C O N T E X T 1 1 1 : S E P T E M B E R 2 0 0 9 39 IHBC Annual School 2009 IHBC Annual School 2009 IHBC Annual School 2009 CHRIS WOOD Making historic buildings even more sustainable Historic buildings are more energy efficient than generally assumed: they can be improved in ways that are sustainable and do not harm their character. The title presumes that historic buildings are already very sustainable, which to a large extent is true. The Bruntland definition of sustainability of 1987 – ‘meeting the needs of the present without compromising the ability of future generations to meet their own needs’ – ties in very well with our conservation aims. Although this definition is expected to be modified at the Copenhagen summit later in the year, the notion of preserving what we have and making maximum use from it is likely to remain. It is important to remember that historic fabric is a precious and finite resource that should also be enjoyed by future generations. The biggest current problem stems from the excessive use of energy and consequential production of greenhouse gases, principally carbon dioxide, which is causing climate change. Herein lies the paradox. The building regulations provide the only means of compulsory improvement of energy efficiency in existing buildings, and these are only concerned with conserving fuel and power. No mention is made of conserving fabric; indeed active encouragement is given to replacement where it improves thermal performance. Although the approved documents accompanying Part L make clear that special consideration should be given to conserving historic buildings, it would seem that this is often ignored. Historic buildings are more energy efficient than most models of thermal performance indicate. They can be improved in ways that are sustainable and do not harm their character or appearance. However, careful thought is needed. The use of energy in buildings accounts for 46 per cent of carbon dioxide produced in the UK. As some 70 per cent or more of buildings that will exist in 2050 have already been built, it is the improvement in performance of these buildings that will make the difference. All EU states are required to improve energy performance under the European Directive (Energy Performance in Buildings Directive), and the UK is complying by progressively increasing the standards within the Building Regulations and the introduction of Energy Performance Certificates. The Glasgow research has allowed testing of potentially innovative solutions.Two windows from the 1930s are being tested, one made of steel, and the other of cast iron and leaded lights. Normally these have a U value of over five.The clear blind is made from material similar to that used in modern lowemissivity glass.The result is that the U value comes down to 2.5, which halves the heat loss.
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