ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN ANN ARBOR AN EVALUATION OF SOLAR HEAT GAIN ON S.UMAR.CONFORT CONDITIONS IN TEE MORTIMER E. COOIEY MEMORIAL LABORATORY.J Go Letis F., N.. alhoon C. T. Larson K. S. Sanvordenker R. J. Annesser Hi A. Ohlgren Project No. 461-1110 April, 1957

PPEFACE This report is presented as a result of an investigation and evaluation of solar heat gain on summer comfort conditions in the Mortimer E. Cooley Memorial I-abo tory located on the North Can'pus of the University of MichigaAnn A Arborx, Michigan. The period studied intensively was from approximately May until September, 1955- since this period was anticipated to reveal some of the most serious solar heating effects. A forthcoming report will reveal results of a similr study undertaken for the -period September, 1955 to May, 1956. The latter study was undertaken to explore effects of a seasonal nature upon solar heating problems in the Cooley Laboratory. The work upon which this report is based was undertaken at the re-quest of Dr. Ro G. Folsom, Director, Engineering Research Institute,* University of Michigan, and of Dr, G. G, Bron, Dean of the College of Engineering, University of Michigan. The authors wish to acknowle-dge gratefully the advice and suggestions of Dr. EB. W. Hewson, Prfessor of Meteorolo y Departmenat.of Civil Engine-ering, the University of Michigan; the cooperation of the U. S. Weather Bureau, Willow Run Stationr and the:ssistance of the Department of Mechanical and Industrial Engineering, University of Michigan, in lending certain measuring equipment for use on this project. The authors also wish to acknowledge the assistance of the results- of earlier work by Dr. L. W. Orr, Research Engineer,- Engineering Research Institute, in the installation and testing of a small group of aluminum shade screens on the Mortimer E. Cooley Memorial Iabo-ratory. ii

TABLE OF CONTENTS Page LIST OF FIGURES iv LIST OF TABLES vi ABSTRACT vii I. OBJECTIVES 1 II. INTRODUCTION 2 III. EXPERIMENTAL PROGRAM 3 IV. DESCRIPTION OF BUILDING 7 V. DESCRIPTION OF EQUIPMENT 17 VI. EVALUATION OF RESULTS 21 VII. LIMITATIONS OF RESULTS 51 VIII. CONCLUSIONS 52 IX. BIBLIOGRAPHY 53 iii

LIST OF FIGURES Figure Page 1 PLAN OF THE SECOND FLOOR OF THE COOLEY LABORATORY 4 2 ELEVATIONS OF TEST ROOMS AND LOCATION OF THERMOCOUPLES 5 3 ENERGY TRANSMITTED BY SINGLE AND DOUBLE GLASS PAES 8 4 DURATION OF DIRECT SOLAR RADIATION TO THE SOUTH SIDE OF COOLEY BUILDING 10 5 ALTITUDES OF THE SUN (1st of the month) AT THE ZENITH 11 6 ALTITUDES OF THE SUN, DEGREES (at Zernith) 1st OF THE MONTH 12 7 PLAN VIEW OF TRACE OF LINE TO SUN ON SPHERE OF LARGE DIAMETER WITH CENTER AT ANN ARBOR, MICHIGAN 13 8 ESTIMATION OF MEAN RADIANT TEMPERATURE FROM GLOBE THERMOMETER 19 9 MAXIMUM DAILY TEMPERATURES FOR LOCATIONS INDICATED MORTIMER E. COOLEY MEMORIAL LABORATORY (June, 1955) 23 10 MAXIMUM DAILY TEMPERATURES FOR LOCATIONS INDICATE)D MORTIMER E. COOLEY MEMORIAL IBORAORY (JUly, 1955) 24 1_2 TEMPERATURE RECORD (Thursday, June 16, 1955) 27 13 OUTSIDE AIR TEMPERATURE EECORD (June 13 to June 19, 1955) 28 14 GLOBE AND AIR TEMPERATURE, DIFFERENCE IN SHADED AND UNVSHADED ROOM 29 15 INSIDE SURFACE TEMPERATURE OF THE GLASS PANES (June 16, 1-95'5) 30 16 COMPARISON OF TEMPERATURES OF ATMOSPHERE,, SCREENS AND GLASS PANES (June 16, 1955) 31 17 COMFORT CONDITIONS IN SHADED ROOM June 7 to June 30, 195 38 18 COMFORT CONDITIONS IN UNSHADED ROOM June 7 to June 30, 1955 40 19 EFFECT OF MEAN RADIANT I SHTER N COMPFORT 43 -20 EFFECT OF MSEAN RADIANT TIEMPERATURE ON COMFORT 45 iv

LIST OF FIGURES (Concluded;) Figure Page 21 EFFECT OF MEAN RADIANT TEMPERATURE ON COMFORT 47 22 SCHEMATIC DIAGRAM SUMMARIZING THE EFFECT OF MEAN RADIANT TEMPERATURE ON SUMMER COMFORT 49

LIST OF TABLES TABLE PAGE I DURATION OF DIRECT SOLAR RADIATION TO THE SOUTH SIDE OF THE COOLEY MEMORIAL LABORATORY (1954) 15 II ALTITUDES OF THE SUN AT THE ZENITH ON THE FIRST DAY OF EACH MONTH (1954) 16 III COMPARISON OF SHADED AND UNSHADED ROOMS JUNE 7 TO JUNE 30, 1955 (SHADED ROOM) 37 IV COMPARISON OF SHADED AND UNSHADED ROOMS JUNE 7 TO JUNE 30, 1955 (UNSHADED ROOM) 39 V MEAN RADIANT TEMPERATURE - EFFECTIVE TEMPERATURE RELATIONSHIP IN AN INTERMEDIATE HUMIDITY RANGE 42 VI MEAN RADIANT TEMPERATURE - EFFECTIVE TEMPERATURE RELATIONSHIP IN A HIGH HUMIDITY RANGE 44 VII MEAN RADIANT TEMPERATURE - EFFECTIVE TEMPERATURE RE LATIONSHIP IN A LOW HUMIDITY RANGE 46 vi

ABSTRACT In this report an evaluation is presented of the results of measurements of temperature- humidity, and of other physical variables upon summer comfort conditions in the Mortimer E. Cooley Laboratory, University of Mi chi gan. Records were kept of sensations of' comfort or discomfort, together with the physical variables studie-d, for three rooms in the Cooley Laboratory. These rooms were: 1) one unshaded. room on the south side of the building, 2) one shaded room on the south side of the building, and 3) one unshaded.room on the north side of the building. It is concluded in. this report that the use of aluminum shade screens on.the south side of the building has greatly increased the percentage of days during which workers on the south side of the building feel comfortable. The increase in the percentage of comfortable days is attributed to the reduction of glare and of direct radiant solar heating of the rooms. Our obse-rvations have led us to agree for the- most part with the upper limits of the "summer comfort, zone" set forth by the American Society of Heating and Air-Conditioning Engineers when the effects of radiant heating are neglecte'd, These upper limits have been estimated by the American S.ciety of Heating and Air-Conditioning Engineers at 66~ minimum and 750 maximum for effective temperature and at 30% minimum and 70% maximum for relative humidity. Our conclusions are that a third coordinate should be considered -when radiant.heating is of importance. These conclusions may be summarized by our tentative definition of a "comfort volume." This volume would be- defined in two dimensions by the limiting. values of'effective temperature and of humidity, mentioned above, for the condition of no radiant heating. A third dimension for this "comfort volume" would be described by the locus of limiting values of (mean radiant temperature minus dry bulb temperature) at which a feeling of discomfort is experienced. The subject whose comfort is under study is understood to be in an environment which is under conditions for- which the American Society of Heating and Air-Conditioning Engineers" comfort chart would predict comfortable reactions when radiant effects between subject and environment are negligible Analysis of the data obtained indicates that roughly one additional degree of mean radiant temperature less dry bulb temperature may be tolerated without discomfort for -each degree of effective temperature less than the maximum of 75:Q. This relationship: appears to be substantially independent of relative humidity between the limits of 309%.nd 70% studied, The limits of effective temperature studied were 680 to 780 and the limits of mean radiant temperature less dry bulb temperature studied were 0 to 7~F. vii

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN I. OBJECTIVES The objectives of this study are two-fold: 1) To evaluate the effect of aluminum shade screens placed outside large windows with southern exposure in the Mortimer- E. Cooley Memorial Laboratory in reducing personnel discomfort caused by radiant solar heating of work areas. 2) To extend the understanding Of conditions required for human comfort in interior work areas by considering the simultaneous effects of radiant solar heating, humidity, and effective temperature. 1

