Heritage Retrofit

16 BCD SPECIAL REPORT ON HERITAGE RETROFIT FIRST ANNUAL EDITION has less challenging heat demand and airtightness requirements. There are many aspects of EnerPhit which are very good such as mechanical heat recovery, but the approach still relies on high levels of insulation and airtightness and will only work well if the relevant products have been installed properly. Although traditional buildings need to retain their vapour permeability characteristics, the high insulation levels which are required (to achieve the specified U-values) inevitably means solid wall insulation. The technical feasibility of installing solid wall insulation will depend on the construction of the building and its location, with due consideration paid to UK weather exposure zones. This might not be feasible in BRE zones three and four (which includes most of Scotland, Wales and Northern Ireland, and the more westerly areas of England). The impact on significance that such works would make also needs to be assessed. HOLISTIC ALTERNATIVES While all these official and credible energy and environmental assessment methods provide tangible outputs, they are all unreliable or potentially problematic when it comes to traditional buildings. The best way of achieving energy efficiency in a sustainable way is to take a holistic approach which considers all aspects of the building. This, however, doesn’t deliver any SAP points which are of course needed for EPCs to improve the official energy performance rating. The STBA retrofit guidance wheel (page 12) is an excellent tool for going through the process of choosing retrofit measures and there isn’t anything better that does this. It takes one through all the options, steering away from those measures which are most risky and less likely to work, and towards those which are less risky and more likely to work. It also advises on how measures interact and therefore what they mean in combination with each other. But again, the wheel needs to be used with caution. It is essential to understand the make- up of the building and its condition, and there is no substitute for a thorough building survey which addresses the cause of problems from a building pathology perspective. In addition a heritage impact assessment may well be required to measure the impact of proposals on the historic significance of a building. There is much concern from the well-informed about the approach we take towards the energy efficiency and sustainability of traditional buildings. One problem is that standards and guidance suitable for modern construction systems are often incorrectly applied to traditional structures, and there is clearly a lack of specialist expertise in this area. However, other forms of retrofit have had even greater detrimental impact on traditional buildings. For example, the retrofitting of damp-proof courses and the associated works (such as the use of impervious plasters and cement renders, and often the replacement of rotten timber floors with concrete) have, just like many forms of energy efficiency retrofit, resulted in changing the hygrothermal performance of traditional buildings. Dampness and mould are common symptoms and both suggest that any form of retrofit needs to be well informed. Several new courses are beginning to address these problems. In particular the new Level 3 SQA Award in the ‘energy efficiency and retrofit of traditional buildings’ had trained 200 people by the end of 2016. However, there are some six million traditional buildings in the UK, and with an acknowledged deficiency in the knowledge and skills of both the professions and building contractors in this area, thousands need to be trained not hundreds. JOHN EDWARDS is a director of Edwards Hart (www.edwardshart. co.uk ), a consultancy that specialises in older buildings and heritage. He is a conservation accredited surveyor and chartered environmentalist qualified to postgraduate level in architectural building conservation. Formerly assistant director at Cadw, he was the lead author for BS7913: 2013: Guide to the Conservation of Historic Buildings . He is a trustee of the IHBC and Professor on Practice at the University of Wales Trinity St David. Above, draught-stripping sash windows at Clovelly, Devon as part of the programme of EPC improvement measures and, top left, simple secondary glazing fitted to a casement window. (Photos: Jonathan Taylor)