Energy Efficiency is the reason for the existance of Part L of the Building Regulations it is an approved document so must be followed. Both new and existing buildings are covered and it targets 'Heat Loss' - 'Air Leakage ' - 'Solar Gain' - 'Efficiency of Heating & Cooling Systems' which includes central heating boilers and controls, hot water storage & controls. Covers energy efficiency and requires minimum SEDBUK ratings of appliances whether for new or replacement installations. Note, when a replacement boiler is installed it is required that the entire system is brought up to the energy efficiency requirements of a new system. SAP = Standard Assessment Procedure. TER = Target CO2 Emission Rate.