C O N T E X T 9 9 : M A Y 2 0 0 7 13 The environmental impact of a building throughout its lifetime (Harris, 1998) Input Stage Output Energy (Earthmoving) Site preparation Carbon dioxide Dirt Noise Loss of amenity Loss of trees Loss of wildlife Energy Components Raw materials Construction Carbon dioxide Dirt Noise Waste materials Energy Materials (Maintenance and refurbishment) Use Carbon dioxide Indoor effects (asthma, sick building syndrome) Energy Demolition Carbon dioxide Dirt Waste material DAVID DREWE Embodied energy: new build v refurbishment When considering the energy cost of development, it should not be assumed that a new energy-efficient building will always be the best option. Embodied energy is the energy tied up in materials as a result of extraction, manufacture, production and delivery. The embodied energy in buildings is that used to produce building materials, to transport them to site and to build with them. The idea of embodied energy has been the subject of research for many years. It has been proposed that energy, including that embodied in materials, could be used as an indicator of environmental impacts. Ted Kesik (2002) quotes typical embodied energy values of some common building materials as 5,170 MJ/m3 for brick;139MJ/m3 for rockwool; 37,550 MJ/m3 for float glass; 1,380MJ/m3 for timber; and 3,770MJ/m3 for fibreboard. One of the arguments put forward for not demolishing buildings is the loss of the embodied energy contained in the existing stock. So lifetime energy should include the embodied energy of the initial construction, energy required for its operation, any improvements and finally the energy for demolition. Should the embodied energy contained within the materials of existing buildings be included in any assessment of total energy? While embodied energy has no doubt been used to construct the existing housing stock, it is in effect a sunken energy cost. The energy and the materials have already been consumed. They can now only be offset in part if the materials can be recycled, recovered or reused. When undertaking comparison calculations, the embodied energy in the original property is cancelled out, so it can be discounted. It is suggested therefore that the embodied energy of existing buildings is not part of any total energy comparison calculations. Is the existing dwelling favoured by ignoring its embodied energy? In the case of demolition and new build, the consequences of the demolition are the loss of the embodied energy and the resources contained in the existing property. This energy cost has to be considered as part of the price paid for undertaking the new build. For refurbishment, the total energy used is the embodied energy of existing materials, plus the embodied energy of materials used in refurbishment, plus the operating energy, plus the energy for demolition. For new build, the total energy used is the (loss of) embodied energy of existing materials (of the demolished house), plus the embodied energy of the new build materials, plus the operating energy, plus the energy for demolition. Embodied energy can be used as an indicator of environmental impacts. Buildings should have the lowest total lifetime energy use possible, indicating the lowest possible environmental impacts. The move towards sustainable development has required consideration of the wider social and economic impacts, as well as environmental ones. Energy use would appear to be able to be used as a good indicator for economic issues. Potential shortages as the result of conflicts, natural disasters or political unrest can lead to a direct impact on our economy. Energy can also be linked to a number of social issues. Pollution, as a result of the production and use of energy, can cause health problems and place increased demands on society to care for or treat those affected. Fuel poverty can add to these health problems, and results in some people experiencing a lower standard of living and financial hardship. The big impact of energy use is on climate change. Predicted increased flooding, higher extremes of summer temperature and water shortages will all affect society.The relationship between carbon dioxide emissions and energy makes energy a good indicator of potential climate damage. One of the most important issues to consider is that an energy-efficient building may use more energy over its lifetime then a less efficient building with a higher operating energy. The energy-efficient building would require not only more energy to construct but also more for maintenance of both its fabric and equipment. It should not therefore be assumed that a new energy-efficient building will always be the best option. References Harris, DJ (1998) ‘A quantitative approach to the assessment of the environmental impact of building materials’, Building and Environment, 34 Kesik, T (2002) ‘Perspectives on sustainability’, Architectural Science Forum, January 2002, www.canadianarchitect. com/asf/perspectives_ sustainability/index_ frameset.htm David Drewe is head of the building services engineering and safety team at English Heritage, and coordinator for the English Heritage Sustainable Development Board.
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