are · words or illustrations in books or maga-zines sometimes are much more easily. seen when the...

ED 037 943

AUTHORTITLEINSTITUTIONREPORT NOPUB DATENOTEAVAILABLE FROM

EDRS PRICEDESCRIPTORS

ABSTRACT

DOCUMENT RESUME

EF 004 115

Sampson, Foster K.Contrast Rendition in School Lighting.Educational Facilities Labs., Inc., New York, N.Y.TR-No-4Jan 70103p.Educational Facilities Laboratories, Inc., 477Madison Avenue, New York, N.Y.

EDRS Price MF-$0.50 HC-$5.25*Classroom Environment, *Classroom Research,Contrast, Glare, Illumination Levels, Lighting,*Lighting Design, Task Performance, *VisualEnvironment

Eighteen significantly different classroom lightingsystems were measured and analyzed in order to determine howcontrasts from different light sources affect the ability to seevisual tasks in the school room. Using criteria and techniquesestablished from previous lighting research, the lighting systems areevaluated according to their characteristics regarding contrastrendition of pencil handwriting. The comparisons and conclusionspresented should be helpful in selecting classroom lighting systems.(JD)

Con st Re ition in1 School Lighting

U,S, DEPARTMFAT OF HEALTH, EDUCATION& WELFARE

OFFICE OF EDUCATIONTHIS DOCUMENT HAS BEEN REPRODUCEDEXACTLY AS RECEVED FROM THE PERSON ORORGANIZATION ORIGINATING IT. POINTS OFVIEW OR OPINIONS STATED DO NOT NECES-SARILY REPRESENT ,OFFICIAL OFFICE OF EDU-CATION POSITION OR POLICY.

oat muell117

re% Educational Facilities Laboratories, Inc. is a nonprofitcorporation established by the Ford Foundation to helpschools and colleges in the United States and Canada with

Cr% their physical problems by the encouragement ofresearch and experimentation and the dissemination of

141 knowledge regarding educational facilities.

CO

U.1

board of directorsMilton C. Mumford, ChairmanChairman of the Board, Lever Brothers Company

Alvin C. Eurich, Vice ChairmanPresident, Academy for Educational Development, Inc.

Clay P. BedfordPresident, Kaiser Aerospace & Electronics

James C. Downs, Jr.Chairman of the Board, Real Estate Research Corporation

Henry DreyfussCorporate Advisor

Morris DuaneAttorney, Duane, Morris and Heckscher

Edwin D. EtheringtonPresident, Wesleyan University

Harold B. GoresPresident, Educational Facilities Laboratories

J. E. JonssonHonorary Chairman of the Board, Texas Instruments, Inc.

Philip M. KlutznickChairman of the Board,Urban Investment and Development Co.

Winthrop RockefellerGovernor, State of Arkansas

Howard S. TurnerPresident, Turner Construction Company

Benjamin C. WillisEducational Consultant(formerly General Superintendent of Schools, Chicago, HQ

officersHarold B. Gores, PresidentJonathan King, Vice President and TreasurerAlan C. Green, Secretary

staffGaila Coughlin, Copy EditorRobert M. Dillon, AIA, ConsultantLucille Gordon, LibrarianBen E. Graves, ConsultantPeter Green, EditorLillian Sloves, Publication AssociateMary C. Webb, Assistant TreasurerRuth Weinstock, Research Associate

Contrast Rendition inSchool Lighting

by Foster K. Sampson

acknowledgments

The following individuals were particularlyhelpful in the work and organization ofthis project, and I wish to express my grat-itude and appreciation: Mr. Ed Gustafsonfor his many hours of help in assisting withthe actual mechanics of the surveys, Dr.H. Richard Blackwell for his assistanceand counsel in the use of the test equip-ment, Mr. Charles D. Gibson for his co-operation and support in locating thedesired types of installations and in ob-taining the cooperation of the differentschool district officials, Mr. Bill Jones forhis discussions and counsel, and Mr. TedCross of Tacoma, Washington, for his as-sistance in locating the specific types ofinstallations in the Tacoma area whichwere needed to round out the selection ofsystems.

I would also like to express my appre-ciation to the many school district offi-cials, principals, and teachers, all ofwhom went out of their way to cooperateand provide facilities to make the surveypossible.

Foster K. Sampson

Library of Congress Catalog No. 70-112052First Printing: January 1970

Additional copies are available fromEducational Facilities Laboratories477 Madison AvenueNew York, N.Y. 10022

tableof

contents

Foreword 7

Introduction 9

Procedure 14

Projects 1-18

Conclusion

Appendix

17-88

89

94

foreword Most lighting research is done in labora-tories where hypotheses are drawn, the-ories developed, and reports written.Some of the theories are applied to designpractice, but few are checked or chal-lenged by field research conducted withthe same competence, instrumentation,and sophisticated procedures as thoseused in the laboratory. Fortunately, FosterSampson's work, which he describes inthis publication, is one of the rare excep-tions to this rule. His field research on thebasic elements of lighting for effectiveseeing should be the forerunner of morefield investigations to check the perform-ance of lab-born theories.

The organization of the study reflectsmeticulous care in data gathering. Scien-tists and research-minded engineers willfind detailed reporting of lighting levelsand distribution, luminance patterns, con-trast rendition factors indicating the light-ing effectiveness of the various installa-tions studied, and other information ofinterest. They will also find relatively newresearch terminology explained and ap-plied. Architects, application engineers,and facilities planners will find compara-tive data on the lighting effectiveness ofa wide variety of luminaire installations.From such data they will be able to evalu-ate the effectiveness of their favorite lightsources and installations better. it is to behoped they also will find the informationthey need to improve their future lightingdesigns.

There has always been a concerned in-terest inside and outside of laboratoriesabout how light could both help and hinderseeing. By far the greatest research andapplication thrust has been toward thepositive aspects of light and seeing - - "themore the better." Foster Sampson inves-tigates the possible negative aspects oflight and seeing. Is the amount of light onthe task the real answer to effective see-ing? Are there such things as good andbad footcandles? Can visual performancebe adversely affected by large or smallamounts of the wrong kind of light? If so,what is the wrong light? How can it becontrolled or eliminated? He also posesother questions such as: Is it possible, withproper competence and instrumentation,to discover more about the positive andnegative relationships of light and seeingin classrooms with a wide variety of lightsources and installation patterns? Arethere a number of factors that must bedetermined, measured, and interrelatedbefore a valid judgment can be madeabout the effectiveness of any given light-ing installation? How valid are some ofthe older theories used to evaluate light-ing installations, such as the brightnessratio formulas espoused by the NationalCouncil on Schoolhouse Construction(now Council of Educational Facility Plan-

ners) some 25 years ago? Can researchfindings reported in proper and accept-able scientific language be made under-standable to the lay public concerned withthe results?

Everyone knows by experience thatwords or illustrations in books or maga-zines sometimes are much more easilyseen when the top of the book or maga-zine is tilted upwards. They may or maynot know that by tilting the reading taskthey are redirecting the reflections oflight sources, increasing the contrast be-tween the print and the background pageand making the task easier to see. In itssimplest terms, this study investigated thesame seeing problem.

This investigation was carried on in 18classrooms located in Washington andCalifornia. Each classroom laboratory wasselected to add to the variety of luminairetypes and installation patterns. The over-all selection represents PA high quality ofschool lighting as it would be found acrossthe United States today. The finest avail-able laboratory-refined instrumentationwas used by a researcher who understoodthoroughly both the problem and theprocess.

The data in this report could be used tochange the order of priorities in many edu-cational facilities budgets. We can deducethat the cost of a lighting system does notindicate its effectiveness in terms of see-ing a task accurately, comfortably, andquickly. Also, we can infer that the extralights in an inefficient lighting system willraise operating costs through consumingmore electrical power and raising theroom temperature which in turn increasesthe air-conditioning load.

When architects and engineers beginapplying the information gathered in thisstudy to the design of lighting systems foreducational facilities, they may discoverthe happy fact that they can produce bet-ter seeing conditions for less money. Afterrecovering from shock, all the peopleconcerned with a building project mightspend some pleasant moments redistrib-uting some of the electrical and mechani-cal budget into such features as air con-ditioning and individualized audio-visualteaching aids.

Charles D. GibsonChief, Bureau of School PlanningCalifornia State Department of EducationandChairman, Executive CommitteeIlluminating EngineeringResearch Institute

introduction

The purpose of this study was to deter-mine how the contrasts in light from differ-ent sources affect the ability to see visualtasks in schoolrooms. How well the con-trast on a visual task is rendered is calledcontrast rendition, and by comparing itwith a controlled lighting situation we canassign a numerical Contrast RenditionFactor. So far, no one has developed thescience of lighting far enough to calculatecontrast rendition factors during the de-sign of a building. But it is hoped that thisreport will help to establish guidelinesthat will eventually enable designers tocompute the effectiveness of lighting in aschool before it is built.

For many years, school authorities,architects, and engineers have made every

effort to provide adequate and comfort-able electric lighting in the most efficientmanner which would be in keeping withthe architecture and the budget for newconstruction. In almost all new installa-tions, the levels of illumination are ade-quate to meet current standards, interiorcolor selections took brightness ratios intoconsideration, and glare from unshieldedwindows was recognized and treated inone way or another. The loss of visibilitydue to veiling reflections was also recog-nized as a problem, but there were nomethods to evaluate these losses accu-rately in actual installations, and conse-quently the problem was not given theimportance that is now evident as the re-sult of this study. It can now be shownthat many systems in common use are lessthan 20% effective in terms of adequate"glare-free" illumination.

The amount of light directed toward theside walls by many systems provides lessthan good chalkboard lighting, and theresultant dark walls seriously reduce thevisibility of pencil handwriting by not re-flecting light to the task. Although thereare advantages in the use of carpeting,the dark colors being used often exag-gerate an already poor situation. Whererecessed luminaires are used, the ceilingbrightness depends almost entirely uponlight reflected from the floor, and darkcarpets often cut ceiling brightness by50% when compared with similar roomswith light-colored tile floors. Dark ceilingsare not desirable because of the discom-fort due to high brightness differences be-tween the ceiling and lighting fixtures andthe bad effect on the visibility of pencilhandwriting. In most of the rooms tested,the level of illumination four feet fromthe side walls was less than 50% of thatfound in the_ center of the room, and atleast three benefits accrue for the sys-tems where more light was placed aroundthe periphery of the room:1 The level of illumination was much

more uniform.2 The side wall and chalkboard lighting

was much better.3 The increase of light reflected from the

sides of the room made a marked in-crease in the visibility of pencil hand-writing.

The early recommendations for schoollighting stressed the need for adequatelevels of illumination for safety and easeof seeing. Even as I Ate as 1930, the primeconsideration was toe level of illumination,and at that time only 15 to 20 footcandleswas being suggested. The importance ofquality was recognized by some broadguidelines which were provided to assure"comfort"

New light sources were developed andinstalled in systems which produced muchhigher levels of illumination. Usually the

new systems used more fixtures, of higherbrightness than in previous installations,and many occupants of these rooms be-came highly conscious of the discomfortand distraction from these glaring lumi-naires, particularly those near the line ofsight. As a result, there was considerablediscussion and study of this problem, andseveral similar but slightly different con-cepts of limitations were expressed interms of brightness values for luminairesand brightness ratios based upon task andsurrounding brightnesses.

Many architects, educators, and engi-neers came to recognize the value ofbrightness control for all areas in whichcritical seeing was done, and there weremany who considered this aspect of "qual-ity" to be more important than quantity.The need for flexibility ir both quantityand quality was also recognized for thosesituations in which "seeing" was not criti-cal.

In 1959, Dr. H. Richard Blackwell, anindependent researcher in the field of lightand vision, presented the results of hisyears of study at the University of Michi-gan under grants from the IlluminatingEngineering Research Institute. Althoughit took time for the people concerned withillumination design to understand the com-pletely new research techniques and toaccept his work, it was finally recognizedas being more important than all previouswork in this field. In order to apply hisfindings to the practical problems of howmuch light was necessary for critical see-ing, Dr. Blackwell developed the "VisualTask Evaluator" to make visual assess-ments of specific "tasks" and relate themdirectly to his research findings. From thisinformation, Blackwell could determine apositive level of footcandles.

Many of the findings came as a surprisebecause of the wide differences in re-quired levels for common school and of-fice tasks.

For example:Task FootcandlesInk handwriting 1.48-point Bodoni type 1.98-point Textype 1.1

Typed original, good ribbon 1.0Transcribing #3 pencil shorthand 76.5Typed carbon, fifth copy 133.0Thermal reproduced copy,

poor quality 589.0

Samples of pencil handwriting weretaken from a group of schoolchildren. Itwas found that they illustrated a wide va-riety of characteristics from large to smallin size and from dark to light in contrast,and the average sample required 63 foot-candles of glare-free illumination. By defi-nition, glare-free illumination results froma uniformly lighted hemisphere over thetask. Because pencil handwriting is a com-

monly found, difficult seeing task in aclassroom, it has been accepted by manyas the basis for recommending 70 foot-candles for classroom lighting.

At about this time, a task committeewas made up of representatives of theAmerican Institute of Architects, The Na-tional Council on Schoolhouse Construc-tion, and the Illuminating EngineeringSociety. This committee was engaged ingathering information and rewriting theIlluminating Engineering Society "Recom-mended Practice on School Lighting," andone team working with John Chorlton ofToronto, Canada, made tedious and pains-taking measurements of the loss of con-trast in pencil handwriting under differentlighting systems. The purpose of this studywas to find a way to make these measure-ments and report on visibility losses dueto veiling reflections. It was found that thebasic research data was clear in showingthat each 1% loss in contrast required a15% increase in illumination, if the char-acteristics of visibility were to be main-tained equal.

Precise laboratory measurements weremade, using pencil dots as the target, andthese studies indicated that losses of con-trast might easily exceed 20% under somelighting systems. Interpreting these factsinto the required levels of illumination fordifferent systems meant that even thebest lighting systems would have to pro-duce much more than 70 footcandles, andthe poor ones would require several timesthe glare-free requirement, just to com-pekisate for the contrast losses due toveiling reflections caused by the lightingsystem.

This development created a stir withinthe lighting and design industry. Othermen in the design and engineering fieldmade crude measurements and presentedpapers proving the importance of thisconsideration. The photographs in Figure1 illustrate the losses in contrast for sev-eral visual tasks under three distinctlydifferent and extreme conditions of I;ght-ing. Through the process of preparingpencil targets and making gross measure-ments, it was soon recognized that com-mercial photometers available at that timewere not capable of making accuratemeasurements using the Visual Task Eval-uator under the same lighting system.

These findings made three major ad-vancements mandatory before accuratetesting of existing systems could begin. Aphotometer and the mechanical deviceshad to be developed which would allowand provide accurate readings of the"background" paper and the "target" areaat several viewing angles. Second, thelarge, heavy, and complex Visual TaskEvaluator had to be simplified and madeportable if it was to be a useful field instru-ment. Third, a standard pencil target had

A

D 11MININIt

ey have colthehe

Figure 1The five samples were photographed underthree distinctly different lighting systems.The left hand column had a single lightsource at the critical angle over the task;the center column was under the glare-freelighting of a uniformly bright hemisphereplaced over the task; and the right handcolumn was lighted from a single lamplocated behind the line of sight of the cam-era. The target on line A has two circlesmade with a nylon tip pen and two circlesof #2 pencil on soft paper. Line B is theactual target used in the photometric equip-

r- A

mimic is tniE the ssIlye an. in rw1

ey have cditive broth(:plines, thement for the contrast rendition valties.These are very carefully and accuratelymade pencil lines in concentric circles.The target on line C is a pencil hand-writing sample with the same contrast andspecularity characteristic as the target im-mediately above. The printed target online D is glossy ink on glossy paper, andthe target on line E is reasonably matte inall respects.

The following observations can be made.The apparent visibility of all tasks in thecenter column is very good, and there areno serious losses due to the uniform over-

/AL

11141L1111

head light source. The right hand columnclearly shows that pencil lines in particularare made easier to see by concentratingthe light from the sides and behind insteadof from overhead. The left hand columnaccentuates the losses from light at thecritical angle. The only two target elementsthat show no serious loss are lines A andE. The nylon tip pen target and the matteblack ink on soft paper show very littleloss of visibility. All the pencil targets andthe glossy printing sample have virtuallydisappeared. In fact the black glossy inkactually appears brighter than the paper.

12

Figure 2 Visual Task Photometer

to be developed which would have thesame contrast and reflective characteris-tics as handwriting, and a method had tobe devised by which this standard couldbe reproduced so that more than one couldbe made available for other researchers.

