Reducing GHG Emissions in the Built Environment
Learn about the building- and material-focused strategies used to lower operational and embodied GHG production
24 May 2022
In 2021, the United States experienced 20 separate weather and climate disasters (e.g., hurricanes, wildfires, and tornadoes) totaling $146 billion in costs. The previous year there were a record-setting 22 disasters responsible for a combined $96 billion in losses. Both years exceeded the previous record of 16 disasters, set in 2011 and again in 2017, resulting in multiple record-setting years in the last decade. And its only accelerating.
Looking ahead, Colorado State University predicts another above average Atlantic hurricane season this year. In addition, last year's wildfire season extended into late December with deadly fires in Colorado, and the National Interagency Fire Center reports that wildfires so far this year have burned 187% of the 10-year average for this Q1 time period. With continuing droughts, the outlook is not good for the rest of this year. These dire projections underscore the need to aggressively address the global climate crisis.
You might be asking, how are climate disasters related to buildings? According to the United Nations, buildings are responsible for 36% of global energy use and more than 39% of greenhouse gas (GHG) emissions (11% from building materials), so buildings are indeed part of the problem and an important place to seek solutions. The cost of not acting is significant.
The two primary GHG emissions from buildings are embodied carbon and operational carbon. Operational carbon refers to GHG emissions associated with building operations, like heating, cooling, lighting, domestic hot water, and electronic equipment. Operational carbon is classified as either source, like natural gas and coal power plant emissions, or site, like natural gas boilers in a building.
By contrast, embodied carbon refers to the GHG emissions associated with the extraction of raw materials, the processing and transportation those raw materials, the manufacturing and distribution of finished building materials, the construction of the building, the maintenance and replacement of those materials, and ultimately the demolition of the building at the end of its life.
In 2019 the American Institute of Architects (AIA) committed to collective climate action through sustainability to reduce operational and embodied GHG production with passive design techniques, by employing energy efficiency measures, adapting existing buildings, and specifying low-impact building materials that increase human health and productivity while withstanding the effects of a changing climate. Designing and building low-carbon buildings, working toward zero net carbon, is an imperative for building professionals.
Much of the GHG emissions reduction effort to date has focused on operational carbon, but meeting reduction goals will require all solutions. Architecture 2030 estimates that the building sector accounts for 39% of global GHG emissions – 28% of that is from building operations, while the remaining 11% is specifically from building materials and construction.
At the rate that buildings are becoming more efficient and renewable energy is expanding, embodied carbon will be responsible for a much larger percentage of building-related emissions. We have put a great deal of emphasis on operational carbon in the past, for good reason, and we still have a way to go on this, but we can no longer ignore embodied carbon and its contributions to GHG emissions.
Embodied carbon in buildings can be reduced with both building- and material-focused strategies. Building-focused strategies including:
- Reusing existing buildings, as even major renovations have less than half of the carbon footprint of new construction
- Maximizing the durability and maintainability of the building enclosure and finishes by selecting durable materials that are easily refurbished, and designing and constructing high-performance enclosures that resists moisture intrusion and air infiltration and conducting building enclosure commissioning (BECx)
- Designing for adaptability and flexibility, so that the building will continue to be valuable and useful as programmatic needs change over time
- Using less material, with choices like avoiding basements (the most carbon intensive part of a structure) or using off-site construction (up to 98% material waste reduction)
The primary material-focused strategies include selecting the lower impact options for key structural and enclosure material types or substituting alternative materials or systems with lower embodied carbon. The embodied carbon of materials is measured using life cycle assessment and documented on Environmental Product Declarations (EPDs). Building level alternatives are quantified using whole building life cycle assessment (WBLCA).
To learn more about strategies to reduce embodied carbon and tools available to help us to quantify embodied carbon in buildings and the individual materials that go into them, watch our on-demand webinar: Exploring Embodied Carbon in Buildings.
Alan Scott, FAIA, LEED Fellow, LEED AP BD+C, O+M, WELL AP, CEM, is an architect with more than 30 years of experience in sustainable building design. He is Discipline Leader, Sustainability, with Intertek Building Science Solutions in Portland, OR.