Buildings & Climate 101

But the 2021 report also shows that lack of progress in reducing gas usage in buildings is the biggest challenge to overcome.

How are Building Emissions Characterized? 

The Greenhouse Gas Protocol, an organization that 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 electricity from the grid (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.

Calculating Building Emissions 

GHG emissions are not directly measured in buildings through a meter in the same way 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. 

In most cases, calculating Scope 1 emissions can be as simple as looking at gas consumption values on utility bills and multiplying it 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 

For grid-level electricity consumption (Scope 2 emissions), calculating emissions is more complicated. Because electricity comes indirectly from multiple generating sources, such as natural gas, hydro, and solar, the associated GHG emissions from electricity consumption varies substantially depending on the building’s location, the time of day, and the 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).

In particular, California’s power sector reduced the use of gas combustion by 40% between 2023 and 2025, and LADWP was scheduled to stop getting electricity from the coal-powered Intermountain Power Plant in Utah in 2025. California’s state law SB100 requires all retail sales of electricity in the state to be renewable or zero emissions by 2045. 

You can approximate your building’s Scope 2 emissions using ENERGY STAR® Portfolio Manager. Once you enter building-specific data, the output includes information about a 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 for the region, which is how it estimates a building’s Scope 2 emissions. This is a useful tool to track energy use and emissions trends over time. 

The emissions outputs generated by ENERGY STAR® Portfolio Manager should be used as a starting point to understand Scope 2 emissions, but other tools provide higher levels of accuracy and allow your company to set meaningful goals for emissions reduction. Two industry standard resources are the GHG Protocol’s Corporate Accounting and Reporting Standard, which provides businesses guidance on GHG emissions inventory, and Scope 2 Guidance which can assist in setting corporate standards.  

Building owners are not in control of grid emissions but can curb their Scope 2 emissions by reducing their overall electric consumption through efficiency upgrades, installing on-site renewable energy, or purchasing off-site green power via a Green Tariff (utility rate plan), Power Purchase Agreements, or Renewable Energy Credits (RECs).

Scope 3 emissions 

Scope 3 Emissions, those that come from an organization’s supply chain and business operations, often represents 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 in which the building is de-constructed or demolished, and disposed of. 

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 the purposes of your decarbonization plan, you can consider existing equipment in the building as having no embodied emissions, since it’s already installed. If existing equipment—such as ducts, pipes, and radiators—can be reused and refurbished, it will help keep embodied emissions low—plus you’ll save some money on the 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.

Setting GHG Emissions Targets 

Given that buildings are responsible for 37% of emissions in California, setting a target to explicitly measure and track Scopes 1 and 2 emissions is necessary to meaningfully address the climate crisis. Taking action to reduce energy consumption and emissions in buildings today is a critical step to enable a 100% clean energy future. 

There are several options to set a target for your building’s greenhouse gas impact. Reducing your building’s emissions over time is primarily a matter of combining energy efficiency upgrades and electrification of all appliances and systems. 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. 

With a clear goal in place and a time-frame in which to reach your goal, tracking progress toward goals is critical. Reducing your energy consumption not only saves GHG emissions, but also reduces energy costs, improves air quality, and creates job opportunities for renewable energy installations and energy efficiency projects.