Document 8Rw4amVZ6QKJ7aEpKBaRvY31o

194 CHAPTER 15 1962 Guide And Data Book to be rather minutely subdivided, whereas the interior tone spaces will commonly be divided into relatively large areas (such as stenographic rooms, lobbies, file rooms, etc.). Ail that has been previously said in this chapter applies to the peripheral cone areas; they will have rapidly changing cool ing loads in summer, due to drifting son and weather, *nd they will require heating in winter. During intermediate seasons one side of the building may require cooling while, at the same time, another requires heating. On the other hand, the anterior zone spaces, whose thermal loads are de rived almost entirely from lights, office equipment, and peo ple, will require oooling at a fairly uniform rate throughout the year. Most often, conditioning of these interior spaces must be done by an independent system which is frequently of the att-ozr type. A considerable portion of the air extracted from these spaces must be reconditioned, mirwH with a rea sonable proportion of outdoor air at each circuit, and re circulated in order to achieve operating economy in cummer and winter. During intermediate seasons, when the outdoor tempera tures approximate what the delivery air temperature should be for toe tone, good results may often be obtained, without the use either of refrigeration or beat, by supplying a sufficient amount of outdoor air and little or no recirculation. Quite usually, the amount of true exhaust removed from office building floors will be relatively negligible, in comparison with the amounts of air to be supplied for conditioning but, in some manner, air must be removed at a rate emparable to rate of supply. Office buildings will commonly be fully occupied during the hottest hours of toe day (and little, or not at all, at night and on Sundays and holidays); therefore their dwersity- factor will be high and their annual load-factor will be low. 2. Hold Rooms. The typical hotel bedroom will be ther mally similar to the peripheral zone rooms in office buildings except that, especially in tropical areas, they may be shaded frequently by outride balconies of some depth. Here toe similarity stops. Normally, there will be an interior bathroom for each guest room and, in certain types of hotels, there may even be a small kitchenette. These will require exhaust ven tilation that is quite often greater than the volume of out door air the bedroom itself would need for adequate ven tilation. Since it is important to keep the bedroom slightly pressurized in order to avoid indrafts of possibly highhumidity air at windows, tire bedroom air-conditioning sys tem must bring in at least an amount of conditioned outdoor air equal to the amount of exhaust ventilation from bath rooms, etc. Also, since the door between public corridors end the bedroom should be tight-closing and, also, will be closed most of the time when the room is occupied, ventilation required for corridors, serving pantries, or other such spaces should be quite independent of the bedroom air-conditioning arrangement. Guest rooms in hotels may be largely unoccupied during the hottest hours of the day (varying with locations and types of hotels), but will commonly be occupied at night and on holidays--thus giving a lower diversity-factor higher load-factor. a 3. Hospital Private and Semi-Private Patients' Rooms. What has just been said of hotels applies in large measure to patients' rooms in hospitals but will be modified somewhat because one bathroom may serve several patients, and be cause doors between patients' rooms and corridors, etc., will be open more of the time than in a hotel. Patients' rooms in hospitals will be occupied day and night forseven days of the week. This causes a still different relation between peak and average load conditions, all of which will affect both the required refrigerating capacity and its *n^nTj operating cost. 4. Apartment Buildings. These buildingB differ from the previous three in a number of ways: a. Typically, the individual rooms are larger. b. Different rooms, even on opposite sides of the hni1*i;n. in many cases, will often have archways or generally, open doors interconnecting them. c. Kitchen exhaust will frequently be a factor that affa-tn required air supply for the main rooms. d. For reasons of esthetics and furniture layout, window areas may frequently be less in proportion to floor area than in the other three building types; especially if compared with office buildings. e. There will be wide differences in electrical and human bad, at different times. One apartment may be crowded with people, with all lights turned on, while another may be completely empty at the same time. The largest human and lighting loads will frequently occur after sundown or late in the day. It is a real question to what extent the air-conditioning should or can allow for the crowded conditions of a dinner party or oocktaQ party. This will to a large extent depend upon the type of house. What may be economically feasible in a luxury apartment may not be practicable for a low- or middle-income apartment. In many apartments, es pecially of the better grades, a considerable part of the population may be away (with all lights, etc., turned off) during some of the hottest periods of the year. Ex perience indicates that for all seasons the overall diversity factor for an apartment house will be very much lower than for other types of multiroom build ings. These differences in buildings have been stressed to bring out the effect that they should have upon intelligent air- conditioning design. For the office building, the hotel, and probably the hospital, the air-conditioning will have a rea sonably steady day-to-day use, so that