DAYLIGHTING IN TWO CENTROIDAL SPACES AT THE UNIVERSITY OF VIRGINIA
INTRODUCTION
The
University of Virginia Rotunda
The Rotunda (1826) at the Academical Village of the University of Virginia
was designed by Thomas Jefferson to be the centerpiece of his celebrated
campus plan. It was the library, the most important building at the university.
It occupied the central location between the two long arcades composed
of faculty pavilions and student rooms. The recently completed Caplin Pavilion
at the University of Virginia School of Law is the centerpiece of a building
ensemble which is similar to the historic Academical Village. It is located
between two parallel linear buildings which define a central green space.
The
Caplin Pavilion at the University of Virginia School of Law
The rotunda building form (a round building in plan, often domed) is present throughout the history of architecture beginning with the Pantheon in Rome (120 A.D.) Other notable examples are the Pisa Baptistery, the Tempietto in Rome, and the Radcliffe Library in Oxford. Hundreds of other buildings throughout history (cathedrals, museums, libraries and capitols) have rotunda forms within their plans. The Caplin Pavilion is a contemporary orthogonal version of this building form.
Hypothesis
The daylighting environment at the present day Rotunda performs well for the current multi-purpose activities despite the fact that it was originally designed as a library. This space with its oculus and perimeter windows at floor level produces an even distribution of daylight on overcast days. On sunny days, there are distribution problems due to the direct sun entering the oculus. This creates visual glare conditions and uneven lighting levels. The artificial lighting can be used to compensate for the low levels of daylight during certain hours of the day and during detrimental sky conditions.
The daylighting distribution in an orthogonal centroidal space such as the Caplin Pavilion is significantly irregular as compared to a circular centroidal space under overcast sky conditions. However, since the overhead daylight is admitted through vertical glazing, the distribution at floor level on sunny days is not markedly different from overcast days and there are no visual glare problems.
Methods
Rotunda measurements
Initial observation and photography were used to determine the parameters
of the investigation. Students then undertook a series of daylighting studies
by taking footcandle readings in a grid pattern at three times of the day
under cloudy and sunny sky conditions. A Minolta TL-1 illuminance meter
was utilized. Brightness measurements in footlamberts were taken to evaluate
glare conditions utilizing a Minolta LS-100 luminance meter. The space
itself was documented in terms of surface reflectances, and glazing transmission.
Photography of the space under varying daylighting conditions was used
to corroborate the physical measurements and illustrate the visual lighting
environment. Subjective evaluation of the lighting environment was determined
by utilizing polar adjective ratings.
|