Architecture’s Carbon Problem

Buildings create about 40% of the world’s carbon dioxide emissions. Architects can help solve this.

Rising global temperatures are causing climate-related natural disasters, and one of the biggest culprits is in plain sight: Buildings. In total, buildings account for about 40% of annual fossil fuel carbon-dioxide emissions (CO2), leading to increases in flooding, fires, hurricanes, and billions of dollars in annual damage. It’s a global emergency of our own making. And if we don’t take action now, we’ll help to accelerate global warming—irreversibly changing life as we know it.

Until recently, understanding the amount of carbon contributed by buildings has largely been a data problem. For years, government agencies and others reported CO2 emissions from buildings as being substantially lower than 40%. That changed when Ed Mazria, FAIA, an architect in Santa Fe, New Mexico, founded Architecture 2030, a nonprofit initiative to transform the global built environment from the major contributor of greenhouse gas (GHG) emissions to a central part of the solution to the climate crisis. Mazria dug into the data behind the materials used to create buildings and came to a new conclusion: The profession of architecture has been on a “carbon binge” for decades.

While transportation garners many of the headlines about CO2 emissions, it surprisingly only accounts for about 23% of global emissions. Building operations, materials, and the construction sector, by contrast, cause most of the rest. “We know the total amount of CO2 that buildings contribute is about 40%,” Mazria says. “The numbers are evolving with the research and are adjusted annually to reflect actual emissions.”

Today the global building floor area is about 2.4 trillion square feet. By 2060, this number is expected to double. What does this mean? For the next 40 years, we’ll be adding the equivalent of another New York City to the planet every 34 days.  If we hope to stop climate change, all of it must be designed to meet zero-carbon standards. Overall, if we don’t reduce our current global CO2 emissions by 65% by 2030—and then to 0% by 2040—climate change will become irreversible.

For architects, this challenge is a pivotal opportunity in design, planning, and construction—a chance to address the carbon binge, drastically lower CO2 emissions, and shape the future of our world.  During the COVID-19 pandemic, large groups of people quickly changed their lives to make an impact, resulting, in part, in significant decreases in nitrogen dioxide (NO2) over China. Similarly, architects can quickly change how they design buildings to positively impact climate change. To support that mission, The American Institute of Architects, the largest design organization in the world, is asking architects, design professionals, civic leaders, and the public to join our efforts and achieve a zero-carbon, resilient, healthy, just, and equitable built environment.

It’s time to show the world what design can accomplish.

The carbon tipping point

According to the National Oceanic and Atmospheric Administration, since the start of the Industrial Revolution in about 1750, CO2 atmospheric levels have risen steadily, causing the earth’s temperature to increase at an unusually rapid pace. Due mostly to the burning of fossil fuels, CO2 levels in our atmosphere have risen 69%, from about 280 parts per million (ppm) in 1750 to 407 ppm in 2018. As a consequence, according to the National Aeronautics and Space Administration, the global average surface temperature rose from –0.07 to 0.98 degrees Celsius between 1900 and 2019—leading to 19 of the 20 warmest years on record, all of which occurred in the past couple decades.

To address global warming, 195 countries met in Paris in 2015. They pledged to keep the world’s average surface temperature from exceeding 1.5 degrees Celsius—and the next 10 years are critical to achieving this goal. The emissions we produce between now and 2040—most of which will come from building operations and construction as well as the manufacture, transport, and construction of materials—will determine whether we meet the goals of the Paris Agreement and prevent the worst effects of climate change.

Right now, the world’s temperature is basically at 1 degree Celsius above preindustrial levels. If we reach 2 degrees Celsius above preindustrial levels, then the Mediterranean basin is projected to experience widespread desertification, coral reefs may almost entirely disappear, and ice sheets will begin to collapse. After that, the world will become what scientists dub a “hothouse earth”: The Amazon rainforest will turn into savanna; hundreds of millions of refugees will flee heat waves in equatorial regions, and sea levels will rise to displace up to 760 million people.

And all because of our carbon emissions.

As a result, the world now has a “carbon budget” that aims to keep CO2 levels from pushing us past 1.5 degrees Celsius—and we’ve almost squandered it. In the past five years, many countries have not heeded the Paris Agreement, doing little to reduce their emissions. Now, to have a good chance of meeting our original goal of limiting global warming to 1.5 degrees Celsius, the world can only release about 340 gigatons of CO2 into the atmosphere—a finite “budget” with our future in the balance.

To achieve this goal, we need to reduce fossil fuel CO2 emissions by 65% by 2030 and then to 0% by 2040.

And the group that can help the world succeed is also one of the least expected: Architects, planners, and the building community. 

Buildings contribute about 40% of global CO2 emissions

For years, architects didn’t consider the CO2 their buildings were emitting.