The difficulties encountered in develop-ing all of the instruments and target sam-ples were numerous; however, the devicesand refinements were in a continuing stateof improvement, and laboratory reportsand research findings kept the industryinformed of the progress. As the instru-ments and targets were refined, visualevaluations using the Visual Task Evalua-tor and contrast measurements using theVisual Task Photometer were made underdifferent lighting systems, and it has veryrecently been established by Dr. Blackwellthat the contrast measurements do agreewith the findings of studies made with theportable Visual Task Evaluator.

The Visual Task Photometer, Figure 2,is a sophisticated combination of a pho-tometer, with meters, balancing electricalcircuits, and a mechanical support for thephotometer, and "task" target. The pho-tometer is supported on a pivoted armwhich can be moved in a vertical plane,and a scale is built in to indicate the "view-ing angle" which can be established from0°, or straight down, to 60° from the ver-tical. At all viewing angles, the photometeris directed at the same small area on thetask carriage. The task is a pattern of con-centric circles drawn with a pencil onwhite paper mounted on a rigid plasticbacking which can be carefully protectedwhen not in use but which can be securedto the carriage for making measurements.When the "background" button is acti-vated on the meter turret, the carriage po-sitions the task so that the backgroundpaper is exposed to the photometer. When

the task button is activated, the carriagemoves automatically to expose the penciltask to the photometer. In making an eval-uation, the entire meter with all of itscomponents is set in the desired location inthe room, and all the circuits are checkedand balanced. By careful operation of themeter complex, a direct reading of theflux contrast is obtained. At least five read-ings are made for each condition, andthese values are then averaged. The Con-trast Rendition Factor (CRF) is determinedby dividing the flux contrast for the testcondition by the flux contrast found atthe same angle of viewing when lightedby a hemisphere of uniform brightness. Inother words, if the flux contrast underglare-free lighting is considered to be100%, then the CRF is the percentage ofglare-free lighting developed under thetest condition.

The author has had a continuing interestin the subject of school lighting in generaland contrast rendition in particular, so,when it appeared that equipment would be

available for field use, application wasmade to Educational Facilities Laborato-ries for assistance in conducting a fieldstudy and publishing the results. Fortu-nately, the project was accepted.

At this time there were only five VisualTask Photometers in existence, and againthe author was fortunate in having onemade available from Dr. Blackwell. TheIlluminating Engineering Research Insti-tute has been the prime supporter of re-search and development of instrumentsfor this phase of illumination, and it wasfrom this organization that funds weremade available for the rental of the in-strument.

It is the purpose of this survey to makemeasurements of contrast rendition undera wide variety of classroom lighting sys-tems in order that comparisons can bemade and conclusions drawn which willbe helpful to educators and engineers intheir selection of future classroom lightingsystems.

procedure

The prime objective of this survey is theevaluation of significantly different class-room lighting systems to determine theircharacteristics regarding contrast rendi-tion of pencil handwriting. In order thatthe recorded information can be studiedin detail and comparisons made, severalrelated aspects of the total environmentwere considered essential. For this pur-pose drawings, tables of illuminationlevels, tables of brightnesses, and photo-graphs, as well as Contrast RenditionFactors are provided for each project,starting on page 17.

The classrooms studied are identified bya project number and the basic lightingsystems are as follows:

Project 1

Project 2Project 3

Project 4

Project 5

Project 6

Project 7

Project 8

Project 9

Project 10

Project 11

Project 12

Project 13

Project 14

Project 15

Project 16

Project 17

Project 18

Single-lamp, surface-mounteddiffusers, 12" wide in continu-ous rows, 5'-0" on center.Polarizing luminous ceiling.Four-lamp, surface-mounted,lens wraparound, 16" wide: incontinuous rows, 10'-0" oncenter.Semi-indirect, perimeter type,suspended, using very highoutput lamps.Wall-mounted coves, usingvery high output lamps.Luminous coffers, 5'-0" square,each using two lamps, shield-ed by plastic diffuser.Single-lamp troffers, 24" wide,diffusing panels, continuousrows 4'-0" on center.Six-lamp, 48" square, surface-mounted, lens bottom unit%10'-0" on center, both ways.Luminous ceiling with vinylplastic diffusers.Four 11'-6" square coffers, in-directly lighted by coves onthe side of each coffer.Two-lamp, surface-mounted,13" wide, lens wraparound incontinuous rows, 7'-0" oncenter.Two-lamp troffers, 24" widelens panels, continuous rows,6'-0" on center.Two-lamp, semi-indirect 13"wide, plastic wraparound lens,in continuous rows, 7'-0" oncenter.Four-lamp, recessed, 5'-0"square diffusing panels incheckerboard arrangement.Two -lamp, recessed, 24" wide,lens panels in a continuousperimeter pattern with a sin-gle group of units in the centerof the rectangle.Two-lamp, recessed, 12" wide,lens panels, in continuousrows, 7'-0" on center.Two-lamp, surface-mounted,13" wide, lens wraparound, incontinuous rows, 10'-0" oncenter.Two-lamp, high output, sus-pended, semi-indirect, in con-tinuous rows 10'-0" on center.

A scale drawing of each project class-room shows the floor plan, each of thefour side walls laid flat beside the relatedside of the plan, and the reflected ceilingplan. Each location at which a measure-ment was made is shown by a dot on thedrawings, and each dot is identified by anumber. Numerals from 1 to 24 are en-

closed in circles, and these establish thepositions at which levels of illuminationare recorded. Numerals 25 and aboveare enclosed in hexagons and indicatethe locations of brightness readings. Posi-tions of the Visual Task Photometer areshown as M1, M2, etc. They are enclosedin triangles with the apexes pointing to thedirection of viewing. The meter positionand direction of viewing is shown on theceiling plan to show the relationship withthe luminaires.

Levels of illumination were recorded for13 locations within the normal seating areaof the classroom and in two or more loca-tions on chalkboards. Three sets of read-ings are reported across the room, the firstset is 4'-0" from the front of the room, thesecond is across the center of the room,and the third is 4'-O" forward of the rearwall. Each of the three sets has three loca-tions, one at the center of that aroup andone at each end, 4'.-0" in from the sidewalls. These are numbered 1 through 9.Another set of four readings, numbered 10through 13, are located on the quarterpoints of the diagonals of the room. These13 readings were taken 30" above the floorand with the meter placed horizontally ona tripod. Readings on chalk-and tackboardwere 5'-0" above the floor and in a verticalplane.

In some projects, the quantity of day-light was so low that all readings weretaken including the daylight, but this smallcontribution was ignored because it didnot affect the basic results of this survey.Some rooms had relatively large windowareas, but were so shielded by arcadesand adjacent buildings that the blackoutcurtains were closed and the results shownonly for the electric system. Where day-light was available to provide a reasonablelevel in itself, readings were made underthree situations; daylight only, electriclight only, and with a combination of thetwo. Where multiple conditions of lightinglevels are reported, readings were usuallymade under the same circumstances forbrightness and contrast rendition.

Brightness readings were taken with aSpectra Spot meter which covers an areaof 3" at 10'-0", and the brightness is readdirectly in footlamberts. The meter wasmounted on a tripod at seated eye height,and all readings were taken from a loca-tion in the center of the room and about6'-0" from the rear wall. The number oflocations at which readings are recordedvary, depending upon the character of theroom and lighting conditions. In the tableof "Brightness Distribution" for each proj-ect, the location of each reading is furtherdescribed with the character of the sur-face, its color, reflection factor, and actualbrightness in footlamberts. In each case,the reflection factor was computed froma direct brightness reading taken on a

surface of known reflection factor, and thedirect reading from the surface itself. Al-though this is not considered "accuratelaboratory practice," the error is not sig-nificant so long as values are recognizedas approximate rather than absolute.

Readings with the Visual Task Photo-meter were taken near the center rear ofthe room. The meter position "Ml" wasfrom 6'..0" to 9'.-0" feet from the rear wall inthe approximate center of the room, andthe photometer was located so that the"mirror image" of a lighting element felldirectly on the task when being viewed at25°. Meter position "M2" was at the samedistance from the rear wall, but the meterwas moved sideways to a point where themirror image falling on the task, whenviewed at 25°, was a point on the ceilingarea halfway between rows of fixtures orlighting elements. Where unusual circum-stances required a variation in this pro-cedure, or additional locations are re..

ported, a description of the meter positionis given as well as the reason for thevariation.

Many studies have been made to estab-lish the most commonly found viewingangle for tasks on a desk or table top.These angles are found to vary with in-dividuals and with the nature of the workbeing performed. However, the most com-mon angle is very close to 25°, and for thisreason 25° has been chosen for the primeangle of consideration. On the other hand,viewing angles as low as 40° from thevertical are not uncommon, and these weremeasured and reported for the benefit ofanyone who might want to extend thecomputations. Viewing angles of 60° aresometimes found, but the general con-sensus is that the factors of visual distor-tion of the task, and the greatly increasedviewing distance, are far more importantthan the loss of contrast at this low angle.

Photographs were made from at leasttwo locations to show the basic characterof the room and to give an approximateidea of the ranges of brightness found inthe space. By studying the drawings,photographs, and tables of "BrightnessDistribution," a good idea can be devel-oped of the total visual environment.

A photograph into a spherical mirror ispresented to give an idea of the brightnessdistribution in the entire space in one ex-posure. For this picture, the camera wasplaced about 5'-6" above the mirror, whichwas on a horizontal table top in the centerof the room. The image is distorted but therange of brightness and relative positionsand sizes can be approximated.

To show the quality of shadow and formrendition by each system, a group of geo-metric forms was photographed on a desklocated in the center of the room. Thecube is 11/2" on each side, the cylinder is11/2" diameter and 11/2" long, the hemi-

15

sphere is 2" diameter, and the 1/4" dowelsare 7" long. All are painted gloss white.The minimum shadow is shown to existunder systems of luminous ceilings andindirect lighting, and the maximum shadowis formed where luminaires are small orwidely spaced, or both. Shadows do formunder the dowel rods when they lie paral-lel to continuous rows of direct type fix-tures, yet the shadow is not apparentwhere rows of fixtures are at right angles.

In each room, the pencil handwritingsample "ark" was photographed at a 25°viewing angle at the M1 meter position.This is probably one of the poorer loca-tions in the room except possibly for loca-tions on the extreme edge or in corners.The M1 position is selected so that reason-able comparisons can be made betweensystems. The same task has been photo-graphed under a luminous hemisphere,and a print is shown beside each projectphoto for visual comparison. The prob-lems of making accurate comparisons ofcontrast rendition by photographic proce-dures in the field are too numerous; how-ever, this might be possible under theextreme controls which are possible in thelaboratory. The difference in contrast ren-dition in the photographs may not be im-mediately seen in all of the examples;however, the gross losses developed bythe poor systems are immediately obvious.

Three values are shown with each proj-ect, for each meter position, with electriclight, and in some cases additional valuesare shown for other combinations of day-light and electric light. Task Illuminance(TI) is the actual level of illumination infootcandles measured at each positionand under each lighting condition. Con-trast Rendition Factor (CRF) is the valueestablished by the Visual Task Photo-meter, shown in Figure 2, and this valueis the measure of capability of the installa-tion to render contrast as compared withthe quality of illumination within a uni-formly illuminated sphere. The CRF de-pends upon several variables, such as thephysical size of the light source, the char-acter of light distribution, and the locationof the sources in relation to the task. Thethird factor, Equivalent Sphere Illuminance(ESI) is the level of glare-free or sphereillumination which would provide the samedegree of visual accuracy as that devel-oped by the installation being surveyed.In Project 1 for example, at the M1 posi-tion the system provided a T1 of 62 foot-candles under the electric lighting, theCRF was found to be .882 and the ESI wasequal to only 27.6 footcandles of sphereilluminance. These three values, whentaken together, allow several basic com-parisons between installations.

The measurements were all made withcare and precision, and they are correctfor each particular test roo . The sa e

lighting system in another room will pro-duce very nearly, but not necessarily ex-actly, the same effects. The differenceswould result from variations in the roomsize, and the reflectance of walls, ceiling,floor, and furniture. The extreme differ-ences found in the ESI values show thewide variations in basically different sys-tems. However, care should be taken notto draw too fine a line between installa-tions which produce nearly comparablevalues.

project 1description

The room is 24'-0" wide, in excess of36'-0" long, and the ceiling height is 9'-6".The drawing includes one end of the room,and the test locations were selected tosimulate a 30'-0" long room. The lightingconsists of continuous rows of five 12"wide, surface-mounted diffusers, with rowsspaced 5'-0" on center. Each luminaire hasone 40-watt rapid-start lamp. There arelarge, clear glass windows facing northand equipped with blackout curtains. Thelevels of illumination are given for theelectric lighting, day lighting, and thecombination of the two.

Wall Elevation

Reflected Ceiling Plan

(---- Wall Elevations

Floor Plan

The uniformity of electric lighting levelsin this space is excellent, and probably re-sults from the relatively large number ofsources and the fact that they cover welltoward the side walls.

The environment brightnesses are quiteacceptable except for the unusually darktackboards, chalkboards, and blackoutcurtains. The contribution of daylightingimproves the brightness balance exceptfor the extreme brightness of the un-shielded window exposure to the northsky.

lightinglevels

Location

'-M1

Electric

Footcandles

Daylight Combination1 69 24 932 66 28 943 57 25 824 75 37 1125 74 63 1376 69 37 1067 66 90 1568 60 160 2209 51 46 97

10 78 30 10811 72 29 10112 72 105 17713 66 90 15614 45 66 11115 51 36 8716 51 45 96

_A_

1.1000 Ai%

brightnessdistribution

19

Footlambert BrightnessReflection

Location Surface Color Factor Elec. Day Comb.

25 Tackboard Tan Burlap 31% 15 18 33

26 Chalkboard Green 15% 7 16 23

27 Tackboard Slate Green 13% 6 8 14

28 Paint Cream 55% 20 30 50

29 Paint Cream 55% 20 35 55


31 Paint Cream 55% 25 26 51

32 Window to corridor 25 25 50



35 Paint Cream 55% 19 22 41

36 Tackboard Slate Green 13% 10 6 16

37 Paint Cream 55% 34 17 51

38 Paint Cream 55% 21 10 31

39 Blackout Curtain Green 6% 25 MEM= OM=

40 Paint Cream 55% 22 19 41

41 Acoustic Tile White 80% 17 19 3642 Acoustic Tile White 80% 20 28 4843 Fixture Diffuser 280 - 30044 Fixture Diffuser - 390 MIMS 41045 Fixture Diffuser 350 OM. 37046 Fixture Diffuser 360 38047 Desk Top Birch Formica 37% 22 51 7348 Floor Oak Wood 38% 10 20 3049 Window MIINM 1750 1750

project 1evaluations

The ESI values are all fairly low in spiteof good CRF, and this is due to the low

Quality Location level of the general lighting. The differ-ence between M1 and M2 is reasonablysmall, no doubt due to the relatively closespacing of the rows. Although the differ-ence between M1 and M3 is very small,this is some indication that rows of lumi-naires transverse to the line of sight causesomewhat less toss than those in line. Thisis also verified in Project 3.

The addition of daylight makes a re-markable improvement in the ESI wherethe line of sight is away from, or at rightangles to, the direction of the windows. Noreadings were taken to simulate childrenlooking towards windows because theveiling reflectances would be bad and thediscomfort even worse.

TI (electriconly)

M1

62

M2

61

M3

69CRF .882 .925 .892

ESI 27.6 35.8 32.1

TI (electric &daylight) 172 188 106

CRF 1.03 1.05 1.00ESI 220.8 279.2 106.1

Sphere Quality Project Quality

projectdescription

The room is 28'-6" x 31'-0" and the ceilingis 8'-0". The lighting system is a luminousceiling of polarizing plastic. The luminousarea is 24'-O" x 26'-0" made up of 2'4"square panels on T bars. There are 12strips of 3, 96", 430 m.a. cool white, slim-line lamps mounted 16" above the diffusers.The plenum space immediately above thelamps is lined with aluminum foil-facedkraft paper. Two sets of illumination levelsare shown here, one with daylight only,and this is supplied through the three 2'4"high x 5'-0" wide windows set high in thenorth wall. Each window is glazed with lowtransmission glass to reduce the directglare from adjacent buildings. The quan-tity of daylight is so small that it has littleor no effect on contrast rendition.

Wall Elevations

11111111111111111M111111111.11111111111111111M1111111111111111

11111111110EMMEI1111111111111111111111111111111

1111111111111111.1111110111111111111

11111111111111 imac e111111111111011131111111111111111111111111111-21=11111111111111111111M11111111111111111111111111111=111111111111111111E


-0 @)-*-0

Floor Plan

21

Wall Elevations

The uniformity of lighting levels in thisroom is not particularly good in that thefour corners are only about 55% of maxi-mum. Had the luminous area been runcloser to the side walls, and had the sidewalls been finished in colors of higher re-flectance, the lighting around the periph-ery would have been better. The front wallin particular has dark chalk- and tackboardover the entire surface above the 30"-highchalk rail.

