For a new or future building, the energy performance of the house with no windows is of the same magnitude as the house with windows, which means that the solar gains of the windows are of the same magnitude as the additional heat loss.
For existing buildings, the house with windows performs better than the house with no windows.
5.6.6 Consequences of future requirements for better energy performance
Current trends in European and national legislation point towards a continued focus on energy in building legislation, which means that the minimum requirements for the energy performance of new buildings as well as refurbishments will be tightened.
As seen in example above, the energy balance of windows depends on the building where they are installed. In figure 5.6.2, there was an example of how much of the annual solar gains can be utilised in an existing building in northern Europe. In a high-performing building the heat loss is low, so less solar gain can be used. In high-performing buildings, the focus of windows will be on low Uw value rather than high g value.
The example shows that the relative saving by using 3-layered glazing is largest for low energy buildings, while only small savings are seen for existing buildings.
Example: solar shading and natural ventilation provide good energy performance and thermal comfort in warm climates.
The performance of a typical building in four cities in warm climates was investigated with the VELUX Energy and Indoor Climate Visualizer. Different combinations of solar shading and natural ventilation were investigated and compared to an air-conditioned house. The investigated cities were Athens, Istanbul, Malaga and Palermo (Asmussen, 2010). The energy performance of the building with air conditioning was in the range of 150 – 160 kWh/m2, which is 3 to 10 times worse than the buildings without air conditioning.