In this study, fluid flow and heat transfer in double, triple and quadruple pane windows are investigated numerically. Computations are carried out for various different gap widths and different outdoor temperatures and, including and excluding radiative heat transfer in the calculations. The results show that temperature profile and flow structure in the cavities of multiple pane windows differ from each other. The heat loss through the windows can be reduced significantly by increasing number of panes which both acts like radiation shield and slows down the flow in the cavity thus suppress the convection currents. Equivalent energy saving of double pane window coated with low emissivity material can be achieved with multiple pane windows even with ordinary window glass. About 50% or 67% of energy savings can be made if the double pane window is replaced by triple or quadruple pane windows, respectively. The benefit of multiple pane windows is more profound in cold regions. (C) 2014 Elsevier B.V. All rights reserved.