Building Decarbonization

As the threat of climate change becomes more pressing, a range of strategies are evolving to equip the government and other entities to mitigate the intensity of climate change, while preparing for and adapting to the dangers it creates.

Climate change mitigation refers to measures to reduce the amount and rate of future climate change by reducing emissions of heat-trapping gases or removing carbon dioxide from the atmosphere.¹

Greenhouse gases (GHGs) trap heat in the atmosphere. They include Carbon Dioxide (CO₂), Methane (CH₄), Nitrous Oxide (N₂O), Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), Sulphur Hexafluoride (SF₆) and Nitrogen Trifluoride (NF₃). They are sometimes grouped together as "carbon" (see "What is the difference between 'Carbon', CO₂, and CO₂e?" below).

Building decarbonization is the process of reducing GHG emissions from buildings, including reduction of GHG emissions from the materials and products used in buildings (embodied carbon) as well as from building operations (operational carbon).

Similar, sometimes overlapping, terms may be used when referring to decarbonization, but they tend to point toward similar strategies that include energy efficiency, the use of renewable energy and other operational carbon pollution-free electricity (CFE) sources, the replacement of fossil fuel combustion equipment with electric models (electrification), and specification of low carbon materials. This module is focused on the decarbonization of federal buildings, through both embodied carbon and operational carbon reduction strategies.

Decarbonization Terms

The many names of "carbon"

The following is a list of terms that are often used somewhat interchangeably to refer to the emissions associated with climate change or global warming: Carbon Carbon footprint Carbon dioxide (CO2) Carbon dioxide equivalent (CO2e or CO2eq) Greenhouse gas (GHG) emissions Fossil fuel emissions Global warming potential (GWP) Climate change (CC) potential These terms overlap significantly but do not share the exact same meaning. Even though the term "carbon" is commonly associated with climate change, it is technically not elemental carbon that contributes to climate change, but carbon dioxide gas along with many other GHGs such as nitrous oxide and methane. Nevertheless, "carbon" is often used as an abbreviation to refer to global warming potential. Source: Carbon Leadership Forum

As the movement to minimize energy use and GHG emissions has gained support and established goals, the terms describing this process and specific supporting actions continue to evolve.

A Zero Energy Building, also known as a net zero building, as defined by the U.S. Department of Energy (DOE), produces enough renewable energy onsite to meet its own annual energy consumption requirements on a net annual basis.

As the U.S. makes stronger commitments to carbon neutrality, the focus increasingly shifts from not only saving energy and adopting clean energy, but also to include finding every other practical way to maximize GHG reduction. While energy reduction remains the central focus, GHG reduction adds such elements as building electrification in order to truly reach net zero operational GHG emissions.

Net Zero Emissions means emitting no more GHGs than are removed or eliminated.

Carbon Pollution-Free Electricity (CFE) is electrical energy produced from resources that generate no GHG emissions. 24/7 CFE means that every kilowatt-hour of electricity consumption is matched with carbon-free electricity sources, every hour of every day.

​​Net Zero Operational Emissions means a highly-efficient building without fossil fuel-consuming equipment. Its annual energy needs are served wholly through onsite renewable energy and/or offsite CFE.

Carbon Neutrality similarly refers to the idea of achieving net zero GHGs by balancing GHG emissions from a building or action so they are equal (or less than) the GHG emissions that get removed through the planet’s natural absorption.² Bringing GHG emissions into balance with what is absorbed by carbon sinks, such as forests and oceans, could involve using carbon storage or low embodied carbon building materials, as well as implementing emerging techniques like carbon removal.

Decarbonization has gained momentum as a preferred term describing the overall process of marrying technological investments, operational changes, and proper accounting to shrink GHG emissions.

Greenhouse Gas (GHG) Emissions

GHGs trap heat in the Earth's atmosphere through the greenhouse effect. At normal levels, this makes the planet livable. However, human activities, including the combustion of fossil fuels, the clearing of forests, and many other large scale actions, have greatly increased the emission of GHGs while reducing their natural absorption into forests and other carbon sinks, throwing our planetary climate out of balance. The resulting climate change is leading to many severe and disruptive impacts varying widely by area, including heat waves, drought, more intense storms, and sea level rise.

