Daylighting is the practice of varying windows properties in a wall exposed to incoming solar radiation to receive enough natural light inside a room during the day.
Daylight can be optimised by varying the glass properties and designs of windows exposed to incoming solar radiation during the day. Beneficial design strategies are considered to give a more comfortable and well illuminated spaces in a building to increase its occupant satisfaction.
As a result, this reduce the heat gain in a building and hence decreases the energy consumption of cooling loads in hot countries like Mauritius.
Exterior window’s overhang and shading device
One of the methods use to minimise solar gain is by fixing solar shades such as awnings, blinds, hoods etc. outside the windows especially those facing the North (considering Mauritius).
Different models of shading that can be fixed according to the building occupants’ taste or selection.
However, east, and west faces need vertical fins to avoid low-angled sun as shown in the figure below.
A more cost effective and easy fixation mean for exterior shading with reduction over 98% with exterior roller blind solar shade. It has a wind and sun sensor installed together to send a signal to the motor to open and retract according to different windy and sunny conditions.
Interior window coverings
Exterior shades are three times more efficient at reducing solar heat gain compared to interior shades. But however, in tall buildings where exterior shading are difficult to fix or inaccessible, interior shading options can be considered. A more efficient solution is to use operable window coverings to reduce heat gain in summer.
- Solar Control glass
Solar control glass is made using a magnetron sputtering method reduces solar heat gain maximising daylight to provide a comfortable environment to live and work in a building. It consists of invisible layers of special materials on the glass which have the dual effect of allowing sunlight in by absorbing the visible ultraviolet (UV) wavelength, while repelling solar heat by reflecting the infra-red (IR) portion of solar energy.
- Reflective coated glass (Coatings)
The inner surface of heat reflecting glasses is given a very thin reflective metallic coating which reflects daylight allowing less heat gain in a building. The solar heat gain coefficient varies depending on the density of the metallic coating applied. The appropriate reflective glass is selected according to the desired amount of light and heat energy transmitted through it during the day.
- Tinted glass and Window films
In cases where the windowpane cannot be changed, tint films can be applied to a glass to alter its properties to reduce solar gains. Some glass tints are usually manufactured by adding colorants to it during production while others can be made by adhering coloured films to the glass.
The type of glass and window film applied causes varying absorptance (the amount of solar energy that the glass and film retain) to reduce heat gain in a building.