The road to sustainability is paved with good intentions. Clients must set written targets to achieve energy-cutting goals

Like most buzzwords, sustainability can be hard to define. At its heart, however, is the need to produce buildings that do not have any adverse effect on future generations as a result of the materials used in their construction. At a time when half of all resources used globally are consumed in the construction and maintenance of buildings and infrastructure, the benefits of sustainability are obvious. So how do you put them into practice?

The key document is the employer's requirements: even if it goes by a different name under the procurement route being used. This is what establishes the client's requirement that a building to be designed and constructed from a sustainability perspective.

The client has to be certain what its goals are, especially if it is dipping its toes into the sustainability water for the first time, and may need to be talked through the options by an expert.

Whatever the client's goals - which could include achieving an "excellent" BREEAM rating, requiring natural ventilation instead of air-conditioning, reducing the building's carbon footprint, waste recycling, the use of water-based paints or recyclable materials - they must be made absolutely clear in the requirements. And all of the construction team needs to be committed contractually to designing and building in accordance with those requirements.

It's hardly rocket science (environment-friendly rocket science, obviously) to draft contracts so that they incorporate an employer's requirements. Nor should it be that tricky to ensure that those requirements are consistent throughout the construction team.

So what issues are there?

The main point to note is that the design period for sustainable buildings is almost always longer than that for traditionally designed ones. A sustainable building may also take more time to construct.

However, that does not mean that it should be more expensive. A recent survey by BRE and Cyril Sweett has shown that costs for sustainable buildings do not have to add significantly to the initial capital outlay and, when whole-life costs are factored in, are a lot cheaper.

In the survey, the whole-life costs of air-conditioned and naturally ventilated offices were compared. In both instances, a comparison was drawn between offices that simply complied with Building Regulations and those that complied with more stringent BREEAM ratings. The air-conditioned but otherwise sustainable office was 55% cheaper in the long-term; the naturally ventilated office was 71% less expensive.

Clients could also consider incentivising their construction teams. For example, contracts could be drafted so that contractors would be entitled to extensions of time or loss and expense for problems in the sustainable-materials supply chain. Clients could also consider using a target-cost approach, with the contractor and consultants sharing a cash benefit if, for example, a building is procured within tightly drawn parameters, such as those for energy efficiency or estimated whole-life savings.

Clients are free to attach as much - or as little - importance to sustainability as they like. However, before they do so, they should read an article by David Quirk in QS Week on 14 September, which argued that waste adds £65 per square metre to the construction cost of commercial buildings in London, and they should consider recent and prospective European Union and UK legislative changes, which may soon force them to take sustainability seriously.

For example, PPS22's renewable energy targets were introduced in August 2004, with energy performance certificates to follow next January and the revised part L of the Building Regulations in April. That does not have to be bad news: sustainability really should make sense to everyone involved in construction. It results in better buildings and is relatively easy to incorporate into your construction documents.

In order for the future of the built environment to be bright, it really should be green.