What are the skylights and what is the purpose of such roof lights?

what-are-the-skylights

Skylights, such as Fenstro RoofLite+, Velux VLT, Optilook, Fakro WGI and many other available on the market are designed for installation in unihabited spaces.

The main purpose for installation is to provide a light and ventilation but the huge advantage is to allow occasional access to the roof if the maintance is needed.

Due to the construction they are recommended for installation in unheated spaces where the interior temperature is similar to the exterior temperature.
Most of these windows is available with double glazing units however due to very basic construction the thermal insulation is very low which leads to the heat loss and they are not recommended for habitable areas.