Many modern office buildings have highly glazed facades. Their energy efficiency and indoor climateis, however, being questioned. Therefore more and more of these buildings are being built with doubleskin facades, which can provide: a thermal buffer zone, energy savings, wind protection with openwindows, fire protection, aesthetics, solar preheating of ventilation air, sound protection, pollutantprotection with open windows, nocturnal cooling and a site for incorporation of PV cells.