The fact that so little light falls upon thewalls makes the entire room appear tohave low levels of illumination. Even thosesurfaces with light-colored finishes barelymeet the minimum brightness recommen-

lightinglevels

dation, based upon task brightness at theM1 position.

The use of low transmission glass in thesmall windows was good in that the win-dows would have been a glare source hadclear glass been used. Also, the floors areparticularly good, and the high reflectancehere was of considerable value in bright-ening the room. The large luminous ceilingarea was exceptionally comfortable. Themost restrictive of current "vecommenda-tions" will accept a large area source ofhigh brightness which does not exceedthree times task brightness. In this project,the maximum brightness occurs directlyoverhead and, even at this extreme angle,it is considerably below the allowablebrightness limit.

"e

Location

Footcandles

Daylight Day and Electric1 .4 692 .8 79

3 .8 66

4 .6 105

5 1.6 120

6 1.5 967 .4 668 1.6 85

9 2.4 6910 .6 10211 .9 9912 1.0 111

13 2.2 105

14 4MII 4215 MI= 4516 MONO 42

('


obt

IMMEMMII +11

Reflection FootlambertLocation Surface Color Factor Brightness

25 Vinyl Tackboard Blue Grey 22% 8

26 Chalkboard Slate Blue 19% 8


28 Vinyl Wall Blue 45% 10IQ


30 Acoustic Tile White 75% 21



33 Vinyl Tackboard Blue Grey 22% 1034 Painted Brick Green 65% 2935 Sky thru Glass (14% transmission) 22536 Painted Door Green 62% 2037 Wood Cabinet Natural Birch 22% 1538 Vinyl Tackboard Blue Grey 22% 939 Acoustic Tile White 75% 3040 Acoustic Tile White 7t)% 3041 Light Polarizer White MINIM 4542 Light Polarizer White 101 5543 Light Polarizer White 111 6344 Light Polarizer White 11111111.1 10045 Light Polarizer White 111 14546 Light Polarizer White 8547 Vinyl Floor Grey 43% 3348 Desk Top Birch 46% 41

24

project 2evaluations Quality Location

M1 M2 M3

TI 100 115 118CRF .900 .939 .932ESP 46.1 72.6 70.0

Sphere Quality

Only four projects had higher ESI valuesat the M1 position, and this project wouldhave had a much better rating if three fac-tors were different. The luminous portionof the ceiling should have been extendedto the wall to provide light on the wall. Alsothe wall colors above the chalkboard lineshould be nearly white, and all tackboardsshould have been as high in reflectance aspossible. The effect of the extremely darkfront wall is seen by the reduction of ESIvalue at M3 as compared with M2.

Project Quality

p roject 3description

The classroom is 29'-0" x 29'-6", and theceiling height is 9'-0". The lighting systemconsists of three rows of six, 4'-0" plastic,lens-type wraparound units, surfacemounted. Each luminaire has four lamps;all of the outside pairs of lamps in eachluminaire are switched together, and all ofthe center pairs of lamps are separatelyswitched. The large windows are coveredwith Venetian blinds. The only daylight inthe room comes through two small tran-som windows close up under a projectingeave. sere are small glass areas high onthe opposite side which look into the cen-tral corridor of the building. Daylight read-ings shown in the table have all room lights"off," but this does not include the contri-bution of the corridor lighting. The illumi-nation in this room from any source otherthan the electric system is so low as tohave no effect on the contrast readings.

CISINV

NM EMI:._ It 4'MI

. --@C

PI' 4:11)

.../if a.0'

41

...:at1.)


4-- Wall Elevations

25

Wall ElevationsElevations -->

Floor Plan

,Iffr

r

From the table of illumination levels itcan be seen that there is little or no differ-ence in the quantity of illumination pro-duced on the horizontal by the inner andouter pairs of lamps. However, the outerpair should, and does, produce a some-what higher level on the chalkboard. Thisroom has only 856 square feet, thereforethe degree of uniformity is somewhathigher than it would have been with thesame number of luminaires in a larrprroom of 960 square feet. Four lamp unitswere used to provide added heating whenrequired, and only two lamps are normallyused during "%arm" weather.

The chalkboards and tackboards havelow rzflection factors, and together theyadd up to quite large areas of too dark

lightinglevels

space. The natural brick surfaces add tothe already dark surround. Any one ofthese surfaces, taken alone, might not beobjectionable; however, the three togetherdevelop a dark environment for the brightlens luminaires which are in themselvesquite bright, particularly the sides of theunits when the outside lamps are used.All brightness readings in this room weretaken from the M4 position. This roomdemonstrates the need for lower bright-ness ratios at higher levels of illuminationbecause it is said that the system is sel-dom used with all four lamps because ofthe high luminaire brightness. A look atthe Brightness Distribution table showsthat the luminaire brightness is somewhatless than double with all four lamps, andthe level of illumination is double.

StationDaylight

Only

FootcandlesCenter Rows Outer Rows

of Lamps of LampsDaylight plus

All Four Lamps1 4 81 84 1692 1 114 117 2323 1 81 81 1634 2 98 99 1995 1 129 128 2586 1 93 93 1877 3 88 86 1778 1 114 114 2299 1 78 75 15/1.

10 3 105 102 21011 1 102 99 20212 3 99 99 20113 1 96 91 18814 4 47 47 9815 2 54 59 11516 2 47 52 101

Zti

-..1011r

1.1111101111111


Location Surface ColorReflection Ctr.Factor Pair

Foot lambertBrightness

OuterPair

BothPairs

25 Painted Ivory 80% 32 43 72

26 Chalkboard Grey 24% 13 14 25

27 Painted Ivory 80% 42 45 82

28 Tackboard Tan 34% 15 18 30


30 Brick Umber 18% 7 7 14



33 Door Natural Birch 26% 9 10 15


35 Cabinet Natural Birch 26% 15 15 26

36 Cabinet Natural Birch 26% 19 19 32


38 Venetian Blind Cream 57% 22 25 42


40 Plaster Soffit seenthrough window 70

41 Luminaire 350 500 800

42 Acoustic Tile White 80% 37 68 120


44 Luminaire (Bottom) 750 610 1100


46 Desk Top Natural Maple 35% 40 40 70

47 Vinyl Floor Green Grey 35% 32 35 62

In this project, four task positions werestudied. At M1 the task was located di-rectly under and in line with a row ofluminaires, and M2 was halfway betweenrows. M3 was located so that the line ofsight to the task was at right angles to thecenter row of luminaires, and the lumi-naires were 25° forward of the task. M4

111111i AN=

was in the same relative position with re-gard to the direction of rows; however, thetask was moved back so that the ceilinghalfway between rows was 25° forward ofthe task.

The M1 position does not follow theusual pattern in that it is to one side of theroom instead of to the rear. This change

Quality

(inside pair lamps)T1

CRFESI

(both pair lamps)TO

CRFESI

TICRFESI

M1

LocationM2 M3

108 92.749 1.00

17.8 91.9

215 185.758 1.00

28.4 185.3(outside pair lamps)

107.764

18.5

M4

125 118.822 1.01

31.5 127.8

250 235.831 1.03

58.1 308.3

125 _.830 -- 33A

27


was made because other rooms with rowsof luminaires almost invariably run fromfront to back. Also, because of the spacingof the rows, it was not possible to get backfar enough behind the rear row to place itin the desired location in relationship tothe Visual Task Photometer. M3 is theclosest approach possible to the "stan-dard" M1 position; however, this M3 ismuch farther into the center of the room.

The results are reported here for all fourmeter locations, both angles of viewing,and for the inside pair of lamps as well asall four lamps. A close study of thesevalues shows that contrast rendition is nota function of lighting level. The CRF forM1 at 25° is slightly less with the centerpair only than with all four lamps. Thesame trend shows for M3 at 25°, and thesedifferences, although slight, are probablydue to the slightly larger area of bright-ness of the luminaire and the ceiling in thecase of the four-lamp rendition. The CRFand ESI values shown for the outside pairof lamps are in each location higher thanthose for the inside pair. This follows thesame basic reasoning as for the four-lampsituation; namely, the larger area providesa source of lower average brightness.

This project is a good example of whathappens with luminaires in widely sepa-rated rows. The contrast rendition in the

Sphere Quality

critical locations M1 and M3 is muchpoorer than the M2 and M4 positions. M1and M3 are much poorer than comparablelocations in rooms with more closelyspaced rows.

Here, as in Project 1, the CRF valuesshow that there is less loss when the nor-mal line of sight is at right angles to theline of luminaires. At the same time, careshould be taken to avoid high brightnesson the sides of luminaires, if they are to runin this direction, because the side bright-ness will be critical from a direct glarestandpoint.

This project is one of the poorest ofthose measured, and demonstrates con-clusively that the use of a relatively nar-row luminaire in widely spaced rows willresult in high loss of contrast. Even thoughthis system produces 108 footcandles withtwo lamps per luminaire and 215 with fourlamps, the CRF is poor in either case. Thissystem demonstrates that the CRF is afunction of the manner in which the lightis directed to the task, not the level ofillumination. The outside pair of lampsproduce a slightly higher CRF than theinside pair for two reasons: the inside pairresults in a narrow light source when com-pared with the wider spacing of the out-side pair plus the light on the ceiling,which is not present with the inside pair.

v...,446..akorift**Aiiiikilillikaind144

Project Quality

project 4descriptionThis room is 24'-0" wide, the window wall,facing east, is 28'-0", and the inside wall is31"-0'. The three-foot differential is due tothe angle of the south wall The ceilingheight is 11,-0". A wide arcade roof shieldsthe east windows. The lighting system con-sists of an open rectangle, approximately17'-0" x 23'-0 ", formed by single-lamp,semi-indirect units using 1500 m.a. powergroove lamps. There are eight 8'-0" lampsand two 6'-0" lamps. The units have aplastic lens bottom panel with a thin dif-fusing panel directly on top of the lens.This combination provides a lower bright-ness when viewed directly than either thelens or the diffuser when viewed sepa-rately.

4-P.11.

Wall Elevations

r


Wall Elevations

29

-

Floor Plan

:iii 1 411 0A"

30

k.

This room is smaller than most of the otherrooms and has a total of about 680 squarefeet, and the ceiling is higher than most ofthe others. The perimeter system providesan unusually uniform distribution with theminimum of 54 footcandles at the center ofthe room only 27% lower than the maxi-mum of 74 footcandles. The photographinto the convex mirror shows the concen-tration of light around the perimeter andthe dark area in the center of the ceiling.The general level of illumination is on thelow side; however, it would have beenmaterially better had the large wall areasbeen finished in colors with much higherreflectance.

lightinglevels

The luminaire and ceiling brightness isexceptionally low and well within recom-mended brightness ratios. Again, the wallcolors were much darker than is sug-gested, and a choice of lighter colorswould have improved the general qualityof the room. Unfortunately, no record wasmade of the brightness, color, or reflectionfactor of the blackout curtains; however,the photographs show them to be aboutthe same brightness as the plywood walls,or 36% reflectance. The clear glass win-dow in the door to the adjoining class-room is exposed directly to the westernsky and creates a problem which could becured quite easily.

Location DaylightFootcandles

Electric Combination1 17 68 852 20 69 893 14 73 874 26 69 955 28 54 826 20 74 947 39 65 1048 43 63 1069 31 72 103

10 21 72 9311 18 72 9012 39 66 10513 35 72 10714 43 34 7715 48 37 8516 33 44 77


Location Surface ColorReflection Footlambert BrightnessFactor Day Elec. Comb.

25 Glass in Door Clear 1750 1750 1750

26 Door Natural Maple 32% 18 8 26

27 Tackboard Warm Tan 37% 17 14 31

28 Chalkboard Brown 17% 14 7 21

29 Plywood Wail Yellow Green Stain 36% 15 36 54

30 Plywood Wall Yellow Green Stain 36% 19 10 27

31 Cabinet Natural Maple 32% 9 13 23

32 Plywood Yellow Green 36% 10 58 75

33 Chalkboard Brown 17% 5 7 15



36 Window To Sky 1900 1900


37A Window To Arcade Soffit 72 72



40 Air Conditioner Buff 25% 9 9 18






46 Desk Top Maple 44% 12 25 37

47 Vinyl Floor Grey 50% 9 22 32




S

32

project 4evaluations Qua iiiy

(electric only)TI

CRFESI

(daylight only)TICRFESI

(combination)TICRFESI

Location

591.02

68.5

361.18

117.8

951.12

235.8

The CRF of 1.02 is excellent when com-pared with all of the other projects, withthe exception of Project 5. It would appearthat good CRF values would be obtainedin the entire seating area regardless of thedirection of viewing, with the exception ofthose locations directly under the lumi-naire, close to the side walls, when lookingin the same direction as the luminaireorientation.

Sphere Quality

The large windows are under a highcorridor roof about 10'-0" wide. As a result,the afternoon sky provided a rather lowlevel of added light in the room, but theCRF values were exceptionally good. AtMl, daylight alone provided a CRF of 18%better than Ware-free. If all students facedaway from the windows, only the teacherwould suffer from the extreme brightness.

CRF and ESI values are given for eachof three lighting combinations, first elec-tric, then daylight alone, and then a com-bination. The electric system is the numbertwo system of all those surveyed in that itshows a 1.02 CRF and with only 59 foot-candles the results are equivalent to 68.5footcandles. This is of course due to thefact that the major percentage of the lightto the task comes from an area outsidethe critical zone for veiling reflectances.The daylight alone produces an excellentCRF of 1.18 and an equivalent of 117.8footcandles will' only 36 footcandles. Hereagain most of the light reaches the taskfrom the sides and behind; a small portionof the total originates from areas forwardof the task. Where students can be placedwith their backs to the windows, the CRFwill be excellent, but the teacher will havea constant major glare source from thewindows as she faces the class.

Project Quality


The room in this project is 31' -0" long by29'-0" wide, and the ceiling is made up offour sloping planes running across theroom. The low points on the ceiling are8'-9" above the floor and the high pointsare 11'-0". The side wall elevations in thedrawing show the shape cf the ceiling.The lighting system consists cf nine, 96°,1500 m.a. lamps behind a formed plywoodvalance. Three lamps are installed in lineon the front wall over the chalkboard andthe same on each side wall. There was nolight across the rear of the room. The bot-tom of the valance is 6'-9" from the floor.Although there are four large windows inthe room, two on each of the outside walls,all testing was done with the Venetianblinds closed. The daylight entering theroom was less than 1/2 footcandle andtherefore negligible as far as the recordedfindings are concerned.

ik..41)

-(21P-

.4.0...


Wall Elevations -->

Floor Plan

Wall Elevations

This is the only example of a cove light-ing system in the western United States tothe knowledge of the author. This sampleshould not be considered the best of itskind; however, there is much that can belearned from the study.

The levels of illumination are far lessthan any other project surveyed. The omis-sion of the valance on the rear wall is un-fortunate, and although the ceiling colorwas good, the shape may have a slighteffect on the over-all efficiency. A lightingvalance on the rear wall would have pro-vided levels at the rear of the room com-parable with those at the front, and thecenter location (#5) would probably havehad 30 instead of only 23 footcandles. The

lightinglevels

large areas of wall surfaces with a fabricfinish of only 24% reflection factor causedan added loss in the lighting levels.

From a brightness standpoint, the high-est values are directly related to the val-ance unit, and they exceed the 10 to 1ratio allowed for the low task brightnessof only 11.5 footlamberts resulting from16 footcandles at the M1 position. On theother hand, the task would have had 30footlamberts if the fourth valance hadbeen installed, and this would have al-lowed the wall and ceiling brightnesses tocome within the desired ratios. The gen-eral brightness of the room would havebeen much better if the wall covering hadbeen chosen with much lighter colors.

LocationFootcandles

Electric1 442 453 434 375 236 41

7 268 149 26

10 4011 4212 2413 2714 5015 43

r

if

111111111

y.


....


