Sharon McHugh considers Kahn's use of natural light at the Kimbell Art Museum
I was asked by VELUX to write about a favourite building that uses natural light in an interesting or innovative way. Whilst there are many great buildings that do that, the choice for me was obvious - it would have to be a building designed by the late, great 20th century Master, Louis I. Kahn. But what building would it be? Kahn was a master of light and many of his buildings reflect his rare ability to make light the subject of the work. But the building that comes to mind as the penultimate tribute to light is the Kimbell Art Museum in Fort Worth, Texas.
At the Kimbell, Kahn was presented with the challenge of naturally lighting the galleries in an environment that was less than ideal for artworks. Fort Worth has blazing sun and 90+ degree temperatures for six months of the year so daylighting the building would prove challenging. Kahn’s lighting solution is an innovative roof design that allows filtered, museum-appropriate light to penetrate the galleries through slots located in roof vaults that run the length of the building. Although Kahn had always envisioned lighting the galleries through these slots, he hadn’t figured out how to diffuse the light once it came into the building.
Taking his cue from the way in which a partially mirrored prism in a single reflex movie camera works, distributing light to both the camera’s eyepiece and the film, Kahn created what he referred to as a ‘beam splitter’. It works by separating the light that comes in through the roof openings and directing it upwards to the undersides of the roof vaults on either side. The reflector is made of a curved screen of polished aluminum that is pierced by tiny holes.
When strong light enters the building the through the slots it is conditioned for museum use by a reflector that bounces it up onto the underside of the Kimbell’s concrete ceilings where it strikes the main body of the reflector allowing a small amount of filtered light into the galleries through the holes. Kahn took to calling these reflectors ‘natural light fixtures’, and indeed they are. He predicted they would produce an effect that would ‘give a silvery glow to the room while allowing visitors to know the time of day’.
Kahn’s prediction was borne out with extraordinary effect. The light in the Kimbell galleries has an ethereal quality and it is widely considered to be the distinguishing factor in the building’s fame.