The practice of converting old buildings from one use to another is almost as old as building itself. Buildings have continuously been adapted to new uses because their structure tends to outlive their function. In more recent times western countries have preserved old buildings and neighbourhoods out of a desire to retain their historical, social and aesthetic cultural contribution.
Well-made buildings, even though they have long since repaid their original investment, are typically capable of rehabilitation and reuse, and a new, vital life. Today the imperative to extend the life cycle of a structure is also related to various sustainability goals: an understanding of embodied energy and energy conservation; the preservation of rare materials, and the thoughtful intensive reuse of sound, well-located buildings.
For some time it has been agreed that the re-use of existing buildings is one of the highest forms of sustainable design. To date however, the sustainable-design measuring criteria have not recognised the value of adaptive re-use. A radical change in attitude towards projects dealing with existing buildings is required in Australia.
The CSIRO Department of Materials Science and Engineering paper on Embodied Energy published in July 2008 recognizes that "The energy embodied in existing building stock in Australia is equivalent to ten years of the total energy consumption for the entire nation." This CSIRO publication studies embodied energy and provides an understanding of how much and where energy is used in the construction of buildings, and the cost benefits of recycling.
"Embodied energy" is the energy consumed by all of the processes associated with the production of a building, from the acquisition of natural resources to product delivery, including mining, manufacturing of materials and equipment, transport and administrative functions. "Embodied energy" refers to the energy and resources already expended to construct an existing building.
The greenest building is the one that is already built. However, the various assessment tools are yet to adequately address the energy and financial savings that come from re-using existing historic materials and structures. Current sustainable-design measuring criteria in Australia substantially under-estimate the importance of embodied energy in measuring energy efficiency and have also under estimated the great efficiency of robust existing buildings. This discrepancy undermines the credibility of the rating system as applied to the largest portion of the built environment: existing buildings.
Demolition and equivalent new construction, no matter how energy efficient, typically requires decades to equal the energy savings of rehabilitating an existing building. As individuals and institutions strive for greener buildings, our industry must acknowledge that adaptive reuse of buildings is the ultimate in recycling.