Context 168 - June 2021

C O N T E X T 1 6 8 : J U N E 2 0 2 1 17 DIGITAL TECHNOLOGY HAMISH McMICHAEL Digital technology in the historic environment Digital technology offers increasing opportunities in conserving historic buildings: through their management and maintenance, and in education and interpretation. 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 detec- tion 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 stun- ning 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 model- ling these historic structures. Twelve years later, with advances in both software and hardware processing, I was com- missioned 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 construc- tion, 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 non- specific 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 geo- metrical 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 Above: A screenshot showing the thermal modelling analysis of the cottage Left: A Grade II listed cottage in South Oxfordshire was used to test the software.

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