Part L (2013 edition, effective 6 April 2014) requires new non-domestic buildings to be 9% more energy efficient than those built under the 2010 edition's standards. This 2013 edition contains a 'concurrent notional building specification' where, if a building is designed and built entirely to it, it would meet the required Target Emission Rate. The Approved Document advises the designer and builder that using the specification may not be the most economic solution for the building. The focus is on building fabric and efficient services being the most effective way of achieving energy efficiency targets in buildings at present. The option for quality assured building detailing has been taken out of the new documents with the only alternative to nothing now being Accredited Construction Details. This Approved Document contains an abridged version of the BRE's latest National Calculaion Modelling Guide. For use in England.