Real estate transformation: in Antony, Kareg, Wild Trees, Cap Synthèse and Outsign demonstrate that a conversion can already exceed the RE2020 thresholds of 2031

Led by Kareg, an investor specializing in the transformation of real estate assets, with Wild Trees, an ESG strategy consulting firm and environmental project management assistance, Cap Synthèse, the developer, and Outsign, the project architect, this program shows performance exceeding the RE2020 thresholds expected for 2031: -60% on the Energy IC indicator and -10% on the Construction IC indicator.

Beyond the quantified performance, the operation illustrates a conviction that is increasingly shared in the sector: the transformation of existing buildings is one of the fastest and most credible levers for decarbonizing the city, responding to the housing pressure and restoring a purpose to tertiary assets that have become obsolete.

A 1990s office building that finds a second life

The asset in question is an office building originally owned by a traditional office-focused real estate investment trust (REIT), built in the 1990s, and therefore over 30 years old. In a struggling commercial real estate market, the asset was at a standstill: inability to re-let the space under favorable conditions, difficulty financing a major renovation, and a lack of the technical expertise, permits, and resources necessary to undertake an ambitious conversion independently. It was in this context that Kareg, on behalf of the GPS fund, won the acquisition process and conceived a residential transformation capable of meeting the site's constraints, the city's expectations, and new environmental requirements. Located within an established urban fabric, the building presented several characteristics conducive to a second life: 12-meter floor depths, 2,85-meter ceiling heights, a load-bearing facade, and a configuration that allowed for leveraging the existing structure, despite certain structural constraints, such as a non-central staircase positioned on the facade.

A transformation project meticulously planned, from feasibility to construction.

The project brings together, very early on, all the expertise necessary for the success of a transformation:

• Kareg, investor, for the genesis and overall management of the operation;
• Outsign, architect, for the design and adaptation of existing buildings;
• Cap Synthèse, promoter, for feasibility, cost of works and operational setup;
• Wild Trees, ESG strategy consultancy, for energy-carbon performance assessment, RE2020 regulatory reading and taxonomy/financing analysis.

The program includes preserving 1,800 m² of floor space out of a final total of 2,400 m², in order to limit the need for heavy structural work and maximize the carbon benefits associated with preserving the existing building. Ultimately, the building will house 32 apartments, with particular attention paid to quality of use: natural light, ceiling height, outdoor spaces, balconies, bicycle parking, parcel lockers, and overall living comfort.

The project began in the summer of 2024 with the identification of the asset and the launch of initial conversion studies. Major milestones then followed in rapid succession: the preliminary design was finalized at the end of 2024, the building permit application was submitted in the spring of 2025, and the final acquisition was completed in September 2025. Today, the project has reached a decisive stage: the tender documents have been approved, marking the start of the immediate pre-operational phase. The next steps are now clearly defined: construction is scheduled to begin in the first half of 2026, with delivery expected in the first quarter of 2028.

An environmental, economic and financial demonstration

The extended RE2020 study conducted on this project demonstrates that, in terms of renovation, preserving existing buildings can produce immediate and measurable results. The project achieves environmental performance levels exceeding those required by regulations for 2031, with a 60% reduction in the Energy Impact Factor (IC) and a 10% reduction in the Construction Impact Factor (IC). Furthermore, preserving the existing structure significantly accelerates carbon savings. In 18 months, the project generates a footprint reduction equivalent to that achieved by RE2020 over a 50-year period. This underscores a reality that is still too often overlooked in investment decisions: in the climate transition, the time factor is just as important as the final result.

According to Raphaël Tréguier, founder of Kareg: "Transforming existing buildings is one of the most effective ways to rapidly reduce the carbon footprint of real estate. This study confirms that preserving an existing structure can achieve higher levels of environmental performance than those expected for new developments in the coming years."

From an economic standpoint, this approach also makes it possible to reconcile sustainability and financial efficiency. By limiting major structural interventions and reducing certain key work items, conversion becomes a credible alternative to demolition and reconstruction, in a context marked by rising costs, regulatory pressure, and land scarcity.

According to Loïs Moulas, founder of Wild Trees: “The transformation makes it possible to reconcile environmental performance and economic efficiency. By retaining a large part of the existing structure, we reduce both the carbon footprint and construction costs, particularly for structural work and infrastructure, which can represent up to 40% of the total cost of a project.”

Finally, the operation sheds light on the new financing models for the city of tomorrow. Between European taxonomy, RE2020 requirements, the zero net land use objective, increasing ESG standards, and evolving asset risk profiles, this transformation appears as an accelerator of urban redevelopment. It creates new risks that must be managed (taking over existing structures, administrative risks, building permits), but above all, it paves the way for financing structures aligned with the expectations of institutional investors.

This operation is part of the strategy of the GPS fund, led by Kareg, with the ambition of developing simple, replicable and efficient transformation projects, capable of simultaneously addressing climate, urban and financial challenges.