An Integrated GPRS-Based Decision Framework for Sustainable Retrofitting of Existing Educational Buildings in Hot-Arid Climates: An Egyptian Case Study

Existing educational buildings in hot-arid climates face substantial challenges related to energy demand, resource consumption, and environmental performance. Although the Green Pyramid Rating System (GPRS) provides a nationally adapted framework for sustainable building assessment in Egypt, a methodological gap remains between GPRS assessment criteria and their systematic translation into technically feasible and economically informed retrofit decisions. This study develops an Integrated GPRS Retrofit Decision Framework and an associated GPRS Implementation Matrix to bridge this gap by linking building deficiencies and GPRS requirements with retrofit strategies, quantitative evaluation methods, performance indicators, economic criteria, and implementation priorities. The framework was applied to an existing educational building at the British University in Egypt as a case study. The methodology integrates building assessment, engineering calculations, TRNSYS 18 dynamic thermal simulation, renewable-energy assessment, water- and waste-management analysis, and techno-economic evaluation. The calibrated TRNSYS model achieved an NMBE of +3.2% and a CV(RMSE) of 8.7%. Results indicate that the proposed rooftop photovoltaic system could provide an estimated annual electricity-cost benefit of approximately EGP 365,616.315, with a simple payback period of approximately 4.17 years, while fiberglass envelope insulation reduced simulated cooling demand by approximately 7.97% relative to the baseline. Additional measures, including piezoelectric flooring, water-management interventions, and waste segregation and recycling, provided complementary energy, resource, environmental, and economic benefits. The principal contribution of the study is therefore a structured decision-support methodology that moves beyond conventional GPRS compliance assessment by integrating technical performance, environmental considerations, and economic feasibility into retrofit selection and prioritization. Application to a single educational building demonstrates the framework’s operational applicability; however, further multi-building and post-occupancy validation is required before broader transferability can be established.