In responses to calls for proposals for urban development zones and mixed-use neighborhoods, one question is coming up more and more often: "What is the project’s rate of soil permeability restoration?" Five years ago, this phrasing was rare. Today, it appears in many urban planning competitions.
For developers and planners, green roof installation is no longer just an optional “green” feature—it’s a design requirement that affects permitting, financing, and the competitiveness of the project.
The Climate and Resilience Act of August 22, 2021, supplemented by the Act of July 20, 2023, sets two national objectives:
In practice, an increasing number of municipalities are requiring their local urban planning regulations to include a minimum biotope coefficient, a minimum area of open ground, and requirements regarding the permeability of parking lots and private roads.
For projects seeking to qualify as "sustainable investments," contributing to the goal of climate change adaptation requires ensuring that they do not increase the risk of runoff and flooding—which means limiting soil sealing.
Indirectly, RE2020 encourages a reduction in impervious surfaces: hot mineral surfaces degrade outdoor thermal comfort and contribute to summer discomfort in homes, as measured by the Dh indicator.
The decision to use permeable surfaces is made primarily during the site plan phase: what percentage of roadways will have permeable paving? What percentage of green spaces will be left as open ground? How should stormwater collection be organized at the plot level?
These decisions have a direct impact on building density, the number of parking spaces, and the cost of road and utility infrastructure. They must therefore be taken into account from the very beginning.
The Surface Biotope Coefficient (SBC) weights each type of surface according to its ecological value: bare ground (coefficient 1), permeable surface (0.5), extensive green roof (0.3), etc. A high SBC in a bid response sends a strong signal to the contracting authority.
Studies by ADEME and Cerema document the impact of vegetation and soil permeability on property values. A project that incorporates open ground, landscaped swales, and green courtyards creates a perceived value differential among buyers.
Unsealed and re-vegetated areas may be eligible for the "Low-Carbon, Tree-Lined City" certification. This provides an additional source of revenue that reduces the net cost of vegetation restoration.
Netcarbon allows you to simulate the following indicators over a 25-year period based on the site plan:
These results can be directly integrated into the RAO technical database, the development permit application, and the appendices of the Taxonomy report.
De-impermeabilization is one of the few strategies that simultaneously addresses regulatory compliance (ZAN, PLU), climate resilience (heat, flooding), and the project’s commercial value. Developers who incorporate it as a design criterion gain a competitive edge over their rivals and stay ahead of future regulatory requirements.
Are you planning a development project and want to maximize your permeable surface ratio? Simulate the impact of your design choices.
