The carbon threshold of the RE2020 applicable to permits submitted since January 1, 2025, lowered by decree n° 2024-1258 of December 30, 2024, changes the game for selecting a builder. Claiming to build “eco-friendly” is no longer enough: the builder must demonstrate their ability to design a building that complies with this new regulatory level, with a documented life cycle analysis.
RE2020 Carbon Thresholds and the Builder’s Actual Capacity
An eco-responsible builder is primarily distinguished by their technical mastery of the carbon aspect of the RE2020, not by their sales pitch. The 2025 threshold imposes a significant reduction in the carbon footprint over the entire life cycle of the building: material manufacturing, transportation, implementation, end of life.
We recommend systematically requesting the complete environmental analysis of the project, rather than a simple summary of the planned materials. A builder who only presents a list of bio-sourced materials without quantifying their overall impact on the life cycle does not meet current requirements.
Point of caution: it is the date of the building permit application that determines the regulatory threshold, not the start date of the construction site. A builder who proposes to delay the permit application alters the applicable regulatory framework. This maneuver should be identified and questioned before signing. Professionals listed on constructeurs-responsables.fr display their level of compliance with the current thresholds, which serves as a useful first filter.
Summer Comfort: An Indicator Often Avoided by Builders
Winter energy performance monopolizes builders’ communication. In contrast, summer comfort remains a frequent blind spot, even though the RE2020 includes an indicator for the number of discomfort degree-hours (DH). Exceeding the upper threshold renders the project non-compliant, regardless of the insulation level.
We observe that the least prepared builders compensate with active air conditioning, which degrades the overall carbon balance. A competent builder balances building compactness, solar protections, and natural ventilation before resorting to active equipment.
During the technical interview, ask the question directly: what summer comfort strategy is planned for the project, and how is the DH threshold respected without systematic reliance on air conditioning? The answer reveals the actual level of mastery.
Bio-sourced Materials: Beyond Wood, the Technical Trade-offs That Matter
Wood dominates communication about sustainable construction. Its relevance is real, but choosing a bio-sourced material does not automatically guarantee the project’s environmental compliance. The RE2020 evaluates the impact of each component over its entire life cycle.
An eco-responsible builder must explain their trade-offs between:
- The load-bearing structure (wood, low-carbon concrete, mixed) and its impact on the building’s overall carbon weight
- Insulation (bio-sourced such as wood fiber, cellulose wadding, or conventional) considering thermal performance and durability
- Technical equipment (heat pump, thermal solar, dual-flow ventilation) and their consistency with the chosen envelope
- The compactness of the building, which directly affects the quantity of materials needed and thus the carbon balance
A compact and well-oriented project can outperform a larger project filled with bio-sourced materials. A builder who never mentions compactness or bioclimatic orientation in their initial proposals misses a fundamental lever.
Guarantees and Insurance: Check the Decennial Coverage for Uncommon Techniques
Eco-responsible construction frequently uses techniques or materials classified as “uncommon” by insurers: specific bio-sourced insulators, hybrid construction systems, raw earth coatings. These techniques require an extension of the decennial guarantee, without which the project owner bears the risk alone in the event of a disaster.
Before signing, we recommend checking three points:
- The builder’s decennial guarantee certificate explicitly covers the materials and processes planned for the project
- The builder has a technical opinion or a technical experimental assessment (ATEx) for the uncommon processes they propose
- The damage insurance, taken out by the project owner, mentions the same processes as those covered by the builder’s decennial guarantee
A discrepancy between the builder’s decennial guarantee and the client’s damage insurance creates a gray area that both parties typically discover at the time of the disaster. This cross-checking is rarely suggested by the builder themselves.
Critical Reading of the CCMI Contract in an Eco-Responsible Context
The individual house construction contract (CCMI) outlines the builder’s obligations. In eco-responsible construction, certain clauses deserve particular attention.
The descriptive notice must precisely detail the bio-sourced materials, energy equipment, and targeted performances. A vague mention such as “high-performance insulation” or “eco-friendly materials” does not constitute an exploitable contractual commitment. Each material and each piece of equipment must be listed with their technical reference in the notice.
The price agreed upon in a CCMI is firm and definitive. If the builder plans to use bio-sourced materials whose cost fluctuates, they bear the risk of this variation. A builder who attempts to introduce price revision clauses related to bio-sourced materials is stepping outside the legal framework of the CCMI.
The mention of RE2020 compliance in the contract commits the builder to the result. In the event of non-compliance observed during the air tightness test or the completion certificate, their liability is engaged. This point is non-negotiable, but it must be explicitly stated to avoid any ambiguity regarding the guaranteed performance level.
Selecting an eco-responsible builder relies on verifying their compliance with the current RE2020 thresholds, their documented summer comfort strategy, the insurance coverage of uncommon techniques, and the rigor of the CCMI descriptive notice. These four technical filters eliminate the majority of operators whose environmental commitment remains declarative.
