- ABSTRACT Whole building simulation may play a key role in the optimization and assessment of the market potential of new building components. In the SOLVENT Project, ESP-r was used for such purposes, in the case applied to a new reversible ventilated window. The innovative character of the window required the development of a specific simulation approach within ESP-r, in order to account for buoyancy in the air channel. A multi-zone approach with an air flow network was developed, and several variations studied. Parametric studies assessed the effect of the number of zones into which the window is divided, heat transfer correlations for the air gap and local loss coefficients for the air flow network.