The paths to zero carbon construction have begun to diverge for England and Wales, with Welsh environment minister John Griffiths launching a consultation on Part L of the Building Regulations that looks set to leave English proposals trailing behind.
The Welsh government has unveiled two options for strengthening Part L for new housing: either a 40% improvement on Part L 2010 from the start of 2015 or a staged 25% improvement in 2014 followed by an additional review two years later that would put Wales on the path to zero carbon by the end of the decade. Current proposals for England, if enacted on the expected timetable, would require a modest 8% energy efficiency improvement for new homes from next year.
Even so, the Welsh proposals have been scaled back in recognition of the challenges facing house builders, who had expected to see a strengthened Part L introduced from next year.
The consultation also gives notice that national minimum standards currently set out in sustainable buildings planning policy will be withdrawn as soon as practically possible. These include the requirements to use the Code for Sustainable Homes (Wales requires a score of Code level three with extra credits for energy for new housing) and BREEAM scores for non-domestic buildings.
Wales ministers gained powers to set their own Building Regulations at the end of 2011, so are no longer obliged to use devolved planning powers to set out their own carbon reduction policies.
The consultation proposals launched last week alongside proposed changes to Approved Documents also set out a range of options for non-domestic buildings (a 20%, 10% or 11% improvement on Part L 2010) and higher standards for the renovation or extension of existing buildings. A series of consultation events across Wales will be held in association with the Wales Low/Zero Carbon Hub.
Two free software tools have been made available that will allow designers to assess the impact of proposed changes. For the purposes of the Part L consultation, there is cSAPw (based on SAP2012) that allows consultees to see the implications of changes to the Regulations, Approved Document ADL1A in January 2015 and to the NCM. For non-domestic buildings, cSBEMw has been developed to implement the changes proposed for Part L2A in Wales in June 2014. Both software tools can be downloaded from the BRE's National Calculation Method website, though architects are warned that neither can be used to demonstrate compliance with current Regulations or to generate an Energy Performance Certificate. 

RIBA Practice Bulletin 656