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

O N L I N E V E R S I O N L1(a) Cooling pipework 4.22 Cooling pipework should be insulated along its whole length. Control should be maximised and heat gain to uninsulated pipes should only be permitted where the proportion of the cooling load relating to distribution pipework is less than 1% of the total load. 4.23 Insulation should be designed so that the maximum permissible heat gains in Table 10 of BS 5422 are not exceeded. 4.24 Provision should also be made for control of condensation by following the Thermal Insulation Manufacturers and Suppliers Association’s HVAC Guidance for Achieving Compliance with Part L of the Building Regulations. Insulating ductwork 4.25 Ductwork that carries warm or cold air should be insulated throughout its whole length to achieve heat transfer no greater than that given in Table 4.6. Table 4.6 also gives indicative insulation thicknesses, which offers one way of demonstrating that the heat transfer value has not been exceeded. Condensation should also be controlled by following the Thermal Insulation Manufacturers and Suppliers Association’s HVAC Guidance for Achieving Compliance with Part L of the Building Regulations. Table 4.6 M aximum heat losses and gains for ducts delivering air for heating and/or cooling Heating duct(1a) Cooling or dual-purpose duct(1b) Heat transfer (W/m2) 16.34 –6.45 Indicative insulation thickness (mm)(2) 21 36 NOTES: 1. Insulation thicknesses should be calculated according to BS EN ISO 12241 using the following standardised assumptions. a. Horizontal duct at 35°C, with 600mm vertical sidewall in still air at 15°C. b. Horizontal duct at 13°C, with 600mm vertical sidewall in still air at 25°C. 2. Thicknesses apply for low-emissivity faced insulation with a thermal conductivity of 0.025W/(m·K) or better. Otherwise consult BS 5422. Domestic hot water 4.26 Domestic hot water storage vessels should meet either of the following. a. Maximum heat losses in Table 4.7. b. Maintenance consumption values in BS EN 89. 31 Building Regulations 2010 Approved Document L Volume 2, 2021 edition O N L I N E V E R S I O N