This work analyzes the techno-economic and environmental performance of a solar-biomass hybrid energy system optimized for small-size residential buildings in cold and Mediterranean climates. Based on real-time consumption data, dynamic simulation in TRNSYS, and a rule-based strategy, a photovoltaic-thermal panel, biomass heating, thermal storage, and an absorption chiller comprise a hybrid system. Performance assessment in Trondheim, Norway, and Rome, Italy, reveals that in both these regions, higher solar irradiation leads to PVT panels fulfilling up to 88% of DHW demand and 72% of cooling demand, while biomass covers more than 66% of heating demand in winter in Trondheim. An optimization using a TOPSIS approach enhances efficiency by 3.7% in Trondheim and 4.3% in Rome, while lowering CO2 emissions by 4.2 kg/MWh and 2.8 kg/MWh, respectively. The levelized cost of energy decreases by up to €16.9/MWh in Trondheim and €16.8/MWh in Rome. These results indicate that the system has a high degree of adaptability towards changing climatic phenomena while being effective in limiting emissions as well as costs, thereby favoring near-zero energy housing in various urban settings.