Conservation of fuel and power: Approved Document L, Volume 2 — Buildings other than dwellings

A O N L I N E V E R S I O N Appendix A: Key terms NOTE: Except for the items marked * (which Building primary energy rate Expressed as kWh / PE are from the Building Regulations 2010), these (m2.year) and determined using the approved definitions apply only to Approved Document L, methodology. Volume 2: Buildings other than dwellings. Centralised electrically heated A domestic hot Air permeability The measure of airtightness of water system in which the water is supplied to the building fabric. It is defined as the air leakage the draw-off points from a device in which water rate per hour per m2 of envelope area at the test is heated by an electric element or elements reference pressure differential of 50Pa. immersed in the stored water. The water heater is situated centrally with a distribution system • The limiting air permeability is the worst to supply water to the draw-off points and has a allowable air permeability. capacity greater than 300 litres. • The design air permeability is the target value Centre pane U-value The U-value determined set at the design stage. in the central area of the glazing unit, making no • The assessed air permeability is the value used allowance for edge spacers or the window frame. in establishing the building emission rate and *Change to energy status Defined in regulation the building primary energy rate. The assessed 2(1) as any change which results in a building air permeability is based on a measurement of becoming a building to which the energy efficiency the air permeability of the building concerned. requirements of these Regulations apply, where Airtightness The resistance of the building previously it was not. envelope to infiltration when ventilators are CHPQA quality index An indicator of the energy closed. The greater the airtightness at a given efficiency and environmental performance of a pressure difference across the envelope, the lower CHP scheme, certified by the Combined Heat and the infiltration. Building automation and control Power Quality Assurance scheme. system. Circuit-watt Refers to the power consumed in Building automation and control system A system lighting circuits by lamps and, where applicable, comprising all products, software and engineering their associated control gear (including services that can support energy efficient, transformers and drivers) and power factor economical and safe operation of heating, correction equipment. ventilation and air conditioning systems through automatic controls and by facilitating the manual Coefficient of performance (COP) A measure management of those building systems. of the efficiency of a heat pump at specified source and sink temperatures, measured using the Building control body A local authority building procedures in BS EN 14511-2. control department or an approved inspector. • Heating COP = heat output / power input Building emission rate The building’s CO emission 2 rate expressed as kgCO /(m2.year). • % COP (COP � 100) is the heat generator 2 efficiency. *Building envelope (in relation to a building) Defined in regulation 35 as the walls, floor, roof, windows, doors, roof windows and rooflights. 84 Approved Document L Volume 2, 2021 edition Building Regulations 2010 O N L I N E V E R S I O N