Your Office Is Breathing Out CO₂ – Do You Know How Much?

Why office buildings matter more than you think

If you work in a typical office, the building around you is probably responsible for more emissions than your entire IT department, maybe even more than your business travel. The U.S. Environmental Protection Agency (EPA) estimates that commercial and residential buildings account for about 13% of total U.S. greenhouse gas emissions, mostly from energy use for heating, cooling, and lighting.⁴

Now zoom in on just office buildings. They:

• Run long hours (or 24/7 for data rooms and security).
• Use a lot of HVAC to keep people comfortable.
• Depend on lighting, elevators, plug loads, and server closets.

So if your company is serious about climate targets, the office footprint isn’t a side quest. It’s one of the main storylines.

Take a mid‑size tech company in Chicago that I worked with. They assumed their biggest emissions came from cloud computing and flights. Once we did the math, the main office alone was responsible for roughly 40% of their total operational emissions. The building was quietly out‑polluting their entire annual business travel.

First decision: what exactly are you measuring?

Before you open a single utility bill, you need to draw the boundary. Otherwise, you’ll end up arguing over whether the landlord’s rooftop chiller counts as “your” emissions.

There are three big questions:

1. Which emissions scopes are in or out?

Most companies follow the Greenhouse Gas Protocol, which splits emissions into three scopes:

• Scope 1 – Direct emissions from sources you own or control. For offices, that usually means on‑site gas boilers, backup generators, and refrigerant leaks from HVAC.
• Scope 2 – Indirect emissions from the electricity you purchase (and sometimes steam, chilled water, or district heating).
• Scope 3 – Everything else in the value chain. For offices, the relevant pieces are usually employee commuting, purchased goods and services (like office supplies or catering), and sometimes capital goods (fit‑outs, furniture).

Most office footprint projects start with Scope 1 and 2 because the data is easier to get and the methods are more standardized. But if your workforce is mostly hybrid or remote, commuting and home‑office energy can be a big piece of the real picture.

2. Which spaces belong to “your” footprint?

This is where things get political.

• If you own the building and occupy it, life is simple: the whole building is yours.
• If you lease part of a larger building, you have to decide whether to:
  • Count only your leased floor area and your own utility meters, or
  • Pro‑rate shared building emissions (lobbies, elevators, parking) based on your share of floor space.

When a marketing agency in New York tried to measure its footprint, they started with just their sub‑metered electricity. It looked tiny. Once they got the landlord’s whole‑building data and applied a floor‑area share, their reported emissions more than doubled. Same people, same work — just a more honest boundary.

3. What time period are you covering?

Most organizations use a calendar year to match financial reporting. The key is consistency:

• Use 12 consecutive months of data.
• Align with your corporate reporting year.
• If you have only partial data (say, you moved mid‑year), document the gaps and how you handled them.

Once those three decisions are clear, you can actually start counting.

Step one: gather the messy data (yes, all of it)

Measuring a building’s carbon footprint is basically detective work with spreadsheets. You’re hunting for four main types of data:

Energy use inside the building

You’ll want, at minimum:

• Electricity – kWh from utility bills or sub‑meters.
• Natural gas – therms or cubic feet.
• Other fuels – diesel for backup generators, propane, fuel oil, etc.
• District energy – steam, hot water, or chilled water from a district system.

Try to get monthly data for a full year. If you’re in the U.S., your utility portal usually lets you download a year’s history.

When a law firm in Dallas did this exercise, they discovered their “24/7” lighting on certain floors was not just a figure of speech. Their overnight and weekend baseload was so high that simply fixing lighting schedules and HVAC setpoints cut their annual electricity use by about 12%, before any fancy retrofits.

Refrigerants and HVAC

This is the category everyone forgets — and it can be big.

Ask your facility manager or landlord for:

• Type and quantity of refrigerants used in HVAC systems.
• Annual top‑ups or leak repairs (pounds or kilograms).
• Any full refrigerant replacements during the year.

Why bother? Because some refrigerants have global warming potentials (GWP) in the thousands. A single large leak can equal the emissions of running your office on electricity for months.

