We had to run two tour groups simultaneously so that everybody could hear a presenter. Thanks to all who came and especially Marion and James for allowing both the exhibition of their house and garden and for running the presentations.
So, is it possible to survive in this house without heating or cooling? Well yes, for most of the year. But when the internal temperature dropped to 16ºC for 2 cloudy days in June they were seriously beginning to question their strategy; then the sun came out, the house warmed up quickly and all thoughts of heating disappeared again, till next time. Still, if you only need a small amount of heating for a few days a year, you are miles ahead of most Canberra houses and you can also minimise your consumption by using a high efficiency heat pump heater (ie reverse cycle air conditioner).
In summer on the worst day (42ºC) it reached 28ºC inside, which was manageable by closing blinds and using the overhead fan during the day and by opening roof vents and sliding doors in the evening. When a northern pergola and deck are added to the build and the garden is more established I am sure summer is never going to be a problem, even with rising temperatures.
By using good northern orientation, air sealed construction, thick insulation in the building envelope, double glazed windows and large amounts of thermal mass in the walls and floor. Roof vents were added for summer passive cooling.
In winter sunlight penetrates the floor, gradually warming the concrete and releasing it as the air temperature drops. The walls absorb warmth from the internal air and release it as air temperature drops helping to stabilise room temperatures.
Marion and James only wish they had spent more on lower conductivity windows and recommended to those visiting that they search for the best performance windows they can afford, as windows are the weakest thermal component of the building envelope.
Marion and James have a long term goal of covering all their northern roof surface area in photovoltaic cells which will allow them to become energy positive and consequently drop their combined CO2 emissions to zero. They also intend to add two small solar hot water services to their existing instantaneous gas hot water systems to further reduce their energy use. Of course, paying nothing for heating and very little for electricity and gas is already helping them save.
The native garden is growing quickly, so too are the veggies and fruit trees and the chooks are happily clucking away, so Marion’s and James’ dream of a sustainable life has advanced significantly.
We hope you settle in to your new home well and once again, thank you for the tour.