This paper draws the attention to the importance of a correct modelling of the inlet temperature of naturally and mechanically ventilated multiple-skin facades. Measurements demonstrate that the assumption of an inlet temperature equal to the interior or exterior air temperature is usually not valid. A sensitivity study illustrates the significance of the inlet temperature as a boundary condition for numerical multiple-skin facade models. Finally, the inlet temperature model and multiple-skin facade model are used in a whole building energy simulation to indicate the importance of a correct inlet temperature on the energy performance. (C) 2004 Elsevier B.V. All rights reserved.