Designation: C 1199 00

Standard Test Method forMeasuring the Steady-State Thermal Transmittance ofFenestration Systems Using Hot Box Methods1

This standard is issued under the fixed designation C 1199; 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.

1. Scope1.1 This test method covers requirements and guidelines

and specifies calibration procedures required for the measure-ment of the steady-state thermal transmittance of fenestrationsystems installed vertically in the test chamber. This testmethod specifies the necessary measurements to be made usingmeasurement systems conforming to either Test MethodsC 236, C 976, or C 1363 for determination of fenestrationsystem thermal transmittance.

NOTE 1This test method allows the testing of projecting fenestrationproducts (that is, garden windows, skylights, and roof windows) installedvertically in a surround panel. Current research on skylights, roofwindows, and projecting products hopefully will provide additionalinformation that can be added to the next version of this test method sothat skylight and roof windows can be tested horizontally or at some angletypical of a sloping roof.

1.2 This test method refers to the thermal transmittance, U,and the corresponding thermal resistance, R, of a fenestrationsystem installed vertically in the absence of solar and airleakage effects.

NOTE 2The methods described in this document may also be adaptedfor use in determining the thermal transmittance of sections of buildingwall, and roof and floor assemblies containing thermal anomalies, whichare smaller than the hot box metering area.

1.3 This test method describes how to determine a fenestra-tion products (also called test specimen) thermal transmit-tance, US, at well-defined environmental conditions. The ther-mal transmittance, which is sometimes called the air-to-airU-factor, is also a reported test result from Test Methods C 236,C 976, and C 1363. If only the thermal transmittance isreported using this test method, the test report must alsoinclude a detailed description of the environmental conditionsin the thermal chamber during the test as outlined in 10.3.

1.4 For rating purposes, this test method also describes howto calculate a standardized thermal transmittance, UST, whichcan be used to compare test results from laboratories withdifferent weather side wind directions and thermal chamber

configurations, and can also be used to directly compare tocalculated results from current computer programs for deter-mining the thermal transmittance of fenestration products.Although this test method specifies two methods of calculatingthe standardized thermal transmittance, only the standardizedthermal transmittance result from one method is reported foreach test. One standardized thermal transmittance calculationprocedure is the Calibration Transfer Standard (CTS) methodand another is the area weighting (AW) method (see 4.3 andSection 8 for further descriptions of these two methods). Thearea weighting method requires that the surface temperatureson both sides of the test specimen be directly measured asspecified in Practice E 1423 in order to determine the surfaceheat transfer coefficients on the fenestration product during thetest. The CTS method does not use the measured surfacetemperatures on the test specimen and instead utilizes thecalculation of equivalent surface temperatures from calibrationdata to determine the test specimen surface heat transfercoefficients. The area weighting (AW) method shall be usedwhenever the thermal transmittance, US, is greater than 3.4W/(m2K) {0.6 Btu/(hrFt 2F)}, or when the ratio of testspecimen projected surface area to wetted (that is, total heattransfer or developed) surface area on either side of the testspecimen is less than 0.80. Otherwise the CTS method shall beused to standardize the thermal transmittance results.

1.5 A discussion of the terminology and underlying assump-tions for measuring the thermal transmittance are included.

1.6 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are provided forinformation purposes only.

1.7 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 Documents

2.1 ASTM Standards:C 168 Terminology Relating to Thermal Insulating Materi-

als21 This test method is under the jurisdiction of ASTM Committee C16 on Thermal

Insulation and is the direct responsibility of Subcommittee C16.30 on ThermalMeasurement.

Current edition approved July 10, 2000. Published September 2000. Originallypublished as C 1199 91. Last previous edition C 1199 97. 2 Annual Book of ASTM Standards, Vol 04.06.

1

Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.

C 177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Guarded Hot Plate Apparatus2

C 236 Test Method for Steady-State Thermal Performanceof Building Assemblies by Means of a Guarded Hot Box2

C 518 Test Method for Steady-State Thermal Heat FluxMeasurements and Transmission Properties by Means ofthe Heat Flow Meter Apparatus2

C 976 Test Method for Thermal Performance of BuildingAssemblies by Means of a Calibrated Hot Box2

C 1045 Practice for Calculated Thermal Transmission Prop-erties from Steady-State Heat Flux Measurements2

C 1114 Test Method for Steady-State Thermal TransmissionProperties by Means of the Thin-Heater Apparatus2

C 1363 Test Method for Thermal Performance of BuildingAssemblies by Means of a Hot Box Apparatus2

E 283 Test Method for Rate of Air Leakage ThroughExterior Windows, Curtain Walls, and Doors3

E 631 Terminology of Building Constructions3E 783 Test Method for Field Measurement of Air Leakage

Through Installed Exterior Windows and Doors3E 1423 Practice for Determining the Steady-State Thermal

Transmittance of Fenestration Systems32.2 ISO Standards:ISO 8990 Thermal Insulation-Determination of Steady-

State Thermal Transmission PropertiesCalibrated andGuarded Hot Box4

ISO125671:2000 Thermal InsulationDetermination ofThermal Resistance of ComponentsHot Box Methodfor Windows and Doors4

2.3 Other Standards:NFRC 100-97 Procedure for Determining Fenestration

Product Thermal U-factors5BS874 Part 3, Section 3.1, 1987, British Standard Methods

for Determining Thermal Insulation Properties, (