We built this Colin Eaton Architect designed ZEN House, (Zero Energy, Solar Heated, Passive House) for Sandra Eaton, her husband John and their 2 children in 2010 using our Warm Stud Timber Frame method. The wall, roof and slab U-values are 0.10W/m2.K or better and the air-tightness level is 0.42ac@50kPa. The 50m3 Solar Slab beneath the house is charged up in Sept/Oct to heat the house in Winter, it stores 750kWh when fully charged which is sufficient to meet the December and January heat demand. 16m2 of Thermomax tubes deliver 10 months hot water, 11 months heating and charge the Solar Slab in Autumn.

From mid November to mid January any heat produced by the Solar Absorbers is directed straight to the under-floor heating and the hot water is heated from 25 degrees to 40 degrees in Nov, Dec and Jan using electricity. The electricity bill (819kWh) for the 2011 Winter (Nov-Feb) was £128 for hot water, lighting and cooking, the client doesn't have night rate electricity. At £0.16c/kWh this works out at 3kWh/m2.annum for heating, lighting, hot water and cooking making it 15 times more energy efficient than a Passive House. The house is ventilated using 2 highly efficient "Breathing Window" Heat Recovery Ventilation units fitted discreetly into the external walls, without ducts of filters, one in the living area downstairs and one upstairs in the landing. Munster Joinery triple glazed 0.8W/m.K PVC windows and doors costing £16,000 were used for the project. 200mm Platinum EPS from Airpacks was used to externally insulate the walls and roof and the studs and rafters were filled with Isover 32.