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN II. ~INTRODUCTION The Mortimer E., Coo. ley Memora.l.Laboratovy,.locate-d at, the North Campus of the University of Michigan, has been occupied for over a year and a half an:d "during this period. the pers.: using the buildin.have become cognizant of many of the practical f-eatures which are inherent in the building design. A salient feat-ure of the desig. is the exrtensive use of plate glass in the north and south xterior'lls. Th m ity of the rooms h one all.. which is essentially of glass, Th. glass used has a blue tint which reduces the diret transmission of sunlight to se degree. The- use of:extensive -areas' of:gl'ass in the building design has provded a desirable impression of space- in the rooms and is regarded with favor from this point of view., However,- the use of glass as an exterior wll has caused the building t'o be unusually responsive to exterior weather condition/s as compad with a building of:onverntional conLstrction. One undesirable teffect of the rapid response of building conditions to weather conditions has been that some of the laboratories and offices on the south side of the building are uncomfortably hot on sunny days during the autumn season. This con.dition is caused by radiant, heating of the work area by sunlight, and by secondary radiation from the window glass heate:d by the absorption of that part of: the sunlight not re-flected or transmitted. As a preliminary step tward inve-stigation and possible alleviation of overheating on the south side of the building, aluminum shade screens- were installed &n six windows of Room 232 of the Cooley laboratory in October, 1954. While the installation of the s hade screens was s in'progress, Dr. L. W. Orr, of the'Engineering.Research Institute', recorded preliminary data- which indicated a definite increase in oiftofrt in the. room on. which the- shade- screen installation was: procee.ding Specific-ally, the -data reported were r'oom temperature inside surface temperature of the shaded glass and inside surface temperature of the unshaded glass:. The more comprehensive -study reported herein was designed to yield sufficient data for -evaluatlon of comfort conditions in rooms. of s-outhern exposure with, and without, shade screens and in one unshaded roor with a northern exposure. It was initially:nticipated that a correlation, of of comfort with radiant heating effects migrt be derived from the experimental data necessary for the desired e.valution of shade scereen perfo.ce, and such has be-en the case. Accordingly, an..pinion. of the shade screen per-formance -and.a preliminary correlatin of the- subjective feeling -of'tomfort" fwith the me.as-urable physical variables of mean radiant temperature, wet bulb temperat,: and dry bulb temperature are presented. _ ~~~~~~~~~~~2

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN III. EXPERIMENTAL PROGRAM A. General An experimental program was developed for this study in such a manner as to insure that necessary data were taken which would relate measurements of physical variables to sensations of comfort or discomfort of the workers in the Mortimer E. Cooley Laboratory. It was desired to obtain records of physical measurements and personnel reactions within the building and also to obtain a record of available weather data external to the building. A general outline is given here of the measurements taken and the methods of measurement used in this study. The pertinent experimental data required and the manner in which they were obtained are listed below. B. Exterior Measurements The exterior weather data were obtained from the Willow Run Weather Bureau, which is located less than ten miles from the Cooley Laboratory and in a similar environment. Values for the following measurements were recorded: 1. Outside air temperature 2. Wind velocity and direction 3. Sky coverage by clouds C. Interior Measurements Wet and dry bulb temperatures were taken daily from April through August, 1955 with a standard sling psychrometer. A recording hygrothermograph was located in the control room, but the data from this instrument are omitted because they offer no basis of comparison with conditions in the test rooms. Globe, room air, glass pane and screen temperatures were recorded at intervals of twenty-four minutes on the temperature recorder. The accompanying plan of the second floor of the Cooley Lab4ratory (Figure 1) and the elevations of the test rooms (Figure 2) illustrate the locations of the thermocouples in the test areas. The globe position was fixed at the same level as the upper portion of the bodies of human beings occupying the test areas. The inside air temperature was measured at a point six inches removed from the globe in order to avoid the possible influence of convection currents induced by the thermal convection of the: globe. The glass pane temperatures were recorded by thermocouples cemented to interior surfaces at the geometric centers of the panes. The screen temperatures were measured by a thermocouple cemented to the screen. 3

N m I' NORTH SIDE UNSHADED ROOM | | | | | T | 1 TST 2 265I 213 217 221 1 225 231 235 239 245 249 115' 1 13 d I 3 8 " 1' 8"' 376-" 184"' I8 4"' 184"' 4707 208 CORRIDOR 220 CORRIDOR 236 CORRIDOR 260 MEH 2 34 r246T71 r24 J 258 [2-6 272 2101 2 -T R Pa [m 7O" 1Wom. 256 262 [i. 232 256 57.1 216 420 | 1284' 5 I LOBBY 222-A 232-A 254-A 262-A 262-B 271-A 212 210 126' 150' 150, 1000** 212 I26~I'SHADE SCREENS m'SOUTH SIDE SHADED ROOM SOUTH SIDE UNSHADED ROOM ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN MORTIMER E. COOLEY BLDG. SECOND FLOOR PLAN SCALE I" 16' FIG. I- PLAN OF THE SECOND FLOOR OF THE COOLEY LABORATORY zS

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN SHADED ROOM -ELEVATION UNSHADED ROOM ELEVATION PLATE GLASS ALUMINUM PLATE GLASS k/ SHADE SCREEN SHADE SCREEN DETAIL -- a = 17~ (LOUVRE ANGLE) b = 370 (ANGLE AT WHICH INCIDENT RADIATION IS 1000/o BLOCKED) t SCREEN THICKNESS =1/16" THERMOPANE THERMOPANE CI'-o; i3'-0" itd' 3"-d THERMOFANE I THERMOPANE O.S. FROSTED I O.S. FROSTED LOC ATI ON INDICATES THERMOCOUPLE FIG. 2- ELEVATIONS OF TEST ROOMS LOCATION a LOCATION OF THERMOCOUPLES

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN The- data recorded were as follows: 1. Shaded Room - Southern Exposure a. Screen temperature b. Inside glass temperature (glass pane, frosted thermopane) c. Globe temperature d. Air temperature:e. Window position, inside shade position and thermostat setting f. Relative humidity 2. Unshaded Room - Southern Exposure a. Inside glass temperature (glass pane frosted thermopane) b. Globe temperature c. Air temperature d. Relative humidity e. Window, inside shade position and thermostat setting 3. Unshaded Room -Northern Exosure ao Inside glass temperature (glass pane) b. Globe temperature c* Air temperature d* Relative humidity.e Window, inside shade position and thermostat setting 6

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN IV. DESCRIPTION OF BUII;DING A, Description of the Rooms Selected for Experimentation The Cooley aboratory ha;s two exterior walls consisting essentially of glass. These walls face either north or south. In order to evaluate the effect of the aluminum shade screens, two rooms on the south side of the building were selected. one of which had. screens and the other of which had none. The room. without screens is referred to as the "unshaded room," while the one with screens is -referred to as the "shaded room." The "control room"' has no screens and faces north. The unshaded "control room receives very little direct solar radiation during the year, except in the sumer months when it does receive solar radiation in the early mornings and late:afternoons. B. Description of Windows in the Cooley Laboratory Figure 2 shows typical elevations of the windows in the Cooley laboratory, The entire wall consists of three sections of windows. "AKlo" glass is used in all three sections. In the upper two sections the' AKlo" glass is clear and in the lowest section it is frosted. In the lower two sections the ItAKlOtr glass is used in combination with clear plate glass to form "Therpane" panels. In the lower two sections the "AIKlo" glass is mounted. on the outside. The "AKlo"' glass is 1/4-inch thick, tinted blue, and is described more fully as "Blue Ridge AKlIo Heat"Abs6rbing Clear" glas s The "Thernopane" panels consist of two sheets of 1/4-inch thick plate glass mounted in the same frame and separated by an air space. Figure 3 illustrates the performance of the- above glass as. advertised by the manufacturer' (4). C. Heating and Ventilating Systems in the Rooms In the noral heating season, the rooms of the Cooley Lbboratory are heated. by a forced circulation warm air -central system. Auxiliary heat is provided. by finned tube convectors located horizontally below the windows at floor level In the summer thet forced circulati.on system is used to distribute air cooled by washing with 650F city water. With the windows closed, about 3.7 air Changes per hour are provided by the air circulating system. The circulating fan has a capacity of 28,000 cfm unir.the conditions of use, In the summer the..d.mpers on the room air inlet ducts -are maintained in the open position and hence the mean sir tvelocity in a particular room might be considered constant if the windows are left closed. However, to.avoidd imposing arbitrary and perhaps difficult-to-maint;ain restrictions on the personnel working in the test rooms, it was decided that windor position would.. left to the discretion of the occupants, on the asstumpion 7

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN Single 1/4" Blue Ridge Aklo heat absorbing clear gloss 48 Absorbed Hot in \ Sunlight 5% 47 % 71 % Enters the room 1/4" B. R. Aklo heat absorbing cleaor \'l O 1/ / — J1/4" plate glass Hoot in ~ ~. —--- 24 Sunlight 1 12 % 42 % 54 % Enters the room FIG. 3- ENERGY TRANSMITTED BY SINGLE AND DOUBLE GLASS PANESINFORMATION FROM REFERENCE (4) 8.

