Direct sunlight enters to several spaces in the three museums. In two of these museums direct sunlight penetrates in galleries where artwork is displayed, that is the case of the Modern Art Museum and the Amon Carter Museum.

The museums were evaluated through site visits to the museums at different times of the year, interviews with curators and facility managers, photometric measurements (with and without electric lighting), photographic documentation of sunlight penetration using fish-eye photography with the SunPath program (Reference 4), and computer simulations using the ECOTECT and Desktop RADIANCE software to analyse the patterns of sunlight penetration and to calculate illuminance and luminance levels throughout the year. The following section describes the evaluation of each museum.

The Modern Art Museum

Large spans of glass illuminate the main entry lobby (north and south-facing), and the sculpture galleries (east-facing), both are two-story high spaces. Most of the galleries in the first floor are windowless and are mainly illuminated by electric light sources. The subtle transition between the highly illuminated east-facing galleries and darker windowless central galleries is successfully achieved through intermediate galleries and passages. Most of the galleries in the central area of the second floor use toplighting as the main source of illumination in combination with halogen lamps. The illuminance levels in these central galleries are well controlled through a series of internal and external louvers that intercepts most incoming direct and diffuse light rays. Light levels in these galleries do not exceed the 200-lux recommended for oil paintings. Along the west side of the second floor are located seven galleries that are illuminated mainly by side light windows with white interior screens (see Figure 2-right).

Sunlight penetration was observed throughout the year along the west-facing galleries, located on the second floor (see yellow areas of Figure 2-right). Illuminance value measured over an oil painting was between 2,000 and 4,000 lux (Figure 5), which are 10 to 20 times higher than the maximum recommended illuminance of 200 lux for oil paintings, as stated in the “IES Recommended Practice for Museum” (Reference 5).

Figure 6 is a fish-eye photo taken from an oil painting’s viewpoint with a sun path diagram, and shows the number of hours the painting is receiving direct sun on its surface. This painting is exposed to direct sunlight mainly during the late afternoon hours between 4:00 and 6:30 PM between the equinox and summer solstice. Many of these west-facing galleries cannot be used to exhibit light susceptible artwork. Several of these galleries had
remained empty since the opening of the museum, and few of them only display sculptures made of metal.

Figure 6: Fish eye photo taken from painting’s viewpoint with sun path diagram, at the Modern Art Museum’s west gallery.