Heritage Retrofit

6 BCD SPECIAL REPORT ON HERITAGE RETROFIT FIRST ANNUAL EDITION RETROFIT IN HERITAGE BUILDINGS Understanding the risks IAIN McCAIG I T IS a widely held view that older buildings are not energy efficient and must be radically upgraded in order to improve their performance. In reality the situation is more complicated and assumptions about poor performance are not always justified. For example, as Dennis Rodwell points out in his article on heritage and sustainability (see page 3), when HM Courts Service analysed their records of energy use they found that ‘…buildings from the early part of the 20th century and before tend to use less energy than the equivalent more recent buildings’. Nevertheless, opportunities exist to improve the energy and carbon performance of many heritage buildings, thereby helping them to remain viable and useful now and in the future. The challenges in striking the right balance between benefit and harm can, however, be considerable. The unintended consequences of getting energy efficiency measures wrong (or doing them badly) include: • harm to heritage significance altered appearance loss of features • harm to human health and building fabric poor indoor air quality condensation and mould growth decay of building fabric • failure to achieve the predicted savings or reductions in environmental impact. Getting the balance right is best achieved through a systematic ‘whole building’ approach. This is a logical process based on conservation planning principles that uses the understanding of a heritage asset, its context, significance and all the factors that affect energy use (not least, the people inhabiting it) as the starting point for devising strategies for energy efficiency. Strategies may vary depending on whether the main aim is to mitigate carbon emissions, cut fuel bills or comply with legislation such as the Building Regulations. Compromises are inevitable, but the whole building approach enables informed decisions to be taken and ensures that improvements are suitable, well-integrated, properly coordinated, effective, cost-efficient and sustainable. It also provides an effective framework for communication between all parties involved in the process, including assessors, designers, installers and the people who will use and manage the building. A ‘Mean, Lean, Green’ philosophy has evolved for the design, construction and use of new buildings. This is based on a hierarchy that begins with the siting, orientation, form, materials and construction of the building to optimise the efficient use of energy and other resources (‘Mean’). Next comes the design, management and control of engineering systems to ensure they can Shrewsbury Flaxmill Maltings (Grade I, 1797), where Historic England is assessing the effects of internal wall insulation on the hygrothermal behaviour of brickwork (Photo: Jonathan Taylor, all other images: Iain McCaig/Historic England)