Systematic numerical study on the effect of thermal properties of building surface on its temperature and sensible heat flux.

Systematic simulations were performed in a city block in Yokohama, Japan, on a clear summer day to study the effects of building surface thermal properties on their radiative and thermal exchange with the atmosphere, and the surface energy balance (SEB) model sensitivity to these thermal properties. To study this practically and systematically, the thermal properties used were determined from a database of commonly used materials for building surfaces in urban Japan, characterizing the typical thermal property values and their combinations. Using suitable simplification and assumption, the main findings included: (a) a combined modification of thermal properties enlarges the cooling effects of individual modifications, reaching 131%–149% of the accumulated reduction in the emitted sensible heat flux (Q H); (b) the difference in the cooling effects of a high-albedo strategy applied to roofs between various thermal properties is up to 76 [W m⁻²] in Q H ; (c) the SEB model sensitivity of the surface temperature (T s) to thermal properties for the façade is close to that of the albedo, at up to approximately 0.1 °C for a thermal conductivity Δ λ c of 1 [W m⁻² K⁻¹] and a heat capacity Δ C a of 1 [kJ m⁻² K⁻¹]; (d) the range in root mean square error of the simulated daily, daytime, and noon Q H caused by generalizing the roof thermal properties is estimated to be 6%–41%, 7%–50%, and 7%–38%, respectively. Overall, the thermal properties of building surfaces are important for their thermal and radiative behavior, and therefore cannot be ignored in SEB modeling. • Importance of thermal property for surface heat balance is verified systematically. • Combined modification of thermal properties enlarges individual cooling effects. • Thermal properties cannot be ignored to evaluate the cooling effect of cool roofs. • Generalizing the thermal properties causes nonnegligible errors in SEB modeling. [ABSTRACT FROM AUTHOR]