Meeting our 2050 net-zero-carbon aspirations and addressing New Zealand’s housing crisis are among the most substantive challenges of our time. Retaining and retrofitting heritage buildings can be part of the solutions to both
“The greenest building,” noted Carl Elefante, former president of the American Institute of Architects, “is one that is already built.”
With a goal to have net zero carbon emissions by 2050, sectors across New Zealand are putting their shoulders to the wheel to meet the challenge. And in the building sector there’s a growing body of research adding weight to Elefante’s maxim, which demonstrates that by adapting and retrofitting existing buildings – including heritage buildings – instead of demolishing them and building new ones, significant reductions in carbon emissions can be made.
Globally, the building and construction sector is responsible for an estimated 38 percent of CO₂ emissions, 10 percent being from the production and supply of building materials and construction.
According to the New Zealand Green Building Council, in Aotearoa New Zealand the built environment makes up 20 percent of our carbon footprint. With current growth, this is likely to rise. As an indicator, emissions from the construction industry increased by 66 percent between 2007 and 2017.
The Government’s Building for Climate Change web page states: “If New Zealand is to achieve its climate change goals, including net zero carbon by 2050, the building and construction sector must play its part”. But how? And how can heritage help? Rachel Paschoalin is a PhD candidate at Victoria University of Wellington and her research addresses these questions.
“After the Paris Agreement, it became clear that globally we had to find ways to reduce emissions,” she says. “The question for me is ‘how can heritage contribute?’”
Rachel is researching the retention and retrofitting of heritage buildings.
In the decision-making process around heritage buildings and sustainability, she says, the whole life cycle of a building, from construction through a 90-year lifespan should be considered.
Several studies, including Rachel’s, have been done in this area and the results have underpinned a best practice database and guidelines for what is known as sympathetic upgrades of heritage buildings. “Early research shows that sympathetically upgrading and reusing existing buildings, rather than demolishing and building new, could dramatically improve a building’s energy efficiency and would make substantial energy savings because the CO₂ emissions already embodied within existing buildings would not be lost through demolition,” states the Historic England Heritage Counts report from 2020.
Adaptive reuse – the repurposing of a heritage building – is an effective way to meet pressing commercial and residential building needs without demolition. Robin Byron, Senior Conservation Architect for Heritage New Zealand Pouhere Taonga, cites Auckland’s Britomart Precinct, centred on the busy train station (itself adapted from the former Chief Post Office building) as one of the most outstanding examples of adaptive reuse in New Zealand.
Apihai Te Kawau, a chief of Ngāti Whātua, the iwi that holds mana whenua of the area, gifted 3000 acres (1214 hectares) of land in the vicinity to Governor Hobson for the construction of a new capital after the signing of Te Tiriti o Waitangi. The existing, predominantly warehouse buildings were largely built in the late 1800s and early 1900s.
A vibrant business district for decades, by the 1990s many of the buildings were shuttered and slated for demolition. Long-term investment, regeneration and management have seen a dramatic transformation of the area, with the heritage buildings restored and repurposed in a multipurpose commercial precinct with a public square at its heart. It has catalysed similar adaptive reuse projects around the motu, such as The Tannery in Christchurch.
The precinct has also been futureproofed for longevity and sustainability. “This example of adaptive reuse has been very forward thinking,” Robin says.
“The buildings have been regenerated – planned, strengthened, upgraded and conserved – in such a way that any subsequent changes in functions and use can be achieved relatively easily. Because of this foresight and flexibility, these buildings can continue to adapt and change into the future.”
In 2015, at COP21, New Zealand signed the Paris Agreement, a legally binding international treaty of carbon neutrality by 2050, which aims to mitigate the worst effects of climate change
In many cases, unused heritage buildings present excellent opportunities to align heritage conservation, environmental responsibility and the needs of the community. Jamie Jacobs, Director Central Region for Heritage New Zealand Pouhere Taonga, cites the Gordon Wilson Flats and the adjacent McLean Flats in Wellington as examples.
“The buildings have outstanding heritage significance for their associations with the state housing programme and its Modernist architectural evolution after World War II,” he says.
“The retention and sensitive adaptation of these heritage buildings for current residential needs would both acknowledge their history and contribute muchneeded high-density housing to central Wellington.
“And by opting to reuse rather than demolish and redevelop the site, the embodied energy of a massive reinforced-concrete building is not lost, and the remains irresponsibly dumped in the tip.”
There are many more good examples of adaptive reuse in action around New Zealand, such as the Old Bank Arcade and the T&G Mutual Life Assurance Society building on Lambton Quay in Wellington.
