Cities Take Action For a Net-Zero Carbon Future

Cutting City Emissions in the Built Environment is Critical.
It’s Also a Huge Opportunity.


To stay within 1.5°C warming, greenhouse gas emissions need to decline 45% below 2010 levels by 2030 and reach net zero emissions by 2050. The built environment accounts for 40% of GHG emissions, so buildings—and the climate impact of their construction and operation—are an essential part of reducing carbon emissions. Meanwhile, our need for buildings is not going away. About 60% of buildings that will exist by 2050 haven’t been built yet. This means constructing a city the size of Stockholm or Milan every week until 2050, or a city the size of Singapore or New York every month.

The good news is that cutting carbon in cities could mean a U.S. $20 trillion boost to global gross domestic product (GDP). In addition, design firms with green building expertise stand to gain from a market set to grow nearly 15% by the end of 2027.

Our sector has a critical role to play. Discover how cities are leading the way and forging new approaches with the help of the AEC sector and how your design team can play a role in cutting your city’s carbon footprint.

What does net-zero carbon mean? Is it different from carbon neutral?


Net zero refers to a state in which the greenhouse gases going into the atmosphere are balanced by removal out of the atmosphere. The term net zero is important because—for CO2 at least—this is the state at which global warming stops.


Carbon neutral means that any CO2 released into the atmosphere from an activity or project is balanced by an equivalent amount being removed.


Climate positive (also known as net negative) means that an activity’s GHG removals exceed its emissions.


High Impact Climate Solutions in Cities

Cities are major contributors to climate change—which means they can also be a key solution to it.

Over half of the world’s population lives in cities. According to UN Habitat, cities consume 78%  of the world’s energy and produce more than 60% of greenhouse gas emissions, yet they cover less than 2% of the Earth’s surface. 

We can greatly reduce our per capita carbon footprint by changing how we plan, build, manage, and power cities and towns. The ideal low carbon and resilient city is well-designed, compact, walkable, and has good public transportation.

Photo credit: Adam Blank

A number of organizations are dedicated to this premise. A partnership between the Cities Alliance, the World Bank, UN-HABITAT and the United Nations Environment Programme (UNEP) works globally to help cities address climate challenges through sustainable urban development. Another organization, called C40, is a network of mayors of nearly 100 cities around the world whose mission is to halve the emissions of its member cities within a decade while improving equity and building resilience. C40 cities earn their place through action—with membership based on performance requirements, not member fees.

Led by the city of Oslo, C40’s Clean Construction Forum helps cities working to achieve zero embodied emissions from buildings and infrastructure by 2050. They focus on reducing emissions from construction materials and machinery by:

  • Understanding the methods and data needed to establish city wide targets; 
  • Collaborating on available standards and tools to assess the environmental impact of materials and construction sites, and;
  • Using cities’ collective power to develop a market for low emission construction materials and construction equipment.

Cutting emissions will require a change in business as usual. According to UN News, “The extraction and manufacturing of materials for buildings such as steel and concrete and construction processes produce carbon dioxide[,] so using low carbon infrastructure will also slash emissions.” 

In addition to reduced emissions, cities built from bio-based materials such as timber that store carbon during their service lives can serve as constructed carbon sinks. They could increase the existing carbon pool of urban areas (1–12 GtC) by 25 to 170%.”


Climate Ready Boston

C40 member Boston is an example of one city cutting carbon and making progress on a number of fronts. New England’s largest city stands to be impacted disproportionately by rising seas due to global warming and launched Climate Ready Boston more than seven years ago to help the region plan for the impacts of climate change with an update in 2019 to boost its focus on curbing carbon.

A cornerstone of the plan is adopting a zero net carbon standard for new construction by 2030 and pursuing strategies to reduce building emissions over the next five years such as a zero net carbon standard for new municipal buildings and a carbon emissions performance standard to decarbonize existing large buildings. Along with these measures, Boston is also promoting policies that support walkable neighborhoods and enable residents to live car-free.

And so far, the city is seeing results: citywide GHG emissions are 17% lower than they were in 2005, and emissions from city government operations have been reduced by almost 25% in the same period. An embodied carbon technical advisory group formed in 2021 is exploring the use of more carbon sequestering materials and the city is setting stricter standards for city-funded low carbon affordable housing, inspiring solutions like six new mass timber affordable housing projects. 

To incentivize low-carbon construction, Boston launched the Boston Mass Timber Accelerator through grants from USDA Forest Service, Softwood Lumber Board, and ClimateWorks Foundation. The initiative provides design teams with technical assistance and funding grants to expand the use of low carbon mass timber products. This March, seven projects received funding ranging from a seven-story commercial office building to an eight-story, 215-unit affordable senior, and assisted living facility—along with other housing projects that provide equitable access to affordable accommodations while reducing their carbon footprint.

