Construction professionals are calling for the communities department to publish the calculation methodology that will enable designers to meet the 2010 Building Regulations announced last week

The calls follow the department’s publication of the Approved Documents to Part L of the Building Regulations covering energy use. They will come into force in October and call for a 25% cut in carbon emissions compared with current standards for all new developments.

However, the methodology designers will have to use to work out if their buildings meet the energy requirements is still only in draft form and has yet to be published.

David Kingstone, associate of Buro Happold, said: “Without it, it is difficult to know what percentage reduction the design will achieve.”

Key changes to Part L include different carbon reduction targets for different commercial buildings and submitting a design-stage CO2 emission rate calculation to Building Control.