A simplified approach to thermal performance calculation for building integrated mechanically ventilated PV facades

The paper presents a methodology for calculating the thermal impact on building performance of an integrated ventilated PV facade. This is based on an extension of the familiar U- and g-values to take account of the energy transfer to the facade ventilation air. Four terms describing ventilation gains and transmission losses in terms of irradiance and temperature components are defined which characterise the performance of the facade in total. Steady state analysis has been applied in order to express these four parameters in terms of the detailed heat transfer process within the facade. This approach has been applied to the ventilated facade of the public library at Mataró, Spain and validated against detailed temperature measurements. Monthly U- and g-values have also been derived and the associated thermal energy gains calculated for the same building façade but transposed to the climate of Stuttgart.