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Applying Standards to the Retrofit of a Georgian Terrace

Our latest project, the refurbishment and retrofit of a Georgian terrace in Cambrian Place, Swansea, has now received listed building consent for a range of work which includes both fabric retrofit measures and also renewable energy technologies. As with any project that involves changes to a listed building, evidence that demonstrates that the changes proposed are necessary, and that all other alternative means of achieving objectives have been explored in detail, is essential. This isn’t just important in order to obtain the consent, but also that the building is treated appropriately. First of all, it has to be explained why we need to achieve certain objectives. Here, the climate change emergency and the laws and regulations associated in dealing with climate change in the key objective, but doing so in a sustainable way.

At Edwards Hart, we have a clear plan on how to contemplate such projects. It involves working to standards and authoritative guidance. It is all too easy, to criticise projects and the consents which have been granted. In this particular project, we have worked to BS EN 16882: 2017, which is the European standard for retrofitting historic buildings. However, we have bolted on other sets of guidance, such as BS 7913: 2013, which is the UK standard for working on traditional and protected buildings. Plus, including working to many of the elements that are contained in PAS 2038: 2021, which is the UK standard for retrofitting non-domestic buildings. The latter may seem a bit odd, as these are dwellings, but this standard explains a robust approach, which is over and above that which is seen in the UK standard for retrofitting dwellings, PAS 2035.

In developing project proposals, working to basic principles, ethics and logical and robust processes, undertaken by those who are competent, should lead to a set of proposals that are the correct ones. This is exactly the approach that was taken in this project and has led to, amongst other things, a host of fabric retrofit measures such as solid wall insulation, and renewables such as photovoltaic panels on the roof above the principal elevation. A risk-based approach was taken, not fabric first, but this approach led to evidencing that fabric retrofit  measures were essential, along with putting the building into good and appropriate repair.

The overall approach combines those issues that are seen as good conservation practice, combined with the essentials in terms of sustainability and retrofit. There are many examples in this project, that highlight that these issues compliment each other. However, there are challenges such as the location for photovoltaic panels. Here it is about evidencing in the first place that they are necessary, and then looking at the range of locations where they could be installed, and bolted onto that is the type of panels.

The evidencing, that solid wall insulation was necessary, involved hygrothermal simulation modelling. Without going into all the detail, such modelling will assume that the walls are in good condition when evaluating alternative types of insulation. The front elevation of the building comprises face brickwork, with many bricks in poor condition. A conservation approach involves minimum intervention, which would mean only replacing bricks where it is absolutely necessary to do so, on the basis that at some time in the future we may replace these other bricks when it becomes necessary to do so. Here, there is a conflict with sustainability and climate change, and the accuracy of the hygrothermal modelling. This is because that unless all the defective bricks are renewed, then the predicted performance achieved by the modelling, will not be achieved. Likewise, when it comes to the repointing of the mortar joints, the modelling will assume that the mortars are fully compacted into the joints, and the only sure way of achieving this is to use repointing irons and not pointing trowels when repointing!

All projects require attention to detail at all stages, and this must include the implementation stage where quality control is paramount. BS 7913 requires quality management processes incorporating inspection and test plans, and this is for good reason. A lack of robustness at the implementation stage, risks that very common phenomenon  of a ‘performance gap’. Here however, it isn’t just the difference between the improved energy performance that is achieved compared to what an energy model would predict, but also the difference in the technical performance of the building fabric and all the risks which that entails.

Edwards Hart were first involved in this project in 2015, with a condition survey which took a building pathological approach, and has provided many various forms of input plus direction for this project ever since, up to the listed building consent stage.

A lot can be learned from this project and is one of the projects used as case studies by Professor John Edwards, who led the Edwards Hart input into this project, in his education work. This includes courses for the Environment Study Centre, and in particular the 2 Day course in the retrofit of traditional buildings achieving the Level 3 Award qualification, which is required by PAS 2035 and PAS 2038.