Conservation of fuel and power: Approved Document L, Volume 1 — Dwellings

O N L I N E V E R S I O N L1(b), L2 NOTE: Low temperature requirements apply to space heating only. Further guidance can be found in the Building Research Establishment’s FB 59 Design of Low-temperature Domestic Heating Systems. Sizing domestic hot water systems 5.11 Domestic hot water systems should be sized for the anticipated domestic hot water demand of the dwelling, based on BS EN 12831-3 or the Chartered Institute of Plumbing and Heating Engineering’s Plumbing Engineering Services Design Guide. Systems should not be significantly oversized. NOTE: For temperature limits to control legionella bacteria in domestic hot water systems, see Approved Document G. Sizing heat pump heating systems 5.12 Heat pumps should be selected to meet the full space heating requirement at the design condition chosen for heat loss calculations. This selection should account for the space heating flow temperature assumed in the heat emitter circuit(s), and not assume any heat will be supplied by additional electric heaters within the design external temperature range. 5.13 Reversible heat pump systems (i.e. those that provide both cooling and heating functions) should be designed such that they are optimised for heating. Controls System controls and zoning 5.14 For wet heating systems in new dwellings with a floor area of 150m2 or greater, a minimum of two independently controlled heating circuits should be provided. 5.15 System controls should be wired so that when there is no demand for space heating or hot water the heating appliance and pump are switched off. 5.16 Domestic hot water circuits that are supplied from a hot water store should have both of the following. a. Time control that is independent of space heating circuits. b. Electronic temperature control. 5.17 Primary hot water circuits for domestic hot water or heating should have fully pumped circulation where this is compatible with the heat generator. 5.18 Wet heating systems should ensure a minimum flow of water to avoid short-cycling. 5.19 For space heating systems, temperature control should be installed for the heating appliance. Thermostatic room controls 5.20 For heating systems in new dwellings, or when a heat generator such as a boiler is replaced in an existing dwelling, each room should be provided with thermostatic room controls. These should be capable of being used to separately adapt the heating output in each room served by the heating appliance. Where justified in accordance with paragraph 5.21, heating may be controlled for each heating zone rather than individual rooms. NOTE: There is no need to install thermostatic room controls in rooms/zones without heating in new or existing dwellings. NOTE: Installing thermostatic room controls may not be technically feasible in some cases. These may include the following. Building Regulations 2010 Approved Document L Volume 1, 2021 edition 37 O N L I N E V E R S I O N