Photo credit: Jacob Licht
The project will focus on the lightweight structural benefits of mass timber for building additions—commercial office building addition and seven stories of new construction.

Boston is also home to a number of mass timber projects under construction including 11 E Lenox St, a 7-story, 34-unit multifamily project in the city’s Roxbury neighborhood.

Designed by Monte French Design Studio, it combines the thermal benefits of mass timber construction and Passive House design, reducing operational energy use by more than 80%. 

Slated for completion later this year, 11 E Lenox’s wood structural system will store 844 tons of CO2 throughout the building lifecycle and offset 327 tons of CO2 when compared to conventional steel or concrete alternatives.

Photo credit: Monte French Design Studio
The project team will assess cost effective implementation of mass timber at Mary Ellen McCormack Redevelopment in a high-rise multi-family residential building—302 units of mixed-income affordable housing in a nine-story building.

Portland’s Climate Action Plan

Over 3,000 miles west of Boston, the city of Portland and Multnomah County, OR is also making headway in the fight against climate change. The city’s Climate Action Plan authored in 2015, aims to reduce carbon emissions 80% below 1990 levels by 2050 with an interim goal of a 40% reduction by 2030.

In 2017, city leaders specified 2030 energy efficiency goals for the built environment, which include achieving zero net carbon emissions in all new buildings and homes.

The City’s June 2020 Climate Emergency Declaration committed to a “climate justice and equity-focused approach that centers Black, Indigenous, other communities of color and youth from those communities in the next chapter of climate action planning and implementation.” In addition to multiple initiatives in support of this approach, the City also amended carbon reduction targets to at least 50% by 2030 and net-zero carbon emissions before 2050. 

Portland has both a Sustainable Procurement Policy and Green Building Policy for City-owned facilities. The Sustainable Procurement Policy outlines best practices for purchasing activities including developing and applying a shadow price for carbon to inform decision-making on capital projects and purchases of goods and services, utilizing sustainably sourced wood for City-owned building and landscape projects, and specifying low-carbon services. Shadow pricing is a method of investment or decision analysis that adds a hypothetical surcharge to market prices for goods or services that involve significant carbon emissions in their supply chain.

Portland’s plan identified over 247 actions to be completed or significantly underway by the end of 2020. Nearly all the actions in the 2015 Climate Action Plan are underway, with 77% of actions complete. The region cut total local carbon emissions to 19% below 1990 levels, and per person, emissions were cut by 42% as of 2018.

Photo credit: Unsplash

Portland is also home to a rapidly growing stock of timber buildings. The state’s rich supply of local, sustainably harvested timber helped make it home to the first certified U.S. producer of mass timber, which opened in Riddle, OR in 2015.

Oregon was also the first state to adopt the 2021 International Building Code to allow tall mass timber buildings. Two mass timber projects in Portland’s Burnside Bridgehead neighborhood standout: Sideyard, a 20,000 square-foot commercial office and infill project that makes the most of a narrow site, and Fair-Haired Dumbbell, a mixed-use office and retail complex designed by FFA Architecture and Interiors that includes two canted six-story towers wrapped in hand-painted artwork. Adjacent to one another, each with their own distinct design, these projects reveal just how versatile mass timber can be while also boosting density and helping to revitalize urban areas with climate-conscious ingenuity. 

Portland is also seeing a rise in the design of nearly all-wood buildings, boosting carbon-capture by combining light-frame wood and mass timber construction—a recent example being the Cascada, a mixed-use project to be built in the city’s lively Alberta Arts District. This project includes hotel, coworking, restaurant, and wellness program space as well as leasable retail spaces.

Photo credit: KUDA Photography

Taking Action In Your City

The actions taken by cities like Boston and Portland can only happen through collaboration with forward-thinking architects, developers, and other building professionals looking to innovate in the fight against climate change.

Design teams can help their city through an increased focus on reducing embodied and operational carbon emissions and by building with bio-based materials, turning urban centers into carbon sinks—and literally converting the built environment from a carbon emitter to a long-term carbon storage solution.

As C40’s executive director emphasized in a past global competition for solutions, “[We need] inventive collaboration to combat the climate crisis—from the skills and creativity of architects, artists, environmentalists and entrepreneurs. The creation of new and exciting developments in cities not only reduces carbon emissions from construction, but also builds the resilient urban environments we need to cope with rising temperatures and more extreme climate events.”

Photo credit: Zixi Zhou
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