This heavily insulated house is the second home to be completed at the Greenaway Gardens eco-community in Waikanae and demonstrates the flexibility of active solar architecture.
6 Rahana Way is a three-bedroom plus study home with a large open plan living area. Bedroom and living room wings, split by the glazed entrance lobby, have extensive north facing timber windows. These allow winter sun to irradiate the polished concrete floor with its 300mm of concrete slab and beams and 250mm of EPS insulation below. This 100 tonne thermal battery moderates interior temperature increases in summer, when high angle sun penetrates the rooms less deeply. Automatic opening high level windows in both wings, driven by a Solarhomes Ventpac Winsum controller, completes the natural conditioning task.
Compare the economics of the natural condition installation with a fossil fuelled heating and cooling solution AKA heat pumps:
- Summer Comfort control energy consumption is low: the window actuators are 5 x 75W but operate for an average total of only 6 minutes per day ie. 0.325KWh per day compare with 10 KWh for 2 Kw heat pump on refrigerated cycle running for 5 hours on a hot day. This is 30 times less electricity consumption.
- Winter is almost as good – the 120W Ventpac fan that transfers living room warmth from sun and kitchen/fireplace heat in the evening to the bedrooms will only run for 4 hours on average using 0.48KWhrs. Bedroom return air travels back to the living room via a sub-floor duct and keeps the whole house non-pressurised. This means no cold, dirty external air source to be heated and filtered as other air handling systems demand!
Innovative gabion rock walls trap heat that rises across the external face of the windows and reduces convective heat loss from the double glazed units. This makes them much more effective insulators on frosty mornings.
We will publish results from thermal logging at 6 Rahana Way progressively over the next two years.