The challenges facing cities around the world have never been more serious—and the call to take a stand on climate change is one that must be answered by leaders everywhere.

City leaders are realizing that addressing the climate is the right thing to do for the environment, and that it presents incredible opportunities to make progress on economic and equity goals, too. Cities are setting ambitious targets for reducing their emissions of greenhouse gases (GHG) and leading the world in the fight against climate change.

C40 Cities, a network of large cities committed to addressing climate change, have led the effort to act on these targets and respond to climate risks, with climate action plans and implementation of both proven and emerging strategies based on science.

With local government authorities typically including construction, land use and zoning, buildings are a logical area for cities to address. Accordingly, the buildings sector has become a key area of focus; for example, 23 of the C40 cities have committed to the Net Zero Carbon Buildings Declaration, and their actions will result in an equivalent of shuttering 50 coal-fired plants.

As cities search for new ways to reduce the carbon impact of buildings, the importance of addressing a building’s full life cycle is gaining attention. This is a welcome development. In fact, USGBC, through LEED, has sought to incentivize attention to materials and construction impacts—along with operations phase impacts—for over a decade.

LEED pushes project teams to evaluate and reduce the life cycle impact on climate and rewards the use of products with lower environmental footprints. Greenbuild 2019 featured a special summit on what is known as “embodied carbon,” and USGBC member company Skanska released its new EC3 tool to help select materials with lower carbon impact.

Now that the need for reducing construction impact has become apparent, leading building organizations such as the Global Alliance for Buildings and Construction, of which USGBC is a member, have become increasingly aware that the embodied carbon associated with the construction phase of buildings will be significant—and will occur in the critical next decade. The construction phase is also amplified in importance, as carbon from operational energy use by buildings is generally going down as buildings become more efficient, and over time, will use more renewable energy. Construction, however, often relies on diesel-fueled equipment, as well as manufacturing and transportation of structural materials and building products.

C40 Cities is tackling this issue as well, adding to its suite of building solutions. A new study published by C40 Cities, Arup and University of Leeds in August 2019 outlines the impact of construction in a call to action.

Designed by the Spanish architecture firm Estudio Herreros, the Munch Museum in Bjørvika, Oslo, is built of environmentally friendly and recyclable concrete and steel. The building’s exterior is covered in translucent, perforated aluminium.

C40 Cities comprises 96 affiliated cities, such as San Francisco, California; London, England; Addis Ababa, Ethiopia; and Sydney, Australia.

The report, “Building and Infrastructure Consumption Emissions,” found that as people pour into urban spaces to live and work, they are fueling a building bonanza. Without new strategies, construction to meet increasing urban populations will translate into more carbon released into the atmosphere.

Building emissions from the construction industry are increasing, and the report estimates that they will rise by 37% by the year 2050.

“Urgent action is needed from all actors—governments, businesses, cities, civil society and residents,” the authors of the C40 Cities report wrote, urging policymakers to “reflect on how their city development plans can help reduce buildings- and infrastructure-related emissions.”

“While mayors can play an important role as leaders and convenors in this effort, there must be collaboration across all sectors of society in order to achieve a better and more sustainable future,” the report says.

C40 Cities recognize that they must address buildings to achieve zero or near-zero economy-wide emissions, over the long term. Many of these cities are now seeing net zero energy and net zero carbon in new buildings, illustrating what is possible. Given the urgency of emissions, however, these outcomes need to become mainstream, and reduction of construction-phase emissions associated with building and renovation must be incorporated into city and sector actions.

Cécile Faraud, clean construction program manager at C40 Cities, says that local governments and civil society need to rethink building design, and cities should study their supply of unused buildings and make use of their existing stock.

Cities could cut their emissions by 11% simply by optimizing the use of buildings that are already available. Faraud believes that many buildings are underutilized and abandoned while they are still useful.

Left: Cécile Faraud is the clean construction program manager at C40 Cities. Right: Mark Watts is the executive director of C40 Cities. Center: The new Munch Museum in Oslo was built with a transparent and open façade of ventilated skin consisting of an external layer of corrugated, perforated aluminium sheets.

Left: Cécile Faraud is the clean construction program manager at C40 Cities. Right: Mark Watts is the executive director of C40 Cities. Center: The new Munch Museum in Oslo was built with a transparent and open façade of ventilated skin consisting of an external layer of corrugated, perforated aluminium sheets.

Making smart choices in design and materials

There is obviously still a need for development, and refurbished buildings aren’t the answer to all of the development problems that cities face. How can developers reduce the carbon footprint of building construction?

