The construction of a building in France is no longer just about assembling walls and a roof. Since the gradual strengthening of the RE2020, every project submitted after January 2025 must integrate significantly stricter carbon requirements than those applied to previous permits. This regulatory context changes the way to design, estimate, and manage a construction site, regardless of the type of building targeted.
Carbon thresholds RE2020: what changes concretely for a permit submitted in 2025-2026
Competitors often treat regulations as a checkbox. The subject deserves more precise clarification. Since January 1, 2025, a new level of the carbon trajectory of the RE2020 applies, with a significant reduction in construction Ic thresholds for individual houses, collective housing, and offices. Decree No. 2024-1258 of December 2024 formalized these adjustments.
For a project owner, the date of submission of the building permit becomes a determining reference. Professionals now clearly distinguish projects submitted before and after 2025, as carbon requirements and certain modulations have changed, even if the legal framework remains that of the RE2020.
A building construction guide structured around these regulatory levels allows for checking, from the sketch phase, whether the construction choices (wood frame, low-carbon concrete, wood-concrete mix) comply with the new thresholds even before consulting companies.
Decree No. 2026-16 of January 15, 2026, also extends the RE2020 to 13 new types of tertiary and industrial buildings (hotels, restaurants, shops, warehouses, among others). A tertiary project launched in 2026 therefore falls under a different framework than an identical project submitted at the end of 2025.
Project design and material choices: arbitrate before the construction site
The design phase concentrates the majority of decisions that will determine the overall cost and regulatory compliance. Waiting until the construction site to decide on materials or energy systems leads to additional costs and re-studies.
Materials and carbon footprint of the building
The strengthening of construction Ic thresholds pushes project owners to examine the carbon footprint of materials from the preliminary project stage. Several sectors are positioning themselves: wood frame, light steel frame (LSF), low-carbon concrete, or wood-concrete mix that combines structural performance and reduced carbon footprint.
Field feedback varies on the actual additional cost of these solutions. Some wood frame sites show a budget comparable to traditional concrete blocks, while others reveal discrepancies related to the local availability of qualified companies. The arbitration depends on the geographical context, the volume of the project, and the expertise of the consulted teams.
Role of the architect and thermal design office
An architect is required to intervene beyond a certain floor area. His role goes beyond drawing: he coordinates urban, structural, and environmental constraints. The thermal design office, on the other hand, validates RE2020 compliance before the permit submission. Without this validation, the project risks rejection or non-compliance upon delivery.
- Soil study (geotechnical study G2): mandatory in areas exposed to clay shrink-swell, it conditions the type of foundations and can modify the budget by several percentage points.
- RE2020 thermal study: it models energy consumption and the carbon impact of the building over its entire life cycle, not just during the usage phase.
- Network diagnostics: connections for water, electricity, sanitation. A plot that appears serviced may require costly network extensions.
Budget and site management: items that estimates do not always show
Establishing a realistic budget requires going beyond the price per square meter quoted by a builder or craftsman. Several items remain underestimated in most initial estimates.
Additional costs related to the land (boundary marking, connections, development tax) represent a significant part of the total budget. The development tax varies by municipality and taxable area, making any generic estimate unreliable. Consulting the urban planning department of the town hall before finalizing the financing plan avoids unpleasant surprises.
Site management itself generates indirect costs: coordination between trades, management of construction waste (subject to sorting obligations since the AGEC law), damage insurance. Omitting damage insurance exposes one to a lack of coverage for ten years in the event of structural damage.
Completion of works and legal guarantees: the project does not stop at the handover of keys
The acceptance of the building constitutes a legal act, not a mere formality. It is on this date that the legal guarantees begin:
- Perfect completion guarantee (one year): covers all defects reported by the project owner, including those noted in the acceptance report in the form of reservations.
- Two-year guarantee: concerns equipment elements that are separable from the building (faucets, shutters, radiators).
- Ten-year guarantee: protects against damages compromising the solidity of the work or rendering it unfit for its intended use.
Issuing precise reservations during acceptance is the only way to compel the company to correct the identified defects within the perfect completion period. A signed report without reservations makes subsequent disputes much more difficult.
For projects subject to the new RE2020 thresholds, environmental compliance is also subject to control upon completion. The air tightness test and the RE2020 completion certificate are required before the declaration of completion.
The construction of a building in 2025-2026 largely takes place before the first excavator. Material choices, the date of permit submission, and the rigor of acceptance condition both the success of the project and the quality of execution on site. Checking RE2020 compliance from the sketch remains the safest way to avoid costly reworks once the site is launched.
