This document specifies inspection procedures for the assessment of energy performance of existing boilers and heating systems. Heat generators types covered by this standard are: - boilers for heating, domestic hot water or both; - gas, liquid, solid fuel fired combustion boilers; - electrically driven and gas driven heat pumps; - thermal solar systems for domestic hot water, heating or both; - other heat generators types, such as cogeneration units. Parts of heating systems covered by this standard are; - heat generators, including generation control; - heating distribution network, including associated components and controls; - heating emitters, including components and controls; - space heating control system; - heat storage and associated components; - domestic hot water production system. This standard covers issues related to energy conservation and environmental performance.