Developers of unit blocks will be given an extra three months to implement new environmentally friendly building regulations, the NSW government says. Infrastructure Minister Craig Knowles said the new October 1 deadline was needed to ensure the multi-unit Building Sustainability Index (BASIX) regulations would be implemented in the most effective way.

BASIX aims to ensure that each new home or unit reduces greenhouse emissions by 25 per cent and potable water by up to 40 per cent.

"We have decided to provide multi-unit developers with a voluntary period of three months prior to the implementation of multi-unit BASIX on October 1," Mr Knowles said in a statement.

Multi-unit BASIX will operate in a voluntary form from July 1, he said.

"The first three months will allow industry to get used to the system, to evaluate the performance of their projects and to generate a BASIX certificate," Mr Knowles said.

Over 10 years, the full introduction of BASIX is expected to save 287 billion litres of water and 9.5 million tonnes of greenhouse gas emissions.