It is difficult to find any new public or commercial building without a prominent rooflighting feature nowadays, or a domestic roofscape without a multiplicity of rooflights. This was not always the case. Rooflighting has gone from nonexistence to ubiquity in the span of about 300 years.
Throughout history buildings and building groups have used lightwells and atria as devices for gaining light, ventilation and security in a dense or deep-plan environment. They were first seen in the earliest cities of civilisation – those of the Tigris/Euphrates valley at least 3000BC. While the atrium form evolved for purely practical reasons and the top lighting element implicit in the form almost ‘accidental’, some early buildings – notably the Pantheon in Rome of circa AD120 – used toplighting deliberately for its dramatic effect, turning the inside of this building into a unique sheltered outside space. The Pantheon illustrates how in relatively wealthy and secure societies architecture, freed of the concerns of defence or specific economy, can start to explore extended possibilities – here lighting from above in addition to its structural callisthenics.
In Britain and throughout most of Europe rooflighting did not appear until developments in the process of glass manufacture made larger and relatively cheap glass sheets available. It is easy to see that in our climate a roof opening such as that of the Pantheon would merely let in rain – so larger overhead openings into buildings, (apart from those in domestic property necessary to allow the smoke of a fire to escape) are not really found until a reliable and inexpensive means of glazing them was possible. In an example of how architectural development mirrors society’s capabilities and aspirations, the ‘advent’ of rooflighting did not occur until both the technology and the ‘use’ for natural toplighting combined to generate first limited use of, and thereafter widespread use of rooflighting. The development of glass manufacture – the most essential part of any rooflight – is a case in point.
Glass manufacture itself dates back to at least 2500BC but its use in windows did not really occur until around 1000AD at which time glass manufacture developed in Europe almost exclusively to supply the ecclesiastic ‘market’.
This was the great age of cathedrals. Glass was manufactured using either the cylinder or spun method of manufacture, neither of which had really changed since they were first introduced. The largest sheet that could be produced using the spun method was approximately 1.3 metres square. But such sheets were expensive and rare – too expensive to use in anything but the most prestigious buildings.
Although spun or crown glass was much preferred for its clarity and lustre the basic size of sheet produced by this method would never increase much in size, was labour-intensive, and consequently has remained a relatively expensive glass. Developments in casting and polishing glass by Perrot and others from 1687 produced promising results. The size and quality of panes manufactured using this process rose rapidly. By 1789 cast glass was machine polished, and by 1794 polished plate glass was available in any size up to approximately 1.9m x 2.97m, though larger panels were still expensive. The casting of glass, not relying upon the ‘art’ involved in glass spinning, lent itself to production on an industrial scale and as the volume of glass produced went up, so the price came down.
Glazed windows, which had been uncommon in all but the largest houses in Britain up to the late 16C became more widespread and were in general use by the end of the 17C. Thereafter, as glazing improved in quality and became cheaper the extension of its use beyond the glazing of vertical windows became feasible. The technology was in place for extended use of glazing by the end of the Regency period, and then along came the Victorians.
The History of Rooflighting
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