The glazing design needs to balance heat, light, ventilation and access to views.
The heating load can be reduced by:
- choosing a glass and frame type with a lower U-value, as this will reduce heat loss;
- choosing a glass and frame type with a higher Solar Heat Gain Coefficient (SHGC), as this will increase the solar gains (but will increase cooling loads);
- using adjustable shading instead of fixed shading to allow winter solar access;
- raising the height of shading or lowering the sill of windows to avoid permanent shading at the top of the window;
- reducing shading overhangs (but be aware that this will increase cooling loads);
- not placing windows where they are overshadowed;
- moving windows to north, northeast or northwest for more solar gains; and
- reducing the area of windows facing south, southeast and southwest to minimise heat loss.
The cooling load can be reduced by:
- choosing a glass and frame with a lower U-value to reduce conducted heat gain;
- increasing shading overhangs or using external louvres or awnings (but be aware that this will increase heating loads);
- choosing a glass and frame type with a lower Solar Heat Gain Coefficient (SHGC) to reduce heat gain from sun striking the glass in summer (but be aware that this will increase heating loads);
- reducing the area of windows facing west, east, northwest.
Other things to consider include:
- choosing a glass and frame type with an acceptable Visible Transmittance for natural lighting;
- choosing shading, rather than tinting, can reduce cooling loads with less of an increase in heating loads;
- choosing operable windows for ventilation and cooling potential; and
- overshadowing by adjacent buildings and existing vegetation;
- locating thermal mass appropriately relative to windows to capture useful heat gains but avoid overheating.