This underground house has been constructed next to a scheduled monument under PPS7 regulations. It has been constructed to a Passivhaus standard of energy efficiency. The space heating and a proportion of its hot water requirements are supplied by a ground source heat pump (GSHP) located in a small plant room inside the house.

We installed a 12kW NIBE F1155 heat pump with a 300 litre unvented DHW storage cylinder. The ground collector consists of four x 200m horizontal loops supplying a 4-way external manifold chamber with header pipes connecting to the plant room. The ground loops were covered over as part of the landscaping during construction. Heat is distributed by underfloor heating throughout.

An 8 kWp PV array is distributed across a south facing roof linked to the grid by a SolarEdge HD Wave inverter which mitigates the impact of partial shading. This helps to offset the electricity consumed by the heat pump.

During late spring, summer and early autumn the majority of the hot water requirement will be met by a PV switch which diverts surplus PV to twin immersion elements in the hot water cylinder, firstly to the top of the cylinder, and subsequently to the lower part of the cylinder.