Water and waste

Water and waste are smaller contributors for typical offices, but they still count:

• Water – gallons or cubic feet from water bills.
• Waste – total weight of landfill, recycling, and compost if your hauler provides it; if not, you may need to estimate based on volume and density factors.

These often fall under Scope 3, but many organizations include them in their “office footprint” because they’re physically tied to the building.

People and movement

If you want to go beyond the bare minimum, you’ll also look at:

• Employee commuting – how people get to the office, how far, and how often.
• Business travel starting from the office – flights and car rentals, if you want a location‑based view.

A software firm in Seattle ran an anonymous commuting survey and found something surprising: biking and walking were already high, but a small group of long‑distance solo drivers was responsible for most commuting emissions. Targeted carpool incentives and transit subsidies made more difference than generic “green commute” posters.

Turning raw data into CO₂: the emission factors game

Once you have all that data, the next step is converting it into emissions using emission factors. This is where you move from “we used 100,000 kWh” to “we emitted X metric tons of CO₂e.”

“CO₂e” just means carbon dioxide equivalent — it lets you combine CO₂, methane, nitrous oxide, and other gases into a single number.

Where to find credible emission factors

For an office in the U.S., good sources include:

• EPA eGRID for electricity emission factors by region.¹
• EPA greenhouse gas emission factors for fuels like natural gas and diesel.²
• IPCC or reputable databases for refrigerant GWPs.

If your office is outside the U.S., your national environment agency or statistics office often publishes electricity and fuel factors.

Electricity: location‑based vs market‑based

Electricity is usually the biggest line item, and it comes with a twist.

• Location‑based approach: Uses the average grid emission factor for your region. This shows the impact of simply being connected to that grid.
• Market‑based approach: Adjusts for specific procurement choices like renewable energy certificates (RECs) or power purchase agreements (PPAs).

If your company buys “green power,” you’ll probably report both:

• Location‑based to show the physical grid impact.
• Market‑based to show the impact of your purchasing decisions.

Fuels and refrigerants

For fuels, the math is straightforward:

Emissions = Activity data × Emission factor

So if you burned 10,000 therms of natural gas and your factor is 0.0053 metric tons CO₂e per therm, that’s 53 metric tons CO₂e.

Refrigerants are similar, but you multiply the mass leaked by the GWP. For example, 20 kg of a refrigerant with a GWP of 1,800 equals 36,000 kg (36 metric tons) CO₂e.

Commuting and travel

For commuting, you have two basic options:

• Detailed: Use survey data on modes, distances, and frequencies, then apply mode‑specific factors (e.g., car vs bus vs rail).
• Simplified: Use average commute distances and modal splits from regional data, then scale by your headcount.

A global consulting firm with a Boston office used detailed surveys for their HQ and a simplified model elsewhere. They found that in Boston, where transit use was high, home energy use on remote days actually rivaled commuting emissions on in‑office days. That led them to include home‑office guidance and support in their footprint strategy.

Building a carbon inventory that finance won’t fight

Once you’ve converted everything to CO₂e, you’ll want to organize the results in a way that makes sense to executives and auditors.

A clear structure usually looks like this:

• By scope: Scope 1, 2, and relevant Scope 3 categories.
• By source: Electricity, gas, refrigerants, commuting, waste, water, etc.
• By intensity: Emissions per square foot and per employee.

Those intensity metrics are where things get interesting. They let you compare:

• Different offices in your portfolio.
• Year‑over‑year performance in the same building.
• Your office versus industry benchmarks (for example, ENERGY STAR scores in the U.S.).

When a financial services firm compared two nearly identical offices — one in Atlanta, one in Denver — the Denver site looked worse at first glance. Higher emissions per square foot. But once they used region‑specific electricity factors, they realized the building itself was actually more efficient; the grid was just dirtier. That changed where they focused their advocacy and procurement efforts.

Common mistakes that quietly ruin your numbers

Even experienced teams fall into the same traps. A few to watch for:

Forgetting the “shoulder months”

People love to look at January and July bills and extrapolate. That’s a shortcut to bad data. Spring and fall can have very different HVAC patterns, especially in mixed‑mode buildings.