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN that windows and doors would be adjusted to give the optimum rocm comfort under the prevailing weather conditions. Spot chec/king with an anemomenter at normal wind conditions of 5 to 15 mplh, indicated that the room air velocity in the vicinities of the globes was in the 25-30 fpm range with the windows closed, and in 50-60 fpn.E range with the windows open. By using the data only for the days when the wind velocity is 5-15 mnph the constancy of room air velocity is justified if window position is specified. Experimentally it was found that a wind velocity of 10 to 15 mph gyve a room air velocity of 50-60 fpm in the vicinity of the globe thermometers located in the test rooms. D. Solar Radiation to the Rooms During the Year Figure 4 illustrates the duration of direct solar radiation to the south side of the building and the solar altitudes during the different months Of the year at the latitude of Ann Arbor, whic is very nearly 420N. Using the American Nautical Almanac (2), and Tables of Computed Altitudes and Azimuths (8), the altitude of the sun was calculated for the first of each month at the time of day when the iun was at the zenith. The duration and altitude: of solar radiation affects solar heating:of rooms with windows facing south. The severity of this effect varies with the seasons. In the summer atmospheric temperatures are high, partly because of the high altitude of the sun. Howve r, the duration of direct solar radiation to the south side of the building is only 8.to 9 hours, In the fall the sun is at lower altitudes than in the summer. Neglecting atmospheric absorption changes, the sun radiates more energy to vertical surfaces in the fall than in the summer because of the more nearly perpendicular impigement and the greater duration of direct solar radiation to the south side of the building. A maximum of more than 11 hours of solar exposure to the south side is reached in the fall. In addition the mean outside temperature is higher in the fall than on days of comparable solar exposure in the spring. These observations assist in explaining the qualitative observation that the period of greatest discomfort caused by solar heating of the south side of the building occurs in the fall of the year. This study was set up to study the spring and summer periodstto observe also the cumulative effect of higher air temperatures and. solar heat gain. A further study will be undertaken to observe similar situations during the fall and winter seasons. The altitudes of the sun when it is at the meridian are plotted in Figure:s 5 and 6. Figure 7 shows the path of the sun as seen from a point at the latitude of Ann Arbor. The figure is a view of the "syt"t with Ann Arbor as c rnter, The obse-rer is looking down and sees the path which the sun traces on the "sky." A more satisfying picture is obtained if one can assume that he is, for example, 50 miles 9

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ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN o 0 JUL. - o AUG. Ao 0 O FaIl JUNSEPT I Winter,S O Spring MAY o'0 A Summer PR. 0!0 10 WAL L FACING SOUTH FIG. 5 - ALTITUDES OF THE SUN (Ist ot the month) AT THE ZE N ITH. 11

ENGINEERING RESEARCH INSTITUTE. UNIVERSITY OF MICHIGAN 90~ JULY JUN 70~ U G. MAY 0 0 0; * 0 ACT~~~~~~~5 SE PT. (AT ZENITH) IltOF THE MONTH EC. JAN. FIG, 6 12

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN N 030 S DI AMETER WITH C E NTER AT LATITAjBDE OF ANANNN ARBOR, MICH GANRBOR 1~~~~1550 FIG.7 PLAN VIEW OF TRACE OF LINE TO SUN ON SPHERE OF LARGE DIAMETER WITH CENTER AT ANN ARBOR, MICHIGAN 13

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN in the air at a point directly over Ann Arbor. He looks down and views the trace made by a line joining Ann Arbor and the sun as this line "cuts" a plastic hemisphere, say lO miles in diameter with its center at Ann Arbor..: The altitudes and azimuths of the sun from sunrise to sunset are plotted for both solstices and for both e-quinoxes. It way be noticed from the figure that during the summer, the sun rises in the northeast sky and sets in the northwest sky. Thus, even though the length of the day is long,. the -sun remains in the south sky for a -comparatively short time. On both solar equinoxes, the solar path is the same, viz,, March 2 Lnd. September 21. It is in these seasons.: that the sun remains in the south sky for a relatively long time. In winter, as may be noticed for the December 21 solar path, the solar altitude is lowest and the length of the day is the shortest. The low duration of solar exposure in the winter would alone result in a small amount of solar heating compared with that to be anticipated during the spring, summer, or fall. At Ann Arbor, the sky is often cloudy in the winter, thus reducing the probable duration of solar heating to the lowest value expected for the entire year. 14

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN TABLE I DURATION OF DIRECT SOLAR RADIATION TO THE SOUTH SIDE OF THE COOIEY MEMORIAL IABORATORY (1954) DAEE TIME IN HOURS January 1 7.8 February 1 8.8 March 1 10.1 March 21 11.1 April 1 1.3 May:1 9.7 June 1 8.4 June 21 8.1 July 1 8.1 Anlglxst 1 9.1 September 1 10.7 September 21 11.1 October 1 10. 7 November 1 9.2 December 1 8.2 December 21.77 15

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN TABLE II ALTITUDES OF TEE SUN AT THE ZENITH ON THE FIRST DAY OF EACH MONTH (1954) MONTH ALTITUDE January 25Q 00' February 31 00o" March 40O 30' April 52~ 301 May 63~ OO' J~une 70 00 O July 71t 0o0' August 67Q 00' September 56Q 30' October 440 30,1 No'ember 330 30' December 260 15' 16

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN V. DESCRIPTON OF EQ IPMENT A. The Globe Thermomenter The. globe the'eter provides a convenient and simple means of evaluating the caombined effects of convection and radiation as they influence human comfort. It con ists of a hollow 6-inch diameter copper shpere coated with matte black paint an containing a therm.eter'with its bulb at the center. The. thermo.meter may be replaced by a tahermocouple in. order to- measure the temperature wlthout disturbing the equilibrium of the globe. The globe is sensitive to radiation, air temperature, -and air movement. If it is placed in an environment in whi.th the walls or other surroundings are warerr than the air, the radiation xeceived by the sphere in this environment will raise the temperature of the globe to a point above that of the surrounding air. Conversely with the surroundings cooler than the airt:-.the globe temperature wiall be. b'l.Ow the air temperature The difference between the globe temperature and the air temperature is a function. of the radiation received from all surfaces in vie~w of the globe. However, in order that this temperature -difference may be used to evaluate the magnitude of the radiation, the air velocity near the globe must be measured and appropriate allowance made to correct the observed difference of globe and air temperatures.. 1. Mea Radiant Temperature A globe must be placed in. a location with constant air velocity and. temperatures for abouut 15 minutes before the globe thermometer reaches a constant -reading. The rates of heat transfer to and from the globe are then...equal. Consider the case in which the surroundings of the globe are waer than the air in which the globe is placed. Then at -equilibrium the globe is re.ceiving- heat y radiation from the surroundings just as rapidly as it is losing' heat by convection to the air. The nmean radiant temperature of the surroundings may be inferred fr.m the temperature: Of the air, the temperature in the globe,:and th properties of the globe, as described below. Application of the Stefan-Boltzmann equation results in Equation (1) for the rate of radiant heat transfer HR to the globe, assuming.an emissivity of 0.95, R = (0.95) (1P73 x 10"9) (TS4 - TG4) (1) and E.uation (2) expresses the rate of convectii re heat transfer HC from the globe: as studied by Bedford and Warner (3) C ='.l69'rv (tg - ta) (2) 17

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Combining Equations (1) and (2) results in Equation (3). TS = 100 )4 + 1.028 v (tg - ta) (3) In equations (1), (2), and (3) the- following definitions are empl-oyed; HR rate of radiant heat transfer to the globe, BTUJ/ER x FT2 HC rate: of convective heat transfer from the globe, BT/HR x FT2 TS = temperature of surroundings, degrees Rankine TG = temperature of gtobe, degrees Ranktine v = air velocity, feet per minute tg = temperature of globe, degrees Fahrenheit ta = temperature of air,, d.egrees Fahrenheit Figure 8, taken from the -work of Bedford and Warner(3) permits graphical solution of Equatio: (3) for Ts. The temperature TS is the absolute temperature of the surroundings of the globe and may be called,Mean Radiant Temperature" or "Mean Black Body Temperature.' The mean radiant temperature TS is meant to be that uniform tenierature to which all surfaces in view of the gilobe must bei -heated: in order to give the globe temperature obtained in an actual- environment. The feeling of warmth or cold for human beings is directly related to the mean radiant temperature of the surroundings B. Temperature Recording Equipment and Procedure Thermocouple temperatures were recorded by an electronic nullbalance 12 record strip-chart recorder. This instrument employed'38;copper constantan calibration, with. a scale of O-2000~F A chart speed of.one inch per hour was used. A balancing time of one second and a printing interval of two minutes provided a record which was nearly free from over-printing. The rapid balancing time was specified solely to permit subsequent use of the instrument in applications requiring more ra.pid printing. 1. Calibration of the Recoirder Thermocouples were connected to the recorder described above, and the system comprising recorder and thermacouples was calibrated against an external standard of temperature. The 18

