Document gaBxaQrqQyy4wd199LDk56nZV

110 CHAPTER 9 1959 Guide Table 11 .... Coefficients of Transmission (U) of Frame Construction Ceilings and Boors* Coefficient* ere expressed m Sfv per (hour) (*qvare foot) (FcArenheft degi on ttitt air (bo win/) caadrtfoos on boft iide* car on the two tide*) and an bated Example--Floor K 5 Eionple of Substitution 346070 Resistances used are given below in this ladle or in Table 3 or 4 Heated room above unheated space Construction Resistance (R) (Heat flow down) 1. Top surface (still air)..................................... 0.92 2. Linoleum or tile (av. R)................................ 0.0$ 3. Felt..................................................................... 0.06 4. Plywood (H in.)........................... 0.78 5. Wood subfloor (*M^n-)................................. 0-95 6. Air space* (7M in.).......................................... I .25 7. Metal lath and Ye in. plas. (It. wt. egg )-.. 0.47 8. Bottom surface (still air)............................... 0.92 Total resistance............................................... 5-43 U - l/R = 1/6-43 -..................................... 0.18 See value 0.18 in boldface type in table below. Resistances used are given below in this table or in Table 3 or 4 Assume heated room is below unheated space so heat flow is up Total resistance......................................... Deduct 1. Top surface (heat flow down). 0.92 6. Air space (beat flow down)... 2.25 8. Bottom surface (heat flow down)................................................. 0.92 S.09 Difference................................................... 2.34 Add 1. Top surface (heat flow up)........0.61 6. Air space (beat flow up)................ 0.8$ 8. Bottom surface (heat now up).. 0.61 2.07 Total resistance.................................................... 4-41 U = l/R - 1/4-41 -.......................................... 0-23 To Adject U Vetoes for Construction with Added Insulation betveon Framing Member*, See Table 16 Direction of H Heal Flow Upward (Winter Conditions) HoeI flow Downward (Summer Condition*) Wood wbfloor felt, ond-- irO, Wood tubfloor (*5^j inj tnw l. bd. IV$ In.) and hard bd. (% In.) and Door tile o r llnloeum in.) Type of Ceiling i 1 s* ii 3? a* 73 j ~ Zo E6 6t t> a SJi | 8 6 t-o 60 4s il | ZA Ei xM *i o 4 !!i 1 i Is* 6, o X iu I z 1 J UO u X c i E Z Retistonce j-- - 0.98 1.38 1J2 1.87 226 -- 0.98 148 1J2 ?47 2.26 uU U U U Uu u U U U U A e C D E F cH 1 i K l _ Gypsum lath (K in-) and H in- plas- (It. Gypsum lath (% in.) and M in- plas. (sand 0.64 0.4! 0.65 0.61 0.30 0.27 0.29 Metal lath and % in. plas. (It. wt. agg.).. 0.47 0.59 0.28 Metal lath and % in. plas. (sand aggJ-- 0.13 0.74 0.31 1.43 0.38 0.22 Insul. bd. lath Q4 in.) and H in. plas. (sand 0.36 0.22 0.38 0.27 0.24 0.26 0.26 0.28 0.20 0.20 0.34 0.24 0.23 0.24 0.23 0.26 0.19 0.19 0.31 0.23 0.21 0.22 0.22 0.24 0.18 0.18 0.28 0.35 0.21 0.46 0.23 0.20 0.40 0.21 0.21 0.44 0.22 0.20 0.43 0.22 0.22 0.51 0.24 0-17 0.31 0.18 0.17 0.30 0.18 0.31 0.21 0.20 0.21 0.20 0.22 0.17 0.17 0.28 0.20 0.18 0.19 0.19 0.20 0.16 0.16 0.26 0.18 0.17 0.18 0.18 0.19 0.15 0.15 0.24 0.17 0.16 0.17 0.17 0.18 0.15 0.14 1 2 3 4 6 6 7 8 Acoustical tile Wood lath and in. plas. (sand agg.) 0.22 0.41 0.24 2.10* 0.30 0.19 O.X 0.21 0.40 0.62 0.29 0.22 0.18 0.26 0.19 0.20 0.17 0.18 0.24 0.18 0.19 0.16 0.17 0.22 0.17 0.30 0.18 0.17 0.18 D.3J 0.19 0.18 0.15 0.25 0.16 0.15 0.16 0.2 0.17. 0.16 0.21 0.45 0.22 0.21 0.16 0-17 0.15 0.15 0.19 0.15 0.16 0.14 0.15 0.18 0.14 0.15 0.13 0.14 0.17 9 10 11 12 13 * See text Motion Overall Coefficienta far bui* of calculation*. * To adjust U values for the effect of added insulation between framing members, at ' Ineludea aaphalt, rubber, and plaatae tile (M in.), ceramic tile, or tenasso (I in.). * Includes thermal resistance of H in. gypsum wall board. Heat Transmission Coefficients of Building Materials 111 per, *%:-in. wood sheathing, studs, gypsum lath, and sand aggregate plaster, with 2-in. fibrous insulation between studs. Softifton: According to the example calculation in Table 5 a wall of this construction with no insulation between studs has a coefficient U of 0.24. Referring to Table 16, Part A, it will be found that a wall of this value with 2-in. fibrous insulation be tween the studs has a coefficient U of 0.087. tained in one step to reenter the same table through Column I. In thi3 way U values may be obtained for combinations of insulation in the framing space. For combinations of fibrous insulations and air spaces, take account of the fibrous component first and the air space second as illustrated in Example 6. This is necessary to assure the ap proximately correct temperature difference across the air space. Attention is called to the necessity of applying the insulat ing material in accordance with the manufacturer's specifica tion. The engineer must evaluate carefully the economic con siderations involved in the selection of an insulating material as adapted to various building constructions. I^ck of proper evaluation, or improper installation may lead to unsatis Examples of the Use of Table 16 Example 3: Find the coefficient of transmission Ui of the frame wall shown as an example at the top of Table 5 wheo (a) a 2-inch blanket fibrous insulation is added between the studs and in contact with the gypsum lath and when (6) aiuminum-foil-backed gypsum lath is added. factory results. Special attention must be given to vapor barriers as outlined in Chapter 10. Moisture from condensa tion or other sources materially reduces the heat-flow