Document paqwVvKbZJ8RRjdd670n9jNj

234 CHAPTER 11 1951 Guide (Item 7) of the cold air entering -by infiltration, or required to replace mechanical exhaust, represents the total heat loss equivalent for any building. DESIGN OUTDOOR WEATHER CONDITIONS There are no hard and fast rules for selecting the design outdoor weather conditions to be used for a given locality or type of building or heating system, and the selection is to some extent a matter of judgment and experience. The outside design temperature seldom is taken as the lowest temperature, or even the lowest daily mean temperature ever recorded in a given locality. Such temperatures rarely recur in successive years. Likewise the wind direction and velocity prevailing at the time of design outside conditions frequently are entirely different from those prevailing during the winter. The A.S.H.V.E. Technical Advisory Committee on Weather Design Conditions has recommended the adoption for heating load calculations of an outside design temperature which is equalled or exceeded during 97\ percent of the hours in December, January, February and March. Complete data of this nature are not available, but Column 7, Table 1, lists this recommended design temperature based on airport station readings for the period indicated, generally the five years, 1935-1939. In most cases these stations are outside of the city and these data apply primarily to rural areas. In general the use of the airport data for buildings within an adjacent city will not make an appreciable difference in design load. Because of the limited data available, design temperatures in common use are listed in Column 9. Many of these values were furnished by A.S.H.V.E. members--the balance were taken from an ACRMA Bulletin,1 manufacturers' publications and other sources,' and a few were estimated. The map. Fig. 1, shows isotherms approximated for these design tempera tures. They may be used as a. guide for localities not listed in the table. Interpolation between these lines is suggested, and due consideration must be given to elevations and other local conditions. Large differences in climate occur within relatively small distances of Weather Bureau stations in hilly and mountainous regions. Experience and judgment are necessary to deal properly with this factor. Column 8 of Table 1 gives the maximum wind velocity which occurred with temperatures the same as, and lower than, those shown in Column 7. Winter average velocities for all temperatures are given in Column 10. Column 6 lists the average annual minihium temperature which is the average of readings of the one lowest temperature occurring for each year the station has been in existence. It is of interest as a guide to the lowest temperature to be expected, except for an occasional extreme of short duration. INSIDE TEMPERATURES . The inside air temperature which must be maintained within a building is understood to be the dry-bulb temperature at the breathing line, 5 ft above the floor, or at the seating level, 30 in. above, the floor, and not less than 3 ft from the outside walls. Inside air temperatures usually specified, vary in accordance with the intended use of the building, and Table 2 presents values which conform to good practice. The proper dry-bulb temperature to be maintained depends upon the relative humidity and air motion, as explained in Chapter 6. - In other Heating Load 235 Table 1. Winter Climatic Conditions* Col. 1 Statb Col. 2 Station^ Col. 3 hi. VATION" FT Ala.----- CO Birmingham---- AP 'AP Montgomery._CO Ari*----- FMKliaongngstmgtaoaffnm--er--y- ,,ACAPOP a: AP (x; AP <x: AP cc CO AP AP (XI (XI AP Los Angeles--_co AP CC Red Bluff____ AP Sacramento cc Sacramento,.. AP (X! AP San Francisco <x: (x: William*____ AP CoL___ cc AP Grand Jasction-CC cc Paehlo......... Conn__ (X AP New Haven----GO _ AP D of C,,. Washington___,CO Washington AP n* Apalachicola cc Jacksonville.. CO Jacksonville--.-AP (XI Kcv Went Miami AP (XI Miami AP Pensacola___ CO Pensaooh_____AP CO Tampa__ n. AP -AP CO Augusta.... AP Macon______ CO AP Idaho__ SSaavvaannnnaahh___ CO AP pBnoipep*--------- CO -AP AP Idaho Falla AP Lewiston_____ CO Pocatello___ CO m Pocatello____ AP Chirsgn CO AP AAPP 733 711 615 143 219 293 226 6957 3473 1122 1112 2561 4853 4899 146 545 463 451, 282 499 740 1925 115 387 281 534 21 341* 346 579 116 22 90 34 164 100" 124 5398 5379 4587" 4770 . 4810 229 20 180 17 128 20 23 104 29 23 48 13 67 113 til 12 1020 424 408 115 56 2818 2849 4150 4744 763 4522 4467 319 601" 61S 660 Cot- 4 Period of Record*1 1893-1947 1893-1945 1939-1947 1872-1947 1940-1947 1872-1947 1938-1944 1899-1947 193S-1939* 1895-1947 1937-1947 Up to 1946 1935-19394 Up to 1946 1932-1947 1876^19464 1882-1945 1945-1947 1879-1942 1942-1947 1937-19464 1931-1947 1935-19394 1886-1947 1887-1939 1939-1947 1877-1947 1929-1947 1877-1934 1944-1947 193S-19394 1877-1947 1938-1947 1871-1940 1939-1947 1875-1947 Ud to 1046 1935-19394 1871-1947 1934-1947 1889-19454 1889-19384 1939-1947 190S-1940 1940-1947 1872-19464 1943-1947 1871-1947 1935-19394 1922-1947 1871-1947 1938-1947 1871-1947 . 1939-1947 1896-1947 1940-1947 1879-1947 1943-1947 1941-1946 1878-19454 1871-19464 1939-1947 1899-1947 1939-1947 1871-1945 1939-1947 1864-19394 1939-1947 1935-19394 WOO-1944 1899-1947 1938-1947 Up to 1946 1935-19394 1935-19394 1935-19394 Col. 5 Lowest Temp, on Record4 F -10 -10 -10 -1 13 -5 9 -25 - 8 16 21 6 19 -19 -18 21 -15 7 -12 7 19 21 - 20 17 23 28 23 17 25 17 17 22 25 34 27 22 -29 -30 -21 -27 -26 -18 -24 -15 --4 -15 18 10 16 41 42 27 28 .7 20 31 10 7 8 16 -28 -13 -18 -23 -28 -23 -23 Col. 6 Average Annual . Min. Temp." op 12 22 18 19 -15 26 -1 27 6 10 25 29 26 37 28 37 37 -11 -2 -1 -1 29 35 23 32 12 22 _j . 1 -12 Col 7 Design Dbt-Bulb Temp, on TAC97H% Baospis1 Col 8 Wind Vel at Design Temp.* Mph 21 7.4 30 84 22 8.6 . 31 5.630 64 6 7.5 21 6j6 33 5.6 35 4.9 27 84' 32 44 36 7-5 32 7.1 43 54 29 84 0 84 2 6.4 4 - 84 11 84 14 7.4 31 74 45 74 38 6.5 10.2 29 7.7 5 . 44 2 84 -7 7.6 6 74 -3 11.7 10.7 Col 9 Col 10 Design Det-Bulb Avo. Wind Temp, in Vkl-Dec. Common Jan.-Frb.* Use* P Mph 5 10 8.0 15 9.9 10 74 -10 7.7 25 5.4 25 5.2 -10 30 6.7 10 84 5 84 25 30 74 25 S.4 35 6.4 30 6.1 30 74 35 64 35 74 25 t-10 74 -15 4.4 -20 74 0 8.7 0 9.4 0 74 25 64 25 94 45 10.6 35 10.1 20 109 30 8.6 10 IL7 10 64 IS 6.7 20 94 -10 9.1 S 4.1 -5 8.9 - . 94 . -10 124 --10 -10 84 Blank spacee indicate data not yet completed.