Preparing and L1B calc for a house that’s had a rear extension added, and a complete new first floor added. This requires a whole house SAP calculation whereby we calculate both new extensions and the existing house. It includes the improvements to the existing house, in this case, external wall insulation, new windows and doors, and a completely new heating system via an air source heat pump. It also includes any existing building fabric that Is not to be improved, in this house that’s very little, just a small area of the ground floor that is solid concrete.
And of course, it includes the new extensions, which are significant in that they consist of a new single storey rear extension and the whole of the first floor and therefore a completely new roof.
The area of glazing to floor area is above the maximum 25% allowed, and this needs to be accounted for in the notional calc to which the proposed is compared, but with the other improvements planned it passes the requirements of Part L
It’s a straightforward calc, complicated a little by a few different ground floor, wall and roof types which all require separate u value calcs. However, the m&e, as mentioned an air source heat pump and hot water cylinder, both underfloor heating and radiators, a wood burner, and a solar PV array split over two roof orientations, and a solar battery. The initial result is good, a SAP/EPC rating B84 so all round a good result.
