Document 0Jv9nKg8KaovXXMGGy1NyRV6k

American Society, of Heating and Ventilating Engineers Guide, 1930 Chapter 2--Heat Losses from Buildings The internal resistance of a material is equal to the reciprocal of its so-called internal conductivity (k) multiplied by its thickness and is rep- Table 7. Conductivities (k) and Conductances (C) of Building Materials and Insulations I resented by the fraction X or -y1c, in the case of materials for which the k .C conductance is given in terms of the construction or thickness stated. For example: The internal resistance of 12 in. of brickwork on the basis 12 of a value of k of 5.0 is 5 or 2.40. The internal resistance of 2-in. hollow Based on Tests Conducted at the U. S. Bureau of StandardsP w, __ the coefficients in Tables 7-11. incl., are expressed in B.t.u. per hour per square iVOte. ----------Dfi-o 1 m. THICKNESS UNLESS OTHERWISE INDICATED BY NOTE b. ' Material Description Density (Lb. per Cu. Ft.) Mean Temp. (Deg. Fahr.) CONDUC-* T1VITY (fe) OR Conduc tance (O Asbestos and cement compressed.....;^ 123.0 86 2.70 clay tile based on the value of C of 1.18 is or 0.847. l.lo In the resistance, method, the sum of the internal resistances of all the materials entering into the construction, is added to the sum of the surface resistances, which are the reciprocals of the surface coefficients or-^~. The resistance of a surface in still air, based on the average value of/j or 1.34 1 is j"|4or 0.746. The resistance of an outside surface exposed to the wind, based on the average value of/Q or 4.02 (3 X 1.34) is or 0.249. The computed value of U obtained by the resistance method is obtained by taking the reciprocal of the sum of the internal and surface resistances of the construction. The solution of Example V in Fig. 3, by means of the resistance method is given in the following summary: Material BrickworkCement Mortar........... .. Hollow Clay Trip Plaster fevDsurrO.......... Total resistance (R)___ 11 Thickness Inches 12 A 2 A Internal CoNDUCTlVITT OR Conductance Surface Coefficients h' l0 Internal Resistance 5.0 (k) 8.0 (k) 1.18 (C) 2.32 (k) 4.02 (/,,) 1.34 (/i) 2.400 0.063 0.847 0.215 3.525 - Surface Resistance 0.249 0.746 0.995'. 3.525 4.520 / ;'. Balsam Wool*1------- --* Cabots QujJtJ-----------Cabots Quilt*----------.Celotex-------- --..... -- Corkboard._j,--.-------CorkboarcL. Corltboard.~_--- Corkboard (Eureka)Dry Zero*---------------Fibrofeltb.................. Flaxlinumb-------------Gyplap-------------------- Hairinsulb............. -- t^iriosulb------------Hair Felt*... Hair Felt*-- Jnsulex or PyrocelL-- Insulex or Pyrocell-- Insulex or Pyrocell-- Insulex or Pyrocell-- Insuiite----------- ------ Linofcltb------ --------- Lith________ ____ -- Magnesia (Rigid). Plaster.. Regranulated cork_ Rock cork-------------Rock wool-------- -- Rock wool--------Rock wool-----------Rock wool-----------Sawdust---------------Shavings-.------------Sheetrock--.........-- Sprayo-Flake----Thermofeltb..--.. Thermofeltb____ Thermofill______ Thermofill--------Thermofillb____ Torfoleum_______ Pressed asbestos------ ------------------------- Chemically treated wood fiber be tween layers of paper----. ECCell gIra1sSs4 buectiwwececun KlErXaUfkt pMaopyeVrA. -.--.A... Eel grass between Kraft paper_______ Rigid insulation made from sugar cane fiber...--_____________________ Pure; no added binder. ---- Pure; no added binder Pure; no added binder.......... ............... Assppnh<aultuic buiinudueur.............--...................... Kapok between burlap or paper.------ Flax and rye fiber.-.,---............. ---- Frulatx fnibl/ceir.-........ --......... ........... ............