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ASHRAE STANDARD PROJECT COMMITTEE74-1988

Stephen J. Treado, ChairmanRichard W. DixonTamami KusudaLouis F Masonick

ASHRAE STANDARDS COMMITTEE 1987-88

Byron W. Engen, ChairmanDon G. Virgin, Vice ChairmanF. Leslie BrownDavid R. ConoverCharles E. DorganErnest C. DowlessTamami KusudaRalph D. LahmonR. Michael MartinDennis E. Miller

Jim L. Heldenbrand, Manager of Standards

SPECIAL NOTE

William R. McCluneyGeorge P Reed, 111Robert L . Van Dyck

Herbert PhillipsJulian E. SjordalHarold E. Straub

Kevin Y. TeichmanWilliam K. ThomasA. Grant Wilson

John 1. WoodworthGeorge S. YamamotoDavid S. Butler, CO

Hans O. Spauschus, EXO

This National Voluntary Consensus Standard was developed under the auspices of the American Society ofHeating, Refrigerating and Air-Conditioning Engineers (ASHRAE) . Consensus is defined as "substantial agree-ment reached by concerned interests according to the judgrnent of a duly appointed authority, after a concertedattempt at resolving objections . Consensus implies much more than the concept of a single majority but notnecessarily unanimity." This definition is according tothe American National Standards Institue (ANSI) of whichASHRAE is a member.ASHRAE obtains consensus through participation of its national and international members, associated

societies and public review.ASHRAE Standards are prepared by a Project Committee appointed specifically for the purpose of writing

the Standard . The Project Committee Chairman and Vice-Chairman must be members of ASHRAE ; while othermembersmay or may not be members, all must be technically qualified in the subject area of the Standard . Everyeffort is made to balance the concerned interests on all Project Committees .The Manager of Standards of ASHRAE should be contacted for :

a. interpretation of the contents of this Standard .b. participation in the next review of the Standard .c. offering constructive criticism for improving the Standard,d . permission to reprint portions of the Standard .

ASHRAE INDUSTRIAL ADVERTISING POLICY ON STANDARDS

ASHRAE Standards are established to assist industry and the public by offering a uniform method oftestingfor rating purposes, by suggesting safe practices in designing and installing equipment, by providing pro-per definitons of this equipment and by providing other information whichmayserve to guide the industry.The creation of ASHRAEStandards is determined by the need for them, and conformanceto them is com-pletely voluntary.

In referring to this Standard and in marking of equipmentand in advertising, no claim shall be made,either stated or implied, that the product has been approved by ASHRAE .

DISCLAIMER

ASHRAE uses its best efforts to promulgate standards for the benefit of the public in light of available in-formation and accepted industry practices. However; ASHRAE does not guarantee, certify or assure thesafety or performance of any products, components or systems tested, designed, installed or operatedin accordance with ASHRAE's standards or that any tests conducted under its standards will be non-hazardous or free from risk .

This is a preview of "ASHRAE 74-1988". Click here to purchase the full version from the ANSI store.

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CONTENTS

Sections Page1 . Purpose . . ., . . . . . . . . . . . . . . � . . ., . . . . . ���� . . . . . . . . �� . � . . . . .32. Scope . . . . . ..,., . . . . . ., . ., . � , . . . . .33. Definitions � . ., . . � , . . � . � , . . . . . . . . . . . . . . . . . ., . . . . � . �

4. Apparatus . . ., . � , . �� . . . . ., . . . . . ., . . . . . . . ., ., . . �

5. Test Specimens � , . ., . . . . . . . . . . . . . . . ., . . ., . ���� , . . . . . ., . . � . . . � , . . . . . . . . . .86, Testing Procedure , . . . . . � , . . . . . . . . . . . . . . . ., . . . � , ., . � , . . . . . �� , . .., . . . . . . . . . . .97, Reporting Test Results . ., . . ., . . . � . . . . ., . . � . . . . . . . . . ., . . . . . . ., . ., . . . . . ., . . . . . . .118. Precision&Accuracy . . . . . . . . . . . . . . . . . . . ., . . . � . . . . . ., . . . . . . ., . . . �� , . . . . .129. References � . . � , . ., ., . . . . � . . . . . . . . � . . . ., . . . . ., . . ., . . . . . . . . . � . . . . . . . � . . � 14

Figure l , . . ., . . ��� . � . . . . . . . . . . . . ., .Figure 2 ., . � . � . . . ., . ., . . . . . . ., ., . . . . . . . . ., . . . . . . . . . . . ., . �� . �� .. � , . . ., ., 7

Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix B . . . . . . . . . . . . . , . . � , . . . . . ., ., . . . . . . ., . . . . . . . . . . . . . . . . . . � � . ., . . . . .14FigureB-1 ��� . �� . . . . . . . . . . . . . . . . . . . . , . .15

FigureB-2 ., . � . . � . . .. . .. .. . � . . . . . ., . . . . . . ., . . . . ., . . . . . . . . . . . .15FigureB-3 . . . . � , . . . . . ., . . � ., . . . . . . . . ., . . . . . . . . . � , . . . . . . � . . . ., . . � . . . . .16Figure B-4 , ., . . . � ., . . . � � � , . . . . . . . . . . . . . . . . . . . . .., . . . . . . . . . . . . . . . . . . . . .. .. 16

ASHRAE STANDARD 74-1988

This is a preview of "ASHRAE 74-1988". Click here to purchase the full version from the ANSI store.

