What Is a Building's Carbon Footprint?

What is a building's carbon footprint?

When we think about a building's emissions, we usually picture heating in winter, air conditioning in summer, and electricity bills. That is true, but it is only part of the picture. Every building has a carbon footprint: the total amount of greenhouse gases, expressed as carbon dioxide equivalent, associated with its existence. And it begins long before anyone turns the thermostat.

In this article, we explain in plain language what makes up a building's carbon footprint, the difference between operational and embodied emissions, and why the latter is becoming so important.

Two sides of the same building

A building's carbon footprint falls into two main categories.

The first is operational emissions: everything a building uses during day-to-day operation, including energy for heating, cooling, hot water, lighting, and powering equipment. This is the part familiar to anyone who has ever paid a utility bill.

The second is embodied emissions: emissions linked to the materials and construction processes themselves. They include extracting raw materials, producing cement and steel, transporting materials to the construction site, erecting the building, as well as later renovations and eventual demolition. This part is less visible because it happens before anyone moves in, but it is just as real.

Together, these two categories form a building's whole-life carbon footprint: from the first tonne of sand extracted to demolition decades later.

Why embodied emissions have suddenly become important

For years, the industry's attention focused on operational emissions, and rightly so: buildings account for a large share of energy use. According to the World Green Building Council report Bringing Embodied Carbon Upfront, the construction sector accounts for around 39% of global energy-related emissions: 28% from operations and 11% embodied in materials and processes.

But this creates an interesting paradox. As we build better, using improved insulation, heat pumps, and renewable energy sources, operational emissions fall. That means embodied emissions make up a growing share of the total. In a modern, energy-efficient building, materials can account for most of its carbon footprint.

Embodied emissions also have one uncomfortable quality: they are immediate and irreversible. Carbon dioxide from cement production enters the atmosphere today, during construction; it is not spread evenly across 50 years of use. WorldGBC estimates that emissions produced before a building is occupied will account for half of the total carbon footprint of new buildings constructed by 2050.

Where embodied emissions come from

The largest contributors are two materials that are hard to imagine modern construction without: cement and steel. Cement production accounts for around 7% of global CO₂ emissions, while steel contributes another 7–9%. Both require extremely high temperatures, and the chemical reactions involved in producing them release carbon dioxide directly.

But it is not just about the structure. Different building elements have different service lives and generate further embodied emissions at different rates:

• foundations and structure — designed for the building's full lifespan,
• façade — usually replaced every few decades,
• interior finishes and fittings — replaced most often.

Every replacement, renovation, and upgrade adds another share of embodied emissions to the building's whole-life footprint.

How a building's carbon footprint is calculated

The life-cycle assessment method, or LCA, is used to calculate a building's whole-life carbon footprint. In simple terms, it adds up emissions from every stage: from raw-material extraction and material production (stages A1–A3), through transport and construction, to operation and end of life.

LCA helps answer practical questions that were difficult to assess until recently: is it better to renovate an existing building or demolish it and build a new one? Which structural option has a lower footprint? How will the choice of materials affect total emissions? This analysis increasingly needs to happen at the concept stage, because that is when the decisions with the greatest impact are made.

What this means in practice

Pressure to reduce buildings' carbon footprints is growing, both from regulations and from investors who expect credible environmental data. For auditors, certifiers, architects, and developers, this means one thing: the ability to calculate and reduce a building's footprint is no longer an extra. It is becoming part of the standard design process.

In future articles, we will cover environmental product declarations and how regulations are changing the market: what EPBD, the EU taxonomy, and certification standards say about embodied emissions.