Faraud suggests that developers reimagine traditional design elements and that cities update specifications for new building construction. If developers eliminate waste at the design stage, they can cut emissions of planet-warming gases by 18%, and smart design can cut building-related emissions by 44% over the next three decades, according to the report.

One approach that is emerging, especially in Europe, is using modular techniques for new construction and some retrofits. This can reduce emissions associated with on-site construction equipment and potentially offer other advantages. However, these techniques are not a one-size-fits-all solution.

Stockholm City Hall, with its spire featuring the golden Three Crowns, is one of the most famous silhouettes in Stockholm.

Modular design techniques allow developers to shift many aspects of building construction away from the field and into manufacturing-style production facilities off-site. Around 60% of emissions from building and infrastructure construction stem from the production and delivery of materials at different points in the supply chain, according to the report.

Faraud points to the Triodos Bank in the Netherlands as an example. Developer EDGE, RAU Architects and Ex Interiors designed the building with a minimal carbon footprint.

Around the world, the building industry is researching ways to reduce the carbon footprint of concrete, steel and other key building materials, as well as to increase the application of wood.

Cities, through innovating in their own construction practices, as well as with incentives, can influence the work of architects, engineers and manufacturers, and according to Faraud, cities can leverage policy to increase demand for low-carbon materials and more efficient buildings.

In addition to fighting climate change by reducing the amount of emissions that waft into the atmosphere, sustainable construction has wide-ranging economic and environmental benefits, what Faraud calls “cross-cutting benefits.”

Scandanavian commitments

The leaders of Copenhagen, Denmark; Oslo, Norway; and Stockholm, Sweden, have committed to reducing greenhouse gas emissions and pollution from building construction. These Scandinavian cities are adopting many of the interventions outlined in the C40 report, and they are collaborating with the C40 Clean Construction Forum to create a global market for cleaner vehicles and building materials.

The forum brings cities together to combine purchasing power for sustainable products. Launched in Oslo in May 2019, the forum’s goal is to support cities that want to build sustainably.

“The mayors of Oslo, Copenhagen and Stockholm recognize that without urgent action to cut emissions generated in the construction of buildings and infrastructure, there is no chance of delivering on the Paris Agreement and preventing catastrophic climate change,” said Mark Watts, executive director of C40 Cities, in a statement.

“As C40’s research demonstrates, citizens will ultimately benefit from cleaner air, quieter streets and lower prices,” he said. “Now it is up to businesses and industry to recognize the risks of inaction and work with mayors and consumers to make sure everyone benefits from the huge opportunities that lie ahead from clean construction.”

Triodos Bank in the Netherlands was designed around the principles of nature and biomimicry. Building heights have been adjusted to remain below the treeline, and a special light plan was developed to prevent the disorientation of bats and to protect fauna. The energy-neutral building consists of sustainable materials and a demountable, wood-hybrid construction that allows for complete disassembly and reconstruction of the office at another location. Photos: RAU Architects

Triodos Bank in the Netherlands was designed around the principles of nature and biomimicry. Building heights have been adjusted to remain below the treeline, and a special light plan was developed to prevent the disorientation of bats and to protect fauna. The energy-neutral building consists of sustainable materials and a demountable, wood-hybrid construction that allows for complete disassembly and reconstruction of the office at another location. Photos: RAU Architects

Stockholm’s emissions calculator

Stockholm is committed to being free of fossil fuels by 2040. Gustaf Landahl, head of department of the Environment and Health Administration, says the city will achieve this goal by limiting emissions from the building industry.

The city developed a calculation method to track the building industry’s embodied carbon, a tool to estimate emissions from machinery to materials. The project is a partnership with the Swedish Construction Federation and the Swedish Environmental Research Institute.

“We are finding values from real construction sites and from the planning of new buildings and making evaluations,” Landahl says. “We are determining the amount of emissions we have per square meter of constructed building.”

With this new information, the city plans to put limits on the amount of GHG emissions released by buildings constructed on city land. “In Stockholm that makes sense, because we own 60% of all the land within the municipal boundary,” Landahl explains.

Stockholm passed similar requirements on the amount of energy that buildings use in their daily operation.

Stockholm Mayor Anna König Jerlmyr shared in a statement that the city has created “a powerful tool to scrutinize the climate impact of the whole building process. Using it will help us steer towards the most climate-efficient solutions,” she says.

