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) Limiting the effects of solar gains in summer 4.16 In new residential buildings, as defined in Table 0.1 of Approved Document O, solar gains should be limited in summer in accordance with the guidance in Approved Document O. 4.17 The guidance in paragraph 4.18 applies to all other buildings not covered in paragraph 4.16, irrespective of whether they are air-conditioned. The intention is to limit solar gains during the summer, in order to either: a. reduce the need for air-conditioning b. reduce the capacity of any air-conditioning system that is installed. 4.18 For each space in the building that is occupied or mechanically cooled, the solar gains through the glazing – aggregated from April to September inclusive – should be no greater than would occur through the relevant reference glazing systems in Table 4.3 with a defined total solar energy transmittance (g-value) calculated according to BS EN 410. In this context, an occupied space means a space that is intended to be occupied by the same person for a substantial part of the day. This excludes circulation spaces and other areas of transient occupancy, such as toilets. Table 4.3 R eference glazing systems for solar gain calculation Type of space (as Average zone Glazing location Glazing area for Framing Glazing defined in the height for reference reference space factor for g-value for National Calculation space reference reference Methodology) space space Side-lit Any East-facing Full-width to a 10% 0.48 façade height of 1000mm Top-lit ≤6m Roof 10% of roof area(1) 25% 0.48 >6m Roof 10% of roof area(1) 15% 0.42 NOTE: 1. ‘Roof area’ determined from the inside of the space looking out. Limiting heat losses and gains from building services Direct hot water and heating pipework 4.19 Hot water pipework should be insulated in all areas inside and outside the building unless it can be demonstrated that the heat is ‘always useful’. 4.20 Insulation should be designed so that the permissible heat losses in BS 5422 for hot water services in non-domestic buildings are not exceeded. Meeting the standards in Table 4.4 is one way of demonstrating that this has been achieved for low temperature systems. 4.21 Insulation thickness should be calculated in accordance with BS EN ISO 12241. NOTE: in most cases, manufacturers will be able to supply information and thicknesses for their specific products. However, Tables 4.4 and 4.5 give indicative thicknesses for typical applications. 29 Building Regulations 2010 Approved Document L Volume 2, 2021 edition O N L I N E V E R S I O N