25 Front Wall Mustard 45% 11026 Valance Baffle Walnut 25% 5

27 Wall Fabric Yellow Green 24% 4528 Chalkboard Brown 15% 9

29 Wall Fabric Yellow Green 24% 530 Wall Fabric Yellow Green 24% 831 Vertical

Venetian Blind Gray 7032 Horizontal

Venetian Blind Grey 3533 Wall Fabric Yellow Green 24% 5034 Wall Fabric Yellow Green 24% 2035 Wood Door Grey 12% 836 Wall Fabric Yellow Green 24% 437 Wall Fabric Yellow Green 24% 438 Wood Cabinet Natural Birch 29% 538A Painted Wall Mustard 45% 739 Painted Door Grey 12% 1

40 Painted Door Grey 12% 9

41 Painted Wall Mustard 45% 7242 Wall Fabric Yellow Green 24% 4843 Wall Fabric Yellow Green 24% 2044 Painted Wall Mustard 45% 7245 Horizontal

Venetian Blind Grey 2946 Wall Fabric Yellow Green 24% 947 Acoustic Tile White 80% 9548 Acoustic Tile White 80% 16549 Acoustic Tile White 80% 4250 Acoustic Tile White 80% 20051 Acoustic Tile White 80% 1852 Acoustic Tile Whiti. 80% 653 Desk Top Maple 49% 854 Floor Tile Grey 28% 5

35

iy

36


M1 M2 M3

Ti 16 42 42CRF 1.12 .915 1.07ESI 29.9 24.7 68.5

The CRF value at M1 in this room is out-standing in that it produces a value 12%greater than sphere quality and with only16 actual footcandles, the equivalent inthe sphere would be 29.9 footcandles. If

the fourth valance had been installed onthe rear wall, the TI would have beenabout 45 footcandles, the CRF about 1.06,and the ESI would have been 69.4 foot-candles. Even with 39 actual footcandles,the ESI would have been 63 footcandles.

The excellent results shown in this proj-ect, in spite of several unfavorable condi-tions, would indicate that designers shouldrecognize desirable aspects and work outcove systems to utilize their advantages.It appears that with proper ceiling shapeand color, better wall reflectance, and alittle more light, the CRF and ESI could bedeveloped economically in spite of theinherent low lighting efficiency of covesystems.

.00


projectdescription

The room is 25'-0" x 30'-0", and the ceil-ing height is 10'-0". The lightin systemconsists of 20, 5'-0" square eler ents ar-ranged as shown on the drawi g. Eachelement of the ceiling system cc^ sists ofa metal coffer in which a plastic diffuserconceals two 40-watt, rapid-start fluores-cent lamps.

-11

11i

4ii

gabAti

,Reflected Ceiling Plan

Wall Elevations

37

Wall Elevations

Floor Plan

t

-

The only daylight in the room comesthrough the glass door and transom, bothof which are of a low transmission glass.The added illumination was insignificant inrelationship to the lighting from the elec-tric system. Access to the interior of thebuilding is through the 10"-0" opening inthe wall for which there is no closure.Light entering the test room through thisopening is not a factor which could upsetthe accuracy of the contrast renditionstudy.

The over-all effect of this system is simi-lar to that of a luminous ceiling with a5'-0' wide unlighted ceiling space on eachside. This wide dark area leaves the twosides of the room with considerably lesslight than in the center. The south side and

lightinglevels

rear wall color are fairly light, and thishelps materially in reflecting light back tothe room. The front and the north walls,on the other hand, are dark, and give theroom a very low key. The lighting ceilingis carried all the way to the front and rearwalls, and this is very good. The only lightto reach the upper portion of the north wallis that bounced from the furniture and car-pet, and unfortunately the carpet is verydark. The entire character of this roomwould have been improved if only fourmore lighting modules had been used. Byomitting six modules in the center of theroom and installing modules to cover theceiling on each side, the walls would allhave been very well lighted, and the sidesand corners of the room would have hadmuch more light on the desks.

LocationFootcandles

Electric LocationFootcandles

Electric

1 45 9 45

2 78 10 69

3 51 11 69

4 54 12 69

5 90 13 69

6 54 14 41

7 51 15 48

8 81 16 42

4

yr

4.


MM.

I

Reflection Foot lambertLocation Surface Color Factor Brightness

25 Chalkboard Wall Olive Green 23% 4.5

26 Chalkboard Wall Olive Green 23% 11

27 Chalkboard Wall Olive Green 23% 9

28 Painted Wall Grey Green 53% 9

29 Painted Wall Grey Green 53% 20

30 Metal Partition Grey Green 53% 31




34 Metal AcousticCeiling White 80% 11

35 Light Diffuser 260



38 Glass Door 180

39 Carpet Olive Green 22% 13

40 Desk Top Pecan Formica 25% 20

39

40

project 6evaluations Quality

IMIIIMEMIliM1111111111

LocationM1 M2

To 83 80CRF .886 .911ESI 35.6 40.8

111111`-'-'

Sphere Quality

This system is only fair in its qualitiesfor contrast rendition. Much of the reasonfor this is in the fact that practically nolight reaches the task from low angles.Even though the source of light is a large,low brightness area, the lack of light fromthe sides really shows. Had the previoussuggestions been followed and light colorsbeen used on the walls and carpeting, theover-all contrast rendition would havebeen much better. Obviously, the architec-ture of the room would be entirely differ-ent, and it is here that the architects havethe right and duty to make decisions.

Project Quality


The room is about 29'-0" by 35'-0", andthe ceiling height is 9'-6". The lighting sys-tem consists of eight rows of 2'-0" widerecessed units with the rows 4'-0" on cen-ter. There are two 90-watt, rapid-startlamps in each 8'-0" long unit, and eachrow is 24'-0" long. This system uses a totalof 48 lamps. The troffers are deep, andthe acrylic diffusers are almost uniformlylighted. Daylight light levels are recordedfor information only. Daylight enters theroom from windows located behind onechalkboard which may be slid sidewaysover the other board when this is desired.In the closed position, no daylight entersthe room, and this is the condition usedfor drawings and light measurements.

Wall Elevations --->


25

. 0

4-0

Floor Plan

41

Wall Elevations

This system covers virtually one half theceiling with luminaires and develops adegree of uniformity similar to the betterluminous ceilings, but with a much higherover-all efficiency. For example, Project2 produces an average of 104 footcandleswith 4 watts per square foot or 26 foot-candles per watt per square foot. Thisproject has an average of 92 footcandlesfrom 2.4 watts per square foot, or 38 foot-candles per watt per square foot. The highreflectances of the side wall and cabinetfinishes help materially in the over-allefficiency.

An interesting improvement in this roomwould be to remove the two center lu-minaires from the four center rows andto put two more luminaires in each of thefour corners between the existing end lu-

lightinglevels

minaires. This would decrease the level inthe center of the room and boost the fourcorners, making the system even moreuniform, and still providing a satisfactorylevel in the center.

The brightness balance in this projectis excellent. The chalkboard is the onlylarge dark area, while most of the wallfinishes, tackboards, and cabinets are ofhigh reflectances. The use of white acous-tic tile on the upper side walls helpsgreatly in removing the feeling of dark-ness often found in projects with recessedlighting. Also, the use of diffusing panelsinstead of lenses provides more light tothe side walls. Only one lamp is shieldedby the 24" wide panel, and consequentlythe brightness is maintained well withinthe allowable ratios.

Location

FootcandlesElectric

Day Only Location

FootcandlesElectric

Day On;y

1 .9 65 10 3.0 93

2 11.0 75 11 1.9 89

3 .7 59 12 1.3 95

4 1A 89 13 1.2 90

5 2.5 108 14 47

6 1.2 81 15 477 .9 66 16 57

8 1.7 81 17 51

9 .7 60

a


* 4044CA

7: A

,,;ttI,L N.- r-6.2

4,1'416

Location Surface ColorReflection

FactorFootlambertBrightness

25 Tackboard Warm Grey 52% 19

26 Painted Door Burnt Orange 25% 10

27 Chalkboard Grey Green 19% 9

28 Tackboard Grey 52% 17

29 Acoustic Tile (Wall) White 80% 3330 Wood Cabinet Natural Birch 32% 12

31 Acoustic Tile (Wall) White 80% 3632 Tackboard Grey 52% 21

33 Wood Cabinet Natural Birch 32% 4534 Tackboard Grey 52% 25


36 Acoustic Tile White 80% 4637 Asphalt Tile Floor Grey 29% 2038 Desk Top Maple 45% 4039 Ceiling Tile White 80% 19

40 Lighting Diffuser White 25041 Lighting Diffuser White 27542 Lighting Diffuser White 27543 Lighting Diffuser White 25044 Lighting Diffuser White 27545 Window with Chalkboard

open (low transmissionglass)

325

43

44


Sphere Quality

Quality Location

M1 M2

TI 90 90CRF .915 .942ESI 46.7 57A

The CRF in this project is very goodwhen compared with other systems usingconventional luminaires in conventionalpatterns, but is not so good as those sys-

ti

tems which provide light from the perim-eter of the room. The choice of diffusingpanels instead of lenses improves the con-trast rendition because of the larger per-centage of light at wide angles with thediffuser. Currently available lenses tendto concentrate light into the offendingzone. Manufacturers are now working onlens designs which will concentrate mostof the light between 30° and 45°, with asmaller percentage between 0° and 30°.When this is available, the CRF will beimproved, but care will be required toavoid direct glare from the higher Ionsbrightness.

Project Quality


This room is 32'-0" wide and 29'-0" long,and the ceiling is 10'-3". The wall oppositethe chalkboard is of the accordion type,opening into an adjacent classroom; how-ever, the wall was closed during this sur-vey. There are two 15" deep beams whichdivide the ceiling into three panels. Thenorth window wall has operable shutterswhich are lighttight, and these were closedduring the survey. The electric lightingsystem consists of nine 48" square, sur-face-mounted, lens bottom luminaires,each with six 48", rapid-start fluorescentlamps.

Wall Elevations

A laa


@- (02

\"2D7-"01, 4-- Wall Elevations

Floor Plan

(**

(372}-.-1

This is one of the more efficient systemswith regard to lighting level, producing anaverage of 127 footcandles with 2.9 wattsper square foot, or about 44 footcandlesper watt per square foot. The degree ofuniformity is normal for conventionallyarranged luminaires. The minimum levelof illumination is 67% of the maximum.This is not so good as those systems whichplace the light toward the perimeter of theroom. With only nine large units, relocat-ing them to provide more light into thecorners of the room would run the dangerof leaving areas of low level between fix-tures. The ratio of spacing width to mount-ing height must be watched carefully toavoid dark areas. The light colors used onthe side walls helped maintain a highroom efficiency. The unusually light floorwas a great help in bouncing light backto the ceiling and upper side walls.

lightinglevels

The brightnesses within this environ-ment were very good except for the un-usually high brightness from the large lenspanels.

The brightness balance within the roomis on the edge of being poor. In all systemsusing conventional recessed lenses, littleor no direct light fall3 on the upper sidewalls or ceiling, and the floor is the pri-mary source of reflected light to theseareas. In this project, the floor has a re-flectance of 40%, one of the highest of allthose surveyed, and, as a result, the 80%ceiling has a brightness of 35 footlam-berts. The room would have been betterif the large areas of stained plywood hadbeen of higher reflectance. The directbrightness from the lens was extremelyhigh, and the brightness difference be-tween the lenses and the adjacent ceilingwas far above normal comfort limits.

LocationFootcandles


Electric1 111 9 102

2 126 10 130

3 105 11 126

4 132 12 126

5 147 13 126

6 117 14 72

7 99 15 72

8 129


F--

1 47



25 Vinyl Tackboard Beige 48% 30

26 Chalkboard Brown 20% 15


28 Tackboard Beige 48% 3329 Tackboard Beige 48% 19

30 Stained Plywood Warm Green 27% 18


32 Drape Orange 24% 16

33 Formica Cabinet White 55% 49

34 Tackboard Beige 48% 21


36 Vinyl Accordion Door Beige 54% 3537 Vinyl Accordion Door Beige 54% 4738 Vinyl Accordion Door Beige 54% 19

39 Vinyl Accordion Door Beige 54% 3040 Stained Plywood Warm Green 27% 17

41 Metal Shutter Cream 27% 2042 Stained Plywood Warm Green 27% 10

43 Fixture Lens 47544 Fixture Lens 100045 Fixture Lens 170046 Acoustic Tile White 80% 3547 Side of Beam Warm Green 27% 13

48 Vinyl Floor Cream 40% 4649 Desk Top Grey 43% 58


1111111111111V 11M=MiMiiffinirMir-lIga. Mite MN

Quality Location

M1 M2 M3

Ti 135 135 120CRF J42 .908 .987ES! 18.3 64.4 109.3

1111MINIMMIELCIIMINW 411111111

As might be expected with such con-centrated sources of direct illumination,the CRF value at the M1 position was theworst of those surveyed even though thisposition was nearer the center of the roomthan in most of the other projects. The M2position was to the left, far enough to put

Sphere Quality

the mirror image halfway between lumin-aires, and the CRF at this point was muchbetter. Meter position M3 was chosen tolocate the mirror image on the diagonalbetween four luminaires, and this locationhas the highest CRF for this project.

The CRF in this project is the poorest ofall those surveyed, only 13.6% of the totallight delivered was effective. Even thoughthe system produced 135 footcandles atM1 position, the quality was so poor thatthe resultant visibility was the same as thatproduced by only 18.3 footcandles ofsphere quality light. The CRF value at M2is very high because little light comes fromthe ceiling at the critical area, and M3 iseven higher because light is coming fromeven better angles. As in most all of theprojects, the M2 position is good for CRF.

Project Quality


The room is 30'-0" square with a 9'-6" ceil-ing height. The lighting system is a lumi-nous ceiling 24'-0" x 28'-0" made up of2'-0" square diffusers on suspended Tbars. There are 12 rows of seven 48",rapid-start cool white lamps mounted 12"above the diffusers. The plenum is linedwith aluminum foil to act as a reflectingsurface.

Levels of illumination are shown forboth daylight and electric light alone. Thelarge windows face east under an arcaderoof and are glazed with low transmissionglass. They were covered by a heavy drapeduring the survey. The interior photo-graphs were taken late in the afternoonand show the windows undraped. On theopposite, or west, wall, there are five 2'-0"high windows which were also coveredwith drapes during the survey.

Wall Elevations

4D

o

-(ei 0)


Floor Plan

Wall Elevations

The brightness ratios in the space arevery good. Although the wall colors werenot high in reflectance, they did not pro-duce a dark-appearing room. The chalk-boards were dark, but the only other areaof low brightness was the white ceiling,adjacent to the luminous ceiling. The onlycure for this problem is to use much lighterfloor colors and white or nearly white onthe upper side walls. Also, in this particu-lar room, the luminous area was stoppedmore than 42" from the wall near whichthis reading was taken.

The room, even with the windows un-shielded, was very comfortable becauseof the use of low transmission glass in thelarge windows which face east. Eventhough the exposure was correct for theinterior brightnesses, and no supplement-ary light was used, the buildings and treesoutside the classroom are also well ex-posed. Had the window glass been clear,the outdoor brightness would have beenexcessive, and the entire view through the

lightinglevels

window would have been badly over-exposed. Discomfort from window bright-ness follows to a degree the over-exposureshown on unretouched photos. It will usu-ally be comfortable in a room where awell-exposed photo of the room interioralso shows the exterior in good exposure.

This room has 900 square feet, used4200 watts, and produced an average of61 footcandles, or 13 footcandles per wattper square foot. This efficiency is very low,particularly when compared with Project2 which is comparable construction anddeveloped 25 footcandles per watt persquare foot. Although no test was made, itis very possible that the diffusing materialis of too low a transmission factor. Thedegree of uniformity is less than shouldbe expected from a uniformly lighted ceil-ing that goes well over toward the sidewalls. The side wall colors are not as highin reflectance as they might be; however,they are not so low as to cause the over-alllow efficiency in the system.

Location

Footcandles

Daylight Electric Location

Footcandles

Daylight Electric

1 1.3 45 9 2.4 36

2 1.9 60 10 1.4 61

3 1.3 38 11 1.4 60

4 1.2 59 12 2.3 64

5 1.8 80 13 2.4 59

6 1.5 51 14 42

7 1.6 44 15 36

8 5.6 60


4;



25 Painted Brick Soft Yellow 65% 15

26 Chalkboard Green 21% 827 Curtain Tan Gold 43% 17

28 Painted Plaster Grey 46% 13

29 Wood Cabinet Oak Color 25% 10

30 Curtain Tan Gold 43% 16

31 Chalkboard Green 19% 7

32 Painted Brick Grey 46% 18

33 Table Top Tan Formica 45% 3334 Asphalt The Tan 27% 15


36 Light Diffusers White 7037 Light Diffusers White 70

38 Light Diffusers White 8839 Light Diffusers White 9240 Light Diffusers White 100


Sphere Quality

Quality Location

Ti 65CRF .886ESI 29.3

The CRF developed in this project wouldbe the same for any nonpolarizing, diffus-ing material. The density of the diffusermay be high or low, but as long as thedistribution characteristics are the same,the CRF will be the same, Although lumi-nous ceilings were considered the ulti-mate in quality, this and the one in Project2 do not prove the point, Wnat this andother projects do prove is that, from thestandpoint of contrast rendition, light fromdirectly overhead is detrimental, regard-less of brightness. The problem is how todirect light to the task from wide, lowangles, rather than from directly overhead,and to do this without creating direct glare.

fn

4

Project Quality


This classroom building is made up of15'-0" square bays and the building isbasically 4 bays wide and more than 10bays long. There are no fixed partitions;however, movable partitions may beplaced on any 30'-0" module. During thetest, partitions were placed to provide a30'-O" square room in one corner of thebuilding. The electric lighting is from 4bays, each with an opening 11'-6" squarein which coves on all four sides light the28" deep coffer. On each of the four sidesof each lighting coffer, there are two 72"long, 1500 m.a., fluorescent lamps. Day-light enters the room only through a cor-ner alcove window, glazed with 15%transmission factor, neutral grey glass.The quantity and distribution of daylightwere not significant 'factors in the contrast,rendition study.

