Retrofitting existing buildings can be significantly more carbon-friendly than demolishing and rebuilding. And earthquake strengthening is essential to keep people safe. NZ has an opportunity to look at the two together. | Content partnership
“The most sustainable building is the one that is already built,” said former American Institute of Architects president Carl Elefante. Meaning that even the highest quality green new build is likely to be less environmentally-friendly than breathing new life into an existing one.
It’s about ‘embodied’ (sometimes called ‘embedded’) carbon – all that energy and those emissions that went into the building materials and the construction process for a building, and will potentially be lost when demolishing it.
These days, embodied carbon is increasingly a consideration when it comes to measuring sustainability in the commercial property sector.
As building owners, engineers, architects and tenants look to reduce the carbon profile of their buildings, calculations around embodied carbon in existing assets, as well as in new builds, are coming to the fore, says Juliane Spaak, structural engineer principal at engineering consultancy Beca.
New builds are inherently more carbon intensive than retrofits, she says. Retaining the structural skeleton and foundations of an existing building saves a huge amount of time and new building materials during construction.
An upgraded building is also likely to have modern building services yielding higher operational performance – for example by swapping out gas boilers for ultra-efficient heat pumps, improving glazing, and installing smart building control systems.
“Some retrofits are indistinguishable from a brand new building,” Spaak says.
The former Civic Administration Building on the edge of Auckland’s Aotea Square is a case study into the benefits of a high-quality building refurbishment.
Designed in the 1950s and completed in 1966, the 18-storey Category A heritage building was one of the earliest high-rise steel structures in New Zealand and a significant example of post-war ‘international style’ architecture. For many years it was the home of Auckland City Council, but more recently underwent an extensive restoration and refurbishment into high-end, central city apartments.
Retaining the steel frame was a big part of the building’s transformation, says Beca general manager structures, Neil Horsfield, who led the structural engineering for the retrofit and repurposing project.
"Reusing the steel means less energy, less carbon and reduced cost – that’s a win, win, win. Making good use of existing buildings and repurposing them, rather than knocking them down and starting again, is becoming increasingly important to our clients."
New Zealand’s Building (Earthquake-prone Buildings) Amendment Act 2016 requires all buildings or parts of buildings that are defined earthquake prone (rated at below 34 percent of ‘new building standard’ (NBS)) to be demolished or strengthened within a specified timeframe.
However property owners and commercial tenants are increasingly looking for retrofitted buildings to be at 100 percent of NBS – or even more resilient, Spaak says.
Combining seismic and carbon retrofits
Given the huge number of existing buildings that are candidates for earthquake-related upgrades, bringing seismic resilience and carbon best practice together in decision-making makes good sense, she says.
If that doesn’t happen, there is the risk that buildings might be demolished that shouldn’t be.
“The demolition of viable older buildings is at odds with society’s desire for a lower carbon economy.” – Juliane Spaak, Beca.
“Put simply, if weaker buildings are not retrofitted they sit as a carbon liability with considerably more carbon likely to be expended remediating damage after a shake,” Spaak says.
“Strengthening a building means a much smaller carbon investment, compared to what a new building would cost, and presents a great opportunity to put new life into a structure.”
For property owners “it can open the door to commercially attractive outcomes, with retrofits that include structural and sustainability upgrades transforming the asset’s revenue generation.
“Commercial tenants are increasingly demanding the buildings they occupy be resilient and aligned with their own climate targets.”
And retrofitting older buildings rather than knocking them down will play a big part in reducing the carbon profile of the property sector.
“The demolition of viable older buildings is at odds with society’s desire for a lower carbon economy,” Spaak says. “The 2011 and 2012 Christchurch earthquakes, the Cook Strait shakes in 2013, and the Kaikoura earthquake in 2016 brought dramatic changes in the way we look at our buildings.”
At the same time, the science and the knowledge around strengthening buildings has increased in leaps and bounds.
Seismic upgrades are an opportunity to look at the quality of the whole building, she says, with the structural refit needed for earthquake strengthening becoming a catalyst to decarbonise the operation of the building and design a space with an adaptable future in mind.
The reverse is also true. Property owners should be looking at adding a seismic retrofit to an environmental upgrade.
“After all, there’s no point having the greenest building in the world if it’s not resilient enough to withstand an earthquake. You’ve not only wasted all the money you’ve spent on efficiency improvements, but you could well end up with a much larger repair job, or even face demolishing the building, with all the extra carbon that entails.”
The recent structural retrofit of Wellington’s 8 Willis Street/Stewart Dawson’s Corner turned an uninviting, eight-storey, 1980s tower that was at just 40 percent of national building standard (NBS), into a 13-storey block with a modern feel and a seismic rating of 130 percent of NBS, Spaak says.
Beca was the structural engineer on the project, but success on a development of that scale depended on collaboration between all the key players – owner, tenant, architect, builder, contractor and structural engineer, she says.
“It was about everyone sharing knowledge, communicating about all the key technical, seismic, environmental and design considerations to create a great solution that addressed all those issues.”
“As well as effectively adding another 50 years of working life to the 40-year-old building, the owner, Argosy Property, also ended up with a 6* Green Star asset,” Spaak says.
"There’s no point having the greenest building in the world if it’s not resilient enough to withstand an earthquake." – Juliane Spaak, Beca
“New Zealand is well-placed to be at the forefront of these so-called ‘adaptive reuse’ projects. The quality of the overall industry in New Zealand is up there with the rest of the world, particularly in the seismic space where we are world leaders.”
Given the series of significant earthquakes New Zealand has experienced in the last decade, building owners need to be making decisions sooner rather than later, Spaak says.
After the 7.8 magnitude Kaikoura quake, a number of commercial buildings in Wellington had to be torn down.
“Watching a relatively modern building being demolished just months before it was scheduled to be strengthened is incredibly frustrating. It also highlights the importance of timeliness in retrofitting assets if the carbon impact of damage from earthquakes is to be minimised.”
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