Technical Booklet F2 Conservation of Fuel and Power in Buildings Other Than Dwellings·Page 10·43
Regulation 43 - Renovation of thermal elements
When thermal elements undergo major renovation or more than 50% of surface area is renovated or replaced, the thermal element must be upgraded to comply with heat loss requirements as far as technically, functionally and economically feasible.
Where the renovation of an individual thermal element—
(a) constitutes a major renovation; or
(b) amounts to the renovation of more than 50% of the surface area of the thermal element,
the renovation shall be carried out so as to ensure that the whole of the thermal element complies with the requirement of regulation 39(a)(i) in so far that it is technically, functionally and economically feasible.
Where the whole or any part of an individual thermal element is to be replaced and such work—
(a) constitutes a major renovation; or
(b) in the case of part replacement, amounts to the renovation of more than 50% of the surface area of the thermal element,
the whole of the thermal element shall be replaced to comply with the requirement of regulation 39(a)(i) in so far that it is technically, functionally and economically feasible.
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