It has used old Formula One tyres on a school roof and recycled denim and T-shirts for wall insulation, but Willmott Dixon won't put a wind turbine on a building just to prove it is green.

"You can get a lot of eco bling, but we are not into that," says Mark Pheasey, operations director for Willmott Dixon Construction (WDC). The building arm of the group has used plenty of wind turbines and solar panels on its projects but they have to be there for the right reason, says Pheasey, who believes getting the energy efficiency, insulation, ventilation and air tightness right is just as important, perhaps even more so. "If you get this wrong it can lead to more waste energy than could be created from any of these items," he says.

At Blaydon in Gateshead, Willmott Dixon is building a new leisure complex and adjoining NHS health centre with a minor injuries unit. Just weeks into the project, there is not much to see except piling being hammered into the ground, a large mound of soil pushed up at the far end of the site and a lot of crushed rubble, but this is already a good example of the Willmott Dixon approach to construction. The Blaydon rubble came from an old squash court at the nearby Gateshead leisure centre, which is also undergoing substantial refurbishment by the Letchworth-based firm. The soil from the build will not be taken to landfill but will be used for levelling the surface of the new development, and the construction process will involve the use of local stone and timber, with the wood offcuts recycled for insulation. Local contractors will also be used. Willmott Dixon, with the help of specialists, has already fulfilled its legal obligation to relocate grass snakes, bats, birds and badgers found there, raising the number of species at a nearby habitat from 16 to 47 in the process. The new Blaydon buildings will have biomass boilers, which use recycled timber to provide 25% of renewable energy, a heating and ventilation system to recover heat and reuse it, and they will use discarded water to flush toilets. Willmott Dixon also plans to use waste steam to provide hot water via a pipeline under the A1.

"We are very much into sustainable building," says Anthony Dillon, managing director of WDC's operation in the north, who believes that everyone at the firm thinks green thanks to the leadership of group chief executive Rick Willmott. "You need that support from up top and you get that from Rick," he says.

According to the Willmott Dixon code, all projects are monitored against and targeted to achieve its 10-point sustainability criteria, which include measures for waste diverted from landfill, the recycled content of the building, energy performance ratings and involvement in a community project. To this end the environmental performance of sites is audited on a monthly basis to keep staff informed of progress against targets and to investigate and correct irregular energy consumption. Waste contractors are also audited. Falling short of expected standards in several areas resulted in two contractors being removed from the supplier list.

Workers certainly appear to know their stuff. Our staff survey shows employees are well aware of the firm's environmental policy and the environmental implications of the work they do, earning the company positive green scores of 83% and 81% respectively. And knowing where to put waste for recycling is second nature (88%).

Willmott Dixon's expertise starts at the pre-construction stage and continues with post-occupancy evaluations carried out by its sister company, Re-Thinking, which ensures occupants know how to get the best out of their new buildings.

Environmental issues are high on the agenda across the group, from its Sustain division, which provides a round-the-clock electrical and mechanical maintenance service, extending the operational life of buildings for a wide range of companies, to Kanvas Interiors, the part of the firm that covers fit-out and refurbishment, and Inspace, its specialist arm in social and affordable housing. Inspace has given domestic electricity monitors to 700 employees to help them understand their home energy use and see the various costs of having devices on or off. Last year, this arm of the business recycled 763 tons of plasterboard that would otherwise have gone to landfill.

The group, which employs almost 3,000 people, aims to be carbon neutral and to send zero waste to landfill by 2012. Its employees believe its environmental commitments are very serious (87%) and they say bosses are open to suggestions for environmental improvements (82%). The firm gets top 25 green scores for being well run and supporting local suppliers and businesses (85% and 76% respectively).