The Journal of the Illuminating Engineering Society of North America: Volume 7 | Number 1 | July 2010

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The Public Perception of Lighting

LETTERS TO THE EDITOR

The article by Houser and others, ‘A Test of the S/P Ratio as a Correlate for Brightness Perception using Rapid-Sequential and Side-by-Side Experimental Protocols’ (Leukos, 6(2):119) is reviewed here with the intent of providing some understanding of why those authors have come to such different conclusions than Berman and others. We discovered that the authors have made a number of subtle, but important errors in their statistical analysis. There are also a number of misunderstandings in their application of trichromacy. Our re-analysis leads to conclusion that their data raises very interesting questions regarding brightness constancy and color effects, but does not support most of their claims regarding trichromacy.

SAVING ENERGY WITH HIGHLY-CONTROLLED LIGHTING IN AN OPEN-PLAN OFFICE

Francis Rubinstein FIES, Abby Enscoe

An installation in a Federal building tested the efficacy of a highly-controlled, workstation-specific lighting retrofit. The study took place in 86 cubicles in an open office with low levels of daylight. A direct/indirect pendant luminaire with three 32 watt lamps, two DALI ballasts, and an occupancy sensor provided both task and ambient light for each cubicle. All three lamps turned on and off according to occupancy on a workstation-by-workstation basis. Field measurements taken over the course of several months demonstrated 40 percent lighting energy savings compared to a baseline that represents a typical Federal building retrofit; the baseline has a lighting power density of 8.9W/m2 (0.83W/ft2) and no advanced controls. A photometric analysis found that the installation provided higher desktop light levels than the baseline did, while an occupant survey suggested that occupants preferred the lighting system to the baseline.

COMPARATIVE STUDY OF WINDOW GLASS INFLUENCE ON DAYLIGHTING IN AN OPEN-PLAN OFFICE

Jitka Mohelnikova

The design of buildings and their daylighting is associated with windows and their glass light transmittance in the response with external daylight conditions. The article presents results of a comparative daylight simulation study focused on evaluation of influence of different window glazings on daylighting in an open-plan office in an administrative building. A clear window glass variation was compared with solar control clear and tinted glass alternatives in the simulations. Daylight study was carried out for the investigated office with and without effect interior furniture.

EFFECT OF MECHANICAL VIBRATIONS ON COMPACT FLUORESCENT LIGHTING LUMINAIRES

JAYALAKSHMI PALADUGU*, DR. RAMA VENKAT**, PAOLO GINOBBI***

In this work, two types of commercially available compact fluorescent lamps (CFL) were investigated for intensity variation due to mechanical vibrations in the range of 0 to 30 Hz. In general, subjecting the lamps to 24-hour vibration affects the total intensity. Percentage variations of peak intensities after vibrations is in the range of + 10 to + 35 percent in case of CFL (Nuvue), whereas for the CFL (Ecosmart), it is in the range of -10 to + 10 percent. Continuous vibration measurements at various vibrational frequencies (intensity measurements at each frequency after subjecting the unit to mechanical vibrations for 10 minutes) show that the CFL luminaires, exhibits a peak in intensity at a vibrational frequency around 25 Hz for a wavelength of 546.78 nm (wavelength of maximum human sensitivity). Intensity variation effects due to vibration are attributed to the dropping off loose phosphor coatings in the inside wall of the glass enclosures. This hypothesis needs to be investigated further.