An Energy performance certificates is required when a building is:
- First erected
- Modified so that it has a greater or lesser number of parts designed or altered for separate use than it previously had
- Modified to include the provision or extension of any of the fixed services for heating, hot water, air conditioning or mechanical ventilation
The person carrying out the building work must:
(a) give an energy performance certificate for the building to the owner of the building;
(b) give to the local authority notice to that effect; and
(c) include in that notice the reference number under which the energy performance certificate has been registered in accordance with regulation 7(4), except in the case of an energy performance certificate issued under regulation 9A (energy performance certificates in respect of excluded buildings).
The energy performance certificate and notice must be given not later than five days after the building work has been completed.
Source: http://www.legislation.gov.uk/uksi/2016/284/pdfs/uksi_20160284_en.pdf
