FOOTPRINT+, the international conference for the decarbonisation of the built environment, took place last week at its new location in Old Billingsgate, London, having grown rapidly since its beginnings in Brighton, near Tenderstream HQ in Brighton. Among a packed programme of events and networking sessions, we attended several panel discussions - including presentations from Tenderstream member companies - covering the complex retrofit and reuse of significant large-scale buildings.

The value of mass timber

An engaging discussion examined the deep retrofit of Metropolis, the former Woolworth’s HQ building at 242 Marylebone, London, originally designed by Richard Seifert. The upgrade, designed by Tenderstream member Allford Hall Monaghan Morris (AHHM), is net zero in operation and has saved an estimated 25,000 tonnes of embodied carbon through building retention, fossil-free fuel in operation, and a mass timber extension.

Ben Cross, creative real estate developer, explained that the project was initiated before retrofit was seen as a popular option. But rather than doing away with the old, the decision was made to, as Ben put it, appreciate ‘the beauty of what exists, the authenticity of the old, and the value of what we already have’. Philip Turner, director at AHHM, related how the design was undertaken throughout the covid crisis, and reflects changing needs to consciously create a destination worth the commute for workers, with 20,000 sq ft of private terraces, gardens, balconies, coffee shops, lounges, and a gym.

The timber extension was particularly experimental, with some difficulties encountered such as problems laying the slabs in Winter, due to rain, and only one specialist builder able to certify a 10-year warranty for the timber flat roof, which made tendering uncompetitive. However, the extension was a success, with the team learning lessons and establishing working methods that will be applied to future projects.

Innovations in the circular economy

Tenderstream member Arup had an overall sustainability role on the redevelopment of London’s 1 Golden Lane, which reimagines the heritage asset at the heart of the city with a design by Hawkins\Brown. Arup associate Rhona Sampson explained that the project took place amidst a changing regulatory landscape, in which considerations of embodied carbon came to the fore, prompting detailed analysis to assess different design aspects.

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By Lucy Nordberg
Tenderstream Head of Research