If a solid floor needs to be replaced, a new solid low carbon concrete floor slab can be installed with insulation beneath suitable for below ground use. Performance target : 0.16 - 0.2 W/m2.K.
If the floor is being retained, 25mm of phenolic foam insulation can be set between treated softwood battens at 600mm centres fixed onto existing concrete floor, with floorboards above. Doors will need to be trimmed and rehung. Shims will need to be fitted to adjust stairs rises to avoid uneven steps Performance target : 0.3 - 0.4 W/m2.K.
Alternatively, vacuum insulated panels 10mm thick with rubber crumb coating can be set between treated softwood battens at 600mm centres fixed onto existing floor, with floorboards above. Care needs to be taken to avoid puncturing the panels. Performance target : 0.15 - 0.3 W/m2.K.
Where there is an exposed floor above ground level (e.g. a first floor overhang) woodfibre insulation can be fitted beneath, with boarded finish to the underside. Performance target : 0.25 W/m2.K.
Further information is available in the Retrofit Pattern Book