For the purposes of this Part—
a domestic PR property, or a non-domestic PR property, is "sub-standard" where the valid energy performance certificate expresses the energy performance indicator of the property as being below the minimum level of energy efficiency,
"minimum level of energy efficiency", in relation to a domestic PR property and a non-domestic PR property, means an energy performance indicator of band E,
an energy performance certificate for a property is "valid" where—
it was entered on the register required to be maintained by regulation 27(1) of the EPB Regulations no more than 10 years before the date on which it is relied on for the purposes of these Regulations, and
no other energy performance certificate for the property has since been entered on that register.