The details of a new house near Adelaide have been published in order to share information about designing with precast concrete for energy and water efficiency as well as bushfire resistance.
The project is located in Belair, South Australia, an area subject to extremes of temperature and high fire danger.
The home of National Precast Concrete Association executive officer Sarah Bachmann and partner Peter Worboyes, the pair says they had to look beyond ordinary precast concrete wall panels.
Comprising a thinner outside concrete layer (typically 70mm) and a thicker inside concrete layer (typically 100mm) which sandwich an insulation layer, sandwich panels offered the necessary high internal thermal mass and external durability and fire protection. The system allows the outside skin to expand and contract with fluctuations in temperature, without compromising the structural effectiveness of the building.
Both surfaces of the precast finish are ready for staining or painting. The sandwich panels also maximise benefits of thermal mass by having the large volume of unlined painted concrete on the inside of the building, where it can be used to regulate indoor air temperature.
During the day, the heat from the sun passes through the windows and is absorbed into the high thermal mass interior walls and into the high thermal mass concrete slab-on-ground (most of which is tiled). At night, that same heat is released slowly back into the interior of the building. The concrete's high thermal mass means it is able to absorb and release heat slowly and allows the inside of the building to remain at a fairly constant temperature both day and night, all year round.
The precast concrete sandwich panels have been teamed with CSIRO-fire-tested and rated double glazed windows and a well insulated steel roof - recommended for high fire danger areas.
Passive solar design measures include eaves to block summer sun but allow the winter sun in on northern windows, high thermal mass internally to absorb and store the winter sun, windows allow good ventilation and are protected from the summer sun with external blinds.
They were careful to specify good wall and roof insulation, double glazing, and sealed all gaps to prevent loss of heat and cool.
An 8.5kW photovoltaic solar panel system has been installed which generates sufficient electricity for the dwelling's use plus return power to the grid. C-Bus home automation minimises power use. Energy efficient air-conditioning provide comfort inside in summer during extended hot spells and in-slab hydronic floor heating further enhances the thermal mass benefits of the floor.
All light fittings and appliances are energy efficient. And heat reflective coatings have been used on the roof and walls.
Tanks collect rainwater and stormwater and supply the majority of the water needs, including irrigation of the drought-tolerant fire retardant garden.
"We wanted to be environmentally considerate in a modern way," says Bachmann. "And we do want to get the message out to the mainstream¬ people like us¬ who are building or renovating."
"We wanted a way to let others benefit from the research we had done and make it easier for them to build sustainably. That's why we set up a website - as a one-stop-shop for people to find all of the information, and why we open our home up for Sustainable House Day".
Visit www.hillsideproject.net for more information.