- 1Cement emits 600 to 900 kg of CO2 per tonne: the chemical calcination reaction is responsible.
- 2Construction emits more than 30 to 50 years of heating in an efficient RE2020 building.
- 3Low-carbon concretes reduce emissions by 30 to 50% without compromising mechanical performance.
- 4Renovation emits 2 to 4 times less than new construction with an equivalent floor area: the best building already exists.
"We discovered that our building's concrete emits more than 30 years of heating." This is what a developer told us on seeing the results of their statutory RE2020 LCA, and their case is far from exceptional. Buildings account for around 27% of greenhouse gas emissions in France, but it is the breakdown that surprises: in an efficient new building meeting RE2020 standards, construction and material emissions often exceed operational emissions over its entire lifespan.
1RE2020 makes LCA mandatory for every new residential building
RE2020: what it actually requires
Having entered into force in January 2022, RE2020 is the first French regulation to incorporate carbon as a performance criterion for new buildings. It requires each building's carbon impact to be calculated over its full life cycle (construction + operation + end of life) through a statutory LCA (Life Cycle Assessment). It sets maximum emission thresholds per m², which progressively tighten until 2031. The building's total carbon therefore joins energy consumption among the compliance criteria.
Carbon becomes a design criterion
This change requires architects, engineering consultancies and developers to incorporate carbon from the design stage. The choice of construction system (concrete, timber, mixed), insulation materials, windows and doors directly affects regulatory compliance. It is a design criterion just as thermal performance or structural strength is.
2Structural materials account for 50 to 70% of the total footprint
Concrete is the largest contributor in a conventional building. Producing cement (concrete's main component) emits around 600 to 900 kg of CO2 per tonne because of the chemical calcination reaction and the energy needed for kilns. Structural steel comes second. Insulation, windows and doors, and technical systems make up the rest. Overall, structural and main construction materials account for 50 to 70% of a new building's total carbon footprint.
Low-carbon concrete, timber, bio-based materials: the alternatives
This finding led the sector to develop alternatives: low-carbon concretes (reducing emissions by 30 to 50% compared with conventional concrete by using cements with less clinker), structural timber (which stores carbon rather than emitting it), and bio-based insulation materials (hemp, straw, cellulose fibre). RE2020 accelerates adoption of these alternatives by setting increasingly demanding thresholds.
3Renovating vs building: the calculation few developers make
In a new building meeting RE2020 standards, construction emissions often exceed operational emissions over 50 years.
When comparing the carbon footprint of major renovation with demolition-reconstruction, renovation almost always wins. Demolition and waste treatment emissions are avoided, the existing structure is retained (having already "amortised" its construction emissions), and only renovation materials generate emissions (insulation, windows and doors, systems). The carbon footprint of renovation is typically 2 to 4 times lower than new construction with an equivalent floor area.
Renovation emits 2 to 4x less than demolition and rebuilding
Calculated over 50 years of operation, per equivalent m²
Renovating: the best building is the one that already exists
Developers rarely make this calculation because they are used to thinking in financial costs rather than carbon costs. But with RE2020, carbon thresholds and pressure from ESG investors, carbon calculation is gradually entering property project planning decisions. We see project owners requesting a comparative renovation vs new construction study with a carbon dimension - something unthinkable 5 years ago.
4The weight of property CAPEX: what we found at a portfolio manager
We worked with a hotel property portfolio manager on the carbon analysis of its investments (CAPEX). The results were striking: renovations accounted for 47% of emissions, new construction 41%, and the remaining CAPEX (equipment, furniture) 12%. The analysis identified that material choices in renovations (types of insulation, windows and doors, finishes) had a major impact, and that works specifications could incorporate carbon criteria without significant additional cost.
Incorporating carbon into works specifications
This type of analysis transforms investment policy: rather than choosing materials solely on price and technical performance, a carbon criterion is added to the specification. Bio-based insulation can be price-competitive while reducing the insulation category's carbon footprint by a factor of 3. For the project owner incorporating these data into decisions, the carbon criterion joins price and technical performance, often without significant additional cost.
5Building LCA: method, data and cost for a developer
A statutory building LCA (under RE2020) uses the INIES database (the national reference database for construction products' environmental characteristics) and certified software. An RE2020 LCA costs 3,000 to 10,000 euros depending on project complexity. This is a modest investment relative to the total cost of a property development, and is now mandatory for every building permit for new residential construction.
For non-residential projects, LCA has been mandatory under RE2020 since July 2022 for offices and education. Since 1 May 2026, Decree No 2026-16 extends it to 13 new building types: hotels, shops, restaurants, nurseries, healthcare, sports facilities, media libraries, universities, airport terminals, industrial and craft buildings; process buildings, temporary structures and overseas territories remain outside scope. Beyond the requirement, large groups' CSRD reporting and investor requirements encourage some developers to aim beyond the thresholds. The BBCA (Low-Carbon Building) label has become a selling point in some markets, showing that the carbon dimension is gradually entering property value.
6Key takeaways
RE2020 has made visible a reality the sector preferred to ignore: construction materials emit more CO₂ than decades of heating. Concrete, steel and foundations account for 50 to 70% of a new building's total footprint.
- Cement emits 600 to 900 kg of CO2 per tonne, largely because of the chemical calcination reaction, with the rest coming from kiln energy.
- For an RE2020 building, construction emissions often exceed operational emissions over half a century.
- Low-carbon concretes reduce emissions by 30 to 50% compared with conventional concrete, with sufficient mechanical performance for most uses.
- Renovation emits 2 to 4 times less than new construction with an equivalent floor area.
- Incorporating carbon calculation at the project planning stage costs a few thousand euros and can change a project's decisions.
7Key takeaways
- Cement emits 600 to 900 kg of CO2 per tonne, largely because of the chemical calcination reaction, with the rest coming from kiln energy.
- For an RE2020 building, construction emissions often exceed operational emissions over half a century.
- Low-carbon concretes reduce emissions by 30 to 50% compared with conventional concrete, with sufficient mechanical performance for most uses.
- Renovation emits 2 to 4 times less than new construction with an equivalent floor area.
- Incorporating carbon calculation at the project planning stage costs a few thousand euros and can change a project's decisions.
Before starting a new project, request a comparative study with a renovation scenario. An LCA costing a few thousand euros can redirect a development costing several million euros and substantially reduce its carbon footprint. For new projects, work with the architect and engineering consultancy from the concept stage to optimise the carbon footprint without waiting for the building permit. Carbon has become a design criterion just as thermal performance or structural strength is, and now guides property investment decisions.
