Knowledge sharers
Building designers – whether architects or engineers – rely on modelling to predict performance outcomes, but how effective and robust are these current IT systems? Judit Kimpian offers some answers
consultants to access design information simultaneously, and carry out quantitative and visual analysis. Once adopted, design options are turned around rapidly and project teams can benefit from an output of well-coordinated production information. Moreover, key data about buildings can be handed over to facilities and asset managers, who can then link this directly to a building management system and to maintenance programmes. This sounds almost too good to be true,
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so it is not surprising that there is already talk about a ‘BIM bubble’. Have we been over-optimistic about the potential of BIM? Have we underestimated the effort that goes into making BIM work for us, and the need to use it in tandem with a number of other specialised tools? If so, how far are we from BIM’s promise of a fundamental industry turnaround to embrace a whole-life approach to construction? Architects and engineers aspire to develop
design proposals based on evidence of performance benefits. Yet too often the feedback is far from instantaneous, and key decisions are made throughout a project with little consideration of how these will affect actual building performance. Building shape, floor-to-floor heights, occupant density, service types, zoning and so on, become very expensive to change down the line – yet all have a major impact on the final outcome. Even when a BIM model is shared amongst consultants as intended, precious time goes by while a proposal is evaluated in terms of structure, services and cost.
38 CIBSE Journal January 2012
he magic bullet of our times, building information modelling (BIM), promises to speed up the design and evaluation processes by allowing
By the time the design team can integrate the outcomes of such analyses in a single, coordinated 3D model, the opportunity to demonstrate the benefits of one solution over the other is often lost. Optimisation of wall U-values is a typical example. Improving these can reduce heating and
cooling loads, but often results in thicker wall build-ups, which in turn lower the net- to-gross ratio. To argue that better insulation outweighs the higher capital cost and loss of net area, we need to present the whole-life benefit at the time this decision is made – which means we can’t afford to spend weeks analysing the consequences. We need much faster feedback. To address this problem, the firms Aedas,
Arup, Hilson Moran and Davis Langdon have devised the ‘tall building simulation’ model (TBS), a demonstrator that is part of a new generation of virtual information models (VIM). VIMs allow designers to map the relationships between key design parameters (hence the term ‘parametric model’) and manipulate these interactively. The TBS amalgamates early-stage
structural, mechanical-electrical and cost analysis to provide instant feedback of the effects of early-stage design and briefing decisions. Changes to a tower’s shape, height, façade specification, structural system type or occupancy can be made instantaneously. The model shows the relating quantities and efficiency indicators, as well as whole-life carbon and cost implications, on the fly. Timing is critical – to agree on the best option, key decision makers need to be aware of the quantitative implications of their decisions. Using such a model, experts from all disciplines can sit around the table and test massing and briefing options together, in real time.
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