resist ance of insulation. Solution; According to Table 5, the U value for this construc tion with no insulation in the air space is 0.24. Referring to Table 16, Part A, for walls, it is found that corresponding to the value 0.24 in Column 1, the coefficient for conditions (a) and (b) are: INSULATED CONSTRUCTIONS--HOW TO USE TABLE 16 () In Column 4, find Ui " 0.087. Use 0.09. () From Table 3, Section C, the effective emissivity E of aluminum foil is 0.05. In Column 8 find Vi = 0.173. Use 0.17. In Tables 5 through 15, U values are given for many com mon types of building wall, floor, and ceiling constructions. For such of these constructions as contain an air space, the tabulated U value is based on the assumption that the air space is empty, and that its surfaces are of ordinary building materials of low thermal reflectivity, such as wood, masonry, plaster, or paper. Considerable benefit in reducing the heat transmission coefficient of a construction can be effected by the application of thermal insulating materials in the air space. Table 16 provides a means of determining, without calcu Example 4' Consider the floor-ceiling construction shown in the example at the top of Table 11, insulated with a sheet of aluminum foil, or paper faced on both sides with foil, (effec tive emissivity E of air space -- 0-05) placed between the joists and dividing the air space into two equal spaces. From Table II, the U value for tne uninsulated construction is 0.18 for heat flow down for summer, and 0.22 for heat flow up for win ter. Determine the coefficient Ui for: (a) Heat Sowing downward from uncooled room above to cooled space below (a summer condition) and, (b) Heat flowing upward from heated room below to un heated space above (a winter condition). lation, the U value of the between-framing area of such con SoltUion: structions with the added insulation installed in the air space. Column 1 of Table 16 refers to the U values of uninsulated (o) Use Table 16, Part D, and corresponding to U * 0.18 in Column 1 find, in Column 11, Ui -- 0.049. Use 0.05. constructions as taken from Tables 5 through 15. Columns 2 to 14 of the table give corresponding coefficients Vi for the (b) Use Table 16, Part C, and corresponding to U = 0.22 in Column 1 find, in Column 11, Ui 0.12. constructions with various insulating applications in the be tween-framing air space, as indicated by the column headings. Table 16 is in 5 parts, (A, B, C, D, and E) corresponding to the type of building element and the direction of heat flow. Each part is based on temperature conditions considered generally appropriate for the case. Any and all U values are based on a series of assumptions as to nominal characteristics. Common variations in condi tions, materials, workmanship, etc., can introduce much greater variations in U values than the variations resulting from the assumed mean temperatures and temperature dif ferences described. From this it is also clear that the use of more than two significant figures in stating a U value is as suming more precision than can possibly exist. Three signifi cant figures are used in Table 16 merely as a means of reducing cumulative errors when the table is used several times to ob "' Special Uses of Table 16 Values of U< for insulating applications or combinations other than those indicated by the headings of Columns 2 to 14 of Table 16 can be ascertained if the table is used appro priately. For instance, going horizontally in the table from Column 2 to Column 3 is equivalent to adding ^ in. of fibrous insulation to the construction. Similarly, going from Column 2 to Column 4 adds 1} in. of fibrous insulation to the con struction. In the same way, going horizontally from Column 8 to Column 11 is equivalent to adding to a construction the insulating value of one additional highly reflective (E -- 0.05) air space, and going from Column 6 to Column 12 in effect adds two non-reflective (E = 0.82) air spaces to the construc tion, etc. Examples 5 and 6 show the combinational use of Table 16 tain a single result. It should ont be assnmpH that the figures are accurate, overall, to three significant figures. Also, a re sult taken from Table 16 should always be rounded off to two significant figures. To use Table 16: 1. Find in Column 1 of the appropriate table the value for U obtained from Tables 5 through 15 for the construction without added insulation. 2. If there is a column which exactly corresponds to the con dition for which you desire the U value, read the answer in this column, opposite the Column 1 value. Interpolate if neces sary. Example S: Determine the coefficient. Ui for the wall of Example 3, with 1J4 in. of fibrous insulation added on one side of the air space. Solution; (/ can be determined in several ways, by using Table 16, Part A, for example; (a) By going from Column 1 to Column 2 three times, for a total of lV$ inches of insulation, as follows; enter Column 1 at 0.24 and find Ui TM 0.166 in Column 2; enter Column 1 at 0.166 and find Ui -- 0.126 in Column 2; enter Column 1 at 0.126 and find Ui *= 0.102 in Column 2. Therefore, for a total of 1J in. of insulation, use 0.10. (b) More simply, by goiag from 0.24 in Column 2 to 0.103 in Column 4.-Use 0.10. 3. If there is no column which fully corresponds to the con dition for which you desire the U value, then obtain the answer by means of two or more steps--each time using the value ob Example 6: Considering again the wail of Example 5, assume that one-inch blanket insulation is to be installed in mid-space, (CeniiuMrd m f. Hi.)