Document Xz3mqerGZ8rwyVgYoG0r9yrbG

172 CHAPTER 9 1955 Guide Table 2. Conductivities (fc) and Conductances (C) op Building and Insulating Materials--(Concluded) (design values)* i :ip 7'hese constants are expressed in Btu per (lour) (square foot) (Fahrenheit degree temperature difference). 77r Conductivities (k) are per inch thickness and conductances (O are for thickness or construction stated, not pcr >' l inch thickness. ' Material Description )ONB ULTI'i V ITT OB ResistancIv Conductance Density (Lb. per Cu Ft) (fe) K Per Foi*v Inch Thid-3 <C) Thick ness ness Listed?- (1) (*1 ROOFING WOODS INSULATING MATERIALS Blanket INSULATING MATERIALS INSULATING MATERIALS Loose Fill Type INSULATING MATERIALS .. Slabs Asbestos-cement shingles.......................................... Asphalt shingles............................................................. Wood shingles.................................................................. 120 70 -- _ 2.85 _ 0.35^ -- : 2.00 -- O.SOit *" 1.00 -- Asphalt roll roofing.................................. ................... Built-up roofing..................................................9i in. 70 l.l 70 -- -- 3.00 0--.91 --i 0.33.?: State......................................................................... Mm. -- -- 20.00 -- 0.05 Sheet metal............................................................. -- 300 -- Negl. Maple, oak, and similar hardwoods....................... Fir, pine, and similar softwoods.............................. 45 1.10 32 0.80 -- -- 0.91 ---A 1.25 Wood fiber*1...............................................................-- 3.2-3.6 Wood fiber, multilayer, stitched expanding*1-- 1.6-2.0 Cotton fiber*1................................................................... 0.8-2.0 Mineral wool, fibrous form, processed from rock. slag, or glass*1.......................................................... 1.5-4.0 0.25 0.27 0.28 0.27 -- 4.00 -- 3.70 -- 3.85 " -? -- 3.70 11.0-12.0 0.30* -- 3.33 Wood or cane fiber................................................ \ 13.0 i 20.0 0.33 0.39 -- 3.00 --, -- 2.56 Glass fiber........................................................................ 9.6 0.25 -- 4.00 --:IZ~ Macerated paper or pulp products.................... Shredded redwood bark........................................ Mineral wool (glass, slag, or rock)........................ Sawdust or shavings............................................... Vermiculite (expanded).............................. .......... 2.5-3.5 2.0-i$.& 2.0-5.0 8.0-15.0 7.0 0.28 0.30 0.45 0.48 -- 3.57 -- -- ,i -- -- 2.22 2.08 Corkbo&rd (without added binder).................... 6.6-8.0 0.27 -- Hog hair (with asphalt binder).......................... 8.5 0.33 -- Cellular glass.......................................................... 9.0 Shredded wood (cemented in preformed slabs) 22.0 1I -- 0.55 3.70 3.00 2.50 1.82 -- --7 Representative values lor ary maten&is at 10 r mean teuipe^atuie, bcuxucu us hue nuunu --- Advisory Committee on Insulation. They are intended as design (not specification) values for materials of-. building construction in normal use. For conductivity of a particular product the user may obtain the' value supplied by the manufacturer or secure the results of unbiased tests. b See also Insulating Materials, Board. c If no sheating is used, building paper will gap into the stud space. The air space thus formed adds t#; the resistance of the combination of siding and paper. For ordinary application of paper, the slight air spstf:'adds about 0.40 to the resistance. II paper is deliberately bowed into the stud space, the added resistance approaches that of a-plane airspace as a limit. The values given include a resistance of 0.06 for the building paper. d Includes paper backing and facing if any. In cases where the insulation forms a boundary (highfy reflective or otherwise) of an air space, refer to Table 1, Sections B and C, to obtain the insulating value the air space for the appropriate effective emissivity and temperature conditions of the space. <3.