Wall Elevations


_0

-0 -0e_o

o

Floor Plan

Wall Elevations

41) 3G-

--6-t-----'-r-

The degree of uniformity of light withinthe seating area of this project is quiteunusual in that the minimum level is only32% lower than the maximum. The highestlevel is not at the center of the room, butit is nearly equal under the center of eachof the lighting coffers.

The brightness balance is very good asfar as high brightnesses are concerned.The small corner window is glazed witha 15% transmission, neutral grey glasswhich produced a brightness of only 300footlarnberts. The brightest areas withinthe coffers were all less than 300 foot-

lightinglevels

lamberts. The chalkboards are of lowerreflectance than many found in otherschools, and even though the areas arereasonably small, it would be an improve-ment to have them lighter. The sage greencarpeting was only 13% reflectance, andconsequently the floor brightness was wellbelow the recommended minimum of onethird task brightness. Also, had the carpet-ing been lighter, the added reflected lightwould have increased the brightness ofthe 28" wide ceiling surfaces between cof-fers. The vinyl wall coverings and paintedwalls are excellently chosen with rela-tively high reflection.

LocationFootcandles

Electric Location

,CIMMI

FootcandlesElectric

1 84 8 96

2 75 9 96

3 78 10 108

4 90 11 105

5 99 12 1085 93 13 111

7 96 14 57


I

L


25 Lo-Tran Glass 15% Trans. -Neutral 300

26 Painted Plaster White 80% 230

27 Stained Wood Brown 21% 9

28 Painted Door Green 35% 19


30 Vinyl Wall Warm Green 53% 25


32 Painted Plaster White 80% 20033 Vinyl Wall Warm Green 53% 3534 Vinyl Wall Warm Green 53% 30

35 Vinyl Wall Warm Green 53% 4036 Vinyl Wall Warm Green 53% 35


38 Vinyl Wall Warm Green 53% 4039 Painted Plaster Green 58% 4040 Chalkboa rd Green 19% 9

41 Table Top Maple 35% 42

42 Carpet Sage Green 13% 11

43 Acoustic Tile White 80% 29044 Acoustic Tile White 80% 8045 Acoustic Tilo White 80% 27546 Acoustic Tile White 80% 41


56

Sphere Quality

Quality Location

M1 M2

TI 110 97CRF .956 .972ESI 79.4 78.6

As would be expected, the CRF valuesin this project rate very well. The largeareas of low over-all brightness producediffuse light which minimizes veiling re-flections, The side walls were all of high

reflectivity, and this added to the low anglelight which is so advantageous. The nor-mal practice of selecting the M1 meterposition to reflect the center of a lightingpanel produced the maximum brightnessat the offending area. In this project, thecenter of the coffer has the lowest bright-ness, and for this reason the M1 positionwas moved forward three feet so that theceiling area reflected in the task was abouthalfway toward the far side of the coffer.M2 was chosen at the same distance fromthe rear wall as Ml, but on the center lineof the room, under the 28" wide panel ofceilirig, between coffers, This project hasthe third best CRF of those tested andshould certainly arouse interest.

101

SOr

Project Quality


This room is 28'-0" by 30'-0" with a 9' -6"ceiling. The ceiling is dropped 20" aroundall four walls as shown on the drawings ofthe wall elevations. The electric systemconsists of four continuous rows of sixluminaires each. The units are surfacemounted, 41 /2" deep and 13" wide, withplastic lens sides and bottom, and withtwo 48" rapid-start fluorescent lamps. Thewindows on the north wall are coveredwith Venetian blinds which were keptclosed during the survey.

it

Wall Elevations

0101

111

....Reflected Ceiling Plan

za

1-1

-(2 30 31

0- 0- C)-

a* 0-

p CD-

O-

I

Floor Plan

41 I

35

Wall Elevations

3

57

The lighting levels are very good andthe minimum level was 59% that of thehighest. In determining this value, the au-thor used the low level at station 7 ratherthan that at station 9 because the wallopening adjacent to station 9 was an un-usual situation. The high reflectance valuesof the walls and floor added materially tothe over-all efficiency of the lighting sys-tem.

The brightness balance in this projectwas excellent excep+ for the extreme lu-minaire brightness when viewed at a ratherhigh angle. The painted walls had a re-flectance of 60% and the floor was 39%,and together these two surfaces reflecteda very good percentage back to the cell-

lightinglevels

ing. At station 47, on the ceiling halfwaybetween rows, the brightness was 36 foot-lamberts. This is excellent when comparedwith 11 footlamberts on the ceiling forProject 6, and 10 footlamberts for Project16. The levels of illumination are differentin each case so the ceiling brightnesscomparisons must be made with this factin mind. If the room is used with the Vene-tion blinds in the open position, the bright-ness of the exterior on sunny or brightdays will be uncomfortable. The glare ondark overcast days will not be a problemnor will the added light be a factor to con-sider. There is much to be said in favor ofwindows that allow vision to the outsidewith proper control of the shielding de-vices.

LocationFootcandles


Electric1 93 10 1292 108 11 1293 102 12 1204 132 13 1235 147 14 546 132 15 607 87 16 81

8 93 17 81

9 84

I

1110r.--

00

air raft_59

_




25 Tackboard Tan 37% 18

26 Painted Plaster Off-White 60% 35


28 Chalkboard Blue Green 16% 10

29 Painted Plaster Yellow Green 52% 28


31 Birch Door Natural 30% 16




35 Cabinet Door Tan 27% 12

36 Venetian Blind White 33




40 Chalkboard Blue Green 16% 15

41 Painted Plaster Yellow Green 52% 35


43 Fixtures 290

44 Fixtures 450

45 Fixtures 1200



48 Desk Top Maple 47% 52

49 Vinyl Floor Grey Green 39% 36

0111111

60

project 1 The CRF values are typical for continu-ous row systems, with narrow units. The

evaluations Quality Location CRF at MI was poor, and 11 of the 18

(electric only)TICRFESI

(electric & daylight)TICRFESI

M1

111

.845,33 8

147.905

68.5

M2

110.943

70.8

1461.01

157.6

t

Sphere Quality

r

projects had higher ratings. Added read-ings for 25° at Ml and M2 indicated theimprovement in CRF by adding 36 foot-candles of daylight. The windows were di-rectly behind the meter positions, and aslong as all students face away from thewindows, there would be a major benefitto those near the windows. Students far-ther from the windows would receive lessbenefit because of the smaller contribu-tion of daylight. The direct glare problemhas already been discussed in other proj-ects.

S

Project Quality


The room is 27'-6" wide, 29'-6" long, andthe ceiling height is 9'421". Daylight entersthrough one window only, and, although itwas not covered, the daylight did not af-fect the results of the survey. The electriclighting system is four continuous rows ofsix 2'421" x 4'-0" recessed, lensed troffers.The rows are 6'-0" on center. Each lumi-naire has two 4" rapid-start lamps, ar-ranged one above the other and high in theunit. Under the pair of lamps there is aV-shaped plastic lens which acts to elim-inate lamp image in the 24" wide lens.

-s

Wall Elevations -->


so -io2

-0

Ci)0--CD

.-o

-0 4-0

Floor Plan

Wall Elevations

The lack of uniformity in the lightinglevels for this project show very clearlythat the placement of luminaires in a roommust be thought out very carefully. In thisinstance, the ceiling is formed by sus-pended "T" bars with luminaires andacoustic panels fitted into the pattern ofT bars. The total number of units producedquite high levels in the center of the room,but rather low values in the corners. Achange in the pattern of T bars could haveallowed a 6'-0" space in the center of theroom instead of the 4'-O" space, and thesix luminaires in each row could have beensplit into two groups of three luminaireswith a 4'-0" space between. This wouldhave reduced the level of light in the cen-ter of the room and added light into thecorners, and the chalkboard on the endwall would have been much better lighted.Other luminaire patterns could have beenworked out in the T bar ceiling to providea more uniform distribution. In this particu-

lightinglevels

lar case, the low level is only 42% that ofthe maximum.

At M1, the level of illumination is 137footcandles, and on this basis, the refer-ence brightness for the task would be 96footlamberts. MoFt of the large wall spaceshave very good reflection factors and con-tribute to a comfortable and efficient en-vironment The only large area of lowreflectance is the folding wall, and a muchlighter color would have been beneficial ifstudents had this surface in their normalline of sight. In this case, however, it is arear wall. The design of the lighting unitis very efficient, and yet, by the interiordesign of the fixture, the lamp image isremoved entirely. The maximum readingeven at a high angle of viewing was cnly370 footlamberts, which is less than fourtimes task brightness. It is true that if thespacing of rows of luminaires were madewider to provide greater uniformity oflighting level, the task brightness at theM1 position would have gone downslightly.

LocationFootcandles


Electric1 71 9 952 105 10 1383 83 11 1244 135 12 1505 171 13 1476 134 14 487 96 15 488 129


am


Fact.nFoot lambertBrightness



27 Vinyl Wall Grey 55% 31


29 Vinyl Wail Grey 55% 36

30 Vinyl Folding Wall Blue Grey 21% 13




34 Floor Tile Beige 37% 37

35 Desk Top Maple 38% 52

36 Wood Door Maple 36% 19

37 Luminaire 260

38 Luminaire 280

39 Luminaire 370

63

project12evaluations Quality

Sphere Quality

Location

M1 M2

TO 137 140CRF .832 .910ESI 36.1 68.5

The CRF values for this project are alittle surprising, the spacing of rows is6'-0" on center, and the units are recessedand 24" wide. In Project 11, the rows are7'-0" on center, the units are surfacemounted, and only 13" wide. On the basisof luminaire spacing and width, the CRFvalues for Project 12 should be better;however, the distribution characteristicsof the surface-mounted unit are wider, andthis quality was more than enough to

x4.

prove slightly better than the recessedsystem. On the other hand, Project 17 has13' wide, surface-mounted units in con-tinuous rows 9'-O" on center and the CRFwas only .798, considerably lower than thisproject. These results point out the im-portance of luminaire spacing, apparentsize, and the distribution characteristicsof the lighting elements.

At a previous testing period, two otherlens patterns were tested in these sameluminaires in this same room, but with adifferent test pattern for the task. Withthat pattern, it was established that, withthe "V" lens removed from the interior ofthe lighting unit, the lamp image becameapparent; however, the CRF decreasedonly slightly. With a diffusing plastic in-stead of the lens, the system providedCRF values only slightly higher than thelens with the "V" shield.

The CRF for this project is considerablybetter than Project 16 which used the 12"wide lens troffer.

Project Quality


This room is 30'-0" square and has a 10'-0"ceiling. It is lighted by four rows of sixluminaires, each with two 40-watt rapid-start Imps. The units are suspended1' -81/2" '7om the ceiling to the bottom ofthe luminaire, which is 13" wide, with anopen top, and the shield is a one-piecewraparound clear plastic fens. Accordingto the manufacturer's information, the up-ward component accounts for 53% of thetotal light output, and the balance is down-ward, with 57% of the downlight in the0' -40° zone and 43% in the 40°-90° zone.The maximum candlepower at nadir is1040 and 500 at 45° which makes thedownward component quite strong in theangles near nadir.

Although the windows are large, theyare under an extremely wide porch areawhich reduces the brightness and illumi-nation far below what would be consid-ered normal for windows of equal size.There were blackout drapes available, andfor the entire survey the drapes wereclosed to eliminate practically all daylight.

Wall Elevations ---)

1

010


10

._0®

-o

.-®

Floor Plan

4149

Wall Elevations

66

The levels of illumination shown on thetable are a clear example of the desira-bility of splitting the six luminaires in eachrow, leaving at least four feet open, andthereby providing a higher level near thewalls, The average would remain aboutthe same, but the minimum level oeincreased and the max;mum reduced. Theside wall colors ire quiic dark as com-pared to other projects, and this featurecauses a loss in the over-all efficiency,This is more important in this project thanin some of the direct systems, because alarge portion of the light from the lumi-naires is directed to the ceiling and is inturn reflected to the work area. A largeportion of the reflected ceiling light falls

lightinglevels

on the side walls and is absorbed by thedark colors.

At position Ml, the task brightness wasfound to be 82 footlamberts, and, on thisbasis, 27 footlamberts should be the low-est acceptable brightness in any darkarea. With the exception of the ceiling andlighting elements, there are very few areas,large or small, that come up to the desiredminimum. Fortunately, the floors are ex-ceptionally light, and this helped. In actualuse, the room will have lower brightnessesbecause tables and chairs will cover alarge portion of the floor, which was prac-tically clear during the survey. The sus-pended luminaires provide a high com-ponent of light to the ceiling, 'Ind thistends to ease the discomfort from ratherhigh fixture brightness.

LocationFootcandles


Electric1 93 9 902 93 10 1203 93 11 1234 129 12 1145 129 13 1176 132 14 847 87 15 848 87


=1!")


FactorFoot lambertBrightness

25 Tackboard Brown 25% 926 Tackboard Brown 25% 1627 Grasscloth Tan 22% 1728 Curtain behind interior

window 729 Curtain behind interior

window 730 Grasscloth Tan 22% 2231 Tackboard Brown 25% 1432 Wood Cabinet Maple 25% 1433 Tackboard Brown 25% 634 Grasscloth Tan 22% 2135 Chalkboard 20% 1936 Grasscloth Tan 22% 2537 Grasscloth Tan 22% 2238 Painted Door White 66% 5739 Tackboard Brown 25% 1240 Grasscloth Tan 22% 1741 Painted Door White 66% 3542 Curtain Dark Brown 10% 743 Grasscloth Tan 22% 1744 Tackboard Brown 25% 1345 Curtain behind interior

window 646 Chalkboard 20% 1747 Grasscloth Tan 22% 2748 Grasscloth Tan 22% 2049 Painted Door White 66% 5050 Ceiling Tile White 80% 19051 Ceiling Tile White 80% 4652 Ceiling Tile White 80% 19053 Ceiling Tile White 80% 3054 Luminaire (from

M1 position) 35055 Luminaire (from



M1 position) 24058 Desk Top Maple Formica 28% 3259 Vinyl Floor Tile Tan 45% 40

67


M1 M2 M3

TI 114 108 87CRF .798 .973 .785ESI 24.9 89.3 18.2

The CRF value of .798 for this project isdisappointing when compared with the.845 CRF found in Project 11 because thereverse condition might easily be antici-pated. In Project 11, the room size is onlyslightly smaller, the walls are brighter,and the rows of luminaires are slightlycloser together. In Project 13, the rela-

Sphere Quality

tively low luminaire brightness and thesomewhat higher ceiling brightness (be-tween rows) should result in a higher con-trast rendition. The larger areas of rela-tively bright walls in Project 11 seem to bethe prime factor which should make thatsystem better than Project 13. A detailedstudy of the effect of wall brightness oncontrast rendition should be made as soonas possible,

The M3 position in this project wastaken directly under the side row of lumi-naires and shows that there is a poorerCRF at this point than in the areas closerto the center of the room. Particularly atthis point, lighter side wall colors wouldhave been much better than the dark ones.The light reflected from the walls wouldhave helped reduce the contrast losses.

Project Quality


The room is 25'-0" x 30'-0" with a 10'-0"ceiling height. The lighting system is madeup of 15 5'-0" square, recessed units, witvinyl diffusers. Each unit has four 40 -watt,rapid-start fluorescent lamps. The unitare in a checkerboard pattern as shown ortithe drawing. There was no daylight enter1ing the room during the survey.

Wall Elevations -4

Reflected Cei ing Plan

-orl

Floor Plan

411 g> ID

Wall Elevations

The degree of uniformity in this systemis well above the average in that the lowestlevel is 70% of the maximum and only20% below the average. In this project, allof the interior walls are movable, and thecheckerboard pattern of the fixtures waschosen to allow a nearly uniform distribu-tion of light into any space, regardless ofthe room size, without the need for movinglighting elements.

