The UK's leading green building trade group has warned that the government will not meet its new target to ensure all new non domestic buildings are zero carbon by 2019 unless it adopts a more flexible definition of zero carbon.

Under new plans announced in yesterday's budget, chancellor Alistair Darling said the government will launch a consultation on the new target's feasibility, adding that the policy would save approximately 75m tonnes of CO2 over the next 30 years.

Meanwhile, public sector buildings will face a more demanding target of ensuring all new facilities are zero carbon from 2018.

To support both the new target for non-domestic buildings and the existing target of making all new homes zero carbon from 2016, Darling said that the government would provide funding to set up a new delivery unit designed to monitor and co-ordinate progress towards the targets. The unit, which will launch later this year, will work with the construction industry to address the obstacles currently hampering development of zero carbon buildings such as green building skills shortages and supply chain issues.

The moves were welcomed by the UK Green Building Council (GBC), which said the targets were "ambitious, but entirely feasible".

However, GBC spokesman John Alker said that the targets could not be met unless the government adopts a flexible definition on what constitutes a zero carbon building.

The government has pledged to set out the formal definition for a zero-carbon home by the end of 2008, following a consultation this summer. It is currently considering whether to stick with the present definition which requires all the energy used in the building to come from onsite renewable energy technologies or near site renewables connected directly to the building.

Alker warned that the whole zero carbon programme would be at risk if such a "restrictive" definition is adopted. "If the government does not allow any energy from offsite renewables to be used in zero carbon homes then the targets can not be met," he said. "We would not be able to meet the targets for homes, but it would make the target for non domestic buildings even less feasible as many of them have much higher energy requirements that just can't be met by onsite renewables alone."

A new GBC task force is currently investigating how a new definition could be structured to allow buildings to utilise renewable energy generated at more efficient offsite locations. "We are not asking that buildings that use a green tariff should receive zero carbon status," said Alker. "We're looking at more sophisticated means of ensuring that the energy used in these buildings is genuinely green."

However, renewable energy groups have expressed scepticism over the need for a more relaxed definition of zero carbon, accusing the construction industry of attempting to water down the standards as a means of protecting their bottom line.
Speaking on condition of anonymity, one renewable energy expert involved in the government's consultation process said that as with recent building industry lobbying to ensure the Merton Rule was relaxed to allow firms to provide renewable energy from offsite locations the construction sector appeared to be trying to wriggle out of costly requirements to invest in onsite renewables.

He added that while some energy from offsite locations may be required to help non-domestic buildings meet the new zero carbon targets any definition would have to remain tight enough to force construction firms to fund the extra renewable capacity. "They should not be given a get out of jail free card that allows them to just dump the requirement for extra green energy on offshore wind farms," he warned.

In related news the Chartered Institu te of Building (CIOB) today announced that it has awarded 300 members Chartered Environmentalists status.

Michael Brown, CIOB deputy chief executive, said that the new accreditation had an important role to play in promoting green construction skills across the industry. "Construction is an environmental industry and its importance to such issues like sustainability, energy efficiency and climate change cannot be underestimated," he said. "We know that the buildings we live and work in are the largest source of carbon emissions and our members and other professionals can be part of the solution to that problem."