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 90..~ w 85 - w (,) 8 w.D~+15 -15, I. L,. nlY - 55 +15 - -15. 70- 150 w 14SCLBI. —:::) 6 -135' 4: 25. SCALE G60 BE z 20 AIR VELOCITY(ftTAnin) "I S -A +5 40 55 w SCALE E -10 - B- B 0 -15 +15 SCALE D SCALE C SCALE A GLOBE THERMOMEI' )x1 GLOBE TEMPERATURE TEM PERATURE (O F) MINUS AIR TEMP. (OF) SCALE E- LEFT SIDE-MEAN BLACK BODY TEMP (OF) RI GHT SIDE - MEAN RADIATION INTENSITY( B.T.U./sq. ft.,hr.) FIG. 8 - CHART FOR ESTIMATION OF MEAN RADIANT TEMPERATURE FROM GLOBE THERMOMETER READINGS based on the nomogroph of BE.J-ORD&a WARNER' JOURNAL of HYGIENE 16, p-458 (19 4

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN tec.nique erployed was. to place the thermocouples in a.water bath together with standardized mercury therm.meter and to cmpare: the- reaord.e tp tempetures with the temperature read by the the.ome-ter. The- mercury thermometer usised was a Princo, number 271726, with a e of. -?Cto +6.oc This thlert.mer bore the de signation NBS52 and had previously been determined. to have a mafimum error of +020OF.. The thermocluple temperatures recorded Aurring calibration of the inst..ent.n.oouple system were in all cases within.+0.50F, of the calibrated. the/m.meter readins.o 2. Temprrature Recorder Outside air temperature was continuously recorded by a bimetallic helix, clockwind recorder located inc.a shaded area on the roof of the Cooley Laboratory. Spot-checking revealed that the temperatures recorded by this instrument deviated less than 1~F. from temperatures indicated by the standard mercury thermometer used in 1., aboveo 3*..:4Lt Recorder A s:li.g Psychroet-e:tr was usedJ-to"obtain -wet-:and: dry-: bulb temperature data once each day in each of the test roomso Calibration of the the'rmomenters mounted on the sling psychro.meter against a National Bureau of Standatds mercury thermol meter indicated the maximum deviation to be O.2OFo A recording hygro-thermograph was located in the control room to record variations of relative humidity directly. The hygro-thermograph measurements were not considered primary data, but a check on daily humidity trends in the building. Co Thermocouple Settings Copper constantan thermocouples were used to measure temperatures recorded by the temperature recorder. The glass surface temperatures were measured by fixing the thermocouple to the glass surface with Canada balsam. The screen temperatures were measured by sealing the the'rmocouple bead with Canada balsam between two fins of the screen. Globe temperatures were measured by thermocouples located at the geometric center of the globe, and room air temperatures were measured. by thermocouples located at the same level as the globe; but removed from the globe a sufficient distance to be outside the influence of the thermal condition at the globe. 20

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN VI. EVALUATION OF RESULTS A, General This study of comfort conditions in the Mortimer E. Cooley Memnorial Laboratory was authorized during the overall period of November, 1954 to September 1, 1955. Requirements of time necessary to establish agreement upon an experimental program and the procurement of instruments resulted in a delay before actual measurements were taken until about February 15, 1955. A temperature recorder of the desired range could not be obtained until about May i, 1955. Preliminary familiarization runs using a 20 point recorder measuring from 0 to 10000F. were conducted from about February 15, 1955 to May 1, 1955. However, poor definition of temperature differences resulted from using the recorder with extremely wide range. Consequently, temperature readings of significance were not taken prior to about May 1, 1955. Further work refining the measuring circuits and conducting calibrations resulted in a further consumption of the month of May, 1955 before fully significant data could be obtained. The results reported in this study have necessarily stressed the measurements of physical conditions which prevailed within specified portions of the Cooley Building during the period of the study. It has been stressed above that no attempt has been made to control the conditions within the rooms under study in order to find the effects of the conditions upon human comfort. Consequently, the evaluations of comfort impressions reported are to be interpreted as qualitative only. A more reliable assessment of conditions of comfort would require the reporting of data at closely spaced intervals by a group of people who are trained. in the reporting of comfort conditions. Such a group would necessarily have to be sufficiently large and sufficiently representative of persons who might use the particular tyhpe of work area involved in order that a statistical sampling of the comfort impressions could be obtained. Most of the comfort impressions reported are those of a small group of one to three persons who were doing office work, drafting, and electronics laboratory work in the rooms under study. As a consequence of the recognized weakness in the evaluation of comfort, the correlation of sensations of comfort to the physical variables mentioned cannot be regarded as definitive. However, the comfort impressions are set forth for what they are worth. Temperatures were recorded in 12 locations in the three rooms under study during the periods reported hereino Humidity measurements were taken daily with a sling psychrometer and were recorded on a seven day strip chart in certain ro-oms Some additional readings of temperature were taken in the exterior air. It can be seen therefore that the measurements of the physical variables are probably much more reliable than the correlation of these variables to comfort sensations of working personnel. 21

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Therefore, probably the most reliable and significant of the results reported for this study are the measurements of temperatures in the working area. One of the questions for which an answer was most desired was that of the probable degree of discomfort resulting to personnel in the working area- of the Mortimer E. Cooley Memorial Laboratory because of the large areas of glass enclosing the south side of the building during periods of exposure of the south side of the building to direct sunlight. The impressions of comfort concerning exposure to the south side of the building to direct solar radiation are covered later in this report. A condensed summary of the results of temperature measurements from the south side of the building is presented in Figures 9, 10, and 11. These figures cover certain selected locations for the months of June, July, and August, respectively in 1955. The temperatures reported are those of a black globe hanging in the center of the room and of the stagnant air near this globe in each of the two rooms both on the south side of the building. One room had aluminum shade screens on the windows and the other had no shade screens on the windows nor any draperies or blinds of any kind on the interior. The temperature inside the black globe in intended to represent an approximation to the feeling of radiant heat which an individual would sense within such a room, and the air temperature is of course self-explanatory. The principal feeling of discomfort in entering a room under direct solar radiation with a south wall of glass is one of radiant heat. One feels a burning or prickling sensation much as he would upon opening the door of a furnace. The black globe measures the radiant temperature of all surroundings including the walls of the room and hence give something of an average radiant temperature of all parts of the room. However, the glass panes making up the south wall of the room generally were at quite elevated temperatures. The mean radiant temperature due to a high radiant temperature on one side and a relatively low radiant temperature on the other side of an individual in a room may not fully represent the potentialities for discomfort in such a situation. Figures 9, 10, and 11 present four temperature points for each day in June, July, and August, 1955. Temperatures were recorded in twelve locations, each location being recorded once each 24 minutes. Consequently, a temperature recording was taken once each two minutes of the entire 24 hour day for the entire 3 month period mentioned above in the summer, 1955. The points chosen therefore are selected from a total of 720 points taken each day. These 4 points represent the maximum temperatures for each point of each day. The maximum temperature did not occur necessarily at the same time for all points. Generally the maximum temperature for the two points in a given room occurred at the same time, within 20 to 30 minuteslof each other and maxima were recorded as being 22

MAXIMUM DAILY TEMPERATURES FOR LOCATIONS INDICATED MORTIMER E. COOLEY MEMORIAL LABORATORY m FIG. 9I1' 105 -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~'' Z A BLACK GLOBE, SOUTH UNSHADED ROOM, T.C. NO.' 0 AIR, SOUTH UNSHADED ROOM, T.C. NO. 5 to0 0c BLACK GLOBE, SOUTH SHADED ROOM T.C. NO. 8 - X AIR, SOUTH SHADED ROOM T.C. NO. 9 C' -I" 95 -.I ~.~ ~ 90 7 ~~~~~~~~~~~~~~~~m 3' w 85 - / 0 K~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 0 —'1 0 75'I 5 10 IS 20 25 JIUNE,1955

