Modelling of facade elements with switchable U-value

Abstract In this contribution, a new model of switchable insulation element is introduced. This element essentially consists of a double glazing unit with a translucent insulating panel mounted inside. Switching of the U-value is achieved by control of an internal convective flow around the insulation panel. The element can be in an insulating state with a low U-value, or in a conducting state with a high U-value. First the new model of the element, based on numerous thermal, hydraulic and optical assumptions, is introduced. The airflow rate is calculated by balancing the pressure drops and the buoyancy driving force. The model is validated against U-value measurements, showing a reasonable accuracy. Finally, the model is used for a parametric analysis, where the influence of different thermophysical properties on the U-value and g-value of the element in insulating and conducting state is investigated.