Task brightness at the M1 position wasdetermined to be 76 footiamberts, therebyallowing a minimum of 25 for reasonablecomfort. Unfortunately, the carpet is quitedark, and this provides a large area of lowbrightness. On the front wall, the chalk-board is from floor to ceiling, and the re-

lightinglevels

flection factor is quite low. The rear wall ofnatural brick is also quite low in reflect-ance, The warm grey partitions and thetackboards are of high reflectance andassist in producing a light environment.The dark carpet absorbs light which mightotherwise be reflected back to the ceiling,and, even though the ceiling color is good,the total light coming to this surface isonly enough to provide a 15 footlambertbrightness, which is too little for the roomin general and is particularly noticeablewhen seen immediately adjacent to thelighting diffuser. The only area of bright-ness brighter than the task is the luminaireitself, and this is only 4.7 times task bright-ness, which is very good for this level oftask brightnels.

LocationFootcandles


Electric1 83 10 1022 95 11 963 84 12 1084 102 13 1115 119 14 606 111 15 577 96 16 608 105 17 639 96

N.


imporwIt.f. s



25 Vinyl Tackboard Grey 42% 2226 Metal Chalkboard Blue 11% 727 Metal Wall Warm Grey 57% 2528 Metal Wall Warm Grey 57% 3529 Painted Door Blue 21% 11

30 Brick Wall Red 25% 1431 Cabinet Door Blue 21% 1332 Metal Wall Warm Grey 57% 3233 Metal Chalkboard Blue 11% o.,/34 Tackboard Grey 42% 2735 Painted Door Blue 21% 1136 Metal Wall Warm Grey 57% 2837 Lighting Diffuser White 27038 Metal Acoustical

Ceiling White 80% 1539 Lighting Diffuser White ,27540 Metal Ceiling White 80% 1841 Lighting Diffuser White 29042 Metal Ceiling White 80% 1543 Lighting Diffuser White 36044 Carpet Blue Green 10% 945 Desk Top Light Oak 24% 26

71

projectdescription

This room is 24'-6" x 37'-0" and the ceilingheight is 9'-4". There are 28 2'-O" x 4' -O"recessed luminaires with low brightnesslenses. Each unit has two 40-watt, rapid-start lamps. The layout is unusual, as thedrawing shows. The daylight in this roomenters through four 18" high by 48" widewindows glazed with low transmissionglass. The illumination contributed wasnegligible.

Wall Elevations

8

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Floor Plan

Wall Elevations

(c)

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(31

project 14 reasonable to say that any one of the fivesystems is markedly superior to another as

evaluations Quality Location far as CRF is concerned. The good and

M1 M2TO

CRF106

.887100

.962ESI 44.2 75.1

bad features in each project seem to bal-ance out to obtain the same general qual-ity. Although Project 14 has the highest TIand ESI values, it has the lowest LEF,whereas Project 9 has the next to the low-est ESI and the best LEF. It is apparent,from a close study of these characteristicsin these and other projects, that due con-sideration must be given to each of themany qualities of each project.

The CRF value for this project rates 8th The dark walls, floors, and ceiling allin the total group; however, Projects 1, 6, worked against good contrast rendition,9, and 18 are all very close, and it is un- as well as good brightness balance.


The uniformity of the lighting level inthe seating area of this project is outstand-ing because the low reading at station 1 is114 footcandles which is 89% of the highreading of 128 footcandles at station 12.This unusual pattern of luminaires alsoprovides excellent light to the side wallsincluding the chalk- and tackboards.

The brightness pattern is also verygood. The minimum brightness should benot less than 29 footlamberts for the task,which was found to be 86 footlamberts.The green chalkboard, with only a 12%RF is too dark; however, the white chalk-board at station 32 is very good. The onlyother large, permanently installed surfacewhich is too dark is the carpet, which has10% reflectance. The desk top is one ofvery few locations which is too dark tomeet these brightness recommendations.Paprr on the tackboards was dark; how-

lightinglevels

ever, the board itself was satisfactory, andcertainly the material on the board shouldbe chosen for its purpose rather than tomeet "brightness recommendations."

It is interesting to note the three read-ings on ceiling brightness, for in two casesthey are 17 and 18 footlamberts, and in thethird case it is 30. The ceiling color is con-stant; however, the difference is the resultof much higher floor brightness in the rearof the room where light green vinyl tile wasused in lieu of dark carpeting.

The luminaires in this project meet the"scissors curve" specification of the Illu-minating Engineering Society, and thebrightness, as measured with the Spectrameter, shows them to be reasonable at thelow angles, and undoubtedly they averagecorrectly. At high angles, above 45°, thelens has a degree of nonuniformity whichallows the lamp image to show up.

LocationFootcandles


Electric

1 114 10 119

2 119 11 126

3 125 12 128

4 120 13 126

5 123 14 69

6 123 15 78

7 120 16 78

8 125 17 84

9 123 18 84

I

--....111 1111111r...._


1,

..-.


25 Chalkboard Green 12% 926 Painted Plaster Cream 68% 2227 Soffit of Eave through

lo-tran glass 10

28 Painted Plaster Cream 68% 4729 Paper on Tackboard Tan 42% 27

30 Paper on Tackboard Green 19

31 Painted Plaster Tan 73% 50

32 Chalkboard White 68% 5533 Tackboard Tan 44% 4234 Painted Plaster Tan 65% 60

35 Tackboard Tan 48% 3836 Formica Cabinet Grey Green 27% 15

37 Painted Plaster Grey Green 28% 2538 Vinyl Linoleum Grey 62% 5639 Wood Folding Curtain Natural Birch 37% 2840 Carpet Olive 15% 1841 Desk Top Pecan Formica 17% 21

42 Vinyl Linoleum Green 41% 4643 Acoustic Tile Clg. White 80% 18

44 Acoustic Tile Clg. White 80% 17

45 Acoustic Tile Clg. White 80% 3046 Luminaire Lens White 31047 Luminaire Lens White 32548 Luminaire Lens White 75049 Luminaire Lens White 30050 Luminaire Lens White 900 on lamp

450 betweenlamps


M1 M2 M3

TI 120 126 120CRF .919 .985 .789ESI 63.6 111.8 24.0

The MI position was chosen to reflectthe first fixture in the center row, to becomparable with other rooms as far as thedistance from the rear wall was concerned.The resultant CRF is probably higher thanit would have been had the location been6'.-0" farther into the center of the room.The lens characteristic provides for a rea-sonably wide distribution of light, and con-sequently the M2 position has a very high

Sphere Quality

CRF. This was not achieved at a loss ofillumination, because 126 footcandles weredelivered at M2 as opposed to 120 at Ml.

At M3 we find again that under a con-tinuous row, particularly at one side of theroom, the CRF values are poorer. Only afew other projects have CRF values forcomparable positions; however, it wouldappear that in most cases the sides ofrooms will be poorer than in the centerareas.

This is one of three projects where thelight delivered to M1 was adequate to beequivalent to at least 63 footcandles ofglare-free illumination. Although Project 5has a much higher CRF, the actual illumi-nation level was far too low. Had Project 5been completed, the total wattage wouldhave been over 3300 watts to provide 45footcandles at the task; however, in thisProject 15, a total of 2800 watts produced120 footcandles at the task.

Project Quality


This room is 27'-3" wide, 31'-9" long, andthe ceiling height is 8'-3". The electriclighting is four continuous rows of five,4'-O" long x 1'-0" wide, two-lamp, fluores-cent luminaires, with lenses, flush in theceiling, and the rows are 7'-O" on center.The four windows are equipped with veryefficient Venetian blinds, which, whenclosed, allow practically no light leaks,and these were closed during the survey.

4-ci)

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43

45

42o

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410

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Floor Plan

Wall Elevations

The uniformity of lighting levels is rela-tively good, and the low ceiling height ofonly 8'-3" required a maximum spacing of7'-0" for the fixture used. Here the designerplaced the row of luminaires on the chalk-board side, only 20" from the side wall.This provided an accent on the chalkboardwhich was desirable, The row adjacent tothe windows was moved in 3'-6", whichallowed the windows to light the outeredge of the room, and the luminaires toprovide higher levels in the class area.This off-center arrangement is not sym-metrical with the 13 stations for measuringillumination, and this should be noted ifcomparisons of illumination levels arebeing made.

lightinglevels

The distribution of light from the narrowlens unit provides little or no direct lighton the side walls, except for the chalk-board wall. As a result, the walls barelymeet the minimum brightness require-ments. It is indeed fortunate that unusuallyhigh reflectances were used on the walls,otherwise the interior would have beenvery poor. The dark carpet provides alarge area which is materially below therecommended minimum. Also, the darkcarpet reflects so little light to the ceilingthat the whole ceiling is also too dark. Thedark carpets are unfortunate, and design-ers and owners should be encouragingcarpet manufacturers to make lighter col-ors available.

,W

LocationFootcandles


Electric1 72 9 662 81 10 963 72 11 994 111 12 935 108 13 936 106 14 427 69 15 398 72 16 63


41111/4"'47-1 AL__4

oir

W alb 7`

Refie.)tion FootlambertLocation SL'rface Color Factor Brightness

25 Tackboard Olive Green 22% 9

26 Paint Ivory 67% 21


28 Accordion Door Maple 38% 15




32 Chalkboard Green 22% 15


34 Tackboard Black Paper 6% 4

35 Wood Cabinet Birch 32% 14

36 Painted Door Ivory 67% 20

37 Venetian Blind Grey 52% 13



40 Painted Door Ivory 67% 23



43 Table Top Birch 38% 37

44 Carpet Olive Green 10% 11



47 Lens 350

48 Lens 1300


M1 M2 M3

TI 90 84 70CRF .766 .977 .690ESI 16.4 111.8 9.2

1MIMMINEMIV

CRF readings were taken at three loca-tions to show the extreme variation underthis system. In the M1 position, under arow of luminaires, the CRF is quite poor;however, at M2, between rows the CRF isexcellent. The low value under the lumi-naires results from the relatively small andbright source in a ceiling of low bright-

ness. Very little light reaches the task fromlow angles, and most of the light originatesin the offending zone. The extremely highCRF found at M2 results from the fact thatthe dark ceiling provides very little lighton the task from the offending zone. Thetwo rows of lights providing the illumina-tion are well to the side and provide aminimum of veiling action. At M3, the taskwas immediately adjacent to a large areaof black paper on a tackboard. The CRF atthis location is lower than any other pointfound in the entire survey, but it must besaid that the location, 24" from the wall, isnot a normal desk location, and the blackpaper is not a normal wall color. The read-ing was taken to show the cumulativeeffect of a small bright source on a darkceiling and with a dark wall, all aspectsbeing very poor for good contrast ren-dition.

Rini-1Am Oua litv Proiect Quality

project 17'description

The room is 29'-0" iong, 27'-0" wide, andthe ceiling height is 9'-6". The lightingsystem consists of three continuous rowsof 13" wide, surface-mounted luminaires,wraparound, with lens side and bottom.In each row there are three 8'-0" units andone 4'-0 ", eacn with two 430 m.a. lamps.The rows are 9'-0" on center. The twosmall windows are glazed with low trans-mission glass, and they face a nearbybuilding. The test was conducted in thelate afternoon and evening, so there wasno daylight contribution.

35,

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4425 -41;

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42.8)14 '15

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Floor Plan

1

Wall Elevations

The level of illumination is surprisinglygood for the relatively wide spacing. Theends of she room were well lighted be-cause the rows were extended to within6" of the wall. If one luminaire had beenomitted from each end of each row, theends of the room would have been poorby comparison. Also, the chalkboard atthe end of the room has much better lightbecause the luminaires run to the end ofthe room.

lightinglevels

The environment brightness is good be-cause the side wall colors are unusuallylight and sufficient light was put on thewalls by the luminaires themselves to pro-vide acceptable brightness. The chalk-boards and tackboards fall below a de-sirable minimum, and the tackboards atleast could have been of lighter color with-out sacrificing utility. The carpet was bet-ter than some, but still too dark to meet theminimum brightness goal.

LocationFootcandles


Electric1 108 9 992 117 10 1233 105 11 1204 120 12 1175 129 13 1176 117 14 547 99 15 728 108 16 69


1111111111m,

Reflection Foot lambertLocation Surface Color Factor Brightness

25 Painted Wall Blue 68% 6026 Painted Wall Blue 68% 2827 Tackboard Slate Green 17% 1428 Chalkboard Blue Green 24% 1329 Tackboard Slate Green 17% 1430 Painted Wall Cream 68% 4731 Chalkboard Blue Green 24% 1732 Cabinet Door Birch 29% 1533 Cabinet Door Birch 29% 2034 Painted Wall Blue 68% 3135 Painted Door Blue 28% 1636 Tackboard Slate Green 17% 1137 Painted Wall Blue 68% 3338 Luminaire 50039 Ceiling White 79% 5540 Ceiling White 79% 2841 Luminaire 68042 Ceiling White 79% 5543 Ceiling White 79% 2744 Luminaire 56045 Desk Top Birch 35% 4546 Carpet Gold 16% 15

project 17evaluations Quality

Sphere Quality

Location

M1 M2

TI 112 115CRF .798 .996ESI 24.2 111.8

11IMiININP 1=11 111111

The M1 and M2 meter positions werechosen to view along the rows of lumi-naires because this gave a better compari-son with other similar systems. Also thetables were arranged so that the childrenfaced in the same way the meter wasdirected. An interesting comparison can

be made with Project 3. There the spacingwas 10'-0" o.c. and the CRF at M1 waspoorer and at M2 it was better. This sup-ports the concept that, as direct-type lumi-naires are spaced wider apart, the contrastrendition directly under the luminaires isreduced. This same thesis is supportedagain by comparing the CRF values forProject 11. All three of these projects havesimilar lighting units, and the only majordifference is in the spacing which is 7'-0"at Project 11, 9'-0" at Project 17, and 10'-0"at Project 3. The lighting effectiveness inthis system is only 26.7% and even thoughthere are 112 footcandles on the task theresults are only equal to 24.2 footcandlesof sphere quality. The CRF for this lightinggeometry is so low that it would require402 footcandles to be equivalent to 63footcandles of sphere quality light.

Project Quality

projectdescription

The room is approximately 31'-6" x 29'40 ",and the ceiling is 9'-6". The lighting systemis three rows of semi-iodirect units withthe 24'-0" rows 10'-0" on center. The unitsare suspended 24" from the ceiling, andeach contains two 96", 800 m.a. fluores-cent lamps. The photographs of the roominterior show the character of the fixture.The narrow lens panel under each lamphas a lay-in diffusing panel over the lensto reduce brightness and eliminate lampimage. The windows in the wall behind theM1 position are small and use 15% trans-mission glass. For this reason, the day-light component is small. The rooms havebeen occupied two years, and one lamphas been replaced in the fixture over thenumber 3 location for reporting lightinglevels. The balance of the system is prob-ably ready for ralamping, and the reportedlevels are minimum, not average.

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Wall Elevations

31 4c)

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32

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The uniformity of the lighting levels inthis room is relatively good in that theminimum at station 7 is 75 footcandles or68% of the maximum of 111 at station 5.The high reflection factor on the upperside walls helps materially in maintaininga fair level around the periphery of theroom. Dark upper side wall colors wouldhave caused the level near the walls to bemeasurably lower. The over-all efficiencyis remarkably high for a semi-indirectsystem. With a total of 2340 watts in aspace with 914 square feet, the averagelevel of illumination is about 96 footcan-dies or better than 35 footcandles per wattper square foot Had the carpet materialbeen of a higher reflectance, the levelwould have been even higher. Also, itshould be noted that the system was twoyears old, and the lamps were nearingtheir end of life.

lightinglevels

As would be expected in a room usingsemi-indirect lighting and light wall andceiling colors, the brightness ratios arevery good. The minimum brightness rec-ommended for this environment would be1/3 of 68 footlamberts or 23 footlamberts.Except for the carpeting and chalkboards,there are no large areas of excessively lowbrightness. The low readings of 40 foot-lamberts on the ceiling are not too bad;however, a better carpet color would havehelped materially in adding to the bright-ness of the ceiling. The distribution ofbrightness on the ceiling is helped in thisinstallation by suspending the luminaireson longer than normal stems. Had theluminaires been mounted closer to theceiling, the brightness would have beengreater directly over the luminaires andsomewhat lower between rows.

LocationFootcandles


Electric

1 78 9 80

2 87 10 96

3 94 11 99

4 102 12 96

5 111 13 966 105 14 577 75 15 548 90 16 72

tom---.1111111111111

111111r.


0

-.NM&



26 Paint Cream 63% 50


28 Door Gumwood 43% 22




32 Chaff, f,oard Brown 25% 21

33 Ta Ji::. :ard Beige 57% 35


35 Pair?;: Cream 63% 35

36 Window 15% trans. glass 33


38 Door Umber Gi.'`% 15

39 Cabinet Birch 20% 18

40 Tackboard Green Painting 40


42 Ceiling Tile White 80% 250





47 Luminaire 260

48 Desk Top Formica 34% 37

49 Carpet Cinnamon 11% 11


88

Sphere Quality

Quality

The basic CRF value for this projectrates seventh and the ESI is also seventh.

