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With computer aided design and computational flow dynamics reaching new heights of technical prowess, it surely wont be long before the single building model leaves infancy. But mention the single model to most building services engineers and you're greeted with an ambivalent response. Like the advent of must-have digital tv predicted to revolutionise our lives and turn the nation's living rooms into cinemas, the reality of the single model lags well behind its vision.

The speed of development of new cad programs is unsurprising, with each software provider keen to market to an audience thirsty for the latest technology. But this is the core problem; the market for constantly revamped 3D virtual products is not perhaps as large as some would believe. To start with, packages are being marketed in part to architects. They have their own modelling methods, and are reluctant to fix what isn't broken. They also prefer to leave the details of cfd modelling to those further along the supply chain.

By the time the architects have caught up with the array of technology that's on offer, the market has moved on. Its unlikely that architects are tapping into the potential on offer through 3D programmes due to a lack of training and expertise. And where ignorance is bliss, know-how rarely follows. What's generally unknown is that 3D modelling also offers the option of 2D within its framework. One is not exclusive of the other. So why are more firms not taking its possibilities on board? The reasons are numerous.

The single model premise requires all parties to be able to contribute to, and understand the data in the single building model. The aim is that data will not need to be recreated at each phase of the design process, thereby improving efficiency, project control and resource management. The building can be simulated in its present, proposed or future state, if product sales jargon is to be believed. This flexible technology allows for movement and change in the ongoing development process.

Sounds ideal in theory. But the number of programmes used by various contributors to the process can lead to a mismatch of technology at a basic level, making data sharing a distant hope. Many programs are not compatible with others, or don't fulfil the intricate needs of the various stages of a project, such as airflow analysis. The financial burden on a firm of running a number of software programs to accommodate this shortfall in detail is large. Interoperability, it seems, is not on the agenda.

"The idea of the common model is conceptually feasible, but the advent of one cad package will never happen unless several big cad firms merge," says Paul Kingston, Hoare Lea's principal of mechanical engineering. "The software packages are not up to scratch, and may be strong in one area and weak in another."

Creative thinking
Add to this the different ways models are used by architects and building services engineers. "Architects think creatively," says Kingston. "From the architects' point of view, computer modelling is used to get a feel for the shape and form of a building in terms of how it will look only. They do renderings, paintings and sketches with CAD, and the benefits are time-saving."

But architects are now asking building services engineers to mock up 3Ds of airflow for competition entries due to its speed according to Stephen Logan, an associate of Connell Mott MacDonald. "We are doing simple, fast simulation models. Architects are using these, and we are getting involved earlier." Kingston has a similar experience: "We get asked to do a lot of concept feasibility studies, and cad speeds up the process by four to five days, which is critical in the concept stage."

According to Dr Darren Woolf, senior engineer with London-based Arup Research & Development, there's a long way to go in development of the single building model despite this being an exciting stage.

He says: "In traditional modelling, you would have poor cad delivered by an architect who doesn't understand the requirements of engineers, so you would have to raise the quality. There was a gulf between what an architect would deliver and what a modeller would receive. In time I hope that gulf recedes."

Kingston agrees this is a frustration: "A lot of architects have problems because they have to think like an engineer when using these models. If an overlap isn't right we will have to rebuild the model; if you have a large building, you have to tighten it up," he says. "But things have come a long way, and a lot more architects are forward-thinking and can see the cost benefits to using modelling."

Shaping the future
However, if the main cost benefits derive from time saving, these must be weighed against the outlay for an array of software, updated programs, and the training needed to bring the industry up to speed on using it. Overlap of expertise in the single building model is inevitable. And there are pros as well as cons. "For a start," says Kingston, "there is now greater understanding between architects and engineers that was non-existent pre-cad."

"If an architect is technically-orientated, you have common ground that wasn't there before; technology bridges the gap as you can both relate in 3D. It's a passport between the two disciplines and you can run through a whole building over the phone."

So the single building model promotes teamwork at every level – no bad thing. The various contractors must work closely together if the single building model is to be achieved. There's an argument that architects resent relinquishing control, and so are reluctant to take up the challenge this concept represents.

Connell Mott MacDonald's Logan says this is unfair: "The reticence of architects to commit to the single building model goes deeper than ignorance or concern about losing control of a project, another criticism levelled at firms. The architect is unwilling to give out the geometry of a building because it freezes everything and cuts off their design flexibility."

"The single model works well in the civil and petrochemical fields where the geometry is established early," he continues. "But it's not how buildings work because it changes shape all the time and the geometry is never frozen. The single model doesn't acknowledge the way buildings are documented. The question many ask is whether the technology should mirror the building process, or vice versa."

For Mike Beaven, principal of Arup Associates, there's no question that the single model is the future of building. "We swear by it," he says. "The model affects the way we work, but its not a panacea because there's shared responsibility as well as ownership. It depends on the contractual relationship as there are efficiencies and risks, and you have to build trust."

What about margin for error? With so many parties involved in contributing data to a virtual model there are bound to be hiccups. From the building services point of view its very challenging to be live on stage so that any changes can be accommodated at the last moment, he says.

Beaven adds the cfd model is generally not a shared database because it's too specific. Arup Associates uses a variety of programmes with the building in 2D modelled in different ways. For a challenging space it uses virtual and physical models. "We use the architect's model to explore the paths, but you wouldn't use it for a wind tunnel test."

Long-term there are a number of obstacles to overcome before the single building model becomes widely accepted. Big firms are already on the bandwagon because they have the finance and expertise to maximise the long-term cost and time-saving benefits it offers. It's now a matter of breaking down entrenched attitudes to ensure others follow suit.

The last word goes to Logan. "If I were backing horses, I'd say think about what our product is. It isn't drawings, it's engineering and the efficiencies we gain in engineering. The future will be making the engineering more efficient, not the drawings."