Sustainable House Day, Conningham, Tasmania

Eagles Drift

This house received the Building Designers Association Tasmania’s design award for the most Environmental & Energy Efficient Building in 2008. A solar passive house, it uses the following design principles:
1.    Highly insulated outer skin. Using straw bale, double glazed windows, R4 roof insulation and an insulted slab to encapsulate the entire living space.
2.    High thermal mass materials inside the building envelope. Dark coloured concrete slab and high density earth block internal walls
3.    Make the most of the available solar radiation. The entire living area is north facing and 90% of this is glazed to floor level, northern floor areas are kept clear. An active shading system as well as cross ventilation and natural airflows cools the house in summer.(The entire heating and cooling cost for the building in its first year was $1.80)  

New Building: Sited on two acres of previously weed ridden cleared land, now  restored with extensive plantings of Tasmanian natives, the house was designed by Guy Greener of Huon Drafting in close consultation with the owners.

Water Harvesting Systems.
No mains water. Rain water is collected from the roof of the house and the shed and stored in two tanks with 56,000 litres capacity and gravity fed back to the house. Grey and black water is recycled for garden use via a Biolytix System which uses worms to breakdown solids and does not use chlorine.
Storm water from the road and surrounding properties is also filtered through reed beds on the property and held in a dam for garden use. This also reduces sediment discharged into the nearby North West Bay.

External walls.
Straw bale: CSIRO has shown straw bale walls insulation rating to be a minimum of R6 other estimates range as high as R12. Straw is a sustainable by product of the grain industry and as sourced locally has a low embodied energy. Straw bale also has super sound insulation qualities and is highly fire resistant. The Creamstone colour chosen for the external walls is the colour of the local sandstone.

Internal walls
Eco-blocks were chosen for their earthy quality and their high thermal mass. They were made in Tasmania from Scotsdale shale with 6% white cement as a stabilizer. They are not kiln baked but rather compressed using 15 tonnes of hydraulic pressure, each block weighs 22 kilos. They are sustainable, long lasting and have low embodied energy.

Roof
Jasper Colour Bond chosen to blend with local surrounds has minimum impact on neighbor’s view. The roof is curved and mirrors the curve of the hills behind the house.  R4 insulation batts and sisalation have been used.

Floor
Waffle constructed slab, insulated around external edge. Slab holds the hydronic heating pipes which will use heated hot water. Given the high thermal efficiency of the house, the hot water is potentially powered by PV panels recently installed. The slab is stained dark colours to absorb heat. The kitchen area is covered with Marmoleum.

Windows
Thermally broken aluminum or wooded frames are used through out with the majority of the windows double glazed. Glass blocks were chosen for the bathroom both for privacy and so that the wall could be curved.

Electrical Generation.
Electricity is provided by 1.2 kW of PV solar panels which are grid connected. These will offset almost all of our power costs over the year with the exception of the service fee.

Heating and Cooling
Fully solar passive. See introduction.

Water Heating
30 evacuated tubes provide most of the solar hot water.

Old Age and Disability
The house has been built on the flat with no internal or external steps or stairs. The doorways, toilet and shower are sized for wheelchair access. The design takes into account the possible need for a live-in carer with a bedroom and living room at both ends of the house and services in the centre. The house has extremely low maintenance and very low running costs.