There’s a saying in some sustainability circles that the greenest building is the one that is already built. The idea is that reusing a preexisting structure is always less carbon intensive and more sustainable than creating a structure completely from scratch. But are things really that clear cut?
In this episode of our Shaping Sustainable Places podcast, we speak with two individuals with deep insights into the question. Kjetil Trædal Thorsen is founding partner at the globally renowned architectural firm Snøhetta. Ståle Rød is Executive Vice President for Skanska Group and a highly experienced civil engineer.
Kjetil says, unfortunately for those seeking black and white answers, there are no 100 percent truths, just yet. Industry professionals across the planet are debating the merits of retrofitting and trying to gain an understanding of when it makes sense to reuse an existing structure – and when it simply doesn’t.
Build or rebuild dilemma
Ståle says the build or rebuild dilemma is coming up more and more frequently with Skanska’s clients. When choosing which route to take, many customers look at factors such as the kind of structure they need for their operation, the regulatory requirements, the sustainability gains, the cost of embedded carbon and the building lifespan.
Kjetil says other factors when considering whether to retain or remove a building include its social and historical significance. He wonders whether it may be worthwhile to keep an old structure that has poor CO2 performance and accessibility if it is significant to the community. How can designers and society find the right balance?
Lessons from the Powerhouse concept
Both Snøhetta and Skanska have been involved in the Powerhouse initiative to create buildings that minimize carbon emissions and are energy-positive over their lifetimes. The first such development was Powerhouse Kjørbo near Oslo, which was constructed by refurbishing two 1970s office buildings. Thanks to renewable energy features such as solar panels, the development will generate more energy over its lifespan than will be used in its construction, operation and decommissioning phases.
While Powerhouse Kjørbo was constructed around an existing building, other Powerhouse projects have been completely new builds. Kjetil says by using the Powerhouse approach and building according to a strict carbon budget, a brand new building can be a sustainable alternative to a renovated one.
Both Kjetil and Ståle are certain that society and customers will be demanding buildings with higher and higher degrees of sustainability. There will be more demand for circularity, and in many places, there will be an expectation that developers preserve as much as possible of existing buildings.
Kjetil says it’s important that we work out how concepts like Powerhouse and low-carbon concrete can be upscaled so that people over the world can enjoy the benefits. He sees a clear trend for construction projects to preserve more of the existing environment. And he believes there will be more emphasis on finding second and third uses for buildings outside of regular hours as a way of maximizing efficiency.
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