Architects know that windows should be shaded in the Australian environment. Precast concrete has great potential for integrally shading windows in facades, thereby increasing occupant comfort as well as saving energy.
Because it is relatively simple to calculate the altitude and azimuth of the sun on any given day, at any given time and at any given location, efficient window shading schemes can be incorporated into the design of precast concrete building facades. For the southern hemisphere, these may be simple horizontal shading for northern facades, vertical louvres and mullions on south-east/south-west facades or free-form arrangements for north-east/north-west aspects.
An example of energy savings is given in the following diagram* which shows the energy totals of cooling loads on an eastern zone typical floor for the months of December, January, February and March with the following building envelope options:
- Flush facade, clear glass, no shading;
- Flush facade, double heat-absorbent glass, no shading;
- Clear single glazing, with shading.
Energy savings from shaded glazing
Typical recessed window facade panels at 80 William Street, providing shade to the glazed areas. Although the recess is relatively shallow it provides a 20% reduction in recurrent cooling loads for the four-month summer period compared to a flush facade system using the same type of glass.