A net zero building is a very energy-efficient building whose remaining energy needs are met by renewable energy, so that over a year it adds no net carbon emissions from operation. Stricter versions also count the carbon embedded in its materials. The answer to “what is a net zero building?” matters more this summer because the European Commission proposed a 90 per cent emissions cut for 2040 on 2 July, the International Court of Justice issued its climate opinion on 23 July, and the United States set an end date for two efficient-building incentives.
Key takeaways
- A net zero building first cuts energy demand, then supplies what is left from renewable sources; there is no single worldwide definition.
- The US Department of Energy defines a zero energy building by an annual balance of delivered and exported energy, while the World Green Building Council defines net zero carbon by emissions.
- Under the EU’s recast Energy Performance of Buildings Directive, new public buildings must be zero-emission from 1 January 2028 and all new buildings from 1 January 2030.
- The Commission’s 2 July 2025 proposal for a net 90 per cent cut by 2040 points to stricter standards ahead.
- The US credit for Zero Energy Ready Homes ends for homes acquired after 30 June 2026.
What is a net zero building?
The phrase covers three related ideas, and it helps to keep them apart.
Net zero energy
The US Department of Energy describes a zero energy building as “an energy-efficient building where, on a source energy basis, the actual annual delivered energy is less than or equal to the on-site renewable exported energy.” Such a building is usually connected to the grid, taking power when it needs it and sending surplus back, and it balances the two over a year.
Net zero carbon
The World Green Building Council defines a net zero carbon building as a highly energy-efficient building with all remaining operational energy use coming from renewable energy. Its “whole life” version also counts embodied carbon, the emissions from making, transporting and assembling materials, and compensates for what cannot be avoided. The council updated its commitment in September 2021 to include embodied carbon requirements for new buildings and major refurbishments.
Zero-emission building in the EU
The European Union uses its own term. A zero-emission building has very high energy performance, needs zero or a very low amount of energy, produces zero on-site carbon emissions from fossil fuels and produces zero or very low operational greenhouse gas emissions, according to the European Commission’s description of the 2024 directive. New public buildings must meet it from 1 January 2028 and all new buildings from 1 January 2030. New buildings above 1,000 square metres must also report life-cycle global warming potential from 2028.
How does a net zero building work?
Every credible example follows the same order of operations:
- Reduce demand with compact form, insulation, airtight construction, good windows and shading.
- Use efficient systems, such as heat pumps, heat-recovery ventilation and LED lighting.
- Supply the remaining energy from renewables, on site where possible and off site where not.
- Measure real performance after occupancy, because modelled savings are not always achieved.
- Count and reduce embodied carbon in structure, envelope and finishes.
Our guide to net zero buildings explains each step in more detail, and the article on sustainable architecture design shows how the same principles apply from the first sketch.
Why are net zero targets in the news this summer?
The EU 2040 proposal
On 2 July 2025 the Commission proposed a net 90 per cent reduction in EU emissions by 2040 compared with 1990, as an amendment to the European Climate Law. It sits between the existing targets of a 55 per cent cut by 2030 and climate neutrality by 2050. The proposal includes flexibilities, among them a capped use of international credits, and still needs the approval of the European Parliament and the Council.
The ICJ opinion
On 23 July 2025 the International Court of Justice unanimously found that states must prevent significant harm to the climate system, cooperate in good faith and submit progressively stronger national climate plans, and it treated 1.5 degrees Celsius as the primary temperature goal. An advisory opinion is not binding in itself, but governments often cite it when writing building codes and procurement rules.
The United States
The law signed on 4 July 2025 ends the Section 45L credit for homes acquired after 30 June 2026. The credit is worth $2,500 for an ENERGY STAR home and $5,000 for a DOE Zero Energy Ready Home, which is a close relative of the net zero idea. The same law ends the Section 179D deduction for commercial property whose construction begins after that date.
What should designers do now?
Set a clear definition at the start, because “net zero” without a scope invites confusion and criticism. Decide whether the goal is energy, operational carbon or whole-life carbon, state the boundary, and keep the calculations. Claims without evidence are a reputational risk, as our article on what greenwashing means explains.
Frequently asked questions
What is the difference between net zero energy and net zero carbon?
Net zero energy balances the energy a building uses with the renewable energy it produces over a year. Net zero carbon looks at emissions, so it also depends on how clean the grid is, and its whole-life version includes the carbon in materials.
Is a net zero building the same as a zero-emission building under EU law?
They are close but not identical. The EU term sets specific requirements, including no on-site fossil fuel emissions and very high energy performance, and it is tied to dates in the Energy Performance of Buildings Directive. A net zero building is a broader idea used in many standards.
Does a net zero building have to be off the grid?
No. Most net zero buildings are connected to the grid, taking power when needed and exporting surplus, and the balance is measured over a year. Going off grid is a separate choice that usually needs larger storage.