France – Lille
Organisation : La Poste Immobilier
Historic commercial property located at 3 rue Paul-Duez in Lille, commissioned in 1954 and subsequently extended with the addition of the fourth and fifth floors. It comprises six above-ground levels and two basement levels.
The site covers approximately 13,800 m². It primarily accommodates La Banque Postale’s office, customer relations and specialist customer support activities. The building has multiple occupants and operates six days a week, with approximately 850 workstations and up to 450 people present on any given day.
Energy performance varies across the building: some areas have been renovated and insulated, while others have little or no insulation. The former Maison de l’Habitat area on the ground floor is currently vacant, and renovation studies are underway.
Heating has traditionally been provided by gas boilers, supplemented by reversible variable refrigerant volume (VRV) systems. Ventilation is provided by balanced supply and extract systems. The building remains occupied during the works, requiring continuity of operations and heating.
The site has a long-term energy management approach, with consumption records available since 2000, monthly monitoring, sensor-based measurement and participation in the CUBE competition.
Notable achievement: Lille CRSF won the Silver CUBE award in the office category, achieving 30.3% energy savings in the 2023–2024 edition.
The main actions implemented to reduce the energy consumption of this building.
Progressive renovation of the building envelope: partial insulation of the basement and ground floor in 2020, the fourth floor in 2023, the second floor in 2024, and the fifth floor in 2023 and 2025.
Full replacement of lighting with LEDs, completed in 2025, with occupancy detection. Some outdoor lighting is controlled by timers or by the security desk.
Removal of the old chillers in 2025 and use of reversible VRV systems to heat and cool several areas.
Installation of limiters on selected thermostatic valves to improve temperature control.
Monthly monitoring of electricity, gas and water consumption, supported by long-term historical data and load profile analysis.
Monitoring of comfort conditions and building use through temperature, humidity and light sensors.
Zoning of the building according to insulation levels, allowing analysis and future control strategies to reflect actual differences between floors.
Weather-based heating monitoring using heating degree days (HDD), with separate analysis for each energy source. Consumption data for 2023–2025 show a reduction in electricity use, while gas consumption remains strongly dependent on weather conditions and heating demand.
Engagement of occupants through the CUBE competition, with widespread adoption of energy-saving habits and regular communication about energy savings.
Local engagement led by “energy champions” and internal representatives, sharing good practices and results with teams.
Temperature management and reduction of unnecessary energy use, particularly outside occupied hours, while maintaining comfort and operational continuity.
Efficient use of spaces and consideration of the site’s six-day operating schedule to adapt equipment operating hours.
Complementary sufficiency and circular economy initiatives: paper sorting and recycling; collection of cigarette butts, batteries and bottle caps; and regular employee awareness activities.
A continuous improvement approach based on measurement, comparison, communication of results, correction of anomalies and user engagement.