Location In each case, these values are better thanthe nonpolarized luminous ceiling andonly slightly less than the polarized ceil-

M1 M2

TI 95 90CRF .889 1.00ESI 40.4 90.0

S.

ing. The high side wall brightness madethe difference. The contribution of lightfrom the high walls helps materially incontrast rendition. The recessed luminousceilings, particularly when they stop sev-eral feet from the side walls, leave thehigh portions of the walls almost com-pletely dark, and this is detrimental tocontrast rendition on the pencil task.

Project Quality

I

conclusion In order to draw direct comparisons of thelevels of illumination found in the differentprojects, a composite bar graph is pre-sented in Figure 3 to show the maximum,minimum, and average levels of illumina-tion within the classroom seating area andon the major chalkboard. In all cases,these values are given for the electricsystem only and do not include any majordaylight contribution. The project numberis shown at the left edge, and the valuesfor each location are plotted on a logscale in columns. Unusual conditions, ifthere are any, are covered in the individualproject reports; however, there are sew' ialinteresting general conclusions which canbe made that apply to this group of rooms.There were no rooms with auxiliary pro-visions for chalkboard illumination, eachdepended upon spill light from the generallighting system, and there are 7 caseswhere the chalkboard lighting was 60 foot-candles or higher. The average level ofillumination on the desks is adequate bypast recommendations, in almost all cases;however, the minimum levels were too lowin 6 projects.

From a study of the ranges from mini-mum to maximum in each project, somevery interesting conclusions may be drawn.Project 5 has only three coves where fourwere required, and the minimum level of14 footcandles is only 31% of the maxi-

Levels of Illumination The chalkboard column gives the level of illu- arithmetic average of locations 10-11-12 andmination on the primary chalkboard. The high- 13, and experience has shown that as a shortest and lowest columns refer to the levels in cut method this is very accurate.the seating area. The average column is the

Proj. FootcandlesNo. 10 20 50 100

1 0 I--H2 o3 o

4 0 1.-415 1.......-1.4 06 ®

7 0

8 0 1.-1-49 1.. 0 --I.!

10 o i--1--I11 0

12 0 1101111P.....1...i13 01-1-i14 o I-i-i15 ® Hi16 01.-4.117 0 I--H18 0 1.--i-1

Chalk-200 board

Lowest Average HighestLevel Level Level Proj.

45 51 71 78 1

45 66 105 120 2

115 154 200 258 3

37 54 71 74 4

50 14 33 45 5

41 45 69 90 6

47 59 92 108 7

72 99 127 147 8

42 36 61 80 9

57 75 95 111 10

60 84 125 147 11

48 71 140 171 12

84 87 118 132 13

60 83 104 119 14

78 114 125 128 15

63 66 95 111 16

54 99 119 129 17

54 75 97 111 18

Figure 3

mum, In Project 12, the four rows of lumi-naires were grouped to the center of theroom which caused the low level to be only41.5% of the high. In the best of the twoluminous ceilings, Project 2, the low levelwas only 55% of the high. In Project 6, thelarge area coffers were grouped in thecenter of the room and, as a result, theminimum was only 50% of the maximum.Eight projects used conventional spacingson the luminaires, and the minimum ranfrom 55% to 70% of the maximum. Project17 is unusual in that the minimum was76.8% of the maximum even though a con-ventional layout of three continuous rowsof surface luminaires was used. In thiscase, the side walls have a reflectance of68% which is much higher than is usuallyfound, and they utilized the side compo-nent of the surface-mounted units to excel-lent advantage. In Project 4, the minimumis 73% of the maximum as the result of theperimeter placement of the semi-indirectluminaires. The best system, Project 15,produced a minimum of 89% of the maxi-mum. This was accomplished with the re-cessed troffers placed at the perim'eter ofthe room.

The uniformity of lighting levels is lessimportant than contrast rendition, in thebroad sense, and the systems which pro-duce the highest ESI, with reasonable effi-ciency, should be selected rather thanthose with uniform levels of illumination.In this study, the contrast rendition wasevaluated in a very favorable location inall rooms. As soon as possible, a similarstudy should be conducted with the meterpositions near the walls and facing in twoor more directions to provide a more com-plete understanding of what happens tocontrast rendition in these circumstances.it is very likely that veiling reflectancelosses are higher in some corner and walllocations. These same locations usuallyhave the lowest levels of illumination, so,on this basis, the corners and the periph-eries of the rooms may be doubly poor andshould be given much more light of goodquality than would be necessary at themore favorable locations in order to pro-vide equal visual efficiency.

The distribution and range of brightnesswithin an environment are extremely im-portant since they affect comfort, eyeadaptation, and contrast rendition. It isagreed by experts in this field that the eyeis most efficient for close visual work whenthe illumination level is adequate and thetask is slightly brighter than its surround.There is general agreement that a uni-formly bright environment would be psy-chologically depressing, and for the last20 years or so it has been accepted thatlarge dark areas in an environment shouldnot be less than one-third the brightnessof the task. Also, large bright areas shouldnot exceed 10 times that of the task where

the levels of illumination do not exceed 50footcandles. Recent research shows thatadaptation is equally affected by eitherdark or bright areas and that the pastguidelines are not stringent enough foroptimal comfort and accuracy, particularlyin installations exceeding 50 footcandles.

Everyone agrees that glare is bad underany circumstances, but very few agree onhow to design or evaluate lighting systemsby a set of specific brightness limits whichwill assure comfort. There are so manyvariables which interact within a lightingenvironment that it is extremely difficult toestablish definite values to cover size, lo-cation, or brightness limitations. It is notpossible to judge the effectiveness of asystem by one simple glance; even a per-son who is thoroughly aware of the pitfallsof brightness control should work in anenvironment for an hour or more beforeattempting to make a qualified judgment.Volumes have been, and more will be,written on this particular subject, and untilthe independent researchers in the field ofvisue.! science can agree on a means ofevaluation, the basic concepts must be ourguide.

There is general agreement that whereno close visual work is to be done, theenvironment brightnesses are relativelyunimportant; however, where visual accur-acy is required, the brightness of the sur-round becomes more critical as the needfor accuracy becomes more important. Ina hospital surgery, for example, everyeffort is made to provide the best possiblevisual environment with littlei.or no con-cern for aesthetics. In a school classroom,on the other hand, although visual accur-acy is important, there are human factorswhich architects and engineers must con-sider in developing a design which ispleasing, comfortable, and efficient.

The basic concept of a comfortable vis-ual environment is that sources of highbrightness be unobtrusive, and that thereshould be no large areas of low bright-ness. This is based upon the principle thatareas of either high or low brightnesscause fatigue and loss of visual accuracydue to the required changes in the adapta-tion level of the eye as it shifts betweenareas of high brightness difference. In gen-eral, no large area should be less thanone-third task brightness, regardless of itsposition within the room. This means thatdesk tops and floors particularly should beas high in reflectance as is reasonable.The available tile materials of at least 30%RF or higher are normally very good.

Side wall reflectances, including largecabinets and tackboards, should be from40% to 60% reflectance, and 80% if pos-sible at locations above the top line ofthe chalkboard. The ceiling should be asnearly white as possible because this sur-face is most important in reflecting light

back to the desk top, and to avoid largebrightness differences between the ceilingand light sources, in or on the ceiling.Every effort should be made to make theceiling at least as bright as the side walls,and it would be very desirable to have thelighter portions of the walls equal to, ormore than, one-half task brightness.

The only two sources of high brightnessare daylight sources such as windows orskylights and the electric luminaires. Itis generally agreed that direct sunlightshould rarely be allowed to come into theroom, and windows In the side wallsshould be properly glazed or shielded inorder to control the brightness to a maxi-mum of 250 to 300 footlamberts. Underhigh illumination levels, say in excess of150 footcandles, the windows might safelybe as much as three times task brightness.The typical position of windows, directlyat and above eye level, makes them par-ticularly bothersome at brightnesses abovethose suggested.

The electric light sources should be asunobtrusive as possible and this can beaccomplished in two ways: by keeping theceiling as light as possible, to minimizethe brightness difference between ceilingsand luminaires, and by reducing the bright-ness of the luminaire to approach ceilingbrightness. This should not be consideredas a requirement which will allow onlyluminous ceilings or indirect lighting, butit is a caution against the situation ob-served in several of the projects surveyed.In project 6, for example, the only light onthe ceiling was reflected from the floors,furniture, and side walls, and, because ofthe unfortunately dark colors, the ceilingwas very dark. The strong brightness dif-ference is annoying even though the lumi-naire brightness is quite low. In Project 16,this extreme brightness difference is evenmore bothersome because of the unusu-ally high luminaire brightness. In this lastcase, the ceiling brightness was only 10 or11 footlamberts, and the lens unit was from350 to 1300, depending upon the angle ofviewing. These values develop a bright-ness difference of from 35 to 1 to 130 to 1.On the other hand, in Project 12 the floorreflectance is 37%, and even though alldesks were in place the reflected lightproduced a ceiling brightness of 27 to 35footlamberts and the well-designed lumi-naires did not exceed 370 footlamberts,providing a maximum brightness differ-ence less than 14 to 1. It is not at all un-reasonable to set an upper limit on thisparticular ratio of ceiling luminaire bright-ness at 20 to 1, with lower ratios definitelydesirable.

Particularly in those cases where re-cessed lighting is used, including luminousceilings, the lighting units should be lo-cated reasonably near the side wall. Thisplacement can provide excellent coverage

for the chalkboards and tackboards, andwhen properly installed, the annoying darkcorner where the ceiling meets the sidewall is made less conspicuous. Project 15is a good example of this design concept,and even this has been improved upon ina very recent installation. In the latter in-stance, the individual recessed luminairesare slightly regressed into the ceiling, al-lowing spill light to illuminate the adjacentceiling coffer. This increases the apparentarea of each fixture, reduces brightnessdifference between ceiling and fixture, anddevelops a degree of shielding so that fix-tures more than 20 to 30 feet away arecompletely shielded from view.

The prime design goal for the develop-ment of a comfortable, yet efficient, visualenvironment is to provide adequate illumi-nation of good quality with a minimum ofbrightness differences. To achieve thesequalities and yet avoid a sense of sterilityrequires talent on the part of the architect,interior designer, and lighting engineer.

Unfortunately, photographs cannot givean accurate evaluation of the range ofbrightnesses.found in these interiors; how-ever, they do give a general idea, particu-larly when evaluated in conjunction withthe Brightness Distribution tables. In allcases, the photographs were made withthe ambient light, and the prints were nottouched-up during processing.

In order to provide an evaluation of theprojects as a group, Table I shows the TI,CRF, ESI, and LEF for each project, usingthe 25° viewing angle, the M1 meter posi-tion, and with electric lighting only. Eachof these factors is basically comparablefor each project. The added factor of LEFis the Lighting Effectiveness Factor whichis obtained by dividing the ESI by TI, andthis value shows the percentage of actualillumination which is effective as sphereilluminance. Adjacent to each of the col-umns showing the four factors, the rank isshown with the highest favorable factorshown as rating first.

Two of the projects, numbers 4 and 5,have CRF values in excess of 1.00 whichmeans that the contrast in the task wasactually greater than it would have been ina uniformly illuminated sphere. This isaccomplished in these two projects bylighting systems which located the lightsources at the periphery of the room. Theceiling in the center of the room wasrelatively dark so that the offending zoneover the task provided only a small portionof the total task illumination.

Only three projects, 4, 10, and 15, pro-vided 63 footcandles or more of spherequality illumination, and the other 15 proj-ects provided less than the recommendedeffective level for pencil handwriting.

Although Project 5 had a CRF of 1.12the illumination provided in this installa-tion was only 16 footcandles, which was

Proj. TI !tank CRF Rank ESI Rank LEF Rank1 62 16 .882 11 27.6 13 .445 82 100 10 .900 6 46.1 5 .461 63 108 8 .749 17 17.8 17 .165 174 59 17 1.02 2 68.5 2 1.16 25 16 18 1.12 1 29.9 11 1.87 1

6 83 14 .886 9.5 35.6 9 .429 97 90 12.5 .915 5 46.7 4 .519 58 135 2 .742 18 18.3 16 .136 189 65 15 .886 9.5 29.3 12 .451 7

10 110 7 .956 3 79,4 1 .722 311 111 6 .845 12 33.8 10 .305 1212 137 1 .832 13 36.1 8 .264 1313 114 4 .798 14.5 24.9 14 .218 1414 106 9 .88i 8 44.2 6 .417 1115 120 3 .919 4 63.6 3 .530 416 90 12.5 .766 16 16.4 18 .182 1617 112 5 .798 14.5 24.2 15 .216 1518 95 11 .889 7 40.4 7 .425 10

Table 1

in this case equal to 29.9 footcandles ofsphere quality illumination.

Projects 16, 3, and 8, rated 18th, 17th,and 16th in terms of ESI, were all below20 footcandles. The same three were thethree lowest in terms of LEF, and Project8 rates 18th with the lowest factor of only.135. All three of these projects are lensbottom systems with relatively small lensarea per lamp. The resulting high bright-ness toward the task is the major factorfor the low performance of all three in-stallations.

Ten of the 18 projects provided 100 foot-candles or more on the task, but of theseonly 2 provided the equivalent of 63 foot-candles or more of sphere quality. Of the5 projects with the lowest ESI, 4 had TI of100 footcandles or more. It should be clearthat high levels alone do not guaranteeconditions for accurate seeing.

Although Project 5 had the highest CRF,L12, it had an ESI of only 29.9 which ratedeleventh. From this it is clear that the CRFrating alone cannot be the whole basis ofcomparison. To be efficient, a satisfactorysystem must meet the requirement for anadequate ESI level, have a high LEF, andto rate well in these two respects, a highCRF is essential.

Of the 10 systems with the highest LEFrating, only one had a brightness, from theelectric lighting, in excess of 390 foot-lamberts. Project 15 rated fourth and had

a maximum of 900 directly toward the lampimage, and from a location almost directlyunder the luminaire. This is a very import-ant point because it shows so well that thesystems that are the most effective in pro-viding high contrast in the task are the oneswhich are also rated best from the bright-ness balance standpoint. This is a mostfortunate situation because the benefitsof good brightness now can be shown topay a bonus in good contrast renditionand vice versa.

The 5 projects with the lowest LEF allhad luminaire brightness in excess of 680footlamberts and the poorest of all shows1700 directly overhead. The poorest sys-tem produced one of the highest levels ofillumination, 135 footcandles, the effectivelevel was only 18.3 for an effectivenessfactor of only .135.

With the data provided in the reportthere is material for numerous other com-parisons between installations. It might bevery interesting for example to computethe watts per square foot in each projectand divide that into the related ESI to givethe ESi per watt per square foot. The dif-ferences would be extreme and the effec-tive systems would prove to be far aheadof the poor ones; however, this value wouldbe a good basis for comparison betweentwo systems which might be comparablein other respects.

The conclusion most quickly apparent

regarding CRF and efficient ESI is thatlight sources of large area and low bright-ness are far more effective than smallsources of high brightness. The luminousceiling and conventional indirect systemscovered nearly 100% of the ceiling andthey had effectiveness factors of from40-45% while the lens systems which cov-ered about 15% of the ceiling had effec-tiveness factors of about 15-25%. Althoughinsufficient tests were made in the courseof this survey, it is reasonable from othertesting that efficient polarizing panels willprovide a CRF of about 10% more thandiffusing panels, and in any geometry oflighting luminaires this 10% improvementcould be expected. Lenses are of manydifferent types and distribute light in differ-ent ways. Those that concentrate the lightdownward will provide low CRF values, far

lower than diffusers; and lenses that havea broader pattern of distribution will ap-proach but not surpass diffusers, whenplaced in comparable arrangements ofluminaires. Work is being done at thistime to develop a lens which will havewide distribution and which will producea minimum of light in the zone which ismost critical to veiling reflectances.

The only two systems with CRF valuesin excess of 1.00 placed the light at theperiphery of the room and it would appearthat this is the best procedure to achievemore than 50% effectiveness. Fortunatelythe effect of placing the light to the sidesof the room has several other good effects.It should provide a more uniform level ofillumination in the room, more light on thechalk and tackboards, and a better bright-ness balance in the visual environment.

