Desert bloom

A project on the scrubland fringes of Austin, Texas could prove to be an important step towards a broader acceptance and wider application of regionally sustainable architecture. The centre for Maximum Potential Building Systems (or more simply Max Pot) is co-directed by Pliny Fisk and his partner Gall Vittori. It encompasses an architect's studio, workshop, research laboratory, teaching centre and experimental concrete plant. On the same plot of land is the Advanced Green Builder Demonstration Home and Workplace, a government and industry sponsored project. With its heavy base, light steel roofs and water cisterns, it is designed to be an example for regionally appropriate architecture into the next century. As such, it emphasises opportunities for recycled and by-product materials, water collection, natural cooling and heating. However, what distinguishes the project, and indeed the work of Max Pot generally, is the breadth of its holistic approach to building.The approach sees built form as a product of an enlightened understanding of the environment in which it is set. This takes the form of a regional mapping which defines the ecological and economical context. Essentially, mapping is used as a tool to identify plant species, soil types, rainfall, wind strength and insolation. As such it defines the biome or bio-region - an area with a distinct set of climatic, vegetation and soil characteristics. However, mapping can also be used as a statistical base to identify human resources such as transport networks, manufacturing processes and job skills.

The Demonstration Home is intended to address social concerns of flexibility and affordability. It is based on a modular system consisting of an endo-skeleton of steel reinforcing rods (98 per cent locally recycled and recyclable) welded together into a box frame to form simple column and beam elements. These are bolted into position and are light enough to be manually manoeuvred. They can be subsequently encased in a precast permanent shuttering and concrete which uses 97 per cent recycled content. (Portland cement is avoided because of its contribution to global warming through excessive carbon dioxide release.)

These column and beam elements generate a set of basic forms such as triangulated roof modules, porches, arbours and guttering supports. The ease of construction - which also entails minimal site disturbance allowing nature to quickly recolonise - and its inherent cheapness mean that a family can itself build a starter home without the burden of a mortgage. As the family grows or salaries permit, the building, through its inherent clip-together structure, can be enlarged or reduced to suit respective needs.

Infill panels are made from recycled or indigenous materials identified for their suitability through the mapping process. The Demonstration Home uses a variety of techniques, including adobe and rammed earth walls, straw bales (with hand stuccoed finish for fire and pest resistance), recycled glass blocks and caliche blocks. (Caliche, a calcium carbonate deposit, covers some 12 per cent of the earth's crust and is widely available in Texas. It can be mixed with sand, fly ash and other industrial by-products to form a solid and durable block for a solar-mass wall or for flooring slabs.) In a biome short of virgin timber, window, door frames and panels are made from a combination of sawn timber chippings and locally recycled plastics to give a new hybrid product that is both thermally stable and weather resistant.

Framing the entrance to the building are two steel cisterns, designed to hold 13 000 gallons of rainwater collected from the roof, This visually embodies both the project's sustainable ethos and the average Texan's demand for water in a dry climate. The on-site rainwater catchment is intended to provide for all of the home's domestic water needs, with the necessary storage capacity estimated from precipitation mapping, including data on the likelihood and duration of droughts. The landscape surrounding the building similarly demonstrates the importance of water in a dry climate. At the foot of the water cisterns is an artificial wetland of reeds and gravel beds. These filter the grey waste water from the house and a solar powered water pump provides a low pressure dosing system across the garden.

The galvanised steel roofing and upper stories sit lightly above the building's mass on the skeletal overstructure providing ventilated shade below. The galvanised steel is locally manufactured with a roof membrane made of recycled tyres. All the south-facing roofs are decked with photovoltaic cells to provide electrical power.

A breezeway separates the two halves of the building - on the one side a workshop/studio, on the other the living area. The breezeway is a climatically responsive form of shaded, outdoor living space borrowed from traditional Texas housing. In a previous project for a farm and market in Laredo on the Mexican border, biome knowledge sharing allowed Fisk to use the climatically relevant form of a wind funnel roof, traditionally used in Iran for cooling. A variation on this is used in the Demonstration Home's clerestory ventilation.