-- Gypsum between layers of heavy paper (H in. thick)A----- 75% hair; 25% jute------ 50% hair; 50% jute------ Felted cattle hair--------- Felted cattle hair.. Cellular gypsum--dry________ ___ --. Cellular gypsum--dry--...................... Cellular gypsum--dry........................... Cellular gypsum--dry-- --.--...... Rigid insulation made from wood pulp Flax fibers between paper...................... Rock wool, flax and straw pulp with boimnduecrr......-. ......--........................................................ 85% magnesia, 15% asbestos--------- Gypsum..........-...................... ........ Anubuouutt % Kin4.. IpNaUrUtiVcIlVeEs.--......---------- Rock wool block with binders.-,__ Fibrous material, made from rock. Fibrous material made from rock.. Fibrous material made from rock.. Fibrous material made from rock.. Ordinary. ------------------------- Ov/riudiinimariyy.................--........--__________ Gypsum mixed with sawdust between layers of heavy paper (0.39 in. thick) Shredded paper with silica binder JJUukteC aRnUdU adOsUbCeOstUoIOs fuibuecrtss,, fieul.tseud---- Hair and asbestos fibers, felted____ Dry, fluffy, flaked gypsum------------ Dry, fluffy, flaked gypsum_____ Dry, fluffy, flaked gypsum__ _.... Peat moss compressed into sheet form 60.5 2.2 4.6 3.4 13.2 14.0 10.6 7.0 14.5 1.0 13.6 13.0 53.5 6.3 6.1 13.0 11.0 30.0 24.0 18.0 12.0 16.9 4.9 ' 14.3 19.3 46.2 8.1 16.7 10.0 14.0 18.0 21.0 60.7 4.2 10.0 7.8 34.0 26.0 19.8 10.2 86 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 86 86 90 86 90 90 90 90 86 86 90 94 90 90 90 90 90 91.5 0.84 0.27 0.26 0.25 0.34 0.34 0.30 0.27 0.32 0.24 0.32 0.31 2.60b 0.27 0.26 0.26 0.26 1.00 0.77 0.59 0.44 0.34 ' 0.28 0.40 0.51 2.32* 0.31 0.37 0.27 0.28 0.29 0.30 1.04 0.71 3.60S 0.28 0.37 0.28 0.60 0.52 0.35 0.29 / = -^- = ^g20 = B.t.u. per hour per. square foot per 1 deg., fahr- difference in temperature between the air on the two sides of tfiewall: In computing heat transmission coefficients of floors laid directly onthe ground (Table 31), only one surface coefficient-(/i) is used. For, ; example, the value of U for a 1 in. yellow pine floor (actual thickness' Woods: Balsa wood-- Balsa woodBalsa woodCypress___--^ MapleMahogany............ Virginia Pine------- White Pine______ Across grain........... Across grain........... Across grain-.------Across grain.-........ Across grain-......... Across grain........... Across grain.......... Across grain______ ` 20.0 8.8 7.3 28.7 44.3 34.3 34.3 31.2 90 90 90 86 86 86 . 86 86 0.58 0.38 0.33 0.67 1.10 0.90 0.96 0.78 in.) placed directly on 5 in. concrete on the ground, is determined as follows: ' < Mn addition to the conductivity values for the authorities listed, considerable work of importance per taining to the heat transmission of various types of construction and materials has been done by the late Prof. John R. Allen and Prof, A. 1. Wood of the Engineering Experiment Station of Pennsylvania State 1 College. bFor thickness stated or used in construction, not per 1 in. thickness. U = 1 , 0.781 5.0 = 0,472 B.t.u. per* hour per square foot 1.34 ^ 1.00 + 8.30 hTNhoetccoonmdpurecstsiveidty. of plaster varies with the composition. Note range of values from 2.32 to 8.0. The average value for plaster is probably about 5.0. On account of the comparatively high conductivity of plaster and the fact that it is seldom applied more than H in. thick, this material does not appreciably per 1 deg. fahr. difference in temperature between the ground and- the air immediately above the floor. f * effect the overall transmission of a construction; excepting in the case of thin uninsulated walls. pSee Chapter LX, by Chas. H. Herter of the Report of the Insulation Committee, A. S. R. E., Annual Meeting 1922, Revised to 1924, entitled. Heat Transmission of Insulating Materials for a more compre hensive collection of heat transmission data relating to building and insulating materials. 22 23 i ,4