Jacob Slifer + Andrea JohnArch 373. Summer 2013. Grondzik

VISUAL COMFORT AND THE PERCEPTION OF GLARE IN THE DAVID LETTERMAN COMMUNICATIONS AND MEDIA BUILDING LOBBY

GLARING WEAKNESS:

THE DAVID LETTERMAN BUILDING

Plan View

HYPOTHESIS

Between the hours of 9am to 3pm, we expect glare to be perceived by the visitors of the David Letterman Building’s lobby due to the prominent amount of unshaded glazing of the east facade. More specifically, the morning hours of 9am to 11 am will have a greater perception of glare by visitors due to position of the sun. We propose that glare can be readily perceived by visitors to the lobby of the David Letterman Communications and Media Building, such that at least half of the visitors will concede some degree of visual discomfort while using the lobby.

METHODOLOGY

Grid pattern created by authors of this study. Each point denotes a location in which luminance was measured.

Our approach to data collection for this case study was divided into two parts; the first being personal interviews of occupants of the David Letterman Building lobby (see interview sample in Results section), and the second being measured readings of luminance taken with a luminance meter. Luminance values around the hours of 10am and 2pm were recorded with the use of a Minolta Luminance Meter Model LS-100

Click icon to add picture1. How often do you use the lobby in the David

Letterman Communication and Media Building? 2. Do you ever notice glare while you are using the

lobby? 3. If so, does this determine whether you continue

to use the lobby at the time? 4. If so, where in the lobby do you perceive glare

to be the “worst,” or most likely to occur? 5. If so, when would you say the glare is worst

during the day? 6. Would you prefer for the lighting in the lobby to

be brighter? Dimmer? Remain the same? 7. Do you ever have difficulty reading from your

books in the lobby? From your phone? Computer?

8. Do you have any other comments you would care to share about the lighting or glare in the lobby?

THE SURVEY

LUMINANCE MAPS

LUMINANCE MAP FOR VERTICAL SURFACES

LESSONS LEARNEDGraphical representation of the seating in the David

Letterman Building lobby, and where glare is perceived to be worst, or most likely to occur

Our hypothesis proved correct, if by a very thin margin, as 50% of interviewees stated they did indeed perceive glare resulting in discomfort. Based on both the measurements and the interview responses we can assert that the vast amount of glazing on the eastern wall is what causes this. There are no shading devices attempting to mitigate direct sun light, and all of the seating is located in close proximity to the windows. Considering that very few visitors said the glare would cause them to avoid the lobby, it may be possible that the lobby is the only convenient location for them to sit when they are waiting before, between, or after classes.

Our only question lies in whether these luminance values would have affected how the David Letterman Building was designed had it’s architect foreseen the discomfort half of its visitors perceive.

LESSONS LEARNEDBased on these tables shown, 100 to 200 cd/m^2 is the luminance range deemed desirable for “moderate” tasks. However, as the luminance maps show, nearly all of the surfaces in the lobby are above this range in the 10am time slot.

The luminance range preferred for wall surfaces is 25-100cd/m^2, but only the higher surfaces and the southern surfaces fall within this range. Task luminance, with a range of 100 to 500 cd/m^2, is much more forgiving. However, it is worth noting that the majority of horizontal surfaces measured were of fabric-based materials. It is likely that more reflective surfaces such as paper would result in higher values.