Achieving near-net-zero energy in hot climates through synergistic retrofit interventions and uncertainty quantification

With existing buildings comprising 80% of projected 2050 building stock, effective retrofitting strategies are essential for meeting global sustainability targets. This study evaluated the energy performance of green roof systems, rooftop photovoltaic panels, and ASHRAE 90.1–2019 upgrades for a representative 250 m2 office building in Abha, Saudi Arabia. EnergyPlus 9.5.0 was used to simulate four retrofitting scenarios. Monte Carlo simulation (1000 iterations) was applied to account for uncertainty in weather data ($$\pm 5\%$$), material properties ($$\pm 10\%$$), and operational parameters ($$\pm 15\%$$). Individual interventions reduced net annual energy consumption by 9.5% (green roof), 19.9% (PV), and 70.0% (ASHRAE), while the combined package reduced net annual energy consumption by 91.0%. The combined retrofitting approach achieved an NPV of 1,203,079 SAR and a payback period of 5.0 years, with PV degradation included in PV-derived savings. This study shows that combining passive and active retrofits with code-based efficiency measures can move existing buildings toward near-net-zero energy, defined in this study as a small positive annual net energy consumption after on-site photovoltaic generation is credited, with net annual energy consumption not exceeding 20 kWh/m2 per year for the case building.