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

O N L I N E V E R S I O N AC Table C1 Continued Proposed works Target Typical construction Comments (reasonableness, practicability U-value and cost-effectiveness) W/(m2·K) Renewal of the ceiling to flat 0.16 Insulation placed Assess condensation risk and make roof area. Existing insulation between and to appropriate provision in accordance with removed as part of the works underside of joists the requirements of Part C relating to the to achieve target control of condensation (BS 5250 and U-value BS EN ISO 13788). Also see BS 6229 for design guidance. Where insulation would unacceptably reduce ceiling height, a lower performance target may be appropriate Solid wall constructions Renewal of internal finish to 0.30 Dry-lining to inner Assess the impact on internal floor area. In external wall or applying a face of wall – general it is reasonable to accept a reduction finish for the first time insulation between not exceeding 5% in the area of a room. studs fixed to wall However, the use of the room, and the space to achieve target needed for people to move around and U-value (thickness for fixtures, fittings and furniture should be dependent on assessed insulation and stud If acoustic attenuation issues are particularly material used) important (e.g. where insulation is returned Insulated wall board at party walls) a less demanding U-value may fixed to internal be more appropriate – the target U-value wall surface to may have to be increased to 0.35 or above, achieve target depending on the circumstances U-value (thickness Assess condensation and other moisture dependent on risks and make appropriate provision in material used) accordance with the requirements of Part C relating to the control of condensation (BS 5250 and BS EN ISO 13788). This will usually require the provision of vapour control and damp protection of components. Guidance on the risks involved is provided in the Building Research Establishment’s BR 262 and, on the technical options, in Energy Saving Trust publications Renewal of finish or cladding 0.30 External insulation Assess technical risk and impact of increased to external wall area or system with wall thickness on adjoining buildings elevation (render or other rendered finish or cladding) or applying a finish cladding to give or cladding for the first time target U-value 8822 AApppprroovveedd DDooccuummeenntt LL VVoolluummee 11,, 22002211 eeddiittiioonn BBuuiillddiinngg RReegguullaattiioonnss 22001100 O N L I N E V E R S I O N