Sources of GHG Emissions

According to the U.S. Environmental Protection Agency (EPA), electric power generation produces 25% of total U.S. GHG emissions; most of that electricity is used by buildings and comes from burning fossil fuels, primarily coal and natural gas. Another 13% of total GHG emissions comes from the commercial and residential sector, mostly due to fossil fuel use in buildings, such as burning natural gas for space heating, hot water, and cooking. This means about a third of U.S. GHG emissions are attributable to building operations.

The percentage of industrial GHG emissions shown in this chart includes the share of GHGs emitted to manufacture, transport and dispose of building materials.

A system of GHG accounting is used to categorize sources of GHGs emitted by organizations into three "scopes". This helps organize, direct, track, and report efforts to reduce GHGs:

• Scope 1 emissions are GHG emissions that come from sources that are controlled or owned by an organization (e.g., emissions associated with fuel combustion in boilers, furnaces, vehicles).³ Scope 1 also includes fugitive emissions from refrigerants.
• Scope 2 emissions are indirect GHG emissions associated with the purchase of electricity, steam, heat, or cooling.³
• Scope 3 emissions are indirect GHG emissions that are the result of activities from assets not owned or controlled by the reporting organization, which the organization indirectly affects through its value chain.⁴

GHG emissions from building operational energy use are primarily covered under Scopes 1 and 2, while emissions related to building material use fall under Scope 3.

Life Cycle Carbon / Total Carbon

Globally, buildings generate approximately 40% of annual GHG emissions,⁵ which may be split into two categories: operational carbon and embodied carbon.

• Embodied Carbon refers to the GHG emissions associated with the manufacturing, transportation, installation, maintenance, and disposal of construction materials.⁶ Embodied carbon is responsible for about 13% of global annual GHG emissions (from materials manufacturing as well as construction activities).
• Operational Carbon refers to the GHG emissions associated with energy used to operate a building.⁶ Operational carbon is responsible for 27% of global annual GHG emissions.
• The sum of embodied carbon and operational carbon is known as life cycle carbon or total carbon.

Carbon Emissions in Buildings
Source: Carbon Leadership Forum

Whole Building Life Cycle Assessment (WBLCA)

Life Cycle Assessment (LCA) is a scientific process to assess and quantify environmental impacts in terms of severity, quality, and extent. A WBLCA looks at a building's environmental impacts from a GHG emissions perspective, or the GHG emissions a building produces throughout its life cycle.

The typical stages of a WBLCA are:

• Stage A: Material production and construction (embodied carbon)
• Stage B: Building operation and use (operational carbon) and maintenance (embodied carbon)
• Stage C: End of life (embodied carbon)
• Stage D: Circularity/reuse

It should be noted that “Stage D” is often optional and can be considered to be beyond the boundary of a typical WBLCA. A WBLCA can be done for new construction, or for existing buildings undergoing a major renovation or fit-out project. It is the most accurate method to estimate the environmental impacts of a building. The graph below sheds more light on the stages and details of a WBLCA.

Life Cycle Cost Assessment (LCCA)

LCCA is a process for evaluating the total cost associated with facility/building ownership. It takes into consideration all costs of building, acquiring, owning, operating and disposing of buildings or building components. A LCCA is most useful when project alternatives have to be compared and when selecting the ones that maximize monetary savings - especially when those alternatives are similar in functionality and performance but differ in terms of upfront and ongoing costs. For example, a LCCA can help determine whether the selection of low embodied carbon materials or a high-efficiency HVAC system is cost effective. As a result, in some cases, initial cost may increase but the cost of operations and maintenance (O+M) will significantly decrease.

For more information, see SFTool’s Life Cycle Perspective pages.

