ASTM_C_1340_-_C_1340M_-_10_2015.pdf

Designation:C1340/C1340M10(Reapproved 2015)Standard Practice forEstimation of Heat Gain or Loss Through Ceilings UnderAttics Containing Radiant Barriers by Use of a ComputerProgram1This standard is issued under the fixed designation C1340/C1340M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice covers the estimation of heat gain or lossthrough ceilings under attics containing radiant barriers by useof a computer program.The computer program included as anadjunct to this practice provides a calculational procedure forestimating the heat loss or gain through the ceiling under anattic containing a truss or rafter mounted radiant barrier.Theprogram also is applicable to the estimation of heat loss or gainthrough ceilings under an attic without a radiant barrier.Thisprocedure utilizes hour-by-hour weather data to estimate thehour-by-hour ceiling heat flows.The interior of the housebelow the ceiling is assumed to be maintained at a constanttemperature.At present,the procedure is applicable to sloped-roof attics with rectangular floor plans having an unshadedgabled roof and a horizontal ceiling.It is not applicable tostructures with flat roofs,vaulted ceilings,or cathedral ceilings.The calculational accuracy also is limited by the quality ofphysical property data for the construction materials,princi-pally the insulation and the radiant barrier,and by the qualityof the weather data.1.2 Under some circumstances,interactions between radiantbarriers and HVAC ducts in attics can have a significant effecton the thermal performance of a building.Ducts are included inan extension of the computer model given in the appendix.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.2.Referenced Documents2.1 ASTM Standards:2C168 Terminology Relating to Thermal Insulation2.2 ANSI Standards:X3.5 Flow Chart Symbols and Their Usage in InformationProcessing3X3.9 Standard for Fortran Programming Language32.3 ASTM Adjuncts:Computer Program for Estimation of Heat Gain or Lossthrough Ceilings Under Attics Containing Radiant Barri-ers43.Terminology3.1 DefinitionsFor definitions of terms used in thispractice,refer to Terminology C168.3.2 SymbolsSymbols will be introduced and defined in thedetailed description of the development.4.Summary of Practice4.1 The procedures used in this practice are based on thethermal response factor method for calculating dynamic heatconduction through multilayer slabs(1,2),5along with a modelfor convective and radiative heat exchanges inside and outsidethe attic.4.2 The operation of the computer program involves thefollowing steps:1This practice is under the jurisdiction of ASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.21 on ReflectiveInsulation.Current edition approved Sept.1,2015.Published September 2015.Originallyapproved in 1999.Last previous edition approved in 2010 as C1340 10.DOI:10.1520/C1340_C1340M-10R152For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.4Available from ASTM International Headquarters.Order Adjunct No.ADJC1340.5The boldface numbers in parentheses refer to the list of references at the end ofthis standard.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.2.1 Response FactorsA separate computer programmust be used to calculate the thermal response factors of thesolid materials surrounding the attic.Input to this programwould consist of the thermal conductivity,specific heat,density,and thickness of each layer,or the thermal resistance ofthe layer if it has negligible density,and the fraction of thecross-sectional area occupied by the framing.Output of such aprogram would be a set of response factors for use as input tothe main program.The adjunct to this practice contains datafiles with response factors for several typical attic construc-tions.4.2.2 Data Input to the Main ProgramThis input includesthe response factors,total hemispherical emittances of theinside and outside surfaces of the attic envelope,solar absorp-tances of the outside surfaces of the attic envelope,length andwidth of the attic,slopes of the two roof sections,distancebetween attic floor and roof at e