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This Forewqrd is not part of this Standard but is providedfor information purposes only.

FOREWORD

Thepurpose of this Standard is to describe amethodfor measuringandreporting the solar optical properties ofsheet-like materials. These properties include spectraltransmittance, reflectance, and absorptance for wave-lengths between 320 and 3000 nanometers andtotal radiantand luminous transmittance and reflectance. This Standardfalls under the Standards Committee classification ofstan-dard method of measurement for test.

This Standard is a revision of the standard originallypublished in 1973 . The principal changes incorporated inthe revision of this Standard are associated with the addi-tion ofa method to determine the luminous (photometric)transmittance, reflectance, and absorptance of sheetmaterials . Also, more detailed information has been add-ed to improve the accuracy and repeatability of themeasurement procedures . These revisions were necessary torespond to increased interest in the daylighting perfor-mance of sheet materials and improvements in sensingelements used for tests .

1 . PURPOSE1.1 To develop astandard method for measuring and re-porting the following solar optical properties of materials:spectral transmittance, reflectance, and absorptance be-tween 320nm and 3000 nm in wavelength, and total radiantand luminous transmittance and reflectance .

2. SCOPE2.1 Procedure Aof this method covers the measurment ofspectral absorptance, reflectance, and transmittance ofmaterials using spectrophotometers equipped with inte-grating spheres. Procedure C of this method covers themeasurement of solar transmittance (terrestrial) of mate-rials using a pyranometer, and enclosure, and the sunandsky as the source of radiation.

2.2 Methods of computing solar-weighted radiant andluminous properties from the measured spectral values arespecified in procedures A and B, which are applicable tomaterials having both specular anddiffuse optical proper-ties. Except for transmitting sheet materials that are inho-mogeneous, patterned, or corrugated, procedures Aand Bof this method are preferred over procedures C, D, andE.

2.3 Procedure B describes the calculation of luminous(photometric) transmittance and reflectance of materialsfrom spectral radiant transmittance andreflectance data,or both, obtained from the performance ofProcedureAofthis method.

2.4 Procedure C of this method allows measurement ofsolar transmittance of materials in sheet form at normalincidence and at angles other than normal incidence and isapplicable to transparent, translucent, textured, or pat-terned sheet materials .

*National Bureau ofStandards (NBS) changed its name to National Institute ofStandards and Technology.

2.5 ProcedureD ofthis method covers the measurement ofsolar photometric transmittance of materials in sheet form .Solar photometric transmittance is measured using aphotometer (illuminance meter) in an enclosure with thesun and sky as the source of radiation, the enclosure andmethod of test being specified in ProcedureC. ThepurposeofProcedureDis to specify a photometric sensor to beusedwith Procedure C for measuring the solar photometrictransmittance of sheet materials containing inhomoge-neities in their optical properties .

2.6 ProcedureEcovers the measurement of the solar radi-ant and luminous reflectances at normal incidence, andatother angles, of sheet materials that are opaque andwhichmay also be textured or patterned.

3. DEFINITIONS

radiant flux 4) : the time rate of flow of radiant energy(watts).radiance at apoint of a surface, Es = d4)/dA: the quo-tient ofthe flux incident on in element of a surface contain-ing the point, by the area of that element, measured in wattsper square meter (W/m2) .

spectral (adj): (1) for dimensionless optical properties,indicating that the property was evaluated at a specificwavelength, ~, within a small wavelength interval, AA aboutX. Symbol wavelength in parenthesis, as L(350 nm), or is afunction ofwavelength, symbol L(X) . (2) For a radiometricquantity, the concentration of the quantity per unitwavelength or frequency, indicated by the subscript lambda,as L,, = dL/dXat aspecific wavelength . Thewavelength atwhich the spectral concentration is evaluated may be indi-cated by the wavelength in parenthesis following the sym-bol, L, (350 nm). Note: Standard solar spectral irradiancedistributions generally lie within the wavelength range from300 to 3000 nm.

solar (adj.): (1) Referring to photometric or radiometricquantities, indicates that the flux involved has the sun as asource or as characteristic of the sun. (2) Referring to anoptical property, indicates aweighted average ofthe spec-tral optical property, with a standard solar spectral irra-diance distribution used as the weighting function .

luminous (photometric) (adj.): Referring to a radiometricquantity, luminous indicates the weighted average of thespectral radiometric quantity, with the product of thephotopic spectral luminous efficiency function' and thestandard solar spectral irradiance distributionz being theweighting function .

illuminance. luminous (or photometric) irradianceabsorptance, cti the ratio ofthe absorbed radiant fluxto theincident radiant flux .radiant (or luminous) reflectance, p. the ratio of the re-flected radiant (or luminous) flux to the incident radiant (orluminous) flux .

radiant (or luminous) transmittance, r. the ratio of thetransmitted radiant (or luminous) flux to the incidentradiant flux.

ASHRAE STANDARD 74-1988

This is a preview of "ASHRAE 74-1988". Click here to purchase the full version from the ANSI store.

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