The requirements regarding conservation of fuel and energy for dwellings are laid out in Part L of the Second Schedule to the Building Regulations 1997 (S.I. No. 497 of 1997) as amended by the Building Regulations (Part L Amendment) Regulations 2011 (S.I. No. 259 of 2011).

The Second Schedule, insofar as it relates to works relating to dwellings, is amended to read as follows: -

L1 A building shall be designed and constructed so as to ensure that the energy performance of the building is such as to limit the amount of energy required for the operation of the building and the amount of carbon dioxide (CO2) emissions associated with this energy use insofar as is reasonably practicable.

L2 For existing dwellings, the requirements of L1 shall be met by: -

(a) limiting heat loss and, where appropriate, maximising heat gain through the fabric of the building;

controlling, as appropriate, the output of the space heating and hot water systems;
limiting the heat loss from pipes, ducts and vessels used for the transport or storage of heated water or air;
providing that all oil and gas fired boilers installed as replacements in existing dwellings shall meet a minimum seasonal efficiency of 90% where practicable.

L3 For new dwellings, the requirements of L1 shall be met by: -

providing that the energy performance of the dwelling is such as to limit the calculated primary energy consumption and related carbon dioxide (CO2) emissions insofar as is reasonably practicable, when both energy consumption and carbon dioxide (CO2) emissions are calculated using the Dwelling Energy Assessment Procedure (DEAP) published by Sustainable Energy Authority of Ireland;
providing that, for new dwellings, a reasonable proportion of the energy consumption to meet the energy performance of a dwelling is provided by renewable energy sources;
limiting heat loss and, where appropriate, availing of heat gain through the fabric of the building;
providing and commissioning energy efficient space and water heating systems with efficient heat sources and effective controls;
providing that all oil and gas fired boilers shall meet a minimum seasonal efficiency of 90%;
providing to the dwelling owner sufficient information about the building, the fixed building services and their maintenance requirements so that the building can be operated in such a manner as to use no more fuel and energy than is reasonable.

Part L - The requirement