RESULTS
Visual Comfort Survey
The survey was completed during heavily overcast sky conditions on Jan. 23 by the six design sections that occupied the 3rd floor (Central) studio area. Figure 1 shows the drafting table arrangement in each section. The illuminance readings submitted on the evaluation forms are summarized below Figure 1, as average values along with the percentages of students who deemed the light quantity as ‘nearly’ or ‘completely adequate’ for the visual tasks surveyed. The measured data revealed interesting comparisons between the use of ambient and task lighting. Light adequacy responses remained fairly high with Task light ON/Ambient OFF; however, the perceived adequacy diminished with Task light OFF/Ambient ON. Given that students use task lamps whenever necessary, the responses suggest a reduction in the current artificial ambient level would not compromise visual comfort.
No consensus was reached as to the minimum daytime ambient light level
necessary for all visual tasks, as student opinions ranged from 15 to 25
footcandles. Clearly this is an issue that should be addressed on
a school wide basis involving all studio areas. For the purposes
of this case study 20 footcandles was selected as the minimum daylight
level, below which supplementary ambient lighting would be required.
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Winter and spring measurements were recorded on February 20 and April 17 from 12:00 noon - 2:00 pm. Coincidentally, on both days sky conditions varied from clear-to-partly cloudy and partly cloudy-to-overcast during intervals of the measurement session. All electric lighting was turned-off with the exception of scattered emergency fluorescent fixtures that were hot wired.
The recorded values are presented in the floor plan images below, Fig 2 - Fig 5 (For an enlarged view click on the desired image). Table II is a summary of this data conveyed as percentages of readings in various illuminance ranges
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Winter Readings:
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Spring Readings:
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The lowest daylight levels, 20 fc and below, occur in the East and West sections where no overhead monitor light is available. Supplementary ambient light is necessary for 65 to 85% of the workstations in those sections. The opposite is true for the Central section where daylight levels, 21 to above 40 fc, are recorded at 75 to 90% of the tables. A modest amount of supplementary light may be required in only a few areas of this section.
Fourth Floor
The admitted daylight levels are uniformly impressive throughout the studios. In the West and Central sections 79 to 90% of the readings fell in the 21 to above 40 fc ranges, due primarily to the extensive North glazing and roof monitor elements. The East section diminished slightly at 64 to 69% in the same footcandle ranges, as less North glazing is present. Supplementary ambient light is necessary in only a few selected areas.
The exposed waffle floor structure, columns, and in-fill masonry walls are painted a light beige color tone; the average surface reflectance is approximately 64%. White pinup boards adorn large areas of the interior walls at a 73% reflectance value. Light transmission through the 1/4" single pane glazing, used throughout the building, averaged at approximately 90%.
Circuit Layouts and Controls
Reflected ceiling plans with the electrical circuit boundaries are presented
in Figures 6 & 7. Placing a transparency of these drawings over
the daylight measurements, Figs. 2 through 5, reveals a ‘mismatch’ of numerous
circuits with the daylight performance in those studios. Other circuits
cover a comparable area but have a long, narrow configuration. These
observations generated many questions concerning how light level controllers
and occupancy sensors can effectively serve both day and night requirements.
There is clearly a need to address these issues in future studies.
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