ASTM_C_236_-_89_1993e1.pdf

Designation:C 236 89(Reapproved 1993)e1Standard Test Method forSteady-State Thermal Performance of Building Assembliesby Means of a Guarded Hot Box1This standard is issued under the fixed designation C 236;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.e1NOTESection 12 was added editorially in September 1993.1.Scope1.1 This test method,known as the guarded hot box method,covers the measurement of the steady-state thermal transferproperties of panels.In distinction to Test Method C 177,which is primarily applicable to homogeneous samples,theguarded hot box method provides for the evaluation of thermalperformance of building assemblies.This test method issuitable for building construction assemblies,building panels,and other applications of nonohomogeneous specimens atsimilar temperature ranges.It may also be used for homoge-neous specimens.1.2 This test method may be applied to any buildingconstruction for which it is possible to build a reasonablyrepresentative specimen of size appropriate for the apparatus.NOTE1A calibrated hot box,Test Method C 976,may also be usedfor the described measurements and may prove more satisfactory fortesting assemblies under dynamic conditions(nonsteady-state)and toevaluate the effects of water migration and air infiltration.The choicebetween the calibrated or the guarded hot box should be made only aftercareful consideration of the contemplated use.1.3 In applying this test method,the general principlesoutlined must be followed;however,the details of the appara-tus and procedures may be varied as needed.1.3.1 The intent of this test method is to give the essentialprinciples and the general arrangement of the apparatus.Anytest using this apparatus must follow those principles.Thedetails of the apparatus and the suggested procedures thatfollow are given not as mandatory requirements but as ex-amples of this test method and precautions that have beenfound useful to satisfy the essential principles.1.3.2 Persons applying this test method shall be trained inthe methods of temperature measurement,shall possess aknowledge of the theory of heat flow,and shall understand thegeneral requirements of testing practice.1.4This standard does not purport to address all of thesafety problems,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE2While various units may be found for thermal properties,theInternational System of units is used exclusively in this test method.Forconversion factors to inch-pound and kilogram-calorie systems,see Table1.2.Referenced Documents2.1 ASTM Standards:C 168 Terminology Relating to Thermal Insulating Materi-als2C 177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Guarded-Hot-Plate Apparatus2C 518 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Heat Flow Meter Apparatus2C 578 Specification for Preformed Cellular PolystyreneThermal Insulation2C 976 Test Method for Thermal Performance of BuildingAssemblies by Means of a Calibrated Hot Box2C 1045 Practice for Calculating Thermal TransmissionProperties from Steady-State Heat Flux Measurements2E 178 Practice for Dealing With Outlying Observations3E 230 Temperature-Electromotive Force(EMF)Tables forStandardized Thermocouples4E 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method33.Terminology3.1 Definitions For definitions of terms used in this testmethod,refer to Terminology C 168.3.2 Symbols:Symbols:3.2.1 The symbols used in this test method have thefollowing significance:1This test method is under the jurisdiction of ASTM Committee C-16 onThermal Insulation and is the direct responsibility of Subcommittee C16.30 onThermal Measurement.Current edition approved Sept.29,1989.Published June 1990.Originallypublished as C 236 60.Last previous edition C 236 87.2Annual Book of ASTM Standards,Vol 04.06.3Annual Book of ASTM Standards,Vol 14.02.4Annual Book of ASTM Standards,Vol 14.03.1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.NOTICE:This standard has either been superseded and replaced by a new version or discontinued.Contact ASTM International(www.astm.org)for the latest information.l5 thermal conductivity,W/(mK),C5 thermal conductance,W/(m2K),h5 surface conductance,W/(m2K),U5 thermal transmittance,W/(m2K),q5 heat flux(time rate of heat flow through Area A),W/m2,Q5 time rate of heat flow,total input to the metering box,W,A5 metering area normal to he