Digital technology in the historic environment
|A Grade II listed cottage in South Oxfordshire and a screenshot showing the thermal modelling analysis of the cottage.|
My interest in the potential of digital models of historic buildings began in 1997 with my dissertation project at the Mackintosh School of Architecture, where David McDonald and I were tasked with building a 3D model of Sir John Soane’s Museum in Lincoln’s Inn Fields. In the days before LIDAR (light detection and ranging) scanning and the widespread adoption of BIM (building information model) software, we used 2D measured surveys to build our 3D models using standard AutoCAD.
We soon realised the size of our task, using complex Boolean functions to create the stunning geometry of Soane’s pendentive domes in the breakfast room. With the limitations of computer processing and image rendering, we focused on creating wireframe models, using these to better understand the geometry of the structure. Our dissertation, shortlisted for the RIBA bronze award, analysed the opportunities for novel analysis that are presented by modelling these historic structures.
Twelve years later, with advances in both software and hardware processing, I was commissioned to work on the refurbishment and extension of the Grand Hotel in Birmingham, a Grade II* listed building on the heritage-at-risk register and under threat of demolition. Occupying almost a whole city block on Colmore Row, opposite the cathedral, the building was built in the late 19th century in several phases, by different architects, and thus had numerous complex levels and different forms of construction, and several mixed uses and tenures.
My team was brought in to help work through various feasibility studies, for adapting and re-modelling the fabric of the building, to bring it up to the standard for a contemporary full-service, boutique hotel. This meant adapting and combining rooms to make them the right size and mix of types, creating new en-suites and circulation routes, and threading new services through the building.
To work through the myriad options to be analysed, we needed to be able to explore and visualise the interventions in 3D, so we took the 2D survey information and built a 3D BIM model. We quickly realised that we needed a complex system of feature tagging and naming, to help categorise and manage the different elements and forms of the building. One major challenge was in modelling the complex, non-orthogonal geometry (such as thick masonry walls with wet plaster) which do not conform to any standard ‘wall’ types of construction in the software. These had to be modelled as nonspecific geometric ‘matter’ (that is, without any smart properties describing them as walls).
In deciding how detailed to make the model, it is important to think through what it will be used for. Its greatest use was for working out the interventions, new openings and the removal of fabric, and for planning vertical routes for new services though the building. It was also important in helping understand load paths through the structure.
This project taught us that the basic geometrical survey does not capture the real form of construction behind the facade or internal wall linings. What may initially be assumed to be a solid wall could be a hybrid form of construction, where following further intrusive investigations the legacy of historic adaptations would be revealed. In some instances whole sections of loadbearing masonry wall had been removed and subsequently re-infilled with timber studwork. The most important lesson was to anticipate the unknowns, to use the model as a tool to identify where further surveys would be needed, and to record this data.
It would theoretically be possible to discover all the layers of a building’s construction behind the veneer, and to input them into a BIM model with all the correct attributes assigned to each element. However, this would be an exhausting exercise which would quickly cost more to produce in time and cost than the benefits of using such a model would ever realise within the life expectancy of a typical project.
An appreciation of where there is real value in the data highlights the greatest area of potential for BIM models: as a record of an asset and works undertaken for future conservation, repair and maintenance. We have all had experience of working on a building and discovering an unknown, whether a structural alteration, repair or service, or of the challenge of trying to identify the specification of a product used in the past. Searching through archived records may reveal some insights, and buildings with more recent interventions may have more extensive records, such as operations and maintenance manuals. However, as a building passes from one generation to the next, often the most valuable source of information, that which is held in the memory of the building’s custodians, is lost.
The greatest potential of technology lies in the ability to collate live, dynamic records of buildings, by tagging data such as notes, photographs, specifications and other records, to a 3D model. This is in effect creating a 3D index for building records. Companies such as Matterport, which offers the creation of an immersive tour of buildings, by using specialist hardware to scan and survey, creating an immersive ‘point-cloud’ of photogrammetric data, are starting to offer such asset tagging as a feature for estate agent viewings.
Those who have invested in specialist headsets such as Magic Leap, Facebook’s Oculus or Microsoft’s Hololens can already bring immersive scans of existing buildings into virtual reality. However, the real transformation will occur with the superimposition of this 3D data into a user’s field of vision, using ‘augmented reality’. Companies such as Google and Apple are investing a vast amount of money in this, and the much-rumoured Apple Glasses are eagerly awaited by the tech sector.
The applications for historic buildings are vast, not just in operation and maintenance, but also for education and interpretation, and even wayfinding and safety. Imagine being able to walk through a building, selecting an icon in your viewer, hovering over a feature such as door or window, and having important data pop-up for you to review. There is enormous potential to collect all relevant data, archive it and use this simple visual index to assist with retrieval.
It puts the value and decision making back into the hands of the building stakeholders, avoiding unnecessary time being spent creating a complex BIM model for no purpose. The benefit lies in focusing the human effort into the analysis of a building for specific purposes. This could be in recording the thermal performance of the building fabric to help analyse its energy use, or even the embodied carbon tied up in its materials and construction. The real technological advances in the sector will come when software developers can start to write algorithms to train computers (machine learning) to recognise certain property features, to assist in analysis and predictions.
This is the approach that my team is pursuing with our new company Ambue. We have recognised the difficulties that residential property owners have to simply and inexpensively explore the potential options to retrofit their homes. We have built a simple software platform with tools to help them create a basic 3D model of their home. They can use this to test various retrofit options, get instant results and make informed investment decisions.
The real revelation has come with testing this tool on historic properties. We built a bespoke model of a Grade II listed cottage in South Oxfordshire to run through our thermal modelling analysis. The home was heated by an oil-fired boiler, a converted oil-fired Aga and open fireplaces. Our software analysis showed that the annual carbon dioxide emissions were equivalent to over 17 tons, compared to the UK domestic average of around five tons.
The analysis showed a range of potential measures to reduce the emissions, ranging from internal wall insulation, floor heating, secondary glazing and loft insulation. Certain measures are problematic, in terms not only of disruption but also of visual intrusion and impact on the historic fabric. But we were able to recommend a combination of non-obtrusive loft insulation, secondary glazing to selected windows and an air-source heat pump, which could reduce emissions by nearly half.
As more properties and datasets are modelled, collected and analysed, we will be able to train the software to look at the best-practice solutions from comparable buildings, with performance data collected from real installations. This will be used to refine the advice and accuracy of the energy-saving predictions, assisting more building owners in making the best-informed decisions about their properties.
This article originally appeared in Context 168, published by the Institute of Historic Building Conservation (IHBC) in June 2021. It was written by Hamish McMichael, an RIBA conservation architect, former director at BGS Architects and co-founder of Ambue.
Related articles on Designing Buildings Wiki
- BIM for heritage asset management.
- Digital techniques for heritage restoration.
- Heritage asset.
- Historic building.
- Historic England.
- IHBC articles.
- Innovation and investigation at the Hill House.
- Laser scanning for building design and construction.
- Listed buildings.
- The influence of digital technologies on conservation.
- The Institute of Historic Building Conservation.