Buildings & Climate 101
Building Performance Foundations
The Connection Between Buildings and Greenhouse Gas Emissions
To better understand GHG emissions and how buildings and their operations contribute to those emissions, this resource will explain how emissions are characterized and calculated.
Progress Toward Building Decarbonization in California
Homes and commercial buildings in California are responsible for 25 percent of the state’s greenhouse gas emissions, and the state has set a target of reducing emissions from buildings 40% below 1990 levels by 2030. Between 1990 and 2018, emissions from buildings rose from 54.4 million metric tons of CO2e to 98.4 million metric tons of CO2e.
According to the 2021 California Building Decarbonization Assessment report from the California Energy Commission, developed pursuant to Assembly Bill 3232 (Friedman, 2018), strategies including electrification, electricity generation decarbonization, energy efficiency, refrigerant leakage reduction, distributed energy resources, decarbonizing the gas system, and demand flexibility can help California achieve its 2030 emissions target.
Next Steps: The 2021 report also shows that the lack of progress in reducing gas usage in buildings is the biggest challenge to overcome.
How are Building Emissions Characterized?
The Greenhouse Gas Protocol, which provides a standard framework and tools for measuring emissions, defines emissions as either direct or indirect.
Direct GHG emissions are from sources that are owned or controlled by the reporting entity.
Indirect GHG emissions are a consequence of the activities of the reporting entity but occur at sources owned or controlled by another entity.
Additionally, GHG emissions are typically characterized by their “scope” or category. There are three scopes: 1, 2, and 3.
Scope 1 emissions are Direct GHG emissions from on-site fuel combustion (e.g. gas used on site for cooking, water heating, and/or space heating) and refrigerant leaks.
Scope 2 emissions are indirect GHG emissions from purchased grid electricity (i.e. usage on an electricity bill) and other centralized energy sources (e.g. steam).
Scope 3 emissions are other indirect GHG emissions, including material extraction and production, waste disposal, commuting and travel, water consumption and disposal, and many others.
GHG emissions are not measured in the same way as water and electricity are. Rather, emissions are estimated based on how much electricity, gas, and other fuels a building consumes.
Scope 1 emissions
Gas combustion in the building, which can occur in a boiler, furnace, or in cooking appliances, emits GHGs directly at the site (Scope 1 emissions) as a byproduct of combustion.
Calculating Scope 1 emissions is as simple as looking at gas consumption values on utility bills and multiplying them by a stable emissions factor. Inputting this information into ENERGY STAR® Portfolio Manager will also automatically calculate a building’s GHG emissions.
Scope 2 emissions
Calculating Scope 2 emissions is more complicated. Because electricity comes indirectly from multiple generating sources, such as natural gas, hydro, and solar, GHG emissions from electricity consumption vary substantially depending on the building’s location, time of day, and time of year. The emissions intensity of grid-delivered electricity is changing, however, due to increased deployment of renewable energy and the decline of coal-fired and gas-fired power plants (see U.S. Energy Information Administration FAQs for details).
You can approximate your building’s Scope 2 emissions using ENERGY STAR® Portfolio Manager. Once you enter building-specific data, the output includes the building’s estimated total GHG emissions and total GHG emissions intensity (the amount of emissions generated per square foot). The platform pulls in grid information to estimate a building’s Scope 2 emissions.
The emissions outputs generated by ENERGY STAR® Portfolio Manager should be used as a starting point to understand Scope 2 emissions. For higher accuracy, two industry-standard resources are the GHG Protocol’s Corporate Accounting and Reporting Standard, which provides businesses with guidance on GHG emissions inventory, and Scope 2 Guidance, which assists in setting corporate standards.
Scope 3 emissions
Scope 3 includes emissions from an organization’s supply chain and business operations, often representing an organization’s largest source of total GHG emissions (see EPA’s Climate Leadership inventory guidance for details). Scope 3 emissions include the embodied carbon that is present throughout the building’s entire lifecycle, spanning from material extraction and processing to building construction, maintenance and renovation, to the end-of-life stage when the building is deconstructed or demolished.
When most companies report on their GHG emissions, they are often only required to include information about Scopes 1 and 2. However, as the effects of climate change exacerbate, organizations are beginning to look at their Scope 3 emissions as well to understand the full impact of their operations.
Scope 3 emissions include embodied carbon emissions.
There’s more to a piece of equipment than its efficiency and energy source. There’s also its embodied carbon emissions, which are the GHG emissions associated with manufacturing and delivering the equipment throughout its supply chain.
For your decarbonization plan, you can consider existing equipment in the building as having no embodied emissions, since it’s already installed. For existing equipment—such as ducts, pipes, and radiators—that can be reused and refurbished, help keep embodied emissions low. You can also save money on replacement costs.
Building owners can factor in Scope 3 emissions by using available tools to make informed choices for material selection or by conducting a whole-building lifecycle assessment.
Architecture 2030 provides a suite of resources and networks to help reduce emissions from the embodied carbon of construction materials.
Calculating Building Emissions
Setting GHG Emissions Targets
Given that buildings are responsible for 37% of emissions in California, setting a target to measure and track Scope 1 and 2 emissions is necessary to address the climate crisis. Reducing energy consumption and emissions in buildings is a critical step to initiate a 100% clean energy future.
Consider these options to set a target for your building’s greenhouse gas impact. You can set emissions targets as:
Total emissions limit (lbs CO2/sq. ft. per year)
Energy reduction targets over time (e.g. percent better each year)
Switching to high-efficiency electric appliances (e.g. heat pump water heaters) to reduce Scope 1 and Scope 2 Emissions
Set a Science-Based Target that aligns GHG emissions reduction targets with what the latest climate scientists say is necessary to meet the goals of the Paris Agreement.
Tracking progress toward goals is critical. Reducing energy consumption not only reduces GHG emissions and energy costs, but also improves air quality and creates job opportunities.
Additional Resources
This material is based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Building Technologies Office Award Number DE-EE0010930. Specifically, this resource has been adapted and localized for California from a resource originally developed for The Building Energy Hub with permission from the Illinois Green Alliance.