1. The window's thermal role

1.1 Summer comfort

Since glazing is transparent, it lets through energy in proportion to its solar factor. If the sun's rays are not shielded before reaching the "enclosed" area, this energy can raise the temperature to an uncomfortable level (all the more so if the thermal insulation of the opaque walls has been carefully designed). Therefore, on facades exposed to the sun (particularly from south-east to south-west), a solar screen must be installed between the exterior and interior of the premises.

Definition: the solar factor is the...