ASTM_C_1549_-_16.pdf

Designation:C154916Standard Test Method forDetermination of Solar Reflectance Near AmbientTemperature Using a Portable Solar Reflectometer1This standard is issued under the fixed designation C1549;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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers a technique for determining thesolar reflectance of flat opaque materials in a laboratory or inthe field using a commercial portable solar reflectometer.Thepurpose of the test method is to provide solar reflectance datarequired to evaluate temperatures and heat flows across sur-faces exposed to solar radiation.1.2 This test method does not supplant Test Method E903which measures solar reflectance over the wavelength range250 to 2500 nm using integrating spheres.The portable solarreflectometer is calibrated using specimens of known solarreflectance to determine solar reflectance from measurementsat four wavelengths in the solar spectrum:380 nm,500 nm,650 nm,and 1220 nm.This technique is supported bycomparison of reflectometer measurements with measurementsobtained using Test Method E903.This test method is appli-cable to specimens of materials having both specular anddiffuse optical properties.It is particularly suited to themeasurement of the solar reflectance of opaque materials.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 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 appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2C168 Terminology Relating to Thermal InsulationE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE903 Test Method for Solar Absorptance,Reflectance,andTransmittance of Materials Using Integrating SpheresE1980 Practice for Calculating Solar Reflectance Index ofHorizontal and Low-Sloped Opaque Surfaces2.2 ANSI/CRRC Standard:3ANSI/CRRC S100 Standard Test Methods for DeterminingRadiative Properties of Materials3.Terminology3.1 DefinitionsFor definitions of some terms used in thetest method,refer to Terminology C168.3.2 Definitions of Terms Specific to This Standard:3.2.1 air massair mass is related to the path length of solarradiation through the Earths atmosphere to the site of interest.Air mass 1 is for a path of normal solar radiation at the Earthsequator while air mass 2 indicates two times this path length.3.2.2 solar reflectancethe fraction of incident solar radia-tion upon a surface that is reflected from the surface.3.3 Symbols:3.3.1 Aarea normal to incident radiation,m2.3.3.2 Qabsrate at which radiant heat is absorbed per m2ofarea,W.3.3.3 qsolarsolar flux,W/m2.3.3.4 rsolar reflectance,dimensionless.4.Summary of Test Method4.1 This test method employs a diffuse tungsten halogenlamp to illuminate a flat specimen for two seconds out of aten-second measurement cycle.Reflected light is measured atan angle of 20 from the incident angle with four detectors.Each detector is equipped with color filters to tailor itselectrical response to a range of wavelengths in the solarspectrum.Software in the instrument combines the outputs ofthe four detectors in appropriate proportions to approximate theresponse for incident solar radiation through air mass 0,1,1.5,1This test method is under the jurisdiction ofASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.30 on ThermalMeasurement.Current edition approved Nov.1,2016.Published November 2016.Originallyapproved in 2002.Last previous edition approved in 2014 as C1549 09(2014).DOI:10.1520/C1549-16.2For 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 Cool Roof Rating Council(CRRC),449 15th Street,Suite 400,Oakland,CA 94612,http:/www.coolroofs.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 or 2.The solar reflectance for the desired air mass is selectablefrom the instruments keypad.The reflectances measured bythe individual detectors are also available from the keypad anddigital readout.The instrument is calibrated using a black bodycavity for a reflectance of zero and one or more surfaces ofknown solar reflectance provided by the manufacturer.Asurface to be evaluated is placed firmly against the 2.5 cmdiameter opening on the measurement head and maintained inthis position until constant readings are d