""C I I 1 r i r'1 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~L~'' ~~~~~~~~110~~C m MAXIMUM DAILY TEMPERATURES FOR LOCATIONS INDICATED MORTIMER E. COOLEY MEMORIAL LABORATORY FIG. 10 1 BLACK GLOBE, SOUTH UNSHADED ROOM, T.C. NO.7 Z 0 AIR, SOUTH UNSHADED ROOM, T.C. NO. 5' 1 BLACK GLOBE, SOUTH SHADED ROOM, T.C. NO. X AIR, SOUTH SHADED ROOM, T.C. NO.9 m9 100 =I 95 - _Fr x~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~Z r ~ — I u: X~~~~~~~~~~~~~~~~~~~~~~~~~~~ wI wt~ s- I — I.U'. 80 o I-~~X o X W~~~~~~~~~~~~ 0 hi I -I, 0 7~~~~01 75- 0lla. I m "rI 5 701~~~~~ID 15 20 25 30 JULY, 1955

110 L MAXIMUM DAILY TEMPERATURES FOR LOCATIONS INDICATED MORTIMER E. COOLEY MEMORIAL LABORATORY FIG. II mr 105 C1 C) I ~~~~~~~~~~~~~~~~~95~~~~~~3' \\ N0 r~~~~~~~~~~~~~~~~~~~~~~r \~~~ ~~~~~x- _~~x —-~~x\ tt w 90~~~~ W9 x r cb ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ cI \J1~ ~~~~~~~~~~~~~ I m w 85- w~~~~~~~~~~~~ C,'N.- X ll o x~~~~~~~~~~~~~X so Leo~~~~~~~~~~~~~~~~~~~~~~~~~~~~i X 0 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~d-n 75- / r,', I' I'~ 03 BLACK GLOBE aSOUTH SHADED ROOM, T.C.NO. It X AIR, SOUTH SHADED ROOM, T.C. NO., ~ ~ ~ ~ ~ ~ rr, \or HDDBo, f.C o0. t 5o 0 25 AUGUST, 1955

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN at the same time. Consequently, the difference between the black globe temperature and the air temperature can be regarded as taken at the same time and therefore representing the maximum elevation of radiant temperature over air temperature for the day indicated The maximum temperature for the shaded room generally occurred seaveral hours later than for the unshaded room. Quite pften the maximum temperatures for both the black globe and the air in the shaded room occurred at about 5 p.m., whereas those for the unshaded room occurred generally in the region of 12 noon to 2 p-m. Examination of Figures 9, 10, and 11 indicates that for all but one or two days reported the black globe temperature in the unshaded room exceeded by a significant margin the black globe temperature in the shaded room. For a large number of the days the temperatures of the black globe and the air in the shaded room approximated the air temperature in the unshaded room. However, on extremely hot days as indicated in FigureslO, and 11 for approximately the latter two weeks of July and August respectively, the air temperature as well as the black globe was significantly higher in the unshaded than in the shaded room. Even without reporting the complete summary of comfort impressions for each day involved in these figures one can surmise that the temperatures shown for July and August indicate a marked improvement in comfort conditions due to the presence of shade screens in the shaded room as compared with the unshaded room. B. Analysis of the Data for a Single Day As indicated above, the temperataure points recorded in Figures 9, 10, and 11 represent for each day only 4 points selected out of a total of 720. In order to show the manner in which the individual temperatures which were recorded varied with the time of':.day, a typical day has been selected for a more complete analysis. Figure 12 is a photograph of the temperature record registered on the temperature recorder for June 16, 1955. Points 5 and 11 did not reproduce in the photographic process. Figures 14, 15, and 16 have been plotted from these recorded data. Figure 14 shows the globe temperatures and air temperatures in the shaded and unshaded rooms as they vary during the day. The day chosen was clear and relatcively hot with a wind velocity of 10 miles per hour. The weather data on this day were as follows: Day - June 16, 1955 (Thursday) Sky Coverage - 0:.1 (clear) Wind - 10 mph; northwest Temperature - maximum 940F. (Figure 10) Minimum 58~F Barometer - 29.30"t high 29.23" low Humidity - maximum 80% 5:30 a.m. and 27% at 5:30 p.m. 26

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ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN The day selected was not the most uncosable experienced in the Cooley Building for the summer as implied by the temperatures in dicated on Figures 9, 1.0 and 11. However the variation of:temperatures throughout the day follows much the same pattern in all days studied in this investigati n. The chief qualification to: this arises from the differig.pparent paths of the sun on the celestial sphere with the change in seasonso As may be inferred by inspection of Figure 15, periodic maxima occurred for the glass pane on the control room located on the north side of the building: an unshaded room, at about 7 a.m. and 7 p.m. for the lkth of June. A similar fact can be noted in Figure 16 at about 7?p.m., where the temperature of the atmasphere apparently arose to a sharp maximum. This same effect can also be noted on the -one week strip chart of Figure 13, indicating the Outside air temperatures during the week June 13 to June 19, 1955. It is believed that these maxima in a windoane on the north side of the building and on the outside air temperature early and late in the day resulted from the fact that the sun was north of the east west orientation of the building at these periods. Consequently, the north side was being subjected to direct solar radiation uring the early morning and late after_noon. The maximum otf:the. outside air temperature in the late afternoon can be interpreted by notingl;.that the recording, thermometer was suspended from the underside of an Overhang;on the north side of a cupola on the roof of the Cooley Building. It was shaded from direct solr radiation from all directions except the northwest. Consequently, the apparent maximum in air temperature at about 7 psm. was probably not a real maximum, since radiation as well as local air temperature was affecting the recorder. It may be noticed from Figure 14 that in the shaded room the difference between the globe and air temperature varies between much smaller limits than the corresponding difference in the unsh&de:d room. However, between sundown and sunrise there still remains a small difference between the globe temperature and air temperature in the shaded room, whereas there is practically no' difference between these temperatures in the unshaded room. This observation means that the surroundings in the shaded room, that is the- walls aAd the- windqws, usually remain wfarmer than the air inside. However, at night the average temperature Qf the surroundings in the unshaded room is about the same as the air temperature inside the room. This behavior apparently means that it takes the shaded room longer to get warm but also longer to cool once the sun goes domn However, the maximum in air temperatures and globe temperatures in the shaded room usually occurred late in the aftern:oon from about 4 to 5 p.m0 Conseqguently, this room had all night to cool off before the w:orkers camne in the next morning. On June 16, 1955,, the maximum intensity of radiation received by the globe in unshade.d rom occurred at 2 p.-m. The difference between the globe and air temperature was 40F, in the unshaded room and 1~F in the shaded room. Assuming the same air velocity 32

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN in the two rooms, the- net radiant energy received by the globe in the unshaded room was 3: 56 BTU/hr/sq.ft., while that received by the globe in the shaded room was 0.9 BTU/hr/sq.ft. In other words the net radiant. -energy received by the globe in the shaded room was about 25T of that received by the globe in the unshaded room. Figures 15 and 16 illustrate the variation of temperature of the glass panes and the air and shade temperatures. The glass pane in the unshaded. room is cooler at night than the one in the shaded. room due to the larger radiation losses to the sky. However, this pazne heats up very rapidly when sunlight strikes the south side of the building, reaching a. maximum of 1000F:on June 16, 1955, compared to the corresponding 850~F in the shaded room~ In other words, the -temperature of the glass pane in the unshaded room responds very qu.ickly to the variations in solar radiation, whereas the shade screens retard the heating and cooling effects of solar radiati1on and atmospheric convection.on the glass pane in the shaded room., It is interesting t- note that the screen temperatures are sometimes lower than the glass temperatures during the priods of solar exposureo The temperature difference referred to is mainly caused by convective cooling if the wind is blowing from certain directions. On days when wind. blows northward, the screen temperatures are low due to convective heat transfer effects. If the wind blows southward, the screen temperature remains at a higher value than if the wind is blowing northward. The screens remain warmer than the outside air at night, probably because of heat transm fer from the rooms. The screens also cool faster than the glass, a consequence of their large s urface area, exposed position, and small thermal capacity. Figure 15 compares variation. of the inside surface temperatures of the frosted thermopanes with those of the single glass panes. The tempe:rature of the glass pane in the control room (facing north) is seen to rise abruptly' in the mornings and late- afternoons when the windows of this room receive direct solar radiation, but remain relatively cool the remainder of the day. This c'ure indicates a rapid rate off response to the variation of the incident radiation to. be irnerent in the glass pane. C. Comfort and Variables Influencing Comfort Before proceeding to the other results and their interpretation, it may be pertinent to clarify some of the technlical terms and the factors affecting human comfort. The most important of these terms are discussed below. Effective Temperature - Effective temperature is an empirically determined. index of the degree of warmth or cold felt by the human body in response to temperaiture, humidity, and air movement The use of the concept of effective temlperature has been described 53

