Sustainable development was defined in 1987 by the World Commission on Environment and Development report as ‘development that meets the needs of the present without compromising the ability of future generations to meet their own needs.’ (Brundtland Report 1987)
Sustainable development is at the core of English Heritage’s strategy for helping people to understand, value, care for and enjoy England’s historic environment. Our work makes a direct contribution to the government’s commitment to sustainable development, not just in our role as a government adviser, but also in the day-to-day operation of the historic buildings and sites that we manage.
English Heritage’s three-fold responsibility is set out in our Sustainable Development Strategy:
- to ensure that the historic environment is recognised as a finite and non-renewable environmental resource in its own right
- to ensure that the value of the other environmental capital embodied in the historic environment is not wasted
- to ensure that our own activities, actions and advice are fully sustainable
Our climate change policy forms an important part of this.
The historic environment is a valuable environmental resource, the repository of a wealth of information about how people interacted with their surroundings in the past. For this reason alone it should be sustained for the benefit of people in the future.
For environmental reasons alone, using existing buildings efficiently must be a global priority. Replacing a building demands a considerable investment of energy: the energy embodied in the old building will be lost, and further energy will be used in its demolition. To this must be added the cost of materials (including transport) and construction of the replacement building. The government’s Performance and Innovation Unit report, Resource Productivity, has noted that ‘energy is consumed in the production of construction materials such as bricks, cement and metals and in their distribution. Over 90 per cent of non-energy minerals extracted in Great Britain are used to supply the construction industry with materials, yet each year some 70 million tonnes of construction and demolition materials and soil end up as waste’ (PIU 2000) This accounts for 24 per cent of the total waste generated by the UK.
A new building would have to be many times more energy-efficient than the old to make this equation balance over a reasonably short pay-back period. It is usually much more efficient to retain the existing building stock, particularly when its energy performance is naturally good, or where it can easily be improved. Retaining old buildings, and seeking to enhance their energy performance in benign ways rather than replacing them is not just in line with heritage conservation but with sustainability.
It would certainly be unwise to automatically condemn the historic building stock on the grounds of energy efficiency. Traditional materials and construction techniques were developed in, and designed for, a world where energy was expensive.
Decisions must be based on a careful appraisal, taking into account:
- the cultural and social significance of the old building
- the embodied energy of the old building, and its whole-life energy costs
- the costs of any improvements to increase the energy efficiency of the old building
- the whole-life energy costs of the proposed new building (including the energy which would be expended in demolition and rebuilding)
- the sustainability of the new building (in terms of both energy and materials);
- the likely lifespan and durability of the new building
- the adaptability of the new building to future energy improvement.
The community context is another part of sustainability: the wholesale demolition and replacement of traditional housing, for example, will be much more disruptive to the local community than targeted improvements.
Traditional buildings are inherently sustainable having been built largely from renewable materials obtained locally: timber, clay bricks and tiles, and local stone. Lead, copper and other roofing metals had long life spans, at the end of which they could be (and usually were) re-melted and recast. Until the 20th century almost all mortars, plasters and renders were based on lime, which was durable but soft and elastic. This kept bricks and stone blocks in good condition and allowed masonry to be dismantled and reused if necessary. Joints could be thinner than with Portland cement, so less material was needed. As with Portland cement, the production of lime releases carbon dioxide, but unlike cement, the setting reaction absorbs and fixes the gas once more. Cement accounts for 3 per cent of the greenhouse gas produced worldwide.
Traditional materials and constructions were of necessity easy to maintain and repair. Timber windows, for example, will survive for hundreds of years given regular repainting, whereas plastic window frames must be replaced. Plastic being a composite material is much more difficult and hence more expensive to recycle.
Using existing buildings wherever possible rather than rebuilding is an excellent way of minimising energy use and greenhouse gas emissions.
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