This course is part of the Metal Architecture Academy

Architects and design professionals need to face future choices right now in designing for a better built environment. The buildings of today must satisfy a supreme standard: they are called upon to achieve functional performance and sustainability, to be resilient and promote occupant health, and to be energy efficient, all while minimizing consumption of materials and resources difficult to replace. As the building industry plays a significant role in fighting climate change, building envelope material selections that improve building performance and lower overall CO₂e emissions are vital. These demands elicit dramatic changes to building envelope design and the components used within. They also require the data and tools necessary to enable broad and swift action across the building industry in addressing embodied carbon's role in climate change.

Photo courtesy of CetraRuddy Architecture, Esto/David Sundberg, and Rockefeller Group

The impact of embodied carbon will continue to grow in importance as a proportion of total structure emissions. Rose Hill, New York City.

Carbon And The Building Industry

Greenhouse gases (GHGs) are gases in our atmosphere which interact with sunlight in the infrared range in a way that increases their temperature. Most gases are transparent to infrared radiation but there are important exceptions such as carbon dioxide, or CO₂. Global warming is the result of increasing levels of greenhouse gases in our atmosphere and has potentially devastating results.

There are many greenhouse gases, but CO₂ is of primary concern because of its high potency and proliferation as a direct result of human activity. Consequently, all greenhouse gases are expressed in terms of their ability to impact Global Warming relative to that of 1 kg of CO₂. Collectively, these gases are termedCO₂ equivalents, abbreviated as CO₂e. The difference between GHG and CO₂e is that different gases are weighted by potency in CO₂e, whereas GHG is an unweighted generalized term. CO₂e emissions are often called “carbon” for short, although that is a misnomer. Strictly speaking, carbon is an element and is a solid at earthbound temperature and pressure ranges.

Photo courtesy of All Weather Insulated Metal Panels

As the operational carbon footprint of a building is reduced, thCO₂e emissions associated with the structure’s materials during their life cycle, called embodied carbon, grow in importance as a proportion of total structure emissions. Caligstoga, Calif.’s Venge Winery with insulated metal panel roof.

Defining Embodied and Operational Carbon

CO₂e emissions occur not only throughout a structure’s operational life but also during the manufacturing, transportation, construction, and end-of-life phases of all built assets – buildings and infrastructure. CO₂e emissions associated with material creation, the transportation, construction and deconstruction, and final transportation and material disposal of a building or infrastructure element are all categorized as embodied carbon. This is different from Operational carbon, which are all CO₂e emissions stemming from the operation and use of the building or infrastructure element during its lifetime. Operational carbon is mostly due to energy consumption and on-site fuel combustion and is not addressed in this course. However, it is important to understand that both contribute to global warming, and it is the reduction of total CO₂e that is important. Trading embodied carbon for operational carbon 1:1 has no net impact.

Embodied carbon, which has largely been overlooked historically, contributes around 11% of all global carbon emissions, according to the World Green Building Council. Architecture 2030 states that the building sector accounts for 39% of global greenhouse gas (GHG) emissions—28% of which is from building operations, while the remaining 11% is specifically from building materials and construction.

While energy use associated with building operations can be reduced over time with measures such as energy efficiency retrofits, shifts towards renewable energy procurement, and on-site renewable energy installations, embodied carbon from building materials and construction are unchangeable once a building is completed, with a possible exception of some unforeseeable reductions associated with end-of-life processes. As the operational carbon footprint of a building is reduced, embodied carbon will continue to grow in importance as a proportion of total structure emissions. CO₂e emissions occurring released before the building or infrastructure begins to be used, sometimes called upfront carbon, will be responsible for half of the entire carbon footprint of new construction between now and 2050, according to the World Green Building Council, threatening to consume a large part of the remaining carbon budget set by the Paris Agreement.

The 11% of GHG accounted for by building materials and construction represents a fixed carbon cost as the embodied carbon is essentially locked into buildings once they are built. The "locked-in" nature of embodied carbon means that the opportunity for architects and building owners to reduce the total carbon footprint of a building, as it relates to building materials, must occur during the design and procurement phases of a project. This clearly underscores the critical importance of thoughtful material selection and detailed specifications at the outset.

Photo courtesy of Jason O’Rear Photography; courtesy of CENTRIA

The products we choose have impacts. An EPD tells the life-cycle story of a product in a single, written report, focusing on information about a product’s environmental impacts, such as global warming potential (GWP), smog creation, ozone depletion potential (ODP), use of limited resources, and water pollution. Chase Center, San Francisco.

The Decade of Getting to Net Zero

Buildings can play a central role in reducing GHG impacts. Architecture 2030, a nonprofit organization dedicated to rapidly transforming the built environment from the major contributor of greenhouse gas emissions to a central solution to the climate crisis, first released a carbon action plan in 2006. The 2030 Challenge calls for all new buildings, developments, and major renovations to be carbon-neutral by 2030. Under the Challenge, all new buildings, developments, and major renovations are designed to meet a fossil fuel, GHG-emitting, energy consumption performance standard of 70% below the regional or national average for that building type. For embodied carbon actions, achieving zero embodied emissions by 2040, the goal presented in the Challenge, will require adopting the principles of reuse, reduce, and sequester. Reuse includes renovating existing buildings when possible, using recycled materials, and designing for deconstruction. Reduce encompasses material optimization and the specification of low to zero carbon materials. Finally, sequester includes the design of carbon sequestering sites and the use of carbon sequestering materials, where doing so is feasible for function and maintenance of public safety standards.

To support the 2030 Challenge, the American Institute of Architects (AIA) created the 2030 Commitment Program, aimed at transforming the practice of architecture to respond to the climate crisis in a way that is holistic, firm-wide, project-based, and data-driven. Over 400 A/E/P firms have adopted the 2030 Commitment, and firms from all over the country have been tracking and reporting projects since 2010, with over 2.7 billion ft2 of project work reported in 2016 alone.

Likewise, the Structural Engineering Institute issued the SE2050 Commitment in 2019, prioritizing the reduction of embodied carbon through the use of less impactful structural materials to achieve a goal of net zero embodied carbon structural systems by 2050. Engineers and architects have a powerful role to play in determining the makeup of the built environment and its health. It is through embracing best practices of sustainable structural design and construction that we will realize the goal of net zero embodied carbon. Fortunately, tools, certifications, and programs exist to enable responsible material selection and establish appropriate embodied carbon reduction targets until net zero is realized.

Environmental Impacts And Material Selection

With the array of today’s analysis methods, selecting materials with confidence is possible. When endeavoring to select components and materials that reduce embodied carbon, knowing with certainty what is in each possible product becomes crucial.

Life-cycle assessment, or LCA, is a technique for assessing the environmental aspects associated with a product over its life cycle. The most important applications are an analysis of the contribution of the life-cycle stages to the overall environmental load, usually with the aim to prioritize improvements on products or processes; and a comparison between products for internal use.1 An LCA provides a description of material and energy flows within the product system and its interactions with the environment, the consumed raw materials, and emissions to the environment. A typical LCA methodology accounts for the environmental impacts associated with the inputs from and emissions to the environment that result from the manufacturing, maintenance, and disposal of products and materials found in the building.