A French Residential Retrofit toward Achieving Net-Zero Energy Target in a Mediterranean Climate

: Cities are paying more attention to building energy use and carbon footprint for attaining sustainability. Within this building sector, there is a growing attention toward development and adoption of energy efficient retrofit strategies. Plagued by the lack of efforts in achieving comprehensive energy efficient retrofit solution sets (passive, active, and renewable energy systems), the authors acknowledge the concept of NZEB toward achieving energy efficiency by 2050. Toward this end, a numerical energy simulation modeling is carried out to retrofit an existing French “Puccini house” using ‘passive, energy efficient building systems and renewable energy’ strategies toward an NZEB target in the Mediterranean climate of Nice. Using Design builder 7.0, the simulated baseline energy model (Case A) is retrofitted through variations in the proposed energy efficient retrofit measures using two case scenarios (Case B: passive retrofit; Case C: energy-efficient building) to achieve NZEB (Case D). Assessing the performance of energy efficient retrofits using % energy reduction, the implementation of a high-performance building envelope is achieved using a thermally insulated external wall (46.82%), upgraded airtightness (20.39%), thermally insulated pitched roof component (33.03%), and high-performance window type—a glazing system (3.35%) with maximized window-to-wall ratio (5.53%). The maximum energy-saving retrofit solutions provide an ambitious reduction in energy consumption by approximately 90% from the baseline. A deep retrofitting of the French house meets the NZEB targets, as it reduces the baseline energy consumption from 194.37 kWh/m 2 /year to 23.98 kWh/m 2 /year using both passive and active strategies. The remaining energy demand is met by the integration of on-site PV panels (EUI= − 27.71 kWh/m 2 /year), which achieve an increase in energy production by 15.5%, while returning energy back to the grid ( − 3.73 kWh/m 2 /year). Findings of this study serve as a guideline for retrofitting traditional French single-family residences, while contributing toward the NZEB goal.