Always use the full 12 months. If you’re missing one bill, estimate based on neighboring months and clearly document it.

Ignoring landlord‑controlled systems

In multi‑tenant buildings, landlords often control:

• Central HVAC plants.
• Parking garage ventilation and lighting.
• Common area lighting and elevators.

If you only count your sub‑metered plug loads and lighting, you’re under‑reporting. Push for whole‑building data and pro‑rate it by your share of floor area if needed.

Treating office fit‑outs as invisible

Office renovations, furniture, and equipment have embodied carbon — emissions from manufacturing and transporting them. Many companies skip this because the data is harder to get, but if you’re doing a major fit‑out, that one project can rival several years of operational emissions.

Some organizations use spend‑based factors (emissions per dollar spent) as a first pass, then refine over time with more detailed product data.

Turning the footprint into action, not just a report

Measuring the footprint is only half the story. The real value comes from what you do with it.

Once you have a baseline, you can:

• Spot quick wins – like fixing HVAC schedules, tightening temperature deadbands, or upgrading lighting in high‑use areas.
• Plan capital projects – chiller replacements, heat pumps, better controls, or envelope upgrades.
• Refine workplace policies – hybrid work patterns, commuting incentives, travel policies.

A media company in Los Angeles used their new office footprint to justify a chiller replacement that had been stuck in budget limbo for years. The carbon data, combined with a clear payback period, finally made the case to the CFO. Three years later, their electricity‑related emissions were down by about 25% for that building.

Tools and frameworks that make life easier

If you don’t want to build everything from scratch in Excel, there are helpful frameworks and tools:

• EPA ENERGY STAR Portfolio Manager – widely used in the U.S. to track building energy and emissions over time.³
• GHG Protocol tools – spreadsheets and guidance for Scope 1, 2, and 3 calculations.
• City or state programs – many jurisdictions with building performance standards provide calculators and guidance.

Even if you use a commercial carbon accounting platform, understanding the steps above helps you sanity‑check whatever the software spits out.

So where do you start on Monday morning?

If this all feels like a lot, strip it back. On day one, you don’t need to model every stapler and coffee pod.

A practical entry point looks like this:

• Decide the boundary: which building, which scopes, which year.
• Collect 12 months of energy data (electricity, gas, other fuels).
• Get basic refrigerant records, even if they’re incomplete.
• Use reputable emission factors (EPA, eGRID, GHG Protocol) to calculate Scope 1 and 2.
• Add commuting if you can run a simple survey.

From there, you can layer in waste, water, fit‑outs, and more sophisticated Scope 3 categories.

The point isn’t to produce a perfect number on day one. The point is to start measuring in a way that’s transparent, repeatable, and honest. Once you do that, your office stops being just a place people show up to work — it becomes a lever you can actually pull in your climate strategy.

FAQ: Measuring the carbon footprint of office buildings

How accurate does my office carbon footprint need to be?

It needs to be decision‑grade, not perfect. As long as your methods are transparent, your data sources are documented, and your assumptions are reasonable, small uncertainties won’t undermine the value. Over time, you can improve accuracy by filling data gaps and using more specific emission factors.

Do I need specialized software to measure my office emissions?

Not necessarily. Many organizations start with spreadsheets, utility portals, and free tools like EPA’s ENERGY STAR Portfolio Manager. Specialized carbon accounting software becomes helpful once you’re dealing with multiple buildings, complex Scope 3 categories, or external assurance requirements.

How often should we measure the building’s carbon footprint?

Annually is the norm, aligned with your financial reporting cycle. Some organizations track key metrics like energy use monthly to spot performance issues early, then do a full carbon inventory once a year for internal and external reporting.

Should we include emissions from employees working from home?

That depends on your goals and materiality. If remote work is a big part of your operating model, it’s worth estimating home‑office energy use and including it in Scope 3. Many companies use employee surveys combined with typical home energy profiles to build a reasonable estimate.

How do we compare our office to others?

Use intensity metrics like emissions per square foot and per employee, and compare them to benchmarks. In the U.S., ENERGY STAR scores and local building performance standards can give you a sense of where you stand relative to peers in the same climate and building type.