The paper addresses a modeling approach to reduce energy use for conditioning a double-skin façade cavity of an existing large pharmaceutical production facility featuring 10 structural levels. Upon an examination of the limits of available building energy software a decision was made towards developing a new computation program, which offers dynamic resolution of the building physics involved while also taking into account the intended control strategy of the fan-supported cavity ventilation. To obtain the full picture of the façade performance during the operation time (24 * 7), simulations were carried out for 10 main representative cases. On the basis of the overall analysis of the simulation results, a façade performance control strategy was found which allows for extensive energy savings during most parts of the year, although, as requested by building operator, the proposed measures do not involve any significant retrofitting of the production facility