The Building Conservation Directory 2023

37 C AT H E D R A L C O M M U N I C AT I O N S T H E B U I L D I N G C O N S E R VAT I O N D I R E C T O R Y 2 0 2 3 | C E L E B R AT I N G 3 0 Y E A R S P R O F E S S I O N A L S E R V I C E S 1 protracted at the interface between the new lime ‘parge’ coat and the woodfibre insulation. Therefore, site working practices were adjusted to ensure this material had some time to dry prior to the application of the insulation board, to reduce risks. In comparison with the uninsulated ‘control’ wall, the monitoring also showed that air movement through the wall section (a contributory factor in heat loss) was considerably reduced in the insulated wall, due to the lime plaster contributing to air tightness at the internal surface of the wall. Lastly, by measuring a U-value for the insulated test wall, the reduction in heat loss previously estimated using the base case measurements was confirmed to be ≈ 0.3 W/m 2 K, the improvement target figure. In-service monitoring In addition, specifically to address uncertainties as to the long-term performance of insulated fabric at New Court, ArchiMetrics was asked to draw up a design for an ‘in-service’ monitoring installation. Ultimately, listed building consent was granted for the retrofit of New Court on the condition that the performance of the historic fabric would be monitored for seven years following the completion of the retrofit to ensure that no harm was caused to historic fabric as a result of the work. Currently, these measurements include insulation, masonry, timbers, external and internal room conditions. Fabric monitoring, in particular, looks at temperature and RH as well as material moisture content (%MC) responses within walls, at floor/wall junctions and in roof elements. ArchiMetrics make measurements in 28 rooms at New Court, with 540 sensor values providing 107,586 data points each day. Data analysis and reporting For the first four years post-completion, ArchiMetrics reported on conditions within the refurbished New Court on a quarterly basis and have now moved to half-yearly reporting. A detailed, comprehensive report is also prepared annually. Data is analysed graphically with a written commentary across a variety of different metrics. Primarily, we are looking for indications of ‘adverse conditions’ (determined by different thresholds) arising and persisting within the fabric and room environments. However, much additional information is gleaned about how the building is performing in general, in response to occupant behaviour, changing external conditions and many other factors. Mitigation In the event that ‘adverse conditions’ are reported, the in-service monitoring is accompanied by a ‘mitigation strategy’. This document sets out a series of steps for the project team to follow to ameliorate or improve negative conditions. If triggered, the effects of the mitigation measures would themselves be subject to the same monitoring and feedback, with the ultimate option, in the event of irredeemable failure, that relevant parts of the retrofit would be reversed to avoid damage to the historic fabric. Of course, if necessary, additional monitoring or measurements can be deployed to assess a specific circumstance or provide new, or different, information. Happily, the monitoring at New Court demonstrates that the careful informed approach to the retrofit of the listed building has been worthwhile and its fabric is performing well. That is to say heat losses have been reduced and there appears to have been no concomitant increase in fabric moisture to levels which might pose a risk. Dissemination While ArchiMetrics’ experiences at Trinity may not illustrate every twist and turn of our workflow diagram, it is a testament to the thoroughness of that project that many of the stages set out in Figure 1 have been tried and tested during that particular project. Other projects will, naturally, only require engagement with more limited parts of this workflow diagram. Nevertheless, the guiding principle will always be ‘what are the project questions?’, as all subsequent decision- making flows from this. These questions can be concerned with the potential risks posed by the retrofit of building insulation, where monitoring and modelling can be essential to provide confidence for this work. However, the questions we might ask of buildings and their performance are potentially endless. They may relate to troubleshooting a specific problem, or ensuring certain conditions are achieved and maintained, sizing mechanical and electrical plant, verifying or quantifying the performance of an intervention or product for example. Whatever the application, if these questions are well defined at the outset of a project and with the help of workflows such as that presented here, we are convinced that modelling and monitoring are a valuable way to increase our understanding of buildings. By acting with this knowledge and carrying it forward to future projects we can deliver meaningful improvements to the performance, safe operation and quality of our built environment. CAROLINE RYE and CAMERON SCOTT are founding partners at the building performance research company ArchiMetrics Ltd (www.archimetrics.co.uk) . The monitoring equipment installed behind the panelling in one of the apartments at New Court (Image: Archimetrics)

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