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN by Yaglou, et al., (9). Effective temperature is a scale of thermo-equivalent conditions indicating the sensation of warmth, and to a degree determining the physiological effects on the human body induced by heat or cold. The numerical value of the effective temperature index for any given air condition is equal to the temperature of saturated air, which at an air velocity or turbulence of 15 to 25 feet per minute (representing practically still air) induces a sensation of warmth or cold equivalent to that of the given condition. Thus an air condition has an effective temperature of 650 when it induces a sensation of warmth like that experiencedin practically still air at 650F. saturated with moisture. Effective temperature alone does not serve as an index of comfort,. Moist air at a comparatively low temperature and dry air at a higher temperature may both feel as warm as air at an intermediate temperature and humidity. However, the sensations of comfort experienced in these three conditions of air would be different, although the effective temperature might be the same. Consequently, humidity must be considered in addition to effective temperature in setting up an index of probable comfort in the absence of large radiation effects Yaglou1 et al. (9) indicated that air with relative humidities above 70% is uncomfortably humid, while air with relative humidities below 30% is too dry for comfort The American Society of Heating and Air-Conditioning Engineers (5) developed a definition of a comfort zone which embodies the probable effects of effective temperature and humidity. The average summer comfort zone is between 660 to 750 effective temperature, the optimum being 71~. The relative humidity limits are placed between 70% and 30Q% The winter comfort zone has boundaries which indicate the comfortable conditions to be at slightly lower temperatures. It should be emphasized that these zornes are not very rigidly defined, but only indicate the conditions under which a large percentage of the subjects participating in the American Society of Heating add AirConditioning Engineers' investigation were comfortable. Mean Radiant Temperature - Mean radiant temperature is that uniform temperature to which all the surfaces in view of a globe thermometer must be heated in order to give the same globe temperature as the actual surroundings give, even though different parts of the surroundings may be at different temperatures. Idmitations of the Comfort Chart - The application of the summer comfort zone of the A.S.H.A.E i(5), is restricted to situations in which the human body has reached thermal equilibrium with the environment. Equilibrium is usually reached after 1-1/2 to 3 hours exposure. The comfort:,zne is further not applicable to conditions Where there is appreciable radiant heating, but only where the heating is of convective nature. The chart is thus meant to be applicable to homes, offices, etc. in which radiant energy interchange plays a minor part in the heating or cooling mechanism. 34

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN A considerable volume of work has been reported by the American Society of Heating and Air-Conditioning Engineers (5) describing some effects of radiation upon the limits of human comfort and enduranceo However, this information has apparently not been incorporated into the definition of the "comfort zone' referred. to above. In addition to being influenced by effective temperature and relative humidity -comfort is also a function of the physiological and psychological response of the human eyes to light ar.ad glare. Thus a person standing in the sun may feel a different degree of coifort than one standing in the shade, even though both subjects may be the same effective temperature, humid-ity, and mean radiant temperature. Glare is pronounced on clear days in modern bu.ildings which make widespread use of glass windows as an exterior wall. Hence light, or the glare from outside of a building7 is an important variable to be dealt with when zone considers human caomfort within a building. The Cooley Laboratory has north and south walls consisting essentially of glass. The use of large areas of window glass gives an impression of space7 but also admits a large amount of light and glare from the sky. Therefore the stu4y of comfort conditions in the Cooley Iaboratory requires consideration of lighting c onditions in addition to effective temperature, humidity, and mean radiant temperature. However, no attempt has been made in this investigation to measure or to evaluate the effect of glare, D. Comparison of the Shaded and Unshaded Rooms. with Resct t. o Comfort 1. Dr Bulb The dry bulb temperatures in the shaded and the aunshaded rooms were not appreciably -different during working hours. This observation is partly the.result of the personnel'at work in adjusting the windows and doors7 but is also due to the release of heat from electronic e quip3nent ope'rating in the shaded room. The amount of heat liberated by the equipment in the shaded room studied was observed to- be between 1000 to 1500 watts. The heat release in the urnhaded room was negligible, the overhead electric lights being the only connected electrical load. 2. Relative Humidity The relative: humidities -in the two rooms were not appreciably different. 3. Difference between Globe Temerature an Air Temperature The significance of any difference between glob temperature and air temperature has already been disecussed in a previous section (VII - A). The eleation of globe temperature above 35

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN dry bulb: temperature was observed to be much larger in the unshaded room than in the shaded room during the working hourso At the time of maximum dry bulb air temperature in the unshaded room on June 167 1955, the increment of the globe temperature over the dry bulb air temperature was 4OF. Thidifference is to be compared with an increment of l~F in the shaded room. Part of this temperature difference of 1OF in the shaded room can be attributed to heat generated in the electronic equipment operating there at that time. However, an estimate of the effect of the presence of this equipment is difficult to formulate and, since the total effect is small, it is assumed that radiation and air heating effects essentially cancel each other when interpreted in terms of globe and air temperatures. 4. C omfor Conditions On the following two charts (Figures 17 and 18) are plotted some of the effective temperature and humidity data observed in the shaded and unshaded rooms studied. The method of presentation adopted in these figures is based on that of the comfort chart developed by the American Society of Heating and Air-Conditioning Engineers (5). That the comfort zsone defined by the American Society of Heating and Air-Conditioning Engineers' chart is not applicable to conditions in the Cooley Laboratory may be seen by.noting the uncomfortable points lying within the t"comfort zone. Though scanty, these data are indicative of the relative number of uncomfortable days experience in the shaded room and in the unshaded room on nrmal working days in June., On very hot days, as experienced in the last week of June, both of the rooms were uncomfortable, although to a different degree. It may be concluded that subjects in the shaded room experience fewer uncomfortably hot days than those in the unshaded room. This conclusion is supported by the data on the glass- temperatures and globe and air temperature differences, which are the measurable variables which contribute to human comfort. E. Relationship of Effective: Temperature and Mean Radiant Temperature It has been mentioned that the American Society of Heating and AirConditioning Engineerst comfort chart is not applicable to rooms where there is an appreciable radiant energy effect. The mean radiant temperature, as defined earlier and as measured by the globe temperature, is probably the. best expression of the overall.effect of radiation at a given point. With the data for the three variables, globe temperature7 effective temperature and relative humidity availabley the possibility of extending the concept of the c:m-fort z'one to include radiant effec-ts presents itself0 The ~ollowing tables and curves represent an attempt at correlating the data obtained in this investigation in terms of simultaneous effects of effective temperat-ure, humidity, — and mean radiant 36

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN TABLE III COMPARISON OF SHADED AND UNSHADED ROOMS JUNE 7 TO JUNEE 30, 1955 SHADE]D ROOM DATE W.Bo, F D.B.'F E.T.O R.H4 FREELING 7 67 72'69 72 uncomfortable 8 65 5 74 70~ 5 63 comfortable 9 63 74.5 70 52 ~5 comfortable 10 65 75.5 71 56.5 chilly 13 61 73 68.5 50 chilly 14 61 73 68. 5 50 chilly 15 60.5 73 68.5 46.5 chilly 16 65 76 71 55 comfortable 17 66X 5' 79 73.5 51.5 uancomfortable 20 69.5 84.8 76 5 46.5 uncomfortable 21 63 82.5 73 35 comfortable 22 64 80.5 73-5 41 uncomfortable 23 62'5 78 71L5 41 uicomfortable 24 63 5 76.5 70 5 46.5 comfortable 2T7 64 81 73 38.5 uncomfortable 28 65~3 82.7 74.5 4o uncomfortable 29 65.5 83 75.5 39.5 comfortable 30 71 77 74 74 uncomfortable 37

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN SUMMER COMFORT ZONE WINTER COMFORT ZONE -- - 90 LLU 80 a: 60 ->. w Icn I.w:3 40 50 60 70 80 90 100 DRY- BULB TEMPERATURE DEGREES F FIG. 17 -COMFORT CONDITIONS IN SHADED ROOM JUNE 7 TO JUNE 30, 1955 + COMFORTABLE O UNCOMFORTABLE V CHILLY 38

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN TABIE IV COMPARISON OF SHADED AND UNSHADED ROOMS JUNE 7 TO JUNIE 30, 1955 UNSHADED ROOM D.ATE W.6.B. F.O DB o...F E.T. R. FEELING 7' 69 77.5 735. 65 uncomfortable 8 65.5 74 70 63 comfortable 9 63.5 76 71 49.5 comfortable 10 66 76.5 72 57.5 corortab1e 13 61 73 68.5 50 comfortable 14 61.5 74 69 48.5 comfortable 15 61-5 74 69 48.5 cortable 16 65. 715 57 unco.fortable 17 66.5 80 73.5 49 unc.omfort able 20 70 5 85 77 5 50 unamfortable 21 65 84 75 34.5 uncomfortable 22 63..5 80 72 5 39 uncomfortable 23 62.5 78 71. 5 41 unc omfortable 24 63 76 5 71 46.5 comfortable 27 63 78,5 717 39 comfortable 28 66 79.9 73.5 47 uncomfortable 29 69 83 5 75 46 uncomfrtable: 30 71.5 77. *5 74 74 uncoaf ortable 39

