A sustainable house

- Michael Lockhart, ECOSPHERE


Sustainability can be achieved in different ways in various areas: energy, waste, water and materials. The Mobb’s family have renovated their house that every year:
•    saves 102,000 litres of town water
•    keeps over 100,000 litres of sewerage out of the ocean
•    cuts municipal waste by several tonnes
•    reduces C02 emissions from powerstations by 8.3 tonnes
•    keeps more than 100,000 litres of stormwater out of Sydney harbour
•    produces 60% of its (clean) electricity
•    saves 4.3 tonnes of coal burning

In addition to these ongoing environmental benefits the Mobbs ensured that their renovations used sustainable materials and techniques.

Energy

The house is still connected to the main grid but the Mobbs have reduced the amount of electricity they use by 60%. They have a solar hot water heater and photo-voltaic power generation. They use reticulated gas (which is a cleaner source of energy than coal generated electricity) for cooking and for boosting the hot water heater when necessary. The Mobbs use all the appliances of a modern house, as well as Michael’s home office, but they are energy efficient ones.

Using other energy efficiency design measures such as insulation and ventilation control they reduce the amount of energy needed to heat and cool the house.

Water

The Sustainable House collects rainwater from the roof. They have enclosed guttering that excludes most leaves and debris. Smaller debris is diverted or collected by grates and meshes in the spouting system. The water is stored in a large tank buried in the back garden. The size of tank was chosen based on a calculation of roof size and average rainfall. The Mobbs did not want any water to leave their property so any overflow from the tank goes into a ‘detention basin’ which is a mini-wetland in their back garden. The basin holds about 800 litres of water before it overflows. This only happened once in a year.

Water from the rainwater tank is pumped into the house using an electric pump. Tests show that the water is comparable in quality to the town water supply.

Waste

No waste and barely any water leaves the Mobbs’ site. They have a wet compost system buried in their backyard. All sewerage and waste water drains into the tank. Also paper, cardboard and kitchen scraps go down a chute into the tank. The tank has three filter beds which are the home to a multitude of organisms that break down the solid waste. The waste ends up as water which is sterilised by passing it through an ultraviolet lamp container. The water is then reused for non-potable (potable water is for drinking, washing and cooking) purposes such as toilet flushing, clothes washing and watering the garden.

Other household rubbish is sorted as it is created. In the kitchen there are separate bins for different types of rubbish. There is little rubbish that cannot be recycled or composted.

Materials and products

The Mobbs ensured that their renovations used sustainable and non-toxic materials. This meant that their timber floors, for example, are made from plantation timber with a tung oil-based sealer instead of toxic polyurethane.

On the market there are sustainable and eco-friendly alternatives to most products.

Transport

The other key area where families impact the environment is through transport. The location of a house affects transport and vehicle use. Proximity to shops, schools, work and public transport all help minimise fuel use and therefore greenhouse gas emissions.

The Mobbs family live in an inner city suburb and work from home so they have reduced transport needs.

* Sustainable House by Michael Mobbs. University of Otago  Press. 1998. For more information about sustainability visit www.ecosphere.co.nz