John Prescott's ODPM has unveiled the long-awaited final details of Part L - just three weeks before the legislation comes into effect.
The government yesterday definitively announced in parliament that it aims to improve energy efficiency standards by a huge 40 per cent - starting from April.
Experts are now frantically poring over the documents to grasp all their implications.
Developers and architects have very little time to come to terms with the new regulations, aspects of which will require the use of specialist software that has yet to be finalised.
But what is known is that any major building work that does not have full approval by 6 April will have to comply with the new regulations.
And any plans that already have approval but do not comply with Part L must start on site by 5 April 2007.
Crucially, failure to meet these deadlines will lead to considerable levels of redesign.
Housing and planning minister Yvette Cooper said: 'By increasing energy efficiency standards our changes make a significant contribution to the government's effort to tackle climate change and offer householders reduced fuel bills too.'
The government has also published updated guidance documents on Approved Document F, which relate to ventilation.
See the new regulations at www.odpm.gov.uk
Look out for updates on what the new building regulations will mean for you on www.ajplus.co.uk
over the next two weeks. by Ruth Slavid