CASE STUDY | LARK RISE reassurance, Bere spoke to Mr Passivhaus himself, Wolfgang Feist. I said: Is this really going to work?, and he replied: PHPP never lies, saysBere. In fact, Feist said the buildingsorientation was potentially beneficial because it would result in thehouse having extremely stable summertime temperatures. Temperature stability is further improved by the exposed thermal mass provided by the buildings concrete structure. The half-buried building is an innovative hybrid of in-situ concrete retaining walls below ground, combined with a high-performance, prefabricated, timber-panelled solution above ground. Because we had to cut into the slope, we needed a strong reinforced concrete retaining wall, explains Bere. The scheme also incorporates eight reinforced-concrete columns, which rise up through the first floor to help the roof structuretoresist wind loads on the timber top floor. In line with the schemes Passivhaus Plus aspiration, the roof has 62m2 of solar photovoltaic panels (PVs), which deliver a peak electrical output of 12.43kW on a sunny day. The PVs output means that, on an annual basis, electricity production is about 2.5 times higher than the homes electricity requirement. Inconveniently, maximum energy consumption in the home The area of solar PV panels on the roof, which deliver a peak electrical output of 12.43kW Schematic of the energy system Photovoltaic collectors is in winter, while maximum output from the PVs is in summer resulting in an electricity surplus between the months of March to October. Initially, the plan was to export this excess power to the local electrical grid. However, the infrastructure was old and the local energy supply company imposed a 4kW energy export limit, which meant the grid was unable to accept the quantities of power generated by the array. Rather than pay to upgrade the local electrical infrastructure, a battery was installed to store some of the surplus energy. Because we went Passivhaus Plus and because the local grid connection was inadequate to handle output from the PVs we put in a battery, 8 months Approximate length of time per year that the building imports no energy from the Grid 4 months Length of time per year when it is nearly zero, despite less-than-optimal use patterns 62m2 Room controller Roomstats and actuators for: cloaks/ WC, sitting, kitchen 28mm DHW distribution from manifold: Bath 15mm Bathroom basins 10mm Shower 15mm Gust basin 10mm Kitchen sink 15mm WC basin 10mm Roomstats and actuators for: boot room master bed, guest bed Ground floor heating manifold 1 Heat pump consumer unit 2 Submeter 3 Household consumer unit 4 Generation meter 28mm External sensor First floor heating manifold MCW distribution: 15mm to all outlets 28mm 28mm 28mm Heating pipework 28mm Power to controls & boost heater 22mm 2 1 MCW 4 Utility meter Incoming mains 1ph 230v DHW 22mm Incoming mains water 3 PV inverter Power to compressor Control cable Liquid 6mm Hot gas 12mm Outdoor unit Refrigerant pipework 24 May 2019 www.cibsejournal.com CIBSE May19 pp24-28 Lark Rise.indd 24 26/04/2019 17:01