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Image: Image of the PDX airport roof under construction provided by Port of Portland. The wooden roof with mass timber components will cover the airport’s expanded main terminal with mass timber used to create a sustainable design. Nickel Alloys Enicrfe-3 Welding Stuff
The City of Portland is a national leader in decarbonization with programs and policies reducing greenhouse gas emission (GHG) in building operations. However, we cannot achieve net-zero carbon without also addressing the embodied carbon of building materials.
The GHG emissions arising from the manufacturing, transportation, installation, maintenance, and disposal of the building materials used to construct a building are known as embodied carbon. A shorthand way to remember this is that these emissions are from the “body” of the building: the concrete, steel, wood, and other materials.
When people talk about building energy, they typically refer to operational carbon – the emissions that occur from energy usage for space heating and cooling, water heating, cooking, lighting, and the use of electronics. To reduce operational carbon emissions, we can install energy efficient appliances, increase insulation and air sealing in a building, and switch our building energy usage to all-electric appliances and systems to be run by renewable energy sources.
However, the GHG emissions of building materials occurs before any of those operational systems are in use. Unlike operational carbon, very little can be done to reduce embodied carbon after a building is constructed. Embodied carbon must be addressed alongside operational carbon to achieve our ambitious net-zero goal.
Locally, construction waste and demolition debris accounts for approximately 30-35% percent (by weight) of the landfill bound waste in Portland’s waste stream. The best way to address embodied carbon is to reuse existing buildings instead of constructing new buildings. This adaptive reuse avoids demolishing existing structures and using new building materials. Existing buildings can also be retrofitted to reduce operational carbon emissions.
Unless we take action to reduce emissions arising from building materials, emissions will continue to increase in the following building material lifecycle stages:
Simply adapting existing buildings won’t be enough to meet the needs of our growing population. An estimate from the American Institute of Architects (AIA) notes that the global demand for new buildings is comparable to constructing one New York City each year for the next 40 years (Architecture 2030). We must address the building materials and methods of new buildings as soon as possible or we lose the opportunity to reduce embodied carbon emissions.
The best way to impact the embodied carbon of a building is early in the building’s design when structural and material decisions are being made, but construction practices and the end of a building’s use also offer opportunities. Common examples of these methods include:
In the Climate Emergency Workplan, the City of Portland supports policies that reduce the embodied carbon of building materials and construction through the use of low-carbon alternatives, adaptive reuse, and whole-building life-cycle assessments (LCAs). The City participates in local, regional, and international coalitions of cities and non-governmental organizations whose missions align with reducing embodied carbon in buildings to share and learn policy practices that will make an impact. Additionally, several plans and policies include provisions that reduce the embodied carbon of buildings in Portland, including the following:
BPS’ work on embodied carbon supports a just transition, which centers the people at the forefront of the climate crisis in the global transition to a clean economy. Increasing the use of low-embodied carbon materials will create good jobs for frontline workers in the growing zero-carbon economy, support the creation of new small businesses, create healthier living spaces for Portland residents, and provide opportunities to preserve and honor historic and cultural resources. Low-embodied carbon materials can also support important local economies and practices, such as indigenous land stewardship and sustainable forestry.
Concrete – Concrete is composed of sand, gravel, cement, and water. Large amounts of fuel are required for heating in the cement production process production and the material also emits carbon as it cures. One method to reduce the carbon impact of concrete is to adjust the formula of the cement towards less carbon-intensive components. If you would like to learn more, this video is informative.
Steel – Melting steel to create building materials such as beams and rebar requires large amounts of fuel. Additionally, there are a limited number of steel manufacturers in the United States, so many steel products are shipped worldwide, adding transportation emissions from steel products in buildings.
Aluminum – Aluminum is frequently used as metal studs in building construction and also as exterior cladding. Similar to cement and steel, aluminum requires large amounts of fuel to produce and transport. An alternative to aluminum is other low-carbon materials such as wood framing, recycled aluminum cladding, or wood or stucco siding.
A whole building life cycle assessment (WBLCA) is completed to determine the total potential CO2 emissions impact of the building materials. One useful tool to complete WBLCAs is Environmental Product Declarations (EPDs), which describe the origin and composition of a material. The assessment allows building design teams to make materials choices that can reduce the overall carbon emissions of a building design. Learn more about WBLCA.
If you are remodeling or building a home, consider using low embodied carbon materials to reduce your GHG impact and improve the long-term efficiency and comfort of your home. Local re-use materials organizations take donations of and resell durable materials such as lumber, sinks, spare tile, plywood, and hardware to local re-use materials organizations.
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