Comprehensive Energy Retrofit of a 1950s Office Building in Algeria: Toward 2030 Efficiency Goals in Mediterranean Climates

Retrofitting conventional buildings is a key strategy for climate change mitigation, as it enhances indoor comfort while reducing energy consumption in countries where old building stocks are a major contributor to energy use and associated emissions. In North African and Mediterranean contexts, deep energy retrofits for mid-century office buildings remain limited, particularly regarding the practical implementation of solutions adapted to local climatic and economic conditions. This study investigates a deep retrofit of a mid-20th-century office building in Algeria, aiming to assess its alignment with Algeria’s 2030 climate and energy efficiency objectives. A holistic methodology combining an energy audit and dynamic simulation with EnergyPlus has been undertaken to evaluate envelope upgrading, HVAC replacement, and renewable energy supplementation. Retrofit strategies selected were defined as representative of technically feasible and cost-effective solutions for Algerian mid-century office buildings, balancing energy performance improvement and economic viability under local climatic constraints. This study analyzed two retrofit scenarios: one with a combination of envelope improvements, heat pump replacement, and supplementation by photovoltaic solar panels, reaching 41% in terms of electricity savings (≈23 t CO2/year avoided), and the other with the VRF system, reaching 54% in savings (≈30 t CO2/year). Consequently, energy intensity is reduced from the base case by around 41–54%. The study contributes to data-driven retrofitting studies and explores innovative, low-cost strategies that respond to regional climatic challenges.