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Can historic buildings join the race to net zero carbon? This was the question posed by Amy Punter, senior associate at services engineer Hoare Lea. Not surprisingly, her answer was ‘yes’ as she demonstrated through two projects.

She explained, in answer to a question about when it is worth saving a building or not, that although the practice wants to keep buildings where possible, ‘We don’t want to categorically retain. The key is to do a collaborative feasibility study.’

There was no question, however, about whether or not to retain the listed Old Admiralty Building on London’s Horse Guards Parade. This was not just a building with heritage and potential – it had issues unlike any other. One of the problems was where to site the 10-tonne air chillers. With roof space at a premium, this would have to be in the main courtyard. However, Punter explained, this is the very courtyard in which the queen’s carriage turns on parade days, so the chillers had to be hidden in a lightwell. Certainly not a run-of-the-mill problem.

Speakers from left to right: Andrew McEwan, Amy Punter, and Donald Matheson

In other ways the challenges were more typical – and not easy. The building had a tendency to overheat. The new design was supposed to address this, while also doubling the occupancy and opening up cellular spaces to give greater connectivity. Architect BDP had to find ways of doing this, improving performance without affecting the appearance. In particular, the arched corridors with mosaic floors were a visual gem that needed to be touched as little as possible.

One of the few interventions that was allowed and that could bring down the heating load was the introduction of secondary glazing. The team also put in mechanical ventilation plant with integral heating and cooling. A lot of effort went into details, such as taking services across the corridors, so that they were as invisible as possible, and into those chillers. To keep them out of view, they were placed as low as possible, but there then had to be detailed design adaptations to prevent recirculation of air.

In the offices, ventilation is contained in a ‘floating raft’. The architect, Punter explained, worked hard with conservation officers to pull bulkheads away from the walls to reveal the historic cornices. The engineers made huge efforts to minimise the visual impact.

A similar attention to historic detail was used by architect Orms on two buildings from a period that, until recently, received far less respect – the 1970s. In one case, the new Standard Hotel, in King’s Cross, London, the practice was working with a building that had been praised when first completed but then fell into disrepair. The aim of the project was to bring it back to life with a new use and, said Andrew McEwan, associate director of Orms,  ‘turn it from urban background to foreground.’

The building had been an annex to Camden Town Hall that was no longer needed when the authority moved to a new headquarters. Originally designed by Camden’s in-house architect, it has a very sculptural and distinctive facade. This has been preserved, with great care taken in the design and commissioning of new windows.

The amount of the building that has remained is impressive – 94 per cent of the existing structure. New supports were woven through for additional floors at roof level. By demolishing a link between this building and the original council building, the team was able to create new public realm. There were some simple moves to signal how much the building had changed and to make it more welcoming. These included a bright red capsule lift on the outside of the building and a new entrance canopy.

The other building was far less distinguished and the architect made more radical changes. 160 Old Street was originally a Royal Mail sorting office. Orms worked with client Portland Estates who wanted to use it as a testbed for technology within offices. ‘We wanted to push the envelope of what a refurbished building could deliver,’ McEwan said.

The team stripped the building back to its concrete cores and frame, and extended it by giving it an external exoskeleton and adding three floors. The central wing on the E-shaped plan had to be removed because it turned out to have non-durable woodwool slabs. One of the key moves was re-using the basements, previously car parks and loading bays. The architect ‘drove courtyards down to create double-height and triple-height spaces’. These spaces were as stripped-back as possible and so successful that they now form the UK and Europe HQ for CNN.

The third speaker, Donald Matheson, director of Matheson Whitely, described a project on a smaller scale. It redeveloped the buildings of art-studio organisation Studio Voltaire. This  complex consisted of studio spaces in former industrial buildings, plus a chapel that had been converted into an exhibition space. The chapel was the only part of the complex of which the public was previously aware. By bringing in some subtle changes, the architect has created additional space in a new mezzanine. This has allowed it to introduce a shop and cafe, as well as some communal studios. The chapel now links to the rest of the complex and there is disabled access throughout.

The project used BIM to model the existing structure and understand which changes it could support. Matheson explained, in answer to a question about his use of digital twins, that, ‘We had so much support from the client,’ he said. ‘We had a rare chunk of time to analyse and document.’ This, he added, enabled the practice to use the technology to the maximum.

What these projects show is that it is possible to work, and work well, with a wide range of existing buildings. And also that, in order to do it well, it needs talent, study, understanding and ingenuity – these buildings are usually far more demanding than new construction is.