In the 20th century, U.S. energy consumption was broken down into five categories: Electricity (consuming about 40% of the total each year), transportation (28%), industry (21%), residential (7%), and commercial (4%). Overall, CO2 emissions roughly tracked with energy consumption, meaning the largest emitter was the most obvious: Electricity.

But, in 2003, Mazria had an epiphany—what if we reconceived the pie chart to include the building sector? While all the other wedges of the pie represented “demand,” electricity was a supply-side system. And for years, it had been considered without taking into account its role in buildings, for which it was mostly generated. So, Mazria combined the energy consumed on-site by the residential and commercial sectors and added the energy consumed from both the electricity used in buildings and in the manufacture, construction, and transport of building materials. Looking at the numbers, he realized a shocking truth: Building operations were responsible for 39% of all the energy consumed in the United States—and that number was estimated to reach about 48% when including embodied carbon consumption.

In this reshaped pie chart, architects were no longer a sliver.

They were almost half of the pie.

And globally, the situation is similar with energy consumption and CO2 emissions.


Operational carbon

To understand how the built environment contributes to global warming, look at its primary emission sources.

Operational carbon is the CO2 emitted when a building is in use. Created by the consumption of energy to heat, cool, light, and power a building, operational carbon has long been a focal point of design for architects. New energy-efficient building design and renovations, as well as the use of renewable energy, have all helped to lower operational carbon levels. Operational carbon will account for about 26% of all CO2 emissions of the buildings constructed in the next 10 years.

Embodied carbon

Next, let’s examine an emission source that has been long overlooked: Embodied carbon.

Embodied carbon is the CO2 released during building construction, including extracting, transporting, and manufacturing materials. It’s all the carbon emitted before a building is occupied. In the next 10 years, embodied carbon will be responsible for 74% of all CO2 emissions of new buildings constructed during that period. Compared with operational carbon, this is a staggering number. The embodied carbon of concrete, steel, and aluminum alone accounts for 22.7% of global CO2 emissions, and most of it is from buildings and infrastructure construction.

For architects, embodied carbon is crucial to consider. Unlike operational carbon, which can be reduced during a building’s lifetime, embodied carbon is locked in as soon as a building is completed. It can never be recaptured.

Building stock to double in 40 years

Here’s why all this matters.

By 2060, the world is projected to add 2.4 trillion square feet of buildings—more than double the current global building stock. Driven by population growth and economic development, most of this construction will take place in cities and emerging markets like India, Africa, and Asia. To ensure we don’t exceed 1.5 degrees Celsius, we must change how we design and build now.

Reaching zero CO2 emissions in the built environment

It sounds daunting, but here’s how we do it.

For years, architects have focused on making buildings more energy-efficient. However, reducing energy does not equate to reducing environmental impact. Going forward, embodied carbon needs to be considered part of each project’s emissions.

A number of architects have already been creating new buildings that produce zero CO2 emissions. Now everyone must do the same.

To reach zero emissions in the existing building stock, we must advocate for new policies that leverage building intervention points and encourage upgrades to energy efficiency at capital-improvement cycles or when clients lease or buy space. We can then hasten the rate of emissions reductions by making changes that include improving the efficiency of building systems, shifting to electric heating and cooling systems powered by carbon-free renewables, and generating carbon-free renewable energy.

To reach zero emissions in new buildings, we must measure and manage embodied carbon. This requires an understanding of how choices in the early phases of development and design will have impacts downstream. Considerations may include urban densification and infill that utilizes existing infrastructure, whether to adapt and reuse an existing building, how to select building materials created with zero emissions, and how to design a building to reduce material use or even sequester carbon.

In addition, educating policymakers about the need to reach zero emissions is crucial. Cities can use their legal, regulatory, and financial resources to reduce embodied carbon through zoning and land-use policies, administrative and financial incentives, and mandates for infrastructure, buildings, and projects.

As a result, entire communities can be transformed. Measures to reduce carbon can improve air quality and land use, create more transit options, and improve health across cities.

Everyone must work together

Architects can’t reach zero carbon alone.

To succeed, we must work with engineers, contractors, civic leaders, clients, and communities to align everyone toward the same goal. And if history is any indication, we can do it.

For decades, architects have implemented widespread changes in the built environment, planning new innovations in design and construction and quickly addressing materials and methods that represent a danger to the public. These changes have included replacing combustible materials, ensuring buildings have efficient evacuation routes, and creating solutions in response to shifting health, safety, and welfare needs.

Now we’re facing a climate crisis, the greatest challenge of our lives—and also the greatest opportunity to create immediate and effective change.

Architecture 2030
International Energy Agency
U.S. Energy Information Administration
Global Alliance for Building and Construction


The Blueprint for Better campaign is a call to action. AIA is asking architects, design professionals, civic leaders, and the public in every community to join our efforts. Help us transform the day-to-day practice of architecture to achieve a zero-carbon, resilient, healthy, just, and equitable built environment.

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