The age-old dilemma of retrofitting versus new builds continues to shape the start of any new construction journey. Historically, a retrofit may have been considered the least popular of the two, burdened with the design constraints inherent with the existing building. However, with a growing emphasis on embodied carbon, recent technology advances and budgets to consider, it’s best to think twice before starting from scratch.
With that said - as always - there’s no one size fits all with decisions like these, and with every project it’s down to the experts to assess on an individual basis whether retrofit or new build is appropriate...
Time, costs & complexities
With the groundworks and structures already in place, demolishing an entire building and constructing from brand new is an expensive and time consuming process. With a retrofit, there’s far less waste as the core concrete of the building will be retained. The original suggestion for a recent project in west London was to demolish nearly all of the space except for the basement. However, the decision was made to retain up to the third floor and some of the structure, mainly due to costs.
What goes up must come down, and cheaper costs do come at a price in the form of coordination and complexity challenges. There are several existing beams and a lift shaft which provide rigidity to the building. The team’s main challenge is to coordinate their designs around these immovable features, which is especially tricky when considering insulating the building to the same level as you would if it was a new build.
Advances in 3D modelling and analysis tools that streamline the process are today’s solution for increased complexity around planning and design. Our project on Albion Street was partially destroyed by fire but protected by its listed status. With its intertwined old and new structures, we were able to use 3D modelling to have full transparency over every detail and achieve a tightly coordinated design which kept the originally ceiling heights. This definitely wouldn’t have been possible to achieve a few years ago designing in 2D CAD, making quality retrofits far more viable using modern software.
Retrofitting almost always comes out on top when considering embodied carbon. Existing structures are already built, meaning their embodied carbon has already been spent. People’s reluctance to use existing structures is primarily driven by the restrictions of design plans. However, planners are now becoming increasingly aware of the embodied carbon narrative, particularly in urban areas such as London, and are now requesting a clear demonstration of the life cycle carbon justifications for new constructions, thus pushing architects and engineers to reconsider their approach and invest additional effort accordingly.
New build, or elements of new build such as the envelope, may be appropriate for buildings with particularly high energy use such as leisure centres, where the operational carbon reduction will be higher.
Pushing the boundaries of innovation
New build trends come and go, offering a ‘one size fits all’ style ready to go on most new project briefs. However, retrofitting involves transforming a building with existing character and contributing to its evolving history to create something entirely unique. This also applies to the energy strategy and services as much as it does the architecture. Because of the constraints already in place, we have to push the boundaries of innovation in order to come up with a bespoke solution rather than starting from scratch
In a modern world where construction trends are often fleeting, it’s clear that retrofitting is a guaranteed timeless embodiment of sustainability and innovation. As technology continues to evolve, and values shift towards a more resource conscious and sustainable future, reasons for considering new builds over retrofits are few and far between.
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