Climate bright spot: Building sector decarbonization is well underway

We are witnessing the remarkable transformation of the U.S. building sector with record emissions reductions that began in 2005.

In the U.S., from the Industrial Revolution (late 1700s) to 2005, as the buildings sector grew, so did sector energy consumption and CO2 emissions. This makes sense. We added about 3 billion to 5 billion square feet to our building stock each year, and as those buildings consumed energy to operate — electricity, natural gas, heating oil, etc. — energy consumption and emissions in the sector went up.

However, in 2005, something extraordinary happened; building operating energy and emissions decoupled from building sector growth:

• Since 2005, the carbon intensity of the entire U.S. building stock (CO2 emissions per square foot of floor area) actually declined by 39.8 percent for residential and 43.7 percent for commercial buildings.
• From 2005 to 2022, the U.S. added 62.5 billion square feet to its building stock — the equivalent to adding about six cities the size of Boston each year – but building sector operating ­energy consumption did not increase (down 3.5 percent) and CO2 emissions declined 28.4 percent.
• From 2010 to 2022, residential and commercial building energy consumers saved approximately $530 billion total from 2010 projected energy costs. That means more money is being spent throughout the economy on clothing, food, education, travel, electronics, construction, equipment and housing.

Of all the electricity produced in the U.S., 73.8 percent goes to operate our buildings. With renewable electricity generation growing exponentially — especially solar and wind — coupled with low- to zero-carbon design and planning; new federal climate programs and incentives; and local governments advancing clean power plans, as well as zero-carbon standards for new buildings and major renovations, ​we should be able to meet or exceed a 50 percent building sector CO2 reduction by 2030.

Similarly, we are seeing a dramatic increase in worldwide activity toward developing renewable electricity due to the Russian invasion of Ukraine. For many countries and cities, supply disruptions and higher prices for fossil fuels underlined the cost and security benefits of locally generated renewable electricity. Renewable sources now make up over 30 percent of the global electricity supply. With renewable electricity getting cheaper every year, the International Energy Agency (IEA) projects worldwide renewable electricity to double over the next five years. In fact, renewables are expected to account for over 90 percent of global electricity expansion during this period. By 2025, renewables will become the largest source of electricity generation worldwide.

Countries are also setting ambitious new targets for emissions reductions, and unprecedented public investments in renewable energy will unlock more technological and efficiency advances. Between 2021 and 2022, more than 150 countries amended their Nationally Determined Contributions (NDCs) or emissions reduction commitments with greater climate ambition, and more countries have committed to net-zero emissions by mid-century. Leaders are also understanding the outsize contribution that buildings and the built environment make to greenhouse gas (GHG) emissions, with 158 of the 196 parties to the Paris Agreement now including buildings in their Nationally Determined Contributions (NDCs).

Since the embodied carbon emissions of building materials, construction and sitework can account for as much as 50 percent of the carbon footprint of new buildings over their lifespan, we must also target halving embodied emissions by 2030. Fortunately, new design strategies and calculation tools to reduce and sequester embodied carbon have been developed (including EC3, Carbon Smart Materials Palette, Pathfinder, Tally, CARE Tool, EPIC and One Click LCA among others) and are increasingly being used.

Why is all this so important?

Because we reached 1 degree Celsius (1.8 degrees Fahrenheit) of global warming and beginning to experience the increasingly destructive impacts of climate change. Keeping warming at 1.5 C (2.7 F) or well below 2 C (3.6 F) to avoid catastrophic global hardships takes greatly accelerated and successful emissions reductions. Nothing succeeds like success — success generates momentum, is a great motivator, leads to further opportunities, discredits misinformation campaigns and provides a proven sector decarbonization model. And, with the world urbanizing rapidly and buildings typically representing most urban emissions, successful decarbonization models are essential.

Ahead of the Paris Agreement in 2015, planetary warming was estimated to rise about 3.6 degrees Celsius. With current policies and targets in place, if met, the projections for warming have come down to 2.4 degrees Celsius.

While it is heartening to share some good news for a change, even if countries were to meet their targets, we still have a long way to go to keep warming at the Paris Agreement’s 1.5 degrees, or well below the 2-degree Celsius target.

Now is the time to build upon positive developments, aggressively accelerate our actions, work collaboratively with colleagues, learn from each other and create a truly global transformation to effectively address the climate emissions gap.

With many of those responsible for the building sector and built environment committed to a 50 percent CO2 emissions reduction by 2030 and zero emissions by 2040, the future looks more promising.

Edward Mazria, FAIA, FRAIC, is founder and CEO of the nonprofit Architecture 2030 and is an internationally recognized architect, author, researcher and educator. Over the past four decades, his research into the sustainability, resilience, energy consumption and greenhouse gas emissions of the built environment has helped redefine the role of architecture, planning, design and building in reshaping our world. He was awarded the 2021 American Institute of Architects Gold Medal for his “unwavering voice and leadership” in the fight against global warming and the 2021 Global Human Settlements Outstanding Contribution Award and Lifetime Achievement Award from the National Council for Science and the Environment, among other honors.

All building sector floor area, operating energy and emissions statistics cited above are derived from the U.S. Energy Information Administration’s “Annual Energy Outlook 2005 to 2022.”­­