management guide'.

They are part of the organisation's strategy to increase the profitability and performance of the services sector through improvements to design, construction and commissioning. On site it has calculated that seven to eight per cent of the working day is lost waiting for materials and equipment, 10 to 12 per cent on waiting for information and amendments, and another 10 per cent on inadequate management of the workforce. In addition, bsria has calculated that providing a dedicated organised area for contractors to work in can treble productivity. There is certainly room for improvement.

For more information contact bsria on 01344 426511.

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