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

O N L I N E V E R S I O N C Appendix C: Work to thermal elements C1 This appendix provides guidance on the cost-effectiveness of insulation measures during various types of work on a thermal element. Table C1 sets out target U-values that would be considered to represent reasonable improvements in ordinary cases and examples of construction that may be used to achieve the proposed performance. C2 If it is not reasonable to meet the target U-values in Table C1, considering technical risk and practicality of the work in relation to the dwelling and impacts on adjoining buildings, then the U-value should be as close to the target value as practically possible. C3 The final column in Table C1 provides guidance on specific issues that may need to be considered to determine an appropriate course of action. In general, the proposed works should take account of all of the following. a. The requirements of any other relevant parts of Schedule 1 to the Building Regulations. b. The general guidance on technical risk relating to insulation improvements contained in the Building Research Establishment’s BR 262. c. For buildings falling within the categories set out in paragraphs 0.8 to 0.13, Historic England’s Energy Efficiency and Historic Buildings: Application of Part L of the Building Regulations to Historic and Traditionally Constructed Buildings. C4 General guidance is available from relevant British Standards. Table C1 Cost-effective U-value targets when undertaking renovation works to thermal elements Proposed works Target Typical construction Comments (reasonableness, practicability U-value and cost-effectiveness) W/(m2·K) Pitched roof constructions Renewal of roof covering: No 0.16 Provide loft Assess condensation risk in roof space and living accommodation in the insulation – 250mm make appropriate provision in accordance roof void. Existing insulation (if mineral fibre or with the requirements of Part C relating to any) at ceiling level, less than cellulose fibre as a the control of condensation (BS 5250 and 50mm, in poor condition, and/ quilt laid between BS EN ISO 13788). Additional provision or likely to be significantly and across ceiling may be required to provide access to and disturbed or removed as part joists or loose fill or insulation of services in the roof void of the planned work equivalent Renewal of roof covering: 0.16 Top up loft Assess condensation risk in roof space Existing insulation in good insulation to at least and make appropriate provision in line with condition and will not be 250mm mineral fibre the requirements of Part C relating to the significantly disturbed by or cellulose fibre as control of condensation (BS 5250 and proposed works. Existing quilt laid between BS EN ISO 13788). Additional provision may insulation thickness between and across ceiling be required to provide insulation and access 50mm and 100mm 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, the practicality of insulation works needs to be considered 80 Approved Document L Volume 1, 2021 edition Building Regulations 2010 O N L I N E V E R S I O N