This study investigated the energy performance of advanced glazing in typical Danish commercial and residential buildings. We used the tsbi3 hour-by-hour building energy simulation program to analyze the demand for heating and/or cooling and peak load of the heating/cooling system as a function of glazing/frame type, size and orientation. The glazing area of the window was varied for each facade corresponding to 0%, 15%, 30% and 50% of the area of the facade. As climatic data we used the Danish Test Reference Year for Copenha gen. Cooling, especially in residential buildings, is not common due to the temperate climate.Two types of glazing were used: Aerogel (U-value 0.6 W/m2K, solar-transmission 0.76) and Low-E double pane (U-value 1.85 W/m2K, solar-transmission 0.73). As frames we used a traditional frame (U-value 2.2-2.4 W/m2K) and a "super-insulated"-frame (U-value 1.5 W/m2K). Results from the models with Aerogel-glazing were compared to results from the models with Low-E glazing. The general result was that a change in glazing from Low-E to Aerogel would cause a saving in the total energy-demand.Apart from the energy-savings a change from Low-E to Aerogel-glazing will have a positive impact on the indoor climate as the inside surface-temperature of the glazing increases due to the lower U-value. The increase in glazing-temperature reduces radiation-asymmetry during winter-time.