Without prejudice to the requirements of regulation 39, where a building is to be erected, or a building other than a dwelling is extended as described in regulation F138(3)(b) , F2minimum energy performance requirements in the form of a target carbon dioxide emission rate for that building shall be calculated F3and expressed using a national calculation methodology.

The building, or extension as described in regulation F438(3)(b) , shall be so designed and constructed as not to exceed its calculated target carbon dioxide emission rate F5, with all carbon dioxide emission rates calculated and expressed using a national calculation methodology .