The groundworkers have been busy working up the reinforcement within the concrete slab ready for the concrete pour this week.
As the entire ground floor and timber frame are entirely supported by the slab, which in turn rests on the polystyrene insulation, it is very important that the concrete slab is sufficiently rigid to ensure that all the point loads (from steel posts, and the timber frame) are adequately distributed over a large area to ensure that the insulation is not crushed.
This does mean more involved groundworks at this stage, and a thicker floor slab compared to a 'conventional' build but the lack of thermal bridges provides much lower running costs Passivhauses are famous for.