Optimizing building heating demand through solar-air temperature integration: A comprehensive analysis of free heating potential and energy savings

This study presents an innovative methodology for estimating building heating demand by incorporating the solar-air temperature concept into heating degree hour (HDH) and free heating degree hour (HDHfree) calculations. Unlike conventional methods that rely solely on ambient temperature, this approach integrates for solar radiation and radiative heat loss, providing a more accurate assessment of heating demand and free heating potential. The results indicate that lowering indoor setpoint temperatures to 18 °C can reduce annual heating demand by 25-40%, while optimizing the heat transfer coefficient (ho=1.8 W/m²K) results in an 82% increase in HDHfree. This increase is attributed to a reduction in conductive heat losses through the building envelope, allowing solar gains to be retained for a longer period while maximizing passive heating effectiveness. Lower ho values also minimize radiative and convective heat losses, enabling the absorbed solar energy to remain within the building for an extended duration, ultimately enhancing free heating efficiency. The study also highlights the importance of material properties, with higher solar absorptivity (0.7) leading to a 40% improvement in energy savings and lower surface emissivity (0.35) contributing to better heat retention. The methodology was validated using data from Muğla, Turkey, demonstrating significant energy cost savings and carbon footprint reductions, especially in electricity-based systems. Future research should focus on refining the solar-air temperature model by incorporating building-specific variables and expanding its application to different climates. This approach offers a valuable contribution to sustainable building design by optimizing passive heating and reducing reliance on mechanical systems.