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN SUMMER COMFORT ZONE WINTER COMFORT ZONE -- 90 C,) 7o 60 79 ~~~w~~~~~~~~~~' LU w 50 60 70 80 90 100 DRY-BULB TEMPERATURE DEGREES F FIG. 18-COMFORT CONDITIONS IN UNSHADED ROOM JUNE 7 TO JUNE 30, 1955 + COMFORTABLE O UNCOMFORTABLE ____ ___ ___ ___ ____ ___ ___ ___ ___ 4 o _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN temperatures upon comfort. A correlation is presented which is applicable only for -the summer and i iintended to.dete'mine the upper limits of the comfort zone "when radiant energy effects were considered. Tables V, VI, and VII present data plotted in Figures 19, 20, and 21, respectively. In Figures 20 and 21 the elevation of mean; radiant temperature over the dry bulb temperature has been plotted aginst the effective temperature at selected values of relative humidity range, and. a straight line has been drawn separating the comfortable and the uncomfortable points. The points on such a line are hence points representing limiting values of comfort. Figure 19, and condition of 750 effective temperature and zero evaluation of MRT over dry bulb temperature is equivalent in termns of comfort to a condition of 710 effective temperatire and a 40 elevation of MRT over dry bulb temperature, Any point lying on the upper side of this line would be considered uncomfortable., while one lying on the lower side would be comfortable. In other words, this line is similar to the boundary line of 75o effective temperature on the.comfort chart in that it separates an uncomfortable zone from a comfortable one. However, the comfort chart correlation applies to the case in which the parameter representing the radiant energy effects, i.eo, mean radiant temperature minus -ry bulb temperature, is maintained constant at OOF. while Figures 20 and 21 represent the data for the case of essentiall.y constan relative humidity and variable mean radiant minus dry bulb temperature. Figure 20 shows a plot of MRT minus dry bulb temperature as a function of effective temperature for the points selected from the high humidity range (.60-70%). The slope of this line shows that 1,-2~F elevation of the MRT over the dry bulb is equivalent to 10 increase of the effective temperature. In Figure 21 are plotted points in the low humidity range, showing that 0.750F. elevation of the MRT-D.B. is equivalent to 10 increase in the effective temperature. In Firgure 19 is plotted the MRT-D.B. in the effective temperature range of 70-75.. "and for the intermediate humidity range. This plot shows that a i~F el.evation of MRT over the dry bulb temperature in this range is equivalent to a 1~OF ele'vation of the effective'temperatures in approachimng the limits of the comfort zo.ne. The data plotted in Figures 19,. 20, and 21 represent the actual -conditions in the selected rooms during working hours without any impositions or restrictions being placed by the experimenters. The -data are found to be widely scattered,. and the correlations are open to further experimentation with controlled variables. The curves indicate a 1.2 to 1, 0.75 to 1, and a 1 to 1 ratio of the elevation of MRT over the dry bulb temperature to the effective temperature in the three figures shown. However, an average value of one degree elevati0n of EMRT over the dry bulb temperature is taken as equivalent to a 10 increase in the effective temperature in the environment "ufder investigationo These results may be compared to those of Haughtey u-mst,. and Suciu (6), who made a similar study for winter conditions and found that for 750 E.T. and 50% relative humidity, a 1.50 change in the MRT 41

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN TABLE V MEAN RADIANT TEMPERATURE - EFFECTIVE. TEMPERATURE RELATIONSHIP IN AN' INTERMEDI.ATE HUMIDITY' RANGE D oB. RELATIVE M,R.T.OF. TEMPERATU REF O E T. HUMIDITY, MRT-D.,B.,OF. FEELING 90 83.5 75 46 6.5 uncomfortable 77 73 o5 65 2 uncomfortable 81 76 71 5 49.5 5 uncomfortable 85 80 73~ 5 49.0 5 uncomfortable 83 80 72.5 39 3 uncomfortable 79 79 74. 5 69 0 uncomfortable 80.5 79 74 62 1.o 5 uncomfortable 85 ~5 82 75.5 49 3 5 uncomfortable 79 5 79.5 735 51.5 0 uincomfortable 84 95 735.5 41 2 uncomfortable 84 81 7105 41 5 unacomfort able 84.5 83 7.5 5 9-5 1.5 uncomfortable 88.5 83 74 5 40 515 uncomfortable 85 81 73 38 5 4 uncomfortable 88 82 73.5 45.7 6 uncomfortable 82 79 72.5 655 5 c3.omfortable 84 - 83 73 35 1 comfortable 78 5 76.5 71 56 D 5 2 camfortable 80 76.5 71 55 5.5 comfortable 83 80 71.5 52 3 comfortable 76 74 70 5 63 2 comfortable 81 5 78 70 5 43.5 3 5 comfortable 795 79 70:.5 42.5 0 comfortable 84.5 77 71.5 52 7 5 unomrfortable 42

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN XSgEt 1t011-ill$ l:, m 0 it lift~!10mW~~~~~~l — P JxX 00111 tX1iwt4t4.....-il- +1|-N....ti" t'tS -l -'+ti-' 0flx-~i'L',........... X ffi 333 S V 1-l1 1lIftI.9p j 11~ I I -I I ri lK1 - i — S > = 4~~~ ~~~~~.., -''. -:-.,-r'.-,:::1'-i+'.-~: -..1'4.:+...i'l'~ -t-'L'' sE~~~~~~~~~~~-~-i —-; il1Ai i=X= Ag tME|_~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~' J i'.=",'.'-I':!"t X-|~ i~~~~~~~~~~~~~~~~~~~~~~~~~~i I t-,,...J.... +~ 9 l. h h % wX i N 0 -i.-_XX........ LZ:.;; k;;;....... -. -...- - ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN TABLE VI MEAN RADIANT TEMPERATURE - EFFECTIVE TEMPERATURE RE LATIONSHIP IN A HIGH HUMIDITY RANGE D.B. RELATIVE M..R.T., F. TEMIPERATURE,- F ETo HUMI.DITY, MRT-D.B., F. FEELING 82 79 72.5 65 5 3 comfortable 78.5 74 70.5 63 4.5 comfortable 79.5 75.5 72.2 64.5 4 uncomfortable 76 74 70.5 63 2 comfortable 75 73 69.5 61 2 comfortable 79 79 74.5 69 0 uncomfortable 80.5 79 74 62 o 5 uncomfortable 72 69.5 68 66 2.5 comfortable 79 77 73 5 65 2 uncomfortable 74 72.5 70 63 1.5 comfortable 82 76 71. 5 57 6 uncomfortable 83 77 5 72 57.5 5-5 comfortable 84.5 77 71.5 52 7.5 uncomfortable 83 80 71.5 52 3 uncomfortable 80 75.5 70 59,5 4 5 comfortable 83.5 79 75 75 4.5 uncomfortable 83.7 77.5 74 74 6.2 uncomfortable 44

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN I r~~~~~~~~~~~~~A_ ISII IE1 iSIE~S1$tlLtlX411 I100 6AW 4H 4X~ I I i~~~IJ_ -i:~ ~ UI, ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ -1I T i l l~~~~~~al 111112S j11 10F1112exiS;m- lillt2 1f1 0W 1FiXS11 111 1 k n!l~l m>l III Ii lllllll I-lllllfEiiilltl0i2l-0il 1 T t II 11 1 111 1ItI I 1 I!1ffS1Ff~~f~illl'lI 1 1l1111 Sli 1 1 r11 -TI 1__1111 4 1 < 1;II-I ITTTnt I' I I~~~~~~~~~~~~~~~~~~~~~~~ I1 ~ lx~mXS; |Utt WIT I11 11 1111 I I LL L al-VIP I I II iIIIII4Isilil~~~~l~~l~l$!lili li I:I I!li II tI iI I i; I rl WIm I — 1 —1-1111111111111 MIIII'iilllI'' I.!Itit Fll, llsIIIIMI t AVX m TfTI-FX IIIIWLIIIIXI ililill4lilAll I IIikll~lll lI I m _ dd-1-1 1-1E +1114111 -~~~~~~~ ~ ~~~~illil iillllililiiiillll =!! ji 111 "Hi i I4 "I i i H Ir T JL_ L! 1 I A -- L!I 1 1 1 1 1-1 1.1 I I I I I I I _I W [t~ltllll~tlllFFEvCTT OF MEA q RQDIAN T Tl MPERATURE I~lilil11111 1ON COMFORT tl~I~l L ~~HIGH HUMIDITY RANGE ( 60% TO 70% ) t:|| 45

