The greenest building is the one that already exists.

(Carl Elefante, former president of the American Institute of Architect)

Although Australia has only 0.33 per cent of the world's population, it is one of the biggest emitters of greenhouse gas emissions per capita, 18.1% of which is from construction. Globally, the construction industry accounts for 36% of energy usage and 40% of carbon emissions. Cities consume one-sixth of the world's fresh water and a quarter of its wood harvest. In addition, they consume two-fifths of all raw materials, or 100 billion tons a year - the equivalent of 300,000 Empire State buildings.

Embedded carbon (carbon released into the atmosphere during harvesting, production, and transportation of materials) accounts for a growing share of a building's life cycle impact. Between now and 2050, 49% of all global carbon emissions will be from material production and acquisition, according to Architecture 2030.

Every square foot built in the U.S. generates 2 pounds of on‑site waste.

(U.S. Environmental Protection Agency)

It is no wonder that there is an industry-wide push to change the way in which we design and deliver buildings. Creating sustainable cities that enhance rather than detract from the environment is arguably the single most pressing challenge facing architects today.

One way architects are beginning to grapple with this challenge is by turning to existing buildings. This new frontier of construction offers a unique set of benefits for environmentally conscious architects and can enable not only climate mitigation but climate adaptation.

Adaptive reuse can be the perfect way to breathe new life into an old building while conserving resources and historic value.

Far and away the best way to reduce carbon is to re-use existing buildings. By recycling structure, we can save up to 40% of emissions. These targets are achievable now.

(Juliette Morgan, Head of Sustainable Development, British Land)

Given that nearly two-thirds of buildings that exist today will still exist in 2050, the path to design resilience must include an adaptive reuse strategy. There are two key strategies when it comes to adaptive reuse. Introducing a new use to an existing building, often with a significant uplift, or incorporating multiple uses into the same space. These strategies minimise the need for constructing new buildings and can truly revitalise communities whilst creating more sustainable cities.

In talking about the 15-minute city, Professor Moreno relates that in order to provide services and activities locally, we must re-imagine how we use existing infrastructure. "In a city like Paris, a building is in use for 30 or 40 per cent of the time. That means for 60 or 70 percent of a day, the building is empty longer than it is in use,". he said. "But still, it’s in very good condition. So, we want to make much more use of a building so that it can host activities other than those for which it was originally conceived". Disused buildings could be converted into co-working spaces under Moreno's concept. On weekends, schools could be opened for cultural activities. Sports halls can convert to nightclubs at night. There can even be cooking classes hosted in cafés in the evenings and concerts held in public buildings on weekends.

In a recent interview, Adam Haddow, Director/partner at SJB expresses the immense opportunity in the way in which we can better respond as a profession to the environment. "We've gone through an incredible period of construction globally, particularly in Australia, but I believe we'll eventually reach a stage where we'll be reusing or adapting old buildings more than creating new ones".

Adaptive reuse provides a ripe opportunity to respect the history of the site, and retain the charm, history and rhythm whilst providing contemporary spaces to work and live in with less of an environmental toll. Developers can reduce the amount of carbon associated with new materials and landfill waste by renovating existing buildings and repurposing spaces and materials. According to the U.S. Environmental Protection Agency, deconstruction rather than demolition of a building can save 90% of a building’s materials.

There is this wonderful symbiotic relationship where existing infrastructure works together with fresh interiors to create a sustainable alternative to building from scratch. There are dozens of exemplary adaptive reuse projects around the world, from nineteenth-century chapels transforming into holiday destinations to a disused water tower being turned into student housing. In a similar sense, we have also witnessed an obsession for shipping container buildings that offer a sustainable building shell with modular construction that can easily be expanded or adapted.

A prime example of a cutting-edge adaptive resume project from my own backyard is the recently completed Quay Quarter, designed by Danish architects 3XN in partnership with local architecture firm BVN,

Quay Quarter is set to change the global landscape of commercial redevelopment. A 50-storey skyscraper designed to appear as a stack of revolving boxes was built around the site's previous occupant at 50 Bridge Street. Rather than tearing down the aging tower, a third of it was removed, and 60% of the core structure was retained. A new building was then added, almost doubling its size. The project resulted in a reduction of 6.1 million tons of carbon emissions, a reduction in environmental impact, and a much shorter construction period, and today the mostly-new building looks proudly on the harbour skyline with its Green Star rating of 6 and NABERS energy rating of 5.5.

We should view the whole process of design through the lens of adaptive reuse, preserving what works while incorporating new features that provide better results. The way architects and professionals in the built environment work together to give new life to existing structures and imagine creative ways to combine programs will be fascinating to watch.

Through adaptive reuse and creative multi-use, we can change the built landscape for the better.