The city is testing the tool and will launch it citywide in 2021. Also, Stockholm is reusing existing buildings and renovating older buildings that are not in use as part of the GrowSmarter initiative. “Since these buildings already have their general construction in place, we don’t have to use lots of new concrete,” Landahl says. “There are a lot of emissions connected to that. We can have much lower emissions—40% lower in some cases—when we refurbish a building, rather than building something new.”

In November 2019 at the Smart City Expo World Congress in Barcelona, the European Commission named Stockholm the world’s smartest city for its leadership with the GrowSmarter project.

Gustaf Landahl is head of department planning & environment at the Environment and Health Administration, City of Stockholm.

Karolinska Institute’s Aula Medica features an exterior comprised of triangular elements that form an airtight, energy-lean façade.

Dropping fossil fuel in Oslo

In 2016, a city-backed measure in Oslo, where municipal building accounts for a fifth of the city’s total construction, asked some public-works building projects to avoid using fossil fuels.

“Contractors responded, and it proved that it was possible and did not drive up overall project costs substantially,” says André Aasrud, a senior adviser to the city’s mayor. “By 2017, demanding fossil-free construction in municipal projects was the norm. This has reduced emissions in this sector by about 20%.”

That’s a big deal, because construction represents 7% of Oslo’s total emissions—the equivalent of 30,000 cars on the road.

Now, Raymond Johansen, Oslo’s governing mayor, is pushing the city even further with a commitment to zero-emission public construction by 2025. One goal is to improve local air quality.

“Biofuel will increasingly become a scarce resource and should mainly be used in sectors where a transition to alternative zero-emission technology is not possible,” Aasrud says.

The city plans to mandate zero-emission private development by 2030, and Aasrud says the private market is responding positively. Norway’s largest contractor has committed to fossil-free construction sites in Oslo and bought zero-emission equipment and machinery.

“New kindergartens, schools and sports halls will in future be built emissions-free and with low climate materials,” Mayor Johansen said in a statement. “The building industry is our closest ally and an enthusiastic supporter. We are confident that by 2030, Oslo’s air will be cleaner, emissions lower and the environment healthier, thanks to the actions we are taking today.”

Oslo is committed to reducing embodied carbon in its buildings. It established a city agency to promote sustainable building projects; FutureBuilt is reducing emissions from transportation, energy and materials at 50 pilot projects.

In 2017, the city asked developers working on city development to calculate the embodied carbon and other environmental impacts of the materials they use when building schools, senior homes, streets, water and other infrastructure projects.

“The agencies that commission construction on behalf of the city are required to keep emissions accounting for all phases of the project, including the embodied carbon from the building materials,” Aasrud said. Developers are using low-emission concrete in most municipal building projects, as a result.

Kilden Kindergarten in Oslo—a FutureBuilt project—harnesses local energy production by using photovoltaics as the roofing material.

Left: André Aasrud is a senior adviser to Oslo’s mayor. Right: Lord Mayor Frank Jensen of Copenhagen.

Left: André Aasrud is a senior adviser to Oslo’s mayor. Right: Lord Mayor Frank Jensen of Copenhagen.

Carbon-neutral Copenhagen

Copenhagen wants to be the first carbon-neutral city. In 2012, city leaders set the ambitious target of net zero emissions by 2025. Copenhagen’s emissions are already down 38% from a 2005 high. In 2017, Lord Mayor Frank Jensen introduced a climate road map. The plan carves a pathway for the city to achieve its goal.

“The City of Copenhagen will provide direct and indirect support for massive investments in green growth between now and 2025,” the climate plan states. “These investments will fund innovation projects in the city and create a large number of jobs in the green sector. Implementation of the Climate Plan is expected to generate more than 30,000 full-time job equivalents by 2025, mainly in the construction industry.”

As part of the reforms, Copenhagen will replace its fleet of construction vehicles and heavy-duty equipment with ones powered by alternatives to fossil fuel, including more sustainable biofuels.

Also, the city is prioritizing retrofits and renovations of its existing buildings while slowing demolitions and encouraging the use of more sustainable building materials. “Optimization includes using the building stock more effectively, by sharing offices or using schools in the evening,” the plan states.

Jensen is leading the city toward more climate-friendly construction and pushing public projects to abandon fossil fuels. “In Copenhagen, we take the first steps to more climate-friendly construction sites,” he said in a statement. “From 2020, we will use fossil-free fuel for our own machinery and heavy vehicles. And we will start pilot projects with requirements for fossil- or emission-free machinery in construction projects.”

Three cities in Europe reflect C40 priorities to reduce emissions