1、Designation:D789715Standard Practice forLaboratory Soiling and Weathering of Roofing Materials toSimulate Effects of Natural Exposure on Solar Reflectanceand Thermal Emittance1This standard is issued under the fixed designation D7897;the number immediately following the designation indicates the yea
2、r 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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 Practice D7897 applies to simulation of the effects offield ex
3、posure on the solar reflectance and thermal emittance ofroof surface materials including but not limited to field-appliedcoatings,factory-applied coatings,single-ply membranes,modified bitumen products,shingles,tiles,and metal products.The solar reflectance and thermal emittance of roof surfacemater
4、ials can be changed by exposure to the outdoor environ-ment.These changes are caused by three factors:depositionand retention of airborne pollutants;microbiological growth;and changes in physical or chemical properties.This practiceapplies to simulation of changes in solar reflectance andthermal emi
5、ttance induced by deposition and retention ofairborne pollutants and,to a limited extent,changes caused bymicrobiological growth.1.2 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish ap
6、pro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2C1549 Test Method for Determination of Solar ReflectanceNearAmbient Temperature Using a Portable Solar Reflec-tometerE691 Practice for Conducting a
7、n Interlaboratory Study toDetermine the Precision of a Test MethodG151 Practice for Exposing Nonmetallic Materials inAccel-erated Test Devices that Use Laboratory Light SourcesG154 Practice for Operating Fluorescent Ultraviolet(UV)Lamp Apparatus for Exposure of Nonmetallic Materials2.2 Other Standar
8、ds:ANSI/CRRC S100 Standard Test Methods for DeterminingRadiative Properties of Materials33.Terminology3.1 Definitions:3.1.1 solar energythe radiant energy originating from thesun.3.1.1.1 DiscussionApproximately 99%of terrestrial solarradiation lies between the wavelengths of 0.3 and 2.5 m,withpeak r
9、adiation near 0.5 m.This spectrum includes ultraviolet,visible,and near-infrared radiation.3.1.2 solar reflectancethe fraction of incident solar fluxreflected by a surface.3.1.3 thermal emittanceefficiency with which a surfaceemits thermal radiation,measured on a scale from 0 to 1,wherea value of 1
10、indicates perfect emission(that is,equal to that ofa black body).3.1.4 thermal radiationthe radiant energy originatingfrom a 300 K(about 27C)black body.3.1.4.1 DiscussionApproximately 99%of thermal radia-tion lies between the wavelengths of 4 and 80 m,with peakradiation near 10 m.4.Summary of Practi
11、ce4.1 This practice presents a rapid laboratory method forweathering and soiling,which simulates natural changes insolar reflectance and thermal emittance of materials in the field.The practice describes a simulated field exposure protocol thatconsists of spraying an aqueous suspension of soot and o
12、thersoluble soiling constituents,including salts and organic matter,onto a specimen of roof surfacing materials.The specimen isexposed in a weathering apparatus before soiling,to provideUV conditioning;and after soiling,to simulate the cleaningeffect of moisture(1).41This practice is under the juris
13、diction ofASTM Committee D08 on Roofing andWaterproofing and is the direct responsibility of Subcommittee D08.20 on RoofingMembrane Systems.Current edition approved Jan.1,2015.Published March 2015.DOI:10.1520/D7897-15.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM
14、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.4The boldface numbers in pa
15、rentheses refer to a 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 5.Significance and Use5.1 The solar reflectance of a building envelope surfaceaffects surface temperature and near-surface
16、ambient air tem-perature.Surfaces with low solar reflectance absorb a highfraction of the incoming solar energy.Sunlight absorbed by aroof or by other building envelope surfaces can be conductedinto the building,increasing cooling load and decreasingheating load in a conditioned building,or raising indoortemperature in an unconditioned building.It can also warm theoutside air by convection.Determination of solar reflectancecan help designers and consumers choose appropriate materialsfor their bu