- * Tentative values pending completion of testing programs. V; ing. For increases of moisture content exceeding about 6 to 12 percent, the conduc- * tivity of frozen soil becomes progressively greater than that of the unfrozen soil..',' Effect of Density. Density affects the thermal conductivity of a soil in about thesame manner for all soils, at any moisture content, and for either the frozen or un-"; frozen condition. On the average, each one pound per cubic foot increase in dry density increases the thermal conductivity by about 3 percent. Effect of Moisture. An increase in moisture content, up to the point of saturation! causes an increase in thermal conductivity. The rate of increase in typical soils was as follows: average conductivities, in Btu per (square foot) (hour) (Fahretf; heit degree per inch), of four sands at a density of 110 lb per cu ft were: 6.8 at 2.5. percent moisture, 8.9 at 5 percent moisture, 11.2 at 10 percent moisture. Five soils' of a fine texture at a density of 100 lb per cu ft, gave average conductivities of 6-v at 10 percent moisture, and 9.5 at 20 percent. Thus, the doubling of moisture con:`` Heat Transmission Coefficients of Building Materials 173 tent within the ranges cited increases the conductivity by approximately 30 or 40 percent. At higher moisture contents the percentage increase would be less. Effect of Soil Characteristics. The thermal conductivity of the soil, at a given density and moisture content, varies in general with the texture of a soil, being rela tively high for coarse-textured soils and relatively low for fine-textured soils. The mineral composition of the soils also affectB the conductivity. Quartz tends to give high values, whereas minerals such as plagioclase feldspar and pyroxene, which are constituents of basic rocks tend to give low values of thermal conductivity. These points are illustrated by the values in Table 3 which lists seventeen soils in approxi mate order of their magnitude of thermal conductivity from greatest to least for seven different density-moisture content conditions. Some of the values in this table have been determined by extrapolation and are consequently approximate. Blank spaces in the table indicate that the density or moisture content, or both, are such that no tests were possible for that condition or that no tests were sufficiently Table 3. Thermal Conductivity : (fc) Values op Soils in Approximate Order op Decreasing Values* Mean Temperature--40 F Mechanical Analysis % by Weight Moisture Content--% Soil Designation Grav el Sand Silt Clay Over 2.0 mm 0.5 to 2.00 mm 0.005 Un to der 0.05 0.005 mm mm 4 100 4 4 10 10 20 Drt Densitt-lr per cu ft 110 120 90 110 90 20 100 Fine Crushed Quartz Crushed Quartz Graded Ottawa Sand Fairbanks Sand Lowell Sand 0.0 15.5 0.0 27.5 0.0 Chena River Gravel Crushed Feldspar Crushed Granite Dakota Sandy Loam Crushed Trap Rock 80.0 25.5 16.2 10.9 27.0 Ramsey Sandy Loam Northway Fine Sand Northway Sand HeaJy Clay Fairbanks Silt Loam 0.4 0.0 3.0 0.0 0.0 (airbaaks Silty Clay Loam i 0.0 Northway Silt Loam j 1.0 100.0 79.0 99.9 70.0 100.0 19.4 70.3 77.0 57.9 63.0 53.6 97.0 97.0 1.9 7.6 9.2 21.0 0.0 0.0 5.5 0.1 2.5 0.0 0.0 0.6 4.2 6.8 21.2 10.0 10.0 27.5 3.0 0.0 20.1 80.9 18.5 0.0 0.0 78.0 11.5 63.8 27.0 64.4 13.6 12.0 16.0 11.5 16.0 10.0 14.0 8.54= 10.5 8.5 11.0 22.0 13.5 9.04= 13.0 6.0 7.5 9.5 5.5 7.5 10.0 6.5 9.5 5.0 6.0 7.0 4.5 4.5 4.5 4.0 6.5 5.5 6.0 k - Btu per (square foot) (hour) (Fahrenheit degree per inch). 15.0 13.5 13 10.0 8.5 7.54= 5.5 9.04= 8.0 10.0 5.0 9.0 7.5 10.0 5.0 9.04= 7.5 9.5 4.04: 7.0 6.04: 7.0 close to permit a reasonable extrapolation of the data.' Granular soils, particularly those with high quartz contents, head the tabulation or have the greatest conduc tivity at a given condition. Sandy loam soils are midway in the table and fine raiP. so'Js s,lch as clay and silt loam are last. .*n}ting Thermal Conductivity. The four diagrams of Fig. 3 are presented to cm in the estimate of the thermal conductivity of any soil. Two of tne charts are or sands or sandy soils, and two for silt and clay soils. One of the diagrams for ach type of soils is for the frozen, and the other for the unfrozen condition. It is expected that these charts will give conductivity values with a precision of 25 per- The effect of such factors as density,, moisture content, freezing, or texture ay be easily approximated by use of these graphs. Specific Heat of Soils Tests to determine specific heat were run on twelve soils. On five of f e sds, tests were made at three or four mean temperatures varying om about 10 to 140 F. The specific heat values of all twelve soils varied y on]y a sma]j amount (about 0.01), and averaged 0.19 at 140 F. The Jecifie heat values of the soils decreased with a decrease in temperature. fte Average value at zero F would be about 0.16. Values at temperatures