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 cold 0.16 Provide loft Assess condensation risk in roof space and loft space. Existing insulation insulation – 250mm make appropriate provision in accordance at ceiling level will be removed mineral fibre or with the requirements of Part C relating to as part of the works cellulose fibre as a the control of condensation (BS 5250 and quilt laid between BS EN ISO 13788). Additional provision may and across ceiling be required to provide insulation and access joists or loose fill or to services in the roof void equivalent. This may Where the loft is already boarded and the be boarded out boarding will not be removed as part of the work, insulation may be installed from the underside; however, the target U-value may not be achievable Renewal of roof covering: 0.16 Cold structure – Assess condensation risk (particularly Living accommodation in insulation (thickness interstitial condensation) and make roof space (room-in-the-roof dependent on appropriate provision in accordance with arrangement), with or without material) placed the requirements of Part C relating to the dormer windows between and below control of condensation (BS 5250 and rafters BS EN ISO 13788) Warm structure – Where there is an increase in structural insulation placed thickness (particularly in terraced dwellings), between and above practical considerations may necessitate a rafters lower performance target Dormer window constructions Renewal of cladding to side 0.30 Insulation (thickness Assess condensation risk and make walls dependent on appropriate provision in accordance with material) placed the requirements of Part C relating to the between and/or control of condensation (BS 5250 and fixed to outside of BS EN ISO 13788) wall studs, or fully external to existing structure, depending on construction Renewal of roof covering – Follow the guidance Assess condensation risk and make on pitched or flat appropriate provision in accordance with roof constructions, the requirements of Part C relating to the as appropriate control of condensation (BS 5250 and BS EN ISO 13788) Flat roof constructions Renewal of roof covering: 0.16 Insulation placed Assess condensation risk and make Existing insulation, if any, less between and over appropriate provision in accordance with than 100mm, mineral fibre joists as required to the requirements of Part C relating to the (or equivalent resistance) or achieve the target control of condensation (BS 5250 and in poor condition, and likely U-value BS EN ISO 13788). Also see BS 6229 for to be significantly disturbed design guidance or removed as part of the planned work BBuuiillddiinngg RReegguullaattiioonnss 22001100 AApppprroovveedd DDooccuummeenntt LL VVoolluummee 11,, 22002211 eeddiittiioonn 8811 O N L I N E V E R S I O N