Adelaide: A downtown sustainable oasis

 The neighbourhood of Christie Walk in downtown Adelaide was built as a demonstration project to show that it is possible to create a neighbourhood that focuses on sustainability in every respect. Christie walk is tucked in between existing urban buildings in a 2000 m² closely developed area. Housing Association has 27 homes, including a townhouse, a block of flats and four straw-bale cottages. None of the privately owned houses are higher than three storeys and have shared outdoor areas. The residents helped to design the houses according to their own individual needs. What the houses have in common is that their design and choice of materials integrating numerous environmental considerations.

The outer and inner walls of the houses are made of porous concrete. The density of the concrete gives it a high heat capacity, which means that during the day it easily and efficiently absorbs and accumulates the heat of the sun. When the temperature falls a night the concrete gradually releases the stored heat. This reduces temperature fluctuations and thus energy consumption in the home. The concrete used to build Christie Walk has a high content of fly ash, a waste product from power stations. Using recycled fly ash reduces the need for the production of new concrete, which emits large quantities of CO2. The straw-bale walls of the cottages retain the heat which is accumulated by the outer layer of plaster. All the floors are of concrete, which also has a high heat capacity, enabling the households to exploit the maximum effect of passive solar heat.

The vegetation in the area forms an integral part of the environmentally friendly on Christie Walk. There is a roof garden on top of the block of flats with a kitchen garden. In addition to providing outdoor space the residents, it also collects rainwater and insulates the ceiling of the flat below so that it does not get too hot. Grapevines on the balconies of the second and third floors provide shade in the summer, and when they lose their leaves in winter they allow the sun into the flats. Rainwater is collected in 20,000 litre tanks beneath the ground. The water is piped to several of the homes, where it is used to flush lavatories and the watering gardens.

Indoors, extensive use is made of materials which do not emit formaldehyde. The floors of most of the homes are covered in environment-friendly linoleum. Other floors are tiled or covered with bamboo. The use of PVC is also kept to an absolute minimum and all the timber used his plantation-grown pine. All the window frames and doors are made of recycled wood and windows are double glazed.

Ventilation of the houses is controlled by natural air currents. Fresh air cooled by nearby vegetation flows into the buildings through windows positioned low in the building. When the cooled air enters it forces the 'air' up and out of the windows at the top of the building. This provides natural ventilation and makes for a healthy indoor climate, while at the same time making air conditioning and necessary. However, some of the houses do have ventilation fans in the roof to circulate the air.

Houses in Australia are usually only built to last 25 years. The houses in Christie walk have been built to last 100 years.