As the dimensions of the site continued to increase, for example, an entire block of downtown Chicago, the dimensions of the interior lightcourt reached a size where an additional ring of offices/hotel rooms could be located across the corridor from the perimeter ring of offices and still, a sufficient central void remained to provide light and ventilation to the additional offices. The exterior wall that was now needed to enclose the lightwell would typically be surfaced with a white glazed brick in order to maximize the reflection of daylight down, deep throughout the space.
Root claimed that a view into such a lightcourt “has proven to be in Chicago quite as desirable” as looking out toward a street. In other words, a double-loaded corridor scheme that lined the site’s perimeter, would also result in a hollow doughnut plan. The Grand Pacific Hotel in Chicago, designed by W.W. Boyington in 1870, (and located immediately to the south of the Rookery, i.e., same size lot) was one of the earlier local examples of this scheme.
There was one notable difference, however, between the previous single-loaded schemes and this new double-loaded scheme: in order to provide fresh air to the inner ring of offices, the skylight that had always been located at the roof, now had to be brought down to the ground floor so that the rooms lining the lightcourt would be exposed to the exterior.
In section, instead of walking into a soaring, multistory atrium, one walked into a rather low, skylighted lobby that was similar to a greenhouse.
Therefore, when one walked into a new skyscraper for the first time, it was easy to perceive if the building was a single- or a double-loaded corridor scheme: if the skylight was down at the second or third floor, the building was a double-loaded corridor scheme; if you walked into a breathtaking, tall multistory atrium, the building was a single-loaded corridor plan.
2.11. THE LIGHTCOURT EXPOSED ON THE EXTERIOR
These rules held only for sites that were free from adjacent buildings on all four sides, a rare opportunity seldom granted to a nineteenth century architect. More often than not, an architect would have to modify these rules to take into account such factors as the shape of the site, the site’s orientation with respect to the south or the sun’s direction, the widths of adjacent streets and the corresponding shadows of all surrounding buildings. For example, a building’s overall image could depend upon what side of the street it was to be erected. It was most desirable to have the lightcourt open to the south to maximize daylight AND to minimize the effect of shadows cast by the building itself. Therefore, if the street ran East/West, and if the site was on the north side of the street, the lightcourt would be exposed in the street front. However, if the site was located on the south side of the street, the street front would read as one continuous plane. Therefore, the exact same building would have a completely different street front depending upon which side of the street it was to be erected.
In his talk, Root chose such a site so that he could show the number of plan variations that an architect would experiment with, and how each would be evaluated, during the process of designing a skyscraper.
The exterior lightcourt could not, however, always be completely enclosed within a building’s interior. In his study of alternative floor plans, Root included some that placed the lightcourt in such a manner that its existence was revealed on a street front of the building. In addition to how this detail would impact the daylighting of the building, he also emphasized how this option would impact the design of the building’s exterior.
Instead of presenting to the street a solid plane that ran the length of the lot the building’s mass would be broken into flanking wings at each corner which would be separated by the void of the lightcourt.
This would give the building’s perception from the exterior a completely different read, or feel, that, obviously, also had to be put into the final design equation. The lightcourt, then, played a central role in the early design process of a skyscraper. Historically, we will see that it will be one of the most important aspects of the early skyscrapers. Not only did the lightcourt determine the overall plan of a skyscraper, and in some buildings it provided an exhilarating spatial experience, especially when one boarded an open cab to ride up to the top floors with the rush of air and space as the elevator made its way to your floor: there were no walls surrounding you, you were in an iron cage that whisked you up at a speed you probably had never experienced until then.
The lightcourt will also be the location in a skyscraper where architects would historically first experiment with reintroducing iron skeleton framing into the exterior wall, following the Chicago and Boston fires.
FURTHER READING:
Hoffmann, Donald. The Architecture of John Wellborn Root. Baltimore: Johns Hopkins University Press, 1973.
Hoffmann, Donald. The Meanings of Architecture: Buildings and Writings by John Wellborn Root. New York: Horizon, 1967.
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The Architecture Professor 