Life-Cycle Cost Analysis (LCCA) | WBDG - Whole Building Design Guide

Programs, Policies and Initiatives

Following are several programs, policies and initiatives to facilitate the decarbonization of buildings:

Executive Orders and Federal Standards for Building Decarbonization

• Executive Order 14057: EO 14057, Catalyzing Clean Energy Industries and Jobs Through Federal Sustainability, sets out a range of ambitious goals to deliver a pathway to reducing U.S. GHG emissions by 50 percent from 2005 levels by 2030 and limiting global warming to 1.5 degrees Celsius.
• Federal Building Performance Standard: The Federal Building Performance Standard requires agencies to cut energy use and electrify equipment and appliances to achieve zero Scope 1 emissions in 30% of the Federal government’s owned square footage by 2030.
• GSA P100 Facilities Standards for the Public Buildings Service (including section 1.9.2.9 “Decarbonization”): The Facilities Standards for the Public Buildings Service (P100) establishes design standards and performance criteria for the GSA Public Buildings Service. This document contains policy and technical criteria to be used in the programming, design, and documentation of GSA buildings.
• Energy Independence and Security Act (2007): EISA reinforces and extends energy reduction goals for federal agencies that originated in EO 13423. Three key provisions are the Corporate Average Fuel Economy Standards, the Renewable Fuel Standard, and the appliance/lighting efficiency standards.
• Energy Policy Act (2005): The Energy Policy Act addresses energy production in the United States, including: energy efficiency; renewable energy; oil and gas; coal; Tribal energy; nuclear matters and security; vehicles and motor fuels, including ethanol; hydrogen; electricity; energy tax incentives; hydropower and geothermal energy; and climate change technology.

Other Initiatives/Commitments

• SE 2050 Commitment: The mission of the SE 2050 Commitment is to support the SE 2050 Challenge and transform the practice of structural engineering in a way that is holistic, firm-wide, project-based, and data-driven. By prioritizing reduction of embodied carbon, through the use of less and/or less impactful structural materials, participating firms can more easily work toward net zero embodied carbon structural systems by 2050.
• 2030 Challenge: In 2005, Architecture 2030 issued this initiative which comprised incremental carbon reduction goals over a 25-year timeline that were consistent with those called for by the global scientific community at the time. Meeting the targets would mean that all new buildings and major renovations would be zero carbon by 2030.
• AIA 2030 Commitment: The AIA 2030 Commitment is an actionable climate strategy that provides a set of standards and goals for reaching net zero emissions in the built environment.
• MEP 2040 Challenge: To address the impact of the built environment on climate change, systems engineers have a critical role to play in both operational and embodied carbon. While operational carbon has been targeted with energy efficiency initiatives for some time, setting embodied carbon targets for systems is quite new.
• Carbon Neutral Cities Alliance: The Carbon Neutral Cities Alliance (CNCA) is a collaboration of leading global cities working to achieve carbon neutrality in the next 10-20 years – the most aggressive GHG reduction targets undertaken anywhere by any city.
• Better Buildings Challenge/Better Climate Challenge: Better Buildings is an initiative of the DOE designed to improve the lives of the American people by driving leadership in energy innovation. Through Better Buildings, DOE partners with leaders in the public and private sectors to make the nation’s homes, commercial buildings, and industrial plants more energy-efficient by accelerating investment and sharing successful best practices. Through the Better Climate Challenge, organizations partner with DOE to reduce portfolio-wide GHG emissions (scope 1 and 2) by at least 50% within 10 years. DOE provides technical assistance and opportunities to learn and share actionable best practices for carbon reduction.

Embodied Carbon Policy Tracker

The Carbon Leadership Forum’s Embodied Carbon Policy Toolkit provides information about existing and proposed embodied carbon policies at the local, state or provincial, and national level around the world.

Acknowledgements

Special thanks to the team of experts including: GSA Public Buildings Service (PBS) Central Office and Region 8; Department of Energy Federal Energy Management Program; Lawrence Berkeley National Laboratory; American Wood Council; The Nesler Group; EHDD Architecture, Interiors & Planning; SOM; the Green Building Advisory Committee; and GSA Office of Federal High-Performance Green Buildings.

1. GlobalChange.gov | Fifth National Climate Assessment, Appendix 5. Glossary

2. United Nations | A Beginner's Guide to Climate Neutrality

3. EPA.gov | Scope 1 and Scope 2 Inventory Guidance

4. EPA.gov | Scope 3 Inventory Guidance

5. Architecture2030.org | Why the Built Environment?

6. Carbon Leadership Forum | The Embodied Carbon Challenge