What is the difference between a roof light, skylight and roof window?

Roof lights, skylights and roof windows have all become terms associated with a variety of products. All three are becoming increasingly popular as a means to maximise space, natural light and offer an energy efficient solution. Here’s a quick guide to help you tell the difference between the three types of system.


Skylights are used in a variety of different ways and range from small scale domestic projects on traditional pitched roofs to large projects which are designed to be installed on flat roofs or terraces. Skylights are one of the most basic types of glazing structure and are often used in hallways and lofts to allow a better flow of natural light. Skylights are often recommended for use in loft spaces when they are only intended to be used as storage space as they are more ornamental than roof windows which can be opened and closed.

Skylights have long been associated with heat loss but modern skylights must now meet a variety of building standards so this is no longer a problem. Click here for the full Xtralite technical library containing hundreds of useful documents about our products and to find out more about the thermal efficiency of our materials. (LINK:


A roof light is usually installed on a flat roof but if it’s fitted on a pitched roof, it is more likely to be fitted ‘out of plane’, or stand out from the roof line more than a skylight or roof window would. In essence, roof lights are extremely similar to skylights.

Roof lights can be fitted in listed buildings where new window openings in walls are not allowed. This is because they do not impact the look of the building from the outside but allow maximum light exposure on the inside.

Roof Window

A roof window is more flexible than a skylight and comes with a greater range of options. They are either used as a single window or form part of a set to create a full wall display that merges onto a pitched roof. In contrast to a roof light, roof windows MUST be fitted in place with the rest of the roof and tend to be smaller than roof lights.

When a loft room is intended to be used as a bedroom or living space, roof windows are a requirement in order to meet fire regulations and also act as an escape window.

In most cases, none of the above requires planning permission but there are a few exceptions so it is essential to check with local authorities before undertaking any work. The central aim is to maximise the amount of natural daylight within a building design and help to save on energy costs. The Department of Energy outlines the benefits and uses for roof lights in the home but the same benefits apply to the work place too.