Buildings are responsible for roughly 34% of global CO₂ emissions and consume about 32% of the world’s energy. That makes the building sector one of the single largest contributors to climate change, rivaling transportation and industry. The emissions come from two distinct sources: the energy used to run buildings day to day, and the carbon released when constructing them in the first place.
Operational Emissions: The Biggest Share
About 28% of global energy-related carbon emissions come from simply operating buildings. That includes heating, cooling, lighting, running appliances, and heating water. Most of this energy still comes from fossil fuels, either burned directly on-site (like a gas furnace) or consumed indirectly through electricity generated at coal and natural gas plants.
The International Energy Agency breaks this down further: about 8% of global energy-related emissions are direct, meaning fuel is burned inside the building itself. The remaining 18% are indirect, produced at power plants that generate the electricity and heat buildings consume. So even if your home runs entirely on electricity, it likely still contributes to emissions unless your grid is powered by renewables.
Heating and cooling dominate building energy use, but water heating is another significant piece. In residential buildings, a standard electric storage water heater can produce more than twice the lifetime CO₂ emissions of a heat pump water heater. Across millions of homes, those differences add up quickly.
Embodied Carbon: Emissions Before a Building Opens
The other 11% of global carbon emissions tied to buildings comes from embodied carbon: the emissions released during the extraction, manufacturing, and transportation of building materials, plus the construction process itself. Cement and steel are the primary culprits. Together, the materials used in construction account for about 18% of global emissions on their own, because producing cement requires extreme heat (typically from burning fossil fuels) and triggers a chemical reaction that releases CO₂ directly, while steelmaking is similarly energy-intensive.
The IEA estimates that construction-related emissions totaled about 2.5 gigatons of CO₂ in 2022. What makes embodied carbon particularly important is that it’s locked in the moment a building is completed. You can retrofit a building to use less energy over time, but you can’t take back the carbon emitted to make the concrete in its foundation. As buildings become more energy-efficient during operation, embodied carbon represents a growing share of their total lifetime footprint.
Refrigerants: A Hidden Source of Warming
Air conditioning and refrigeration systems contribute to climate change in a way most people don’t consider: refrigerant leaks. The chemicals circulating inside cooling systems are potent greenhouse gases. R-410A, still common in many buildings, has a global warming potential thousands of times greater than CO₂ per molecule.
Research on variable refrigerant flow systems in office buildings found that even when a cooling system uses less energy overall, refrigerant leaks at a rate of 10% per year can push its total greenhouse gas emissions higher than a conventional system. Switching to lower-impact refrigerants like R-32 reduces emissions, but only meaningfully in certain climates, and only when leak rates are kept low. This means that maintenance and refrigerant choice matter nearly as much as the energy efficiency of the system itself.
The Urban Heat Island Effect
Buildings don’t just emit greenhouse gases. They also reshape local climates in ways that amplify energy demand. Dense clusters of buildings, roads, and parking lots create urban heat islands, where temperatures run significantly higher than in surrounding rural areas. The mechanism is straightforward: dark surfaces like asphalt and conventional roofing absorb solar radiation and re-emit it as heat, while tall buildings trap warm air and block cooling winds.
The difference is measurable. Research comparing common building and paving materials found that dark asphalt (with an albedo, or reflectivity, of about 0.17) reached average surface temperatures of 51°C, while white concrete slabs (albedo around 0.50) stayed near 40°C, a 21% reduction. The temperature gap between the material surface and the surrounding air dropped by about 67% when switching from asphalt to lighter materials. Higher surface temperatures in cities directly increase cooling demand in nearby buildings, creating a feedback loop: more air conditioning means more electricity consumption, more emissions, and more waste heat pumped back outside.
High-albedo materials like reflective roofing and lighter-colored pavement are a proven, low-cost strategy for breaking this cycle. But these surfaces degrade over time. Dirt, weathering, and UV exposure reduce their reflectivity, meaning regular cleaning or recoating is necessary to maintain the benefit.
A Rapidly Growing Problem
The scale of the challenge is about to increase dramatically. From 2020 to 2060, the world is expected to add roughly 2.6 trillion square feet of new floor area to the global building stock. Architecture 2030 puts that in perspective: it’s the equivalent of building an entire New York City every month for 40 years. This construction boom, driven largely by urbanization in developing countries, will lock in enormous quantities of embodied carbon and create decades of operational energy demand.
If those new buildings are constructed with conventional materials and powered by fossil fuels, the sector’s emissions will continue to rise even as efficiency improves in existing buildings. The IEA has called for global energy efficiency improvements to double from 2.2% annually to more than 4% by 2030. Hitting that target across all sectors, including buildings, would reduce global energy demand by 190 exajoules and cut CO₂ emissions from fuel combustion by nearly 11 gigatons by 2030, roughly one-third of current global emissions.
Where the Biggest Reductions Come From
Decarbonizing buildings involves tackling each layer of the problem. For operational emissions, the most impactful changes are electrifying heating systems (replacing gas furnaces and water heaters with heat pumps), improving insulation and building envelopes to reduce heating and cooling loads, and cleaning up the electrical grid so that the power buildings consume is generated from renewable sources. Each of these steps compounds the others: a well-insulated building with an efficient heat pump running on clean electricity produces a fraction of the emissions of a drafty building with a gas boiler on a coal-heavy grid.
For embodied carbon, the levers are different. Using lower-carbon concrete mixes, recycled steel, and sustainably sourced timber can significantly reduce the upfront emissions of new construction. Extending the lifespan of existing buildings through renovation rather than demolition avoids embodied carbon entirely. And designing buildings for eventual disassembly and material reuse keeps those resources out of landfills and out of the emissions column.
At the urban scale, reflective surfaces, green roofs, and strategic tree planting reduce the heat island effect and lower cooling demand across entire neighborhoods. Choosing low-impact refrigerants and maintaining cooling systems to prevent leaks addresses one of the more overlooked sources of building-related warming. None of these strategies alone solves the problem, but together they represent the difference between a building sector that continues driving a third of global emissions and one that begins pulling its weight toward climate targets.