B2.11 Increase use of low carbon building materials
Create incentives or requirements to increase the use of low-carbon building materials such as cross-laminated timber and low-emissions cement.
According to the Urban Land Institute’s “Embodied Carbon in Building Materials for Real Estate”, about 40% of the global emissions from buildings come from the energy used in producing the materials used to construct them. According to a researcher quoted in the Center for Sustainable Infrastructure’s “From Waste Management to Clean Materials” (p. 43), because Seattle’s buildings use less energy and clean electricity, the embodied energy in the materials in a new office building there may account for 80% of its lifetime emissions.) Bruce King’s The New Carbon Architecture argues that a building’s embodied energy matters even more if you think we have to reach a certain level of reductions by 2050, because the construction emissions occur now, and saving from lower operating emissions only occur over the whole life of the building, stretching well past 2050. Thinking about embodied emissions means upgrading a current building may well produce lower emissions over time, even if the retrofit is considerably less efficient than a new building would be.
“Case Studies in the Economics of Low-Embodied-Carbon Buildings”, by the Rocky Mountain Institute, includes three case studies using Skanska cost data from an actual mid-rise commercial office building, a multifamily building, and a tilt-up-style building in the Pacific Northwest; it concludes that using standard materials could produce reductions of about 40% in their embodied carbon while increasing costs less than 1%.
Vancouver, BC’s Zero Emissions Buildings policy sets a target of reducing embodied emissions in new construction by 40% by 2030. The city did a life cycle analysis of the potential for embodied carbon reduction in a typical concrete high-rise residential building, and a report reviewing the policy as a whole. Its Green Building Policy for Rezoning requires developers to report embodied carbon in their projects.
California’s Buy Clean California law requires state agencies to consider the carbon emissions of the full supply chain for some steel components, flat glass, and mineral wool board insulation in building new construction or infrastructure projects. HB2744, which was introduced in our Legislature in 2020 but did not get voted on in the House, would have required prioritizing the use of low carbon materials in the awarding of state construction contracts. HB1103 made a somewhat different, but unsuccessful, try in 2021.
Skanska’s EC3 tool is an open-source database of construction material information based on environmental product declaration (EPD) data for over 16,000 materials, searchable by performance requirements and design specifications; project location; and global warming potential. In the current pilot period, participating development projects are realizing embodied carbon reductions of up to 30 percent without significant additional financial impacts for companies; in most cases they’re cost neutral.
Architecture 2030’s Carbon Smart Materials Palette provides guidelines and recommendations about a wide range of common building materials, from steel to carpet, with links to research. (Among many other things, it says plywood has half the embodied carbon of the equivalent OSB.)
Cross-Laminated Timber –
See A5.10 Cross-Laminated timber.
Low Emissions Cement –
Marin County recently adopted low carbon concrete code requirements, developed in collaboration with other local jurisdictions and the local building industry through the Bay Area Low-Carbon Concrete Codes Project. Hasting-On-Hudson is adding low carbon concrete requirements to their code, and hosted a webinar on the issues, “The Hastings Resolution: Decarbonizing Concrete Through Local Action”.
Portland has a Low Carbon Concrete Initiative. (As part of it, they did a pilot project comparing six new sidewalk ramps using concrete with more slag in it with six ramps at the same intersections using a regular mix.The six lower-carbon mixes resulted in a reduction of 4.5 MT of CO2e compared to using 100% cement mixes. Portland replaces up to 1,000 curbs a year to make them compliant with the Americans with Disabilities Act, and estimated that using the tested mix with the highest slab ratio would lower the carbon footprint of the concrete for them by 1,211 MT CO2e a year, about 27% of the annual emissions of the electricity for their street lights and traffic signals.
There are a number of ways of reducing cement emissions. Some are commercially available; others are start-ups or research projects. Carbon Brief has an overview of the issues…. The Rocky Mountain Institute has a Concrete Solutions Guide.
Adjusting current technologies –
Aether cement claims to achieve a 20% to 25% reduction in emissions by reducing the percentage of limestone in the raw materials, lowering kiln temperatures, and needing less energy for grinding the clinker. Low carbon calcined clay cement (LC3) uses widely available materials and can reduce CO2 manufacturing emissions by up to 30%, using current plants’ equipment.
CO2 injection curing –
Hawaii’s Department of Transportation is committed to using CO2-injected concrete in new construction, and Honolulu’s Council adopted a resolution signaling the city’s willingness to consider it in proposals. (Some other cities mentioned in this article are considering similar steps. CarbonCure CO2 injection equipment is supposedly used by over 150 companies ; the process is supposed to cure the concrete more rapidly, and reduce its carbon footprint by roughly 4.5%. (They have a technical data library with FAQ’s and research.)
EP Henry’s ECO Bristol Stone pavers are made with Solida Cement, reducing the carbon footprint of the concrete by up to 70% by lowering kiln temperatures and using recycled CO2 captured from industrial emissions to cure the concrete more rapidly.
Alternative cementitious materials –
Replacing some of the cement in concrete with alternative cementitious materials like fly ash or slag is a well-established practice; US Concrete’s EF Technology family of concrete mixes uses these. (Betolar, in Finland, provides methods for industrial customers to convert a variety of waste materials into geopolymerized construction materials.
BioMason –
BioMason is a startup that employs bacteria to “grow” a durable cement in ambient temperatures between loose grains of aggregate, producing building materials without emitting greenhouse gases.
K-briqs
K-briqs are made with 90% recycled content from construction and demolition waste, and no cement. Manufacturing them uses less than 10% of the energy required to produce a traditional kiln fired brick. They look like a normal clay brick, weigh the same, and behave like one, but offer better insulation properties. The company is in Scotland, where 85% of the bricks are currently imported, and has invested in machinery that can produce 3 million bricks per year.
3-D Printed concrete
Doing the concrete structrues for Britain’s high-speed rail project is estimated to reduce emissions by 50%.
Watershed Materials
Watershed Materials uses high pressure, local materials, and much less cement to make low emission block in the shape of standard concrete masonry units.
Hemp building materials –
HempWood manufactures engineered wood products from hemp fibers in a variety of forms including boards, flooring, and pallets. Hempwool insulation batts are also available, and hemp fiber and lime can be used to produce hempcrete insulation. The EcoBuilding Guild sponsored a webinar on these.