In Dunedin, a former bus depot has been incorporated into the Toitū Otago Settlers Museum, while the Hocken Collections research library is housed in a former cheese factory.
In Oamaru, Casa Nova, an early stately home and Category 1 building, has been converted into boutique accommodation and a restaurant.
However, it is critical to note that while retaining an existing heritage building helps to reduce emissions, it may not be enough. Rachel’s research shows that the most dramatic reduction in carbon emissions comes from improving the health and energy efficiency of a retained heritage building through retrofit.
There are challenges to doing this in New Zealand, not least of which is a need for guidelines. While a bestpractice database and well-established guidelines for retention and retrofitting of heritage buildings exist in Europe and the US*, there is no such thing here.
“The guides contain broad frameworks as well as specific technical advice,” says Rachel. “For example, for improving insulation, how to deal with windows and so on, based on research and practice.”
Rachel’s project over the past three years has been to investigate from both policy and a practice perspectives how to adapt and tailor those existing international guidelines for New Zealand, allowing for unique environmental factors such as seismic strengthening and building materials.
Perhaps the most significant barrier in practice, though, is the cost of labour and materials. A carbonreducing retrofit comes with a big price ticket in New Zealand, as Wellington architect James Solari notes.
“We have a limited availability of good skillsets aligned to older, more traditional construction techniques, so they become fairly specialist skillsets,” he says.
“Material costs are also perceived to be reasonably high here compared with overseas markets; this being a factor for our lack of scale relative to the international construction market, as well as very high freight costs.”
mana whenua: those with tribal authority over land or territory by virtue of possession and/or occupation
motu: island; country
CoreLogic data backs this perception, showing steadily rising costs in the sector over the past decade, with an increase in the cost of building materials in 2021 of 5.5 percent.
The Commerce Commission is currently investigating the market for residential building materials, looking at potential competition issues.
Despite these challenges, James is enthusiastic about the possibilities of adaptive reuse. He says awareness of the issue is growing and cites Anne Lacaton and Jean-Philippe Vassal, who won the prestigious Pritzker Architecture Prize in 2021 as an example. The duo’s “rallying cry”, as the Guardian puts it, is: “Never demolish, never remove – always add, transform and reuse”.
James’s Wellington-based company, Solari Architects, is at work on a project converting a 1970s office space into apartments, demonstrating how reuse and retrofitting projects can also offer more climatefriendly solutions to our housing crisis.
Initially, the firm considered demolishing the former Works Depot on George Street in Thorndon.
“But once we understood the opportunities the building had, the good bones of architecture and the scope for repurposing,” explains James, “a more exciting solution emerged.”
The unique profile of the roof is a particular feature in the design for the 45 new apartments.
“It’s turning something forgotten into something useful. It’s retaining and capturing something in time,” he comments.
Another project converting a 1930s office building into apartments is almost complete, and the repurposing and retrofitting of a former surf shop in Lyall Bay has turned it into a warm, well-insulated, energy-efficient home for its owners.
A building’s longevity – its ability to become ‘future heritage’ – is another important concern for Solari Architects.
“We need to encourage well-designed solutions that will stand the test of time and make long-term contributions,” says James.
He points out that in the necessary rush to meet our existing and future housing needs, the question of building longevity might easily fall through the cracks. He believes New Zealand is lacking a good framework and decision-making tools for intensification.
“While some of our processes are not useful, where we need them they are lacking,” he says.
“The process frameworks we work under lack proper qualitative controls. The experiential aspects of good design overlaid with quality construction create longevity. Good design needs to be a much higher priority.”
A case in point is the proposed three-storey, threehouse infill plan. Through removing the consent application process, considerations such as a building’s longevity, as well as environmental factors such as light, warmth and ventilation, could go largely unchecked.
“Reducing emissions is also about putting people in the right places,” says James, as one example. “Encouraging higher density living in places with good community centres and public transport links is key.”
Rachel’s approach emphasises the need for multiple perspectives, with many stakeholders contributing to the decision-making process on the retention and retrofit of heritage buildings, including professionals in heritage, architecture, the building industry and policy.
“The concept of sustainability is not only focused on environmental issues,” she says.
“We have to think about economic, social and cultural aspects. In the same way, when we are thinking about retrofitting a building, we also have to think about all the different benefits we can gain. Not just protecting the building.”
Rachel’s paper can be read online at www.mdpi.com/ 2571-9408/4/4/203/htm
*The guidelines referred to in the article are known as En 16883:2017 (European) and Guideline 34-2019 (United States).