93

appendix

The basic element in the evaluation ofcontrast rendition for any lighting systemis the CRF which is developed by directmeasurements; however, there are twoother values modifying the complete storywhich, when taken together, can producethe Equivalent Sphere Illuminance and theLighting Effectiveness Factor (LEF). Sincethe steps are exactly the same for eachmeter position in each project, this infor-mation is presented in tabular form follow-ing this explanation. And, since the 25°viewing angles are the only ones whichare directly comparable for all projects,only these 25° CRF values for each' meterposition are tabulated along with the de-velopment of the ESI and LEF. The CRFvalues for 40° viewing angles are givenwith each project evaluation; however,these values are not directly comparablebecause of the irregularity of some of thelighting patterns. The values are shownfor the benefit of those who might wish toknow what they were, but they will not beincluded in the following tables.

The most direct way to explain thereasoning and derivations of the variousvalues is to describe each of the qualities,using the M1 position of Project 1 as theexample.

Task Illuminance is the footcandle leveldeveloped by the system being evaluated,at the M1 meter position, in this case 62footcandles.

Luminance Factor is the preferred no-menclature for reflection factor, and in thecase of this task, the factor is .72 and thismeans that 72% of the light falling on thetask is reflected from it.

Task Luminance is the preferred nomen-clature for task brightness, and the unitof measure is the footlambert. In this re-port, the Task Luminance is computed ineach case; however, for greater accuracy,a measured value would be preferred. Themajor part of this survey had been com-pleted prior to the time at which this sys-tem of evaluation was developed, andbefore the need for the Task Luminancewas recognized. Fortunately, a record waskept of lighting levels at each meter posi-tion even though they did not coincide withthe standard locations at which levels ofillumination were recorded. In this exam-ple, Task Luminance is 44.6 footlamberts.

Relative Contrast Sensitivity (RCS) is avalue taken from a table based upon

Blackwell's research in vision. The two re-lated values in this table are task bright-ness in footlamberts and the RCS. It isrecognized that as brightness increases,the efficiency of the eye increases in itsability to see contrast. The RCS values areexpressed as a percentage and as a func-tion of luminance. RCS is considered tobe 100% at 2920 footlamberts and 36.2 at2.92 footlamberts. In that the relationshipsof RCS and footlamberts do not fall on astraight line, the use of the table is muchmore accurate than values taken fromcurves or individual calculations. The in-clusion of the RCS factor adds to the accu-racy of the total consideration because itproduces a credit for the systems whichproduce higher illumination levels and dis-counts the systems with low levels. In theexample, this value is 66.2.

Contrast Rendition Factor has alreadybeen defined and is the value resultingfrom the contrast measurements and theirrelationship to the task contrast whenmeasured in glare-free illumination. In theexample this value is .882.

Effective RCS is the product of RCS andCRF. The effectiveness of a system of rela-tively high RCS may be good or not de-pending upon the CTIF, so the product ofthe two expresses this quality. In the ex-ample, the Effective RCS is 58.4.

Effective Sphere Luminance is deter-mined by working back in the basic RCStable from the Effective RCS of 58.4 tofind the Effective Luminance, which inthis case is 19.85.

Effective Sphere Illuminance is deter-mined by dividing the Effective SphereLuminance by the Luminance Factor, andthis value in our example is 27.6 footcan-dies. On this basis, because of the smallloss due to low luminance and the some-what larger loss due to veiling reflectances,it is established that the 62 footcandlesproduced by the system is only as effec-tive as 27.6 footcandles of glare -free illu-mination.

Lighting Effectiveness Factor (LEF) isdetermined by dividing the EquivalentSphere Illuminance, 27.6, by Task Illumi-nance, 62, to establish the value of .445which means that the effective illumina-tion is 44.5% of the level actually pro-duced by the system.

The following tables are complete foreach project and are given for the benefitof those who wish to follow the derivationsin detail. The most important value is theESI. This shows whether or not the com-bination of all factors produces an ade-quate level of sphere quality illumination.LEF is also important because this valueshows whether or not the lighting systemis effectively designed to use the lightproperly. A satisfactory ESI can be at-tained by brute force of pouring on light,but if this is the case the LEF shows it up.

project 1

project 2

Quality Meter LocationsM1 M2 M3

CRF at 25° (electric) .882 .925 .892

CRF at 40° (electric) .948 .985 .942

CRF at 25° (electric & daylight) 1.03 1.05 1.00

CRF at 40° (electric & daylight) 1.09 1.11 1.05

(electric)

Task Illuminance (TI) 62 61 69

Luminance Factor (LF) .72 .72 .72

Task Luminance (TL) 44.6 43.9 49.7

Relative Contrast Sensitivity (RCS) 66.2 66.0 67.1

Contrast Rendition Factor (CRF) .882 .925 .892

Effective RCS (ERCS) 58.4 61.1 59.9

Equivalent Sphere Luminance (ESL) 19.85 25.80 23.08

Equivalent Sphere Illuminance (ESI) 27.6 35.8 32.1

Lighting Effectiveness Factor (LEF)

(electric & daylight)

.445 .587 .465

TI 172 188 106

LF .72 .72 .72

TL 124 135.4 76.4

RCS 75.4 76.2 71.1

CRF 1.03 1.05 1.00

ERCS 77.7 80.0 71.1

ESL 159.00 201.00 76.40

ESI 220.8 279.2 106.1

LEF 1.28 1.48 1.00


CRF at 25° .900 .939 .932

CRF at 40° .972 .998 .991

TI 100 115 118

LF .72 .72 .72

TL 72 82.8 84.9

RCS 70.5 71.9 72.1

CRF .900 .939 .932

ERCS 63.5 67.5 67.2

ESL 33.20 52.30 50.40

ESI 46.1 72.6 70.0

LEF .461 .631 .593

project 3Quality

M1Meter Locations

M2 M3 M4CRF at 25° (inside pairs) .749 1.00 .822 1.01CRF at 40° (inside pairs) .797 1.06 .913 1.06CRF at 25° (both pairs) .758 1.00 .831 1.03CRF at 40° (both pairs) .814 1.06 .925 1.07CRF at 25° (outside pairs) .764 - .830 -

T1

(inside pairs)

108 92 125 118LF .72 .72 .72 .72TL 77.8 66.2 90.0 85.0RCS 71.3 69.7 72.6 72.1CRF .749 1.00 .822 1.01ERCS 53.4 69.7 59.7 72.8ESL 12.80 66.20 22.70 92.00ESI 17.8 91.9 31.5 127.8LEF .165 .999 .252 1.08

(all four lamps)T1 215 185 250 235LF .72 .72 .72 .72TL 154.8 133.2 180 169.2RCS 77.5 76.1 78.9 78.4CRF .758 1.00 .831 1.03ERCS 58.7 76.1 65.6 80.8ESL 20.45 133.40 41.80 222.00ESI 28.4 185.3 58.1 308.3LEF .132 1.00 .232 1.311

(outside pairs)TI 107 - 125LF .72 - .72TL .770 - .90RCS 71.2 - 72.6 OVUM

CRF .764 - .830ERCS 54.4 - 60.3ESL 13.32 - 24.04ESI 18.5 - 33.4LEF .173 - .267 =MVO,

project 4

project 5

project 6

Quality M1 Meter LocationElect. Day Combined

CRF at 25° 1.02 1.18 1.12

CRF at 40° 1.06 1.20 1.14

TI 59 36 95

LF .72 .72

TL 42.5 25.9 68.4

RCS 65.7 61.1 70.0

CRF 1.02 1.18 1.12

ERCS 67.0 72.1 78.4

ESL 49.30 84.80 169.80

ESI 68.5 117.8 235.8

LEF 1.16 3.27 2.48


CRF at 25° 1.12 .915 1.07

CRF at 40° 1.14 .908 1.12

TI 16 42 42

LF .72 /2 .72

TL 11.5 30.2 30.2

RCS 52.9 62.6 62.6

CRF 1.12 .915 1.07

ERCS 59.2 57.3 67.0

ESL 21.54 17.80 49.30

ESI 29.9 24.7 68.5

LEF 1.87 .588 1.63

Quality Meter LocationsM1 M2

CRF at 25° .886 .911

CRF at 40° .940 .964

TI 83 80

LF .72 .72

TL 59.8 57.6

RCS 68.7 68.4

CRF .886 .911

ERCS 60.87 62.31

ESL 25.60 29.40

ESI 35.6 40.8

LEF .429 .510

project 7

project 8

ti

project 9


CRF at 25° .915 .942CRF at 40° .980 1.11

TI 90 90LF .72 .72TL 64.8 64.8RCS 69.5 69.5CRF .915 .942ERCS 63.59 65.47ESL 33.60 41.30ES1 46.7 57.4LEF .519 .638


CRF at 25° .742 .908 .987CRF at 40° .794 .905 1.02

TI 135 135 120LF .72 .72 .72TL 97.2 97.2 86.4RCS 73.2 73.2 72.3CRF .742 .908 .987ERCS 54.31 66.47 71.37ESL 13.19 46.40 78.70ESI 18.3 64.4 109.3LEF .136 .477 .911

Quality Meter LocationsM1

CRF at 25° .886CRF at 40° .941

TI 65LF .72TL 46.8RCS 66.6CRF .886ERCS 59.0ESL 21.10ESI 29.3LEF .451

project 10

project 11


CRF at 25° .956 .972

CRF at 40° .987 1.02

TI 110 97

LF .72 .72

TL 79.2 69.8

RCS 71.5 70.2

CRF .956 .972

ERCS 68.35 68.23

ESL 57.20 56.60

ESI 79.4 78.6

LEF .722 .810


CRF at 25° (electric) .845 .943

CRF at 40° (electric) .916 1.01

CRF at 25° (electric & daylight) ,905 1.01

CRF at 40° (electric & daylight)

(electric)

--

TI 111 110

LF .72 .72

TL 80 79

RCS 71.5 71.4

CRF .845 .943

ERCS 60.42 67.33

ESL 24.32 51.00

ESI 33.8 70.8

LEF(electric & daylight)

.305 .644

TI 147 146

LF .72 .72

IL 106 105

RCS 74 73.9

CRF .905 1.01

ERCS 66.97 74.64

ESL 49.30 113.50

ESI 68.5 157.6

LEF .466 1.08

project 12

project 13

project 14


CRF at 25° .832 .910CRF at 40° .902 .995

TO 137 140LF .72 .72TL 98.6 100.9RCS 73.4 73.6CRF .832 .910EROS 61.07 66.98ESL 26.00 49.30ESI 36.1 68.5LEF .264 .489

Quality

CRF at 25°

CRF at 40°

M1

.798

.879

Meter LocationsM2

.973

1.03

M3

.785

.873

TI 114 108 87LF .72 .72 .72TL 82.0 77.9 62.6RCS 71.8 71.3 69.1CRF .798 .973 .785EROS 57.30 69.37 54.24ESL 17.80 64.30 13.08ESI 24.9 89.3 18.2LEF .218 .827 .209


CRF at 25° .887 .962ORF at 40° .947 .947

TI 106 100LF

.72 .72IL 76.3 72.0RCS 71.1 70.5CRF .877 .962ERCS 63.06 67.82ESL 31.80 54.10ESI 44.2 75.1LEF .417 .751

project 15

project 16

pro ject 17


CRF at 25° .919 .985 .789

CRF at 40° .933 1.06 .860

TI 120 126 120

LF .72 .72 .72

TL 86.4 90.6 86.4

RCS 72.3 72.7 72.3

CRF .919 .985 .789

ERCS 66.44 71.61 57.04

ESL 45.80 80.50 17.30

ESI 63.6 111.8 24.0

LEF .530 .887 .200


CRF at 25° .766 .977 .690

CRF at 40° .836 1.05 .734

TI 90 84 70

LF .72 .72 .72

TL 64.8 60.5 50.4

RCS 69.5 68.8 67.2

CRF .766 .977 .690

ERCS 53.24 71.55 46.37

ESL 11.82 80.50 6.65

ESI 16.4 111.8 9.2

LEF .182 1.33 .131


CRF at 25° .798 .996

CRF at 40° .865 1.06

T! 112 115

LF .72 .72

TL 80.6 82.8

RCS 71.6 71.9

CRF .798 .996

ERCS 57.14 71.61

ESL 17.45 80.50

ESI 24.2 111.8

LEF .216 .972

project 18Quality

CRF at 25°

CRF at 40°

TI

LFTLRCS

CRFERCS

ESL

ESI

LEF

Meter LocationsM1 M2

.889 1.00

.943 1.05

95 90.72 .72

68.4 64.870.0 69.5

.889 1.0062.23 69.5029.10 64.8040.4 90.0

A25 1.00

other reports from EFLThe following publications are available without charge from the offices of EFL:477 Madison Avenue, New York, 10022.

A College in the City:An Alternative.A report of a new approach to the plan-ning of urban campuses, with facilities dis-persed through the community, designedto serve community needs and to stimulatecommunity redevelopment.

Bricks and Mortarboards.A guide for the decision-makers in highereducation: how the colleges and universi-ties can provide enough space for the bur-geoning enrollments of this decade; howthe space can be made adaptable to theinevitable changes in the educational proc-ess in the decades ahead. (One copy avail-able without charge. Additional copies$1.00.)

Campus in the City.EFL'S annual report for 1967 and an essayon the physical problems and trends inplanning of urban colleges and universi-ties and their potential role as a catalystin the remaking of the cities.

College Students Live Here.A report on the what, why, and how of col-lege housing; reviews the factors involvedin planning, building, and financing studentresidences.

Design for ETVPlanning for Schoolswith Television.A report on facilities, present and future,needed to accommodate instructional tele-vision and other new educational pro-grams. Prepared for EFL by Dave Chapman,Inc., Industrial Design.

Design for Paperbacks:A How-To Report on Furniturefor Fingertip Access.Physical solutions to the problems of dis-playing paperback books for easy use inschools.

Educational Change andArchitectural Consequences.A report on school design that reviews thewide choice of options available to thoseconcerned with planning new facilities orupdating old ones.

The Impact of Technologyon the Library Building.A position paper reporting an EFL confer-ence on this subject.

Relocatable School Facilities.A survey of portable, demountable, mobile,and divisible schoolhousing in use in theUnited States and a plan for the future.

The Schoolhouse in the City.An essay on how the cities are designingand redesigning their schoolhouses tomeet the problems of real estate costs,population shifts, segregation, poverty,and ignorance.

The School Library:Facilities for Independent Studyin the Secondary School.A report on facilities for independent study,with standards for the size of collections,seating capacity, and the nature of mate-rials to be incorporated.

School Scheduling by Computer/The Story of GASP.A report of the computer program devel-oped by MIT to help colleges and highschools construct their complex masterschedules.

SCSD: The Project and the Schools.A second report on the project to developa school building system for a consortiumof 13 California school districts.

Transformation of the Schoolhouse.A report on educational innovations in theschoolhouse during the last decade. Withfinancial data for the year 1968.

profiles of significant schoolsA series of reports which provide information on some of the latest developments inschool planning, design, and construction.

Schools Without Wallsopen space andhow it works.

Three High Schools Revisited: Andrews,McPherson, and Nova.

Middle Schoolscontroversy and experi-ment.

On the Way to Workfive vocationally ori-ented schools.

case studies of educational facilitiesA series of reports which provide information on specific solutions to problems in schoolplanning and design.

8. The Schools and Urban Renewal.A case study of the Wooster Square re-newal project in New Haven, Connecticut.

9. Air Structures for School Sports.A study of air-supported shelters as hous-ing for playfields, swimming pools, andother physical education activities.

/O. The New Campus in Britain:Ideas of Consequence forthe United States.Recent British experience in universityplanning and its implications for Americaneducators, architects, and planners.

technical reports1. Acoustical Environmentof School Buildings.Acoustics of academic space in schools.An analysis of the statistical data gatheredfrom measurement and study.

2. Total Energy.On-site electric power generation forschools and colleges, employing a singleenergy source to provide light, heat, airconditioning, and hot water.

3. 20 Million for Lunch.A primer to aid school administrators inplanning and evaluating school food ser-vice programs.

college newsletterA periodical on design questions for col-leges and universities.

Credits

Designed by Michel GoldbergPrinted by Georgian Lithographers, Inc.Photographs by the author

11. Divisible Auditoriums.Operable walls convert little-used audi-toriums and theaters into multipurpose,highly utilized space for the performingarts and instruction.

12. The High School Auditorium:Six Designs for Renewal.Renovation of little-used auditoriums inold and middle-aged schools to accommo-date contemporary educational, dramatic,and music programs.

13. Experiment in Planning an UrbanHigh School: The Baltimore Charette.

filmRoom to Learn.A 22-minute color film on The Early Learn-ing Center in Stamford, Connecticut, anopen-plan early childhood school with fa-cilities and program reflecting some of thebest current thinking. Prepared by TheEarly Learning Center under a grant fromEFL and available on loan without chargefrom Association Films, Inc., 600 MadisonAvenue, New York, New York 10022, andfor purchase at $125.00 from AssociationFilms,Inc.

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