By 2050, two-thirds of the expected global population of 10 billion will live in cities of some kind, according to a report by the UN Department of Economic and Social Affairs. To manage this growth, cities will add up to 230 billion square meters of new floor space to building stock, the UN Environment and International Energy Agency estimated—a number that would roughly double the floor area in today’s buildings. “This means adding a floor area equivalent to the area of Manhattan in New York City every month for the next 40 years,” explained a report by Jacobs.
This growth will naturally lead to considerable carbon dioxide emissions. By 2040—the year Architecture 2030 has targeted for eliminating CO2 emissions from the built environment to keep global warming below an increase of 1.5 degrees C.—approximately two-thirds of the global building stock will be buildings that are in use today. “Without widespread existing building decarbonization across the globe, these buildings will still be emitting CO2 emissions in 2040 and we will not achieve the Paris Agreement’s 1.5-degree C. target,” the organization said.
Hitting this target and accommodating the coming floor area growth requires us to dramatically reduce the carbon footprint of both new and existing buildings—to change the way we design, construct and operate them in order to avoid the potentially catastrophic effects of releasing that much carbon dioxide into the atmosphere. That’s why governments and commercial real estate owners are embracing decarbonization—phasing out carbon-emitting fuels, using building materials with less carbon and otherwise addressing the built environment’s carbon emissions.
What is Decarbonization?
With new buildings, decarbonization is about the embedded carbon in the materials you choose, explained Brenna Walraven, BOMA Fellow, president and CEO of Corporate Sustainability Strategies and a member of the BUILDINGS advisory board. Concrete, steel and cross-laminated timber all have a different carbon footprint, as well as different performance qualities. “Also, how far away are your materials from?” Walraven asked. “Are you getting that marble from Italy, or are you using material that’s sourced within a few hundred miles of your project and dramatically reduces the carbon associated with the development?”
For existing buildings, decarbonization is tied to energy consumption. Are you burning fuels like propane or natural gas on-site? How much electricity are you using, and how does your utility generate it? Are you using renewables on-site? All of these factors enter into the carbon footprint equation.
Why is the Conversation Changing?
Seemingly overnight, the sustainability conversation has changed from a focus on energy efficiency to decarbonization. “I think we’ve finally reached the point where climate change is accepted as a significant influencer on more of our daily life than ever before,” said Gunnar Hubbard, principal and sustainability practice leader for Thornton Tomasetti. “It’s coming quicker than we could have imagined in terms of becoming hotter or colder or windier, and that’s triggered folks to start saying ‘Could we be doing more? What should we be doing now to have an impact?’”
Many governments have accepted the science of climate change too, and some are starting to require major emissions reductions.
Washington, DC, adopted a 2022 law that calls for the District to adopt a net zero energy building code that would apply to new construction and substantial building improvements; it also has a current net zero energy building code that presents an alternative pathway for buildings to comply with DC energy codes. California also has an ambitious carbon neutrality program.
“Even if you don’t want to be a leader, [public policy] is going to start requiring it in some form or fashion,” Walraven said. “Let’s not wait until we’re hitting the iceberg. Let’s say ‘Decarbonization may be required. Net zero may be required. How do I get there?’”
Start Your Decarbonization Journey
Playing offense on decarbonization starts with measuring your emissions. As the old saying goes, “You can’t manage what you don’t measure.” As you start your decarbonization journey, you’ll typically hear of emissions grouped into Scopes 1, 2 and 3.
Scope 1 is generally understood as direct emissions—the carbon dioxide you’re generating on-site by burning fossil fuels. “Do you have a gas-fired boiler? Do you use propane on your property?” asked Walraven. “Those are direct emissions you’re emitting into the sky.”
Scope 2 represents indirect emissions that are associated with the use of electricity. You’re not burning fossil fuels on-site, but your utility might be burning them on your behalf and then sending you the electricity they generate.
Scope 3 is generally understood as everything else, and it’s the hardest to define for reporting. One question to ask yourself is whether you’re controlling a certain source of emissions operationally. If you are, it probably falls into Scope 1 or 2; if not, it’s most likely in Scope 3.
“If you have an office building with tenants, you’re controlling when the building starts and stops. You’re controlling the equipment being used and when it’s being used. Those are your Scope 1 and 2 emissions,” explained Walraven. “But if we’re talking about an industrial tenant warehouse building, the tenants should be controlling not only the meter—meaning that they pay the bill directly to the utility—but they decide when the building starts and stops and whether to operate on the weekend. That would be Scope 3 because you don’t control them operationally, the tenant does.”
Once you can get your arms around how to measure your emissions, it’s time to start cutting them. Try these tips to cut your operational carbon.
1. Make sure your building is operating as intended. “Are you walking in periodically at night to make sure everything is shut off that’s supposed to be shut off?” Walraven asked. “Are you talking to your tenants about operating hours on the weekends?”
2. Control solar heat gain. Look at window tinting or having occupants close the blinds during the day.
3. Conduct a lighting retrofit. The costs of LEDs have come down drastically in the next few years, and the technology has come a long way. Now is the time to upgrade inefficient fixtures.
4. Decrease operating hours for mechanical systems. Look at occupancy patterns and see if you really need to run the HVAC system for as many hours as you currently do, suggested Bill Prindle, ICF Climate Center senior fellow and vice president of sustainable energy and climate for the global advisory and technology services provider.
5. Look at upgrades and replacements. Is some of your major equipment nearing the end of its useful life? You may be able to make the business case for a more efficient version. “When the replacement cycle comes around, there are a lot of efficient options,” Prindle said.
6. Tighten up your envelope. “We always recommend sealing and insulating. Sealing air leaks is the cheapest thing you can do to reduce cooling loads,” Prindle said. “Insulation depends on the building type, climate zone and what’s currently in the building shell, but there can be cost-effective solutions there.”
7. Explore green power purchasing. “Once you’ve done what you can to upgrade the building’s performance, you still need to find a way to purchase clean energy,” Prindle said. “Many utilities these days offer a green power purchase option. Typically, it will add a penny or two per kilowatt-hour to your bill.”
You may have already taken some of these steps, Walraven noted. “Decarbonization is the new energy efficiency,” she added. “As you get more efficient and decarbonize, generally speaking it’s going to save you money, improve the performance of your asset and have a bigger impact longer-term on reducing the impacts of climate change.”
Decarbonization Tools and Resources
Ready to start lowering your carbon emissions? Explore these helpful tools to help you chart your path.
BOMA International’s Carbon Reduction Challenge: BOMA International has launched a benchmarking program with a resource center to gather best practices in one central place. “The program we’ve established … shows that the commercial real estate and building industry is very concerned about making sure we have a positive impact on the environment,” explained Don Davis, vice president of advocacy and building codes for BOMA International.
Better Buildings Initiative: Among the resources offered by the Department of Energy is a tool that allows users to evaluate financing mechanisms for retrofits, helping you make the business case for more efficient equipment.
Embodied Carbon in Construction Calculator: This tracking tool enables reductions in embodied carbon by displaying the upfront supply chain emissions of building materials.