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN TABIE VII MEAN RADIANT TEMPERATURE - EFFECTIVE TEMPERATURE RELATIONSHIP IN A LOW HUIDITY'RANGE D B.. REvLATIVE M.R.T. OF TEMPERATUREFo. E.T.0 HUMIDITY, MRT-D.Br~F. FEELING 89 85 75 34 45 4 uncomfortable 83 80 7205 39.0 3 uncomfortable 83 78 7105 41 5 urcomf ortable 84.5 79 7o 7 39 5o 5 comfortable 76 71 66 39 5 comfortable 76.e5 72 67 37 4,5 uncomfortable 70 70 68.5 34 0 uncomfortable 82 77 69 34 5 uncomfortable 78.5 78.5 70 5 310.5 0 uncomf rtable 89.5 83.5 72 27 6 comfortable 82.5 79 70 36 3.5 comfortable 77 75 68.2 38 2 comfortable 83 80 70.5 39 3 comfort able 84 5 83 73.5 39.5 1.5 uncomfortable 88.5 83 74, 5 40 5 ~5 uncomfortable 85 81 73 38 5 4 un omf ort able 46

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ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN was equivalent to 1~ change in the effective temperature in approaching the limits of the comfort zoneo Houghten's experiments were done in winter and in absence of any ay appreciable sky glareo The above results were summarized in Figure 22, where a dimension of MRT minus DoB. on the vertical coordinate is added to the usual two dimensions of effective temperature and relative humidity of the comfort chart. The use of this modified comfort chart can perhaps be best illustrated by an example. For instance, assume that the data are as follows: Effective temperature - 680 Relative humidity - 50% Mean radiant temperature minus dry bulb temperature - 50F. Point A is located in the plane of the figure by values of the relative humidity and the effective temperature. It should be noted that this point could also be located from the wet bnd dry bulb temperatures at constant low air velocity. Point B in space is lo~atsd by first moving from point A horizontally to the left to the 45 line (which corresponds to MRT-D.B. = 00 line), then vertically to MRT-D.B. = 50Fo line and then horizontally to the right to point B directly above point A. It is seen that point B is inside the surface of the comfort volume (solid zone). Hence this air condition would be comfortable. If,. however, for the same point A, the MRT minus dry bulb temperature were 80F, the corresponding point would lie outside the boundaries of the comfort zone defined by the planes LMPQ, LMN, MNOP, and OPQ. It would be possible to display the relationship for limiting conditions of comfort among mean. radiant temiperature less dry bulb temperature, wet bulb temperature, and dry bulb temperature by means of an alternative method of plotting. In this alternative method a two-dimensional plot would be used. Contour lines of constant limiting values of mean radiant less dry bulb temperature could be superimposed upon the usual American Society of Heating and Air-Conditioning Engineers' comfort chart. Such a method of plotting would avoid reference to a project;ion of a three-dimensional figure and would probably be more convenient in a practical work. A contour plot was not used to present the results of this study since contours of mean radiant less dry bulb temperature were parallel to lines of constant effective temperature. This is a result of the assumption:of the equivalence of one degree of (MRT-D.B.) to one degree of effective temperature, regardless of humidity. The use of the contour- plot should not be overlooked, however, if future work indicates that there is a marked dependance upon relative humidity of comfortable tolerance to mean radiant temperature less dry bulb temperature. It would be of interest to extend the correlation discussed above to deteimining the limits of the conditions which could be called 48

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ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN comfortable. Interesting speculations are possible as to the maximum depression or elevation of effective temperature which might be counteracted comfortably by means of radiant heating or cooling, respectively. A speculation upon further application of the correlation of mean radiant, dry bulb, and wet bulb temperatures to human comfort is that of correlating the limits of human endurance to extremes of temperature and humidity. The authors make no attempt to explore this subject in. this report, but merely suggest that the application of the method of.correlation discussed above relatilative to comfort conditions might be extended to studies of human endurance in environments in which the factors of air temperature, humidity and radiant temperature are variables subject to measurement or control. 50

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN VII. LIMITATIONS OF RESULTS The present program of investigations was designed primarily to evaluate the performance of the alumirnum shade screens on the south side of the Cooley Laboratory, and to obtain comfort data from the personnel during the usual period of occupancy, 8o00 a.m. to 5:00 p.mo The data have been obtained by imposing the minimum of restrictions or inconveniences on the personnel. Thus, for example, the windows, the thermostat settings, etc., have been left entirely to the discretion of the personnel. These uncontrolled variables have mnAde the correlations subject to random scatter of data. The globe thermometer has certain limitations in that it does not take into account the direct;ion of radiation, but iLndicates the overall amount of radiation, whereas the human being is sensitive to the distri bution of radiation, as well as the rate of radiant heat tran'sfer. It should also be mentioned that no attempt was made to estimate a possible effect from the presence of screens on the windows of the areas surrounding the unshaded roomo Such an effect might cause the data from the shaded room to be influenced by the heating of the unshaded room. Conversely, the presence of the warmer unshaded room ad" jacent to the shaded room would influence data taken in adjacent shaded roomso Although the effect may be small, it should be noted that such an interaction existed. and was beyond the control of the experimenters. The building functioned as an integrated whole, a-nd the rooms studied were not truly isolated. from their surroundings. The data, as mentioned above, were scattered. The observers were not numerous nor were they selected or trained to evaluate comfort objectively. Since the subjects were performing their normal duties of office work, drafting, and elctronics laboratory work, it was not possible to establish equili-brium between the subject and surroundings in.all cases. Hence the correlations and conclusions are considered an attempt to utilize the data collected, but are not considered by the authors to be definitive. It is expected that a statistical study of -extensive data would define a "comfort volume" not by rigid boundaries, but by bolnds within which a given percentage of a cross section of subjects would experience a feeling of cotafort. 51

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN VIII. CONCLUSIONS A. The screen installation on the south side of the C:ooley laboratorya is helpful in increasing personnel'comfort in the building. Typically the net incident radition entering the shaded room is about onefourth that entering the unshaded room. Further, the shades appreciably reduce the glare from the sky. B. The- screens reduce the radiation from the shaded room to the sky at night as compared to that from the unshaded room. This situation might be advantageous in the winter time, in that the heating load might be lower and the occupants of the building might feel wam.er because of an increas e in the temperature of the windows to which they are exposed C. The inside surface temperature of the double-walled glass panes are lower than those of the single panes. The possibility of installing the double -walled thermopanes in place of the single panes might be considered. The thermopane would be of advantage in the winter by reducing or perhaps eliminating condensation of moisture on the inside glass surfaces. Double panes would also reduce the winter heating load. D. The mainatenance of comfortable conditions in the building may become more difficult in the fall than in the summer because of the longer duration of direct solar radiation to tthe south side. because of the lower solar altitudes, and because of a relatively high outside temperature in early fall.. E. The mean radiant temperature is an important variable in human comfort. In the rooms studied in this investigation receiving considerable radiation and glare, 10F, elevation of'the mean radiant temperature over the d-ry bulb is approximately eqguivalent to 1~.elevation of the effective temperature-. Fo A study of solar azimuths and altitudes indicates that, of the direct solar radiation incident upon -the building studied, most of the radiation is received by the south side of the building. A more detailed study of the solar azimuths and altitudes might be helpful in determining the optimum orientation of future buildings of similar nature. 52

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN!IX BIB LOGRAPBeH 1o Architectural Forum, 96, 144, (1952). 2. Ae ric. Nautic 9al Alm nac U. S. Government Printing Officice, Washingtona. D. C.. 954) 3. BeIdford, T., and Warner, C. G.,. Journal oSf Hygine, 16, 458, (1934). 4. "Blue Ridge Alo Glass," Libbey ens-FordA Glass Company, Bulletin6 5 H eating, Ventilating and Air Conditioning Guide., American Society of Heating and Ventilat:ing.Engineers,- New York., (1948). 6.. Houghten, F.. C, GZunst, S. B., -and Suciu, J., A.S.H. V. E. Transcti~s, j, ~93, (1941) 7. "Kai'ser.Aluminum Suade Screenn.ing,".Ak.I.oA., File No. 35, 1,- March, 1954. 80 Tables of Caomputed Altitudes and Azimuths, U. S. Navy Department, HydNrographic Office, Bulletin NO. 214, Vol. V, (1.940) 9. Yaglou, CO P.,- et al., A.oSoH.V.oE. Transactions, 38, 410, (1932)O 53