Issue 11

There is a good deal of confusion about what constitutes sustainable construction, and many sweeping claims for buildings, products, and even materials purporting to be ‘sustainable’. In reality such things are neither sustainable nor unsustainable in themselves. However, used in an appropriate way they can contribute to a sustainable community, society, or way of life. Sustainable construction can be considered as a subset of this broader sustainable development in which economic growth and social progress for all is coupled with effective protection of the environment and prudent use of resources. There are many definitions but one of the easiest ways to understand sustainability is to consider the legacy that we leave. Whether through environmental pollution, depletion of non-renewable resources or social inequity, we need to recognise the impacts of our actions on others, and the rightful aspirations of those who currently enjoy living standards lower than our own. It has been estimated that three planet Earths would be required to support the current world population at a standard of living equal to that of the UK! What does this mean? In striving for sustainable development we are looking to continue our economic progress, and to do so without impeding similar progress in other parts of the world (indeed there is a case for encouraging this) without damaging our natural environment (again it could be argued that we should be striving to improve this, because of the damage which has been done in the past) recognising the needs of the whole of society. There is a growing recognition of the importance of this, and many governments are signing up to agreements committing to significant improvements, for example in reduced carbon dioxide emissions. However there is also an understanding that measures must be affordable and this has introduced the consideration of economics in addition to those associated with environmental and social issues. Some commercial organisations are also recognising that there are business advantages in adopting sustainable principles in their operations. R. J. Plank, BSc, PhD, CEng, FIStructE, MICE School of Architectural Studies, The University of Sheffield, The Arts Tower, Western Bank, Sheffield

A computerised relational database management system is used to represent and calculate the embedded energies and carbon coefficients of building materials. The embedded energy requirements are also calculated on the basis of the lowest quality energy (called a ‘bio-equivalent’ basis), in addition to the more conventional basis of Tonnes of Oil Equivalent. Comparisons are then made between alternative materials for building components such as purlins, walls, roofs and windows. Among the more common construction materials considered, the lowest energy option is timber while the highest is steel, with concrete in between. Timber products have negative carbon coefficients as well, i.e. they store more carbon than is emitted in their use for house building. The walls and wall plastering contribute significant proportions of the gross energy of a building, indicating that the use of low energy materials for walls and the elimination of wall plastering will make significant contributions to reducing the embedded energy of buildings. The ratio between total embedded energy and annual operational energy for selected buildings ranges from 14 to 35 for the houses, while for an office building with air-conditioning loading, it is around 5. S. P. Pooliyadda, BSc Eng, MPhil Structural Project Engineer, London Borough of Haringey Professor W. P. S. Dias, BSc Eng, PhD (Lond), DIC, CEng, MIStructE, FIE (SL) Department of Civil Engineering, University of Moratuwa, Moratuwa, Sri Lanka