A numerical study is conducted of laminar free convection from a vertical window glazing adjacent to an insect screen. The insect screen is modelled as an isotropic porous medium using a Brinkman-extended Darcy model. The results are validated against measurements from the literature. The effects of Darcy number and Rayleigh number on the convective heat transfer are obtained for a Prandtl number of Pr = 0.72 (air). The objective is to characterize the effect of insect screens on free convection from windows and develop a general correlation, suitable for use in building energy simulation. This extended abstract reports the recent progress of this work.