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(a) Airtightness in existing dwellings 4.23 When carrying out work in existing dwellings, care should be taken to reduce unwanted heat loss through air infiltration by doing all of the following. a. When installing pipework or services, taping and sealing around service penetrations. b. When installing or renovating thermal elements, the element being installed should be draught- proofed, and air-leakage gaps should be filled. c. When installing windows, roof windows, rooflights or doors (all of which are controlled fittings), the controlled fitting should be well fitted and reasonably draught-proof. NOTE: Particular attention should be paid to Approved Document F and Approved Document J when making an existing dwelling more airtight. Limiting heat losses and gains from building services Hot water and heating pipework 4.24 In a new system, all of the following new pipework should be insulated. a. Primary circulation pipes for heating circuits where they pass outside the heated living space, including where pipework passes into voids. b. All primary circulation pipes for domestic hot water. c. All pipes that are connected to hot water storage vessels, for at least 1m from the point at which they connect to the vessel. d. All secondary circulation pipework. 4.25 In an existing system, when a boiler or hot water storage vessel is replaced, any accessible pipes in the dwelling should be insulated. 4.26 Heat losses from insulated pipework should not exceed those given in BS 5422 for hot water services at 60°C, regardless of the actual design temperature. Meeting the standards in Table 4.4 is one way of demonstrating that heat losses will not exceed those given in BS 5422. Table 4.4 Minimum thicknesses of pipework insulation for hot water services and space heating applications using high performance insulation Nominal internal pipe diameter (mm) Minimum insulation thickness(1) (mm) for low temperature hot water systems Less than or equal to 10 5 Less than or equal to 25 10 Less than or equal to 50 15 Less than or equal to 100 20 NOTE: 1. Thicknesses apply for insulation with a thermal conductivity of 0.025W/(m·K) or better. For other circumstances, consult BS 5422. Building Regulations 2010 Approved Document L Volume 1, 2021 edition 31 O N L I N E V E R S I O N