C O N T E X T 1 4 9 : M A Y 2 0 1 7 11 G R E E N R E T R O F I T The retrofit process Retrofitting traditional buildings depends on understanding how they differ from modern construction. John Edwards, guest commissioning editor, introduces the retrofit process and the theme of this issue of Context. Retrofit is often defined as adding something that a building did not have when it was constructed. This may seem like an odd place to start when there could be ways to make existing building fabric more energy efficient without adding anything to it. Unfortunately, jumping into retrofit as the first thing to do seems to be the most common approach. The Every Home Counts report on retrofit is indicative of this (see John Preston’s article, page 13). While that report mentions an holistic approach, that is not really what it is, otherwise it would not start with retrofit. There are some very important steps to take if one is contemplating retrofit of any building, and most certainly a traditional or historic one. This is because the onesize-fits-all approach treats all buildings as if they were modern. The first lesson must be that traditional buildings are very different and should be treated differently. In a nutshell, traditional buildings are permeable and modern buildings rely on vapour barriers. The need to retain vapour permeability and the risks we take when we do not are well explained in the article on dampness (page 15) and by Colin King on retrofit risks (page 23). It is essential to understand the location of the building and the weather exposure zone it is located in. For example, London and Swansea are only 200 miles apart, but Swansea receives four times as much rainfall as London. Understanding the type of building, its age and original construction, including the materials it is constructed from, is critically important. So are how the building has been altered and repaired, and its condition. A thorough survey is required, taking a building-pathological approach, as outlined in the article on dampness, and using the latest technology, as described by Jo Atkinson (page 17). The condition survey should include an analysis of how the building is used and the suitability of that use. For example, is proper use made of the existing ventilation? Is sufficient ventilation provided? Is a particular use prone to producing high levels of humidity? Married to data about its condition, this type of information can help us understand how a building performs. The next stage involves consideration of ‘works’ that should be undertaken to the building’s existing fabric. Putting the building into good repair and devising the means by which to manage moisture is essential. Damp building fabric can be up to 30 per cent less energy efficient than that which is dry. This points towards maintaining and repairing buildings properly, and not doing anything that will trap moisture. Only after ‘energy efficiency works’ have been carried out should ‘measures’ be considered. An energy performance certificate (EPC) will detail recommended measures. These should be considered critically. EPCs for dwellings are produced by a method known as RdSAP (Reduced Data Standard Assessment Procedure). Due to its relative simplicity, with standardised rather than real data being used, RdSAP is an inaccurate means of determining energy efficiency and so can produce unreliable recommendations. For example, RdSAP does not consider how a building is used or its condition, and its raw data on, for example, the thermal efficiency of solid walls is flawed, as Caroline Rye and Cameron Scott explain. A more robust approach is to use a BRE Domestic Energy Model (BREDEM) method such as the Home Energy Master Plan. Even with this, caution should be exercised. There can often be a conflict between energy advice and advice based on building pathology. As Carsten Hermann implies (page 20), this may be because The holistic retrofit process following BS 7913: 2013 up to the advice and design stage: Dealing with existing fabric first Condition survey Work to existing fabric, making it more energy efficient Energy efficiency assessment Test proposals with heritage impact assessments Advise, then design ‘works’ and ‘measures’ Consider and evaluate mix of possible ‘works’ to existing fabric and retrofit ‘measures’, using the STBA Guidance Wheel Determine which proposals are likely to work. Carry out cost benefit analysis, which may result in reconsideration Consider use Building pathology The heritage impact assessment process considers all types of issue Influence and list List of recommended measures Amended proposals
RkJQdWJsaXNoZXIy MjgyMjA=