Most building projects have a long expected life, and for infrastructure projects the life can be very long indeed. But we don’t know what the world will be like in the future – who can predict social change, technological change or climate change? There’s a big risk that today’s well-intentioned design decisions will turn out badly.

As many people have realised, it is a good idea to design for flexibility. A flexible design can respond to events, even when they unfold in unpredictable ways.

It’s an excellent principle, but no design could be so flexible as to cope will every possible contingency, even with unlimited resources. Design for flexibility does not make the designer’s job easier – in some ways it is harder, because flexibility is so elusive. Up to now design for flexibility has had to rely on expert judgment, a.k.a. guesswork.

This has changed with the introduction of a new and powerful approach to analysing and measuring flexibility, based on the concept of lifecycle options. CAR is at the forefront of this new development. It recognises that the essence of flexibility is that the initial designer’s decisions are overlaid by new decisions made by other people in the future – changing the use pattern, spatial subdivision, engineering systems, etc. Design for flexibility means deliberately providing as many future decision opportunities as possible. These are the lifecycle options.

This is illustrated in the diagrams. When a building is designed the architect makes many decisions, for example between alternative components A and B. It is unrealistic to assume that the initial decision will be repeated every time a component is replaced (model I). In a more realistic world view a new decision is made at each replacement (model II). In fact new components are sure to appear (and old ones disappear), so future decision makers will choose between new alternatives (model III). The future decision opportunities provide flexibility for future decision makers to respond to unfolding events.

A crucial advantage of the new approach to flexibility is that the value of lifecycle options can be quantified by simulation, and compared to the cost of providing them. Only if the value is greater than the cost should flexible strategies be pursued. This test encourages investors to adopt flexibility where it is cost-effective, and minimises the risk of over-investing in expensive flexibility that could never realistically be used.

The lifecycle options approach can be applied to any kind of flexibility. To take a simple example, demountable partitions give the option to reconfigure an office quickly and economically if and when the layout requirements change. Demountable partitions cost more than fixed partitions: the difference is the cost of acquiring the lifecycle option to reconfigure.

On a much larger scale, there is current interest in the adaptation of the built environment for climate change. Because the rate and severity of future climate change is unpredictable, design for adaptation is best achieved by providing lifecycle options that will allow future decision makers to respond appropriately to the trajectory of climate change that actually occurs. The adaptation potential of the existing built environment can also be studied by identifying and analysing its embedded lifecycle options.

CAR was an active participant in the CILECCTA project, an EC-funded research project that developed new software for analysing lifecycle options.

Publications

Ian Ellingham and William Fawcett. New Generation Whole-life Costing: property and construction decision making under uncertainty, Taylor & Francis, 2006.

William Fawcett. ‘Investing in flexibility: the lifecycle options synthesis.’ Projections vol.10, 2011, pp.13-29. See ‘Investing in flexibility’ below.

William Fawcett, Martin Hughes, Hannes Krieg, Stefan Albrecht and Anders Vennström. ‘Flexible strategies for long-term sustainability under uncertainty’Building Research & Information vol.40, no.6, 2012.

William Fawcett, Martin Hughes and Ian Ellingham. ‘Quantifying the benefits of Open Building’ Long Lasting Buildings in Urban Transformation (18th International Conference on Open Building), Beijing, November 2012.

William Fawcett. ‘The two paths’, Scroope, Cambridge Architecture Journal, no. 22, 2013, pp. 58-63, University of Cambridge Department of Architecture.

William Fawcett, Ignacio Robles, Hannes Krieg, Martin Hughes, Lars Mikalsen and Oscar Ramón Ramos Gutiérrez. ‘Cost and environmental evaluation of flexible strategies for a highway construction project under traffic growth uncertainty’ Journal of Infrastructure Systems, Online publication, September 2014.