Comprehensive Performance Analysis and Low-Carbon Retrofitting Strategies for an Existing 5A-Grade Office Building

This study presents a monitoring-calibrated, systems-level retrofit assessment for a 15-year-old Grade-A office building in Beijing, China (temperate monsoon climate). One year of continuous monitoring (2023–2024) was combined with calibrated multi-physics simulations (EnergyPlus/DesignBuilder, Radiance, representative CFD) to evaluate retrofit scenarios for lighting, envelope and HVAC systems. Baseline EUI = 108 kWh·m−2·yr−1 (total site electricity ≈ 3,088,893 kWh·yr−1). HVAC accounted for ≈48% of site electricity. Key findings: (1) LED lighting retrofit delivered measured lighting savings of ~26.7% (simulated potential up to ~32.7%) but may increase cooling loads in some operating regimes (simulated +8.3%) if not coordinated with HVAC and envelope measures; (2) glazing upgrades and airtightness improvements materially increase HVAC savings; (3) a prioritized, phased retrofit (lighting → envelope → HVAC) can capture ~80–85% of integrated carbon reductions while lowering immediate CAPEX and business disruption; (4) scheduling major HVAC upgrades before the cooling season and envelope works during transitional months improves operational and economic outcomes. Calibration and uncertainty metrics are reported (annual energy error < 5%).