12 C O N T E X T 1 4 9 : M A Y 2 0 1 7 of the limitations of energy assessors’ competency. For example, it is sometimes recommended to block redundant chimney flues to save energy, but flues need ventilating to help keep them free of dampness. When looking at possible measures, choosing the least costly and simplest first is the most appropriate approach. This follows what is known as the ‘energy hierarchy’, by which the most costly and major interventions are looked at only after all other possibilities have been explored. The STBA (Sustainable Traditional Buildings Alliance) guidance wheel, described by Carsten Hermann, is an excellent tool to use when considering each measure. In using this wheel, the choice of measures should have all been well considered. One should only use it, however, if a proper condition survey has been carried out, and if the wheel is being used by someone who is truly competent. The wheel lacks some measures and does not include things other than ‘measures’ which would often improve energy efficiency. The outline of what has been described thus far follows BS 7913: 2013: Guide to the Conservation of Historic Buildings. This British Standard calls for the undertaking of heritage impact assessments. If the building has a high level of historic importance, it might have a conservation management plan, and conservation management policies that should guide the overall approach and the suitability of measures. If it does not, it should contain information on significance values for use within heritage impact assessments. Most buildings do not have a conservation management plan or any other analysis of significance, in which case significance values will have to be ascertained. BS 7913: 2013 sets out how this can be done. It explains that any analysis of significance needs to be proportionate. In most cases this will involve a quick and dirty exercise that provides the highlights of historic significance. All traditional buildings have some degree of significance, even if it is very minor. BS 7913: 2013 contains what could be described as a checklist of issues to consider. These could relate to appearance, for example, or to a deeper meaning such as a reason why the building was built. However, in measuring the impact on significance a justification for the proposal has to be made. That will include an analysis of any alternatives to making the building more energy efficient and questioning technical feasibility. The broadest of issues must be considered. A heritage impact assessment measures the impact of any proposal on significance and seeks to mitigate the impact. As highlighted above, this means considering matters of significance and technical issues alongside each other. If the proposals are changed during the process of a heritage impact assessment, this can again be considered through the STBA wheel, followed by a heritage impact assessment, with the cycle repeated until the optimum outcome is achieved. One must not forget the need for a cost-benefit analysis that will consider the cost of proposals and the payback period, allowing different options to be considered and reconsidered. This process is intended to provide a robust means of properly considering what needs to be done, and to ensure an optimum balance between all issues. It is a means of managing risks, which can be devastating if things go wrong, as Colin King describes. King stresses the importance of building physics, which is the means to calculate the effects of measures. However, with so little accurate data on the thermal value of existing building fabric, many calculations made to predict the changes in hygrothermal performance can be seen only as something to guide us, and they need to be treated with caution. We may have to develop and deploy solutions that could be described as well-informed rules of thumb. When it comes to implementing works and measures, the risks continue. Many studies highlight the almost endemic deficiencies in quality control, as highlighted in reports by BRE. Quality control is paramount. While some claim that employing a clerk of works is the answer, the real answer lies in a more professional approach to quality management at the outset. A quality-management strategy should be developed in accordance with BS 7913: 2013. This involves determining which elements carry the greatest risks and which have the maximum negative impact, and concentrating on those throughout. Matters such as installing rainwater gutters will not be concentrated on, as they can be inspected at the end of a project to determine whether they are satisfactory. Compare that to, say, the installation of internal wall insulation, involving many activities where short cuts can be taken and consequences that may not be known about for many years. A process that involves evidencing the satisfactory completion of each part of the process is necessary. Reducing risks depends on professional project and construction management with expertise in traditional building retrofit. There are many types of retrofit project. Most of those that are executed badly are the large-scale projects funded by government and utility companies. There are also many smaller projects, some of which will form part of projects that were broader and have simply added in retrofit elements. Many such projects may have been very well considered and executed. Others may not, but are not highlighted so publicly. The most common feature that exposes such projects is the use of impermeable insulation, as witnessed even in the best of our television ‘expert’ portrayals of exemplar projects involving traditional buildings. The answer must involve a greater degree of competence from those involved. Individuals may seek out training courses, but many of these do not focus on all the features raised here. The only course delivering a qualification in this subject is the Construction Industry Training Board’s ‘Energy Efficiency Measures for Older and Traditional Buildings’. This two-day course, independently accredited by the Scottish Qualification Authority, is offered through the Environment Study Centre (environmentstudycentre.org). John Edwards is a director of Edwards Hart, a consultancy specialising in older buildings and heritage. He is conservation accredited and certified, and a chartered environmentalist qualified to postgraduate level in architectural building conservation. Formerly assistant director at Cadw, he was the lead author of BS7913: 2013: Guide to the Conservation of Historic Buildings. He is a trustee of the IHBC and professor of practice at the University of Wales Trinity St David. An 1853 house in Cwmdare, south Wales. A Reduced Data Standard Assessment Procedure and a Green Deal assessment (defunct) recommended options for replacing the windows with payback periods between 32 and 63 years. The process did not consider repairing the existing windows and providing secondary glazing, which would have achieved comparable energy efficiency.
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