Whilst rooflights could properly have been said to have started with the central courtyards or atria of the Roman house, these were open to the sky and rain; and despite providing daylight to the surrounding dwelling space, would not have modified the exterior climate in the manner of a roof light.

The rooflight by definition permits daylight to enter from above through a glazed opening in the roof protecting the interior from wind and weather. The early rooflights were perceived either as domes such as that at Chiswick House with ordinary windows in the sides allowing in the daylight, but by the nineteenth century structural techniques had developed sufficiently to allow fully glazed barrel vaults or glazed domes to be placed above areas of building remote from the side walls and the proximity of windows. Examples of nineteenth century shopping malls still exist today where these overhead lights permit daylight to reach deep into the interior of buildings.

Much innovation was used in the nature of these roofights, and it is of interest to study the section of the Soane Museum, to see the many different shapes and sizes of overhead light Soane devised to introduce daylight to the different spaces, in what was at the time his private house.

Shopping Centre in Leeds. Barrel vaulted rooflight

¿S Section through the Soane Museum

By the twentieth century the use of rooflights had been reduced almost entirely to industrial buildings, and the CIBSE Lighting Guide LG10, 'Daylighting and Window Design' (published October 1999) illustrates a number of different types, the most common of which were the shed roof, the sawtooth, and the monitor.

Rooflight profiles

The advantages and disadvantages are set out in CIBSE LG10 indicating that the original shed roof, the cheapest solution, has serious defects and is unlikely to be used today; whilst the many different forms of monitor roof can be adapted to fit most roof situations to solve the daylighting problems below.

New roof forms are still being developed for the admission of daylight to large open areas not restricted to industrial buildings . . . from supermarkets to universities and swimming pools. An excellent example of an early solution to a factory in which the services are rationalized and placed inside ducts which are a part of the overall roof structure and do not obstruct the daylight is shown in Lighting Modern Buildings pp. 138/9, the York Shipley Factory; whilst the roof design for the Sainsbury Supermarket in Greenwich (Case Study pp. 164/167) shows an elegant solution to the roof form, providing a high level of daylight to the store.

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