Insect screens are always installed outside windows to prevent insects in most buildings in China. This in turn negatively impacts the natural ventilation performance. Small-scaled wind tunnel experiments were conducted in an environmental cabin to determine the effect of insect screens on natural ventilation performance. A combination of statistical analysis and data calculation was used to obtain the resistance characteristics of four different insect screens

and the effect of screens on ventilation rates were obtained via experiments. An insect screen resistance model was utilized to inspect the effect of porosity and validate field measurements. Furthermore

the accuracy of the precise model and simplified model exceeded 80%. The results indicated that the discharge coefficient of insect screens increases as the air velocity increases and finally tends to be constant. As the porosity increased

the discharge coefficient increased to a higher stable value because the air velocity increased. The accuracy of the new model improved by approximately 34% when compared with that of the model in the literature.