Cost effective U-value targets for solid wall internal finish renovation

Solid wall constructions Renewal of internal finish to external wall or applying a finish for the first time: 0.30 W/m²·K. Dry lining to inner face of wall – insulation between studs fixed to wall to achieve target U-value – thickness dependent on insulation and stud material used, or insulated wall board fixed to internal wall surface to achieve the required U-value – thickness dependent on material used. Assess the impact on internal floor area. In general it would be reasonable to accept a reduction of no more than 5% in the area of a room. However, the use of the room and the space requirements for movement and arrangements of fixtures, fittings and furniture should be assessed. In situations where acoustic attenuation issues are particularly important (e.g. where insulation is returned at party walls) a less demanding U-value may be more appropriate. In such cases, the U-value target may have to be increased to 0.35 or above depending on the circumstances. Assess condensation and other moisture risks and make appropriate provision in accordance with the requirements of Part C. This will often require the provision of a vapour control and damp protection to components. Guidance on the risks involved is provided in BR 262 and, on the technical options, in Energy Saving Trust publications. Consider 'breathability' and hygroscopicity of wall construction, ref Part C.