Model behaviour

The construction industry has been edging towards greater collaboration between its various disciplines over recent years. But until now, it has been held back - not only by conflicting goals, but through the input of inaccurate data, which means errors can be perpetuated throughout projects. In other cases, the right data is not available at the right time, or current work may be overwritten or misunderstood. But all this may be about to change: a new method called Building Information Modelling (BIM) has started to make an impact on the way buildings are designed and constructed.

BIM is based on the creation and collection of information about a building. Because this information is constantly captured as the project progresses, reliable, co-ordinated, and consistent digital representations of the building are always available to the team. In other words, a BIM approach means creating one central model of a design, behind which is an integrated database. Because all revisions are always reflected throughout the model, this data is always current and reliable.

BIM is based on parametric building modelling technology - a tool for thinking about buildings. Just as a change made in a spreadsheet is expected to update everywhere automatically, so it is with a parametric building model.

This functionality has no end of benefits. For one, design optimisation is made simpler as experimenting with "what-if" scenarios becomes part of the natural design process. Consequently, in using a BIM tool, high quality data is available for building services engineers sooner in the process. The earlier information is available, the more readily designs from both architects and engineers can be adapted to suit their needs and the greater the impact on the final design.

Easier analysis

BIM captures much of the data needed for supporting sustainable design as the project proceeds. In addition, the integration of these tools with commercial analysis tools can greatly simplify often cumbersome analyses.

By linking the building model directly to the analysis software, all members of the team can get immediate feedback on design alternatives at all stages of the process. By keeping different design options active as the design matures, they are able to study several scenarios during the schematic and design development stages to make informed decisions before the construction document phase begins. This ensures that relevant information is available earlier, making the analysis an integral part of the process, not a separate activity.

Probably the most high profile project adopting the BIM methodology is the Freedom Tower, the first commercial building to rise on the former World Trade Center site in New York. Here, the architects Skidmore, Owings & Merrill LLP (SOM) chose Autodesk Revit Building to help realise its vision. The system was initially used on the original design for the building's complex subgrade levels only, but after experiencing its benefits, the design team have gradually expanded their use of the system's so it encompasses the entire project.

SOM created a digital BIM of the Freedom Tower which incorporated data from third-party applications used to perform people-flow and energy analyses. The model was used to explore the form of the building as a whole, as well as each individual floor. This data-rich model enabled the architects to rationalise the analytical data and study its construction method to ensure it was buildable. It also enabled the engineers to re-engineer the building to meet safety and security benchmarks. With parametric change technology, these revisions were immediately co-ordinated throughout the entire project, minimising the time required for re-drawings.

"Creating and working in a single, comprehensive, digital model of the Freedom Tower has been a process revolution," says Carl Galioto, partner at SOM's New York office. "Our team can explore and evaluate design options much more effortlessly than ever before."

Closer to home, BAA is working in a similar way on T5 at Heathrow. Here too, the project is based around a central 3D CAD model that holds all data - both graphical and non-graphical - and it will continue to do so for the entire life of the project, from concept to facilities management. It has many advantages: "As well as doing it quicker, we can have more confidence in the information, as we know it's good quality. So we are eliminating the knock-on effect of one small mistake being perpetuated and so amplified into a major error," says Nigel Stroud, T5 programme CAD manager.

But the true advantages of the team's work will only be realised in years to come. The real point of BAA's vision is to help minimise maintenance and operational costs throughout the whole lifetime of the building. All BAA's maintainable assets are recorded in its asset management system, "AIMS", and all information from the single CAD model will be transferred into this system. "If, in 15 years time, BAA is still using the same model that we are using now, albeit with more information added, then we have achieved our goal," says Stroud.

Common use

Will there come a time when most projects use BIM? The technology is available to make this happen. The latest software releases are especially tailored to enable building services engineers to work in this way and collaborate more closely with other professionals in the team. Only when BIM becomes the norm will we be able to better build sustainable buildings - and still enjoy better profits across the board.