Robustness of Near-Optimal Envelope Sets Across Climates: Physical Realization, HVAC Weighting, and a 4608-Run EnergyPlus Study

Fixed external shading is often optimized in isolation, although annual loads also depend on glazing, thermal storage, the window area, the climate, and plant efficiency. We tested whether these variables produced one transferable optimum or climate-conditioned near-optimal sets, defined as designs within 5% of each climate’s grid minimum. A balanced overhang depth-to-window-height ratio (D/H), solar heat gain coefficient (SHGC), and effective thermal-capacity factorial grid was simulated with EnergyPlus across six climates and four window-to-wall ratio (WWR) profiles, including a 60% high-glazing extension and 50% internal gain sensitivity. Across 4608 annual simulations, SHGC dominated cooling-dominated climates, whereas capacity dominated mixed and heating-dominated reference cases; halving gains changed five of six sampled optima. Physical archetypes preserved five of six best combinations, while heating, ventilation, and air-conditioning (HVAC) weighting changed the dominant factor in two climates and the best design in four. A non-fitted two-node resistance-capacitance (RC) model maintained ρ≥0.965 in 18 Phoenix/Helsinki parameter combinations but required climate-specific shortlist widths to recall near-optimal sets. These results support the reporting of climate-conditioned priorities and near-optimal sets, with reduced models, HVAC weighting, and gain scenarios used as diagnostics rather than final predictions.