Enhancing thermo-optical performance of transparent roofs via water-mist technology: Insights from wind tunnel experiments

Water-mist spray technology offers an energy-efficient and pollution-free approach to improve the thermo-optical performance of transparent roofs. However, existing studies primarily focus on its evaporative cooling effect, with limited research on shading effects and no precise quantification of its impacts on building envelopes. This study examined the cooling and shading effects of water-mist spray on transparent roofs and quantified its influence on thermo-optical performance through wind tunnel experiments with orthogonal design. Results showed that the technology reduced interior surface convective heat flux by 3.3–11.5 W/m², long-wave radiation intensity by 20.3–45.2 W/m², and transmitted solar radiation by 12.0–55.0 W/m². Under various conditions, reduction rates for solar transmittance, visible transmittance, and solar heat gain coefficient were 6.5%–15.6%, 5.2%–15.2%, and 8.5%–18.6%, respectively. Heat gain mitigation primarily occurred via radiation attenuation, with reductions of 30.4%–54.9% in solar radiation, 39.0%–60.4% in long-wave radiation, and 5.1%–17.2% in convective flux. The shading effect alone accounted for at least 30.4%–54.9% of the total heat gain reduction. Spray parameters (mist layer thickness, nozzle pressure) showed stronger correlations with thermo-optical indicators than environmental factors (air temperature, solar radiation), enabling dynamic performance adjustment similar to smart glazing but at lower cost. This study provides the first quantitative assessment of water-mist shading effects via wind tunnel experiments and develops empirical models with high accuracy (R²: 0.85–0.95), offering a theoretical foundation for engineering applications. Overall, the proposed technology lays a solid foundation for the dynamic regulation of thermo-optical performance in transparent roofs using a passive and low-cost approach. © 2026 Elsevier Ltd.