The Building Conservation Directory 2020

38 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 0 C AT H E D R A L C O MM U N I C AT I O N S Even inside buildings drones are proving their usefulness; ones with external protective cages are now becoming available that can literally bounce off the walls as they fly through a dangerous building or confined space gathering measurements. BIM (building information modelling) software can be used to integrate technologies such as laser scanning, photogrammetry, moisture readings and thermal imaging, creating powerful graphic data models that can be shared and interrogated through different media such as fly-throughs, animations and web shares. Time-lapse video animations combining precise laser scanned point clouds with photogrammetry can be used to provide easily understood photo-realistic 3D models that are an ideal platform for accurately displaying thermal imaging and moisture content. These allow building pathologists to consult with a wide circle of experts and stakeholders. Integrated data models allow the viewer to turn the datasets on and off in much the same way as we currently use 2D layers on public GIS viewers. Storing video and 3D mesh models for viewing online through a standard web browser makes the information easily accessible to a geographically scattered team. 3D formats are already embedded in the property and construction sectors. BIM software suites such as Revit are the default 3D tools to model and document buildings, but their usefulness for many heritage projects is limited partly because their functionality is based around designing new buildings, and partly because the conservation community lacks experienced users. This creates an exciting arena in which building pathologists can create a merged live and virtual laboratory. Much work has been done by the SPAB and Historic England to compare predictive building performance software such as WUFI and RdSAP with real life outcomes, concluding that real life performance is difficult to model with existing software. Data collation and storage is the area of biggest change and challenge. Many buildings have already been scanned to 3D point clouds and inserted into BIM models such as Revit onto which moisture readings (some at depth) can be modelled, but it is doubtful whether these models remain ‘live’ documents or become accessible to pathologists. TAKE UP Three identifiable drivers are overcoming the challenges in the adoption of these technologies for historic environments; consumer appetites, the policy environment and practice standards. In terms of consumer appetite for improved pathology, most people are aware that moisture in buildings causes deterioration of materials, chiefly by timber decay, corrosion of embedded metals (in particular ferrous metals) and stone erosion (by salt crystallisation and frost action). In extreme cases, this can lead to structural failure, but mostly the lifecycle of the elements is shortened and early replacement is required. For historic buildings, this means that the building’s importance, significance or authenticity are impaired. Where the erosion is to an element that also has artistic interest, such as panelling, carvings and fine furnishings, the loss is all the more regrettable. Demand for environmental monitoring therefore tends to be led by organisations that manage large and sensitive collections or interiors, while in the residential sector demand is often driven by concerns for health and wellbeing, as dampness can support molds such as Aspergillus which are known to cause breathing difficulties for some. Commercial factors will inevitably determine which emerging technologies appeal to clients’ budgets. The cost of equipment and ease of use are the most obvious factors, meaning that even relatively unreliable moisture measurement techniques, such as resistivity meters, are still very widely used. Microwave moisture meters are currently about ten times as expensive and require some skill to interpret, so take-up is slower. Thermal imaging on the other hand is cost effective and similar enough to the interpretation of visible light images that take- up has been good. Clients are increasingly prepared to invest in remote monitoring and re-inspection because they understand the value of more than one data set in evaluation. Many are also increasingly participative in the diagnostic process, and informed about how good investigation can avoid costly, disruptive and potentially futile interventions. In terms of policy, destructive testing is generally considered the last resort for historic environments. Emerging technologies in non-destructive testing allow regulators to take a tougher line when examining evidence to justify destructive tests. Furthermore, the practice of carrying out surveys quinquennially is becoming more common, providing reliable baseline data which can avoid the need for further investigation and unnecessary interventions – or equally, it may trigger investigations in a timely and informed way. Historic England, Historic Environment Scotland and others have invested heavily to provide a knowledge base about non- destructive testing and monitoring, and practice standards are evolving to build on that knowledge base. The RICS is jointly publishing new guidance around the diagnosis of dampness for historic buildings with key partners from the heritage sector, placing heavy emphasis on monitoring and building the evidence base. Although hypothesis-led diagnosis is likely to remain the primary diagnostic method in the mainstream, emerging technologies allow building pathologists to move to evidence-based diagnosis in complex cases, most particularly for historic buildings. Practitioners will need to work together to join up the measurement and building pathology disciplines, by investing heavily in training and skills sharing. The historic environment community as a whole will also need to work together on the practical and ethical challenges posed by data storage and access issues. Heritage assets are managed best where their survey and maintenance records are available as a shared resource, but the range and volume of data held on local authority HERs is becoming unsustainable on a not-for-profit basis. Private sector solutions on the other hand, expose the historic environment sector to the risk of ‘data hostaging’ if inadequately resourced. The collection and storage of great data requires a commitment to costs and trust that it will be well curated. Getting a line into curators’ budgets for such work will depend on whether the data and learning outcomes are going to be freely shared, or whether private owners, say, for commercial or security reasons, need the data to be protected. Shared access to heritage data would also allow stakeholders to draw broader conclusions about the state of the historic built environment. However, limiting data to highly-valued heritage assets only (whether in terms of significance or monetary value) would exclude the majority of historic buildings and, in turn, those buildings’ users, reducing the value of the resource. Owners’ appetite for evidence-based diagnostics, and practitioners’ skills set to provide them, are thus only part of the story. The historic environment sector also needs to work together to overcome the challenges that curating the data freely and fairly present. This seems a worthwhile endeavour, because if converging technologies do transform building pathology practices, there will be far reaching benefits for the whole historic environment. LYNDA JUBB is a director of Moisture Map Ltd and Jubb Clews Ltd. She is a fellow of the Royal Institution of Chartered Surveyors, a member of the Institute of Historic Building Conservation and lead author of the 2009 RICS guidance note on historic building conservation. STEVE BURY is a metric survey consultant at Moisture Map Ltd, and Director of Bury Associates. He is a member of the Survey Association and a contributor to Historic England’s Guidance note on BIM for Heritage. A rectified photograph of Tonedale Mill extracted from visible light drone footage to record both condition and metric data (Image: Jubb Clews Ltd)