Document 1gkbx8pvZ7db0G8vdjXG82NqK

American Society of Heating and Ventilating Engineers Guide, 1930 11. Calculations: See summary of heat loss calculations, Table 46-A, and heat loss calculation sheet for living room, Table 46-B. Table 46-A. Summary of Heat; Loss Calculations for Residence Shown in Fig. 10 Hook ob Space No. Room Glass Trans* mission Losses i 2 3 4 5 >6 7 8 9 10 11 12 Living Room...................................... Dining Room...................................... Kitchen....................... ;................... Dining Alcove--................................. Entry.................................. :.............. Vestibule..___ ____________ Bedroom (A) and Closet. _ Bedroom (B) and Closet.............. Bedroom (C) and Closet........ ......... Upstairs Hall .................i.................. Bath._................................... ............... Attic (heated). ................................ 7,100 2,640 1,060 1,370 1,888 1,854 3,773 3,960 2,900 1,450 1,450 3,040 Other Trans mission Losses - Infiltra tion Losses 9,040 4,640 3,300 3,718 1,312 1,436 3,558 4,070 3,765 . 920 1,940 28,021 8,970 742 663 807 4,320 3,900 1,445 1,445 1,660 1,660 1,660 1,425 Total m 25,110 ' 8,022 5,023 5,895 7,520 7,190 8,776 9,475 8,325 4,030 5,050 32,186 Grand Total of heat required for building in B.t.u. per hour at --8 deg. with a 17-mile southwest wind--..................... _.................................... 126,602 -h Table 46-B. Heat Loss Calculation Sheet for Living Room (Fig^ 10) Part of Buildino Exposure Net Surface Area or . Crack Length Co efficient Temp. Difference Net. B.t.u. Exposure Factor c Total ' B.t.ov . Wall................. Glass..--........... Crack Hein. E E E Wallb............... Doors.............. Crack He in... S S s Wall................. Glass................ Crack H6 in.a w w w Floor................. ; Over Basement 75.6 15.0 19.0 127.6 42.0 40.0 75.6 15.0 19.0 241.0 0.263 1.13 0.5 0.263 1.13c 2.50 0.263 1.13 0.50 0.339 78 1,550 78 1,320 78 (742)d 1,550 1,320 78 2,620 1.15 3,010 78 3,710 1.15 . 4,260 78 7,800 1.15 8,9704 78 1,550 1.15 1,780 78 1,320 1.15 1,520 78 (742)d 33c 2,700 2,700 Grand Total of heat required for room in B.t.u. per hour at --8 deg. with a 17-mife southwest wind...... ............................ ..................................... 25,110 aWindows weatherstripped. bChimney figured as part of wall, that is, of the same construction. oTmnsmission coefficient taken same as glass for entire door. dThree sides of this room are exposed and therefore only the wall having the greatest infiltration loss is used m estimating the total leakage for the room. If the infiltration loss for the south side of the roomlcon- taining the two outside doors had been less than half the total infiltration loss for the room, then half the total leakage would have been used. . , Air temperature, at floor assumed 65 deg. fahr. Air temperature in basement assumed 32 deg/fahr. 78 Chapter 2--Heat Losses from Buildings PREVENTION OF CONDENSATION ON . INTERIOR BUILDING SURFACES Condensation on the interior surface of buildings is often a serious nroblem. Water dripping from a ceiling may cause irreparable damage to manufactured articles and machinery. It often results in short-cir cuiting of electric power and lighting systems, necessitating shut-downs and incurring costly repairs. It also causes rotting of wood roof struc tures, corrosion of metal roofs, and spalling and disintegration of gypsum and other types of roof decks not properly protected. Condensation is caused by the contact of the warm humid air in a building with surfaces below the dew-point temperature, and can be remedied in two ways, (1) by increasing the temperature of such surfaces above the dew-point temperature, or (2) by lowering the humidity. Dehumidification, of course, is not permissible w;here a high relative humidity is necessary for manufacturing processes. Hence, the only alter native is to increase the surface temperature by decreasing the inside surface resistance. This can be accomplished by increasing the velocity of air passing over the surface, or by increasing the overall resistance of the wall or roof by installing a sufficient thickness of insulation. The latter method is generally used, and the thickness of insulation is determined by ascertaining the amount of resistance to be added to increase the temperature of the interior surface above the dew-point temperature for the maximum conditions involved. This in turn is based on the fundamental principle that the drop in temperature is proportional to the resistance. The thickness of~insulation required to prevent condensation on the interior surface of a wall or roof can be determined by means of the following formula: where x =k t -to fi (t .- to) x = thickness in inches of insulation to prevent condensation. k = conductivity of insulation in B.t.u. per hour per square foot per degree fahrenheit per inch thickness. U -- coefficient of transmission of uninsulated wall or roof in B.t.u. per hour per square foot per degree fahrenheit. fi = conductance of interior surface of wall Or roof in B.t.u. per hour, per square foot per degree fahrenheit. t = dry-bulb temperature of air near wall or roof surface, to = dew-point temperature of air near wall or roof surface, to = minimum outside temperature (usually taken as 15 deg. above lowest temperature on record for locality of building). (17) Example showing Use of Condensation Formula The following example will illustrate the use of this formula: Determine the thickness of insulation required to prevent ceiling con. densation on a roof constructed of 1-in. yellow pine sheathing covered with built-up roofing for an inside temperature at. the ceiling of 85 deg. 79