investment and operat ing costs may be related to income earned. The apartment house, in most cases, must cope with the fact that some tenants will use the air conditioning much than others, and some may object to paying a premium price for what they do not use or need. Systems entirely suitable for one type of multiroom building may not be the best for another type. For instance an apartment bouse owner may be more in terested in low initial investment, whereas the hotel or office building may be more interested in low annual operating and maintenance costs. ZONING REQUIREMENTS The first approach to a zoning problem is an examination of the building plans to determine the zoning requirements- Any multistory building must be divided into four peripheral zones (usually east, south, west and north), iuiWbm it is long and narrow with blank ends. The cooling load varies con siderably as the sun progresses around the building. The presence or absence of this solar heat is one of the principal reasons for toe zoning requirement. A fifth zone is created by any interior spaces with a load derived largely from people and lights. The peak load for each outside zone must be determined by a detailed cooling estimate, considering the hours of maximum solar heat gain. These estimates for each zone must be further analyzed to determine the peak load for toe building as a whole. Assuming that the sun-exposed walls are of approxi mately the same area--and not shaded by other buildings-- the building peak (at 40 deg north latitude) will normally public Buiiding Air Conditioning 195 Toble 1 .... Total Sensible Heat Gain Through Unshaded Single ftate Gtast far 35 Id 4S deg Nrtt tofifwde for Aog. I TO. 0*g. s"n~ Btu per (HowHSqverc Foot) TnM Ooortotrae (or SoJcr Azzonrffi) 0*gr 0 30 60 90 120 150 ISO 210 240 270 300 330 11 0800 11 45 170 183 170 82 14 9 9 9 9 9 0900 11 31 141 167 162 120 38 12 10 10 10 10 15 1000 17 21 62 121 136 132 70 23 20 20 20 19 1100 24 26 30 66 108 111 95 46 26 26 26 24 18 1200 32 32 32 34 53 96 m 94 57 34 32 32 19 1300 35 35 35 35 35 53 104 . 127 120 73 40 35 1400 36 36 36 36 36 40 87 150 156 140 80 41 36 20 1500 35 35 35 35 35 35 61 156 185 190 162 55 20 1600 34 34 34 34 34 34 38 111 191 212 198 85 20 1700 34 34 29 29 29 29 30 63 181 202 189 100 19 1800 40 23 22 22 22 22 24 38 113 138 142 115 Summation Avxbaoe 308 352 626 762 820 754 669 829 1072 994 908 525 28 32 57 69 75 69 61 75 97 90 84 48 Note: Underlined figure w peek value (or tie* orientation. occur,at 4:00 p.m. on or about August 1 when the west sun is at a peak and transmission- gains may likewise be at a maximum The tendency, however, to assume that the peak load on all buildings will occur at 4:00 p.m., may frequently be in error. If the time of the peak load is not obvious, the designer should carefully check the load at, say, 2:00 p.m. when the sun may be diming simultaneously on both the south and west windows, or at 10:00 ajn. when the sun is on both east and south windows. Likewise, in toe northern hemisphere the angle of incidence of the south sun is decreased during the late fall and early winter, which greatly increases the solar heat gain on a south exposure. While this condition may not increase the load for toe building as a whole, it will represent a demand peak for the south zone. In any case, the proposed zoning should be carefully analyzed for several different hours and for different seasons to insure adequate capacity at any time during the year. SOLAR HEAT GAINS Table 1 shows total sensible heat gains through unshaded tingle plate glass, per net square foot of glass, for various orientations, including both direct radiant energy and trans mission due to temperature-difference. Table 1 is based entirely on metoods.described earlier in the 1961 Guide And Data Book except that the differential between outdoor dry-bulb temperature and (an assumed) 75 P indoor dry-bulb has been assumed to vary (as shown in Table 1), increasing gradually from early morning until late afternoon. For this chapter, it will suffice to say that the use dther of heat-absorbing glass or of good reflective inside Venetian blinds will reduce the total by 40 to 50 percent under maximum sunshine and temperature conditions. This per centage will vary somewhat with time of day, orientation, weather, etc. It may also be noted that in early October total beat gain will be greater than in July and August by about 50 percent for true south exposure. This percentage decreases systematically to about 9 percent at 60 deg (azimuth) either side of south. INTERNAL LOADS Aside from the sun effect, there are other variable loads. The use of lights will vary from room to room according to the type of work being done and to personal preference. There may likewise be heat loads from business machines in certain areas. Lighting Loads In accordance with the most recent practice in office build ingB, fluorescent lighting will vary from 3 to 5 watts per sq ft of floor area and incandescent lighting from 4 to 7 watts per sq ft. In some instances where concealed lighting is used, the lend may be as high as 10 watts per sq ft. At one time, it was considered that only half the lights in outride sun-exposed bays would be in use when the sun is shining and, therefore, only half the heat gain from these lights was included simul taneously with the maximum solar heat gain. However, ex perience has proved that toe occupant uses all of the lights (including those nearest the windows), hence the total lighting load should be included. In hotels, apartment buildingB and hospitals, toe average lighting load is frequently 2 to 3 watts per sq ft. Such lighting can, as a rule, be ignored in outride rooms, or rather con sidered non-concurrent with maximum sun load. I