The increasing energy demand of university buildings in tropical hot/dry climates, coupled with unreliable electricity supply and rising operational costs, necessitates effective energy retrofit strategies and renewable-energy integration. This study aims to develop a simulation-based framework for evaluating energy-efficient retrofit measures and supporting photovoltaic (PV) integration in existing university buildings in Nigeria. The research addresses the limited application of quantitative simulation tools, validated energy assessment methods, and climate-responsive retrofit frameworks for higher education facilities in developing regions. A case study approach was adopted using a lecture theatre at Federal University Birnin Kebbi, Nigeria. Empirical environmental measurements were combined with dynamic building simulation using the Integrated Environmental Solutions Virtual Environment (IESVE) to evaluate four fabric scenarios: as-built theatre (T1), retrofitted theatre (T2), ASHRAE 90.1, and Passivhaus benchmarks. The simulation assessed room cooling sensible load and annual energy performance under tropical hot/dry climatic conditions. Results showed that T1 recorded the highest annual cooling load of 1303.22 MWh, while T2 reduced the demand to 1235.73 MWh, achieving approximately 5.2% improvement and an annual energy saving of 67.49 MWh. Although Passivhaus (1161.35 MWh) and ASHRAE 90.1 (1194.70 MWh) demonstrated superior benchmark performance, the retrofit scenario provided a practical pathway for improving existing institutional buildings. The developed framework establishes a systematic approach linking building assessment, simulation-based fabric optimisation, and PV integration planning. Future studies should incorporate detailed PV system sizing, energy storage analysis, economic evaluation, and long-term operational validation to enhance implementation potential across Nigerian and Sub-Saharan African educational facilities.

Keywords: Building retrofit; Energy simulation; IESVE; Photovoltaic integration; University buildings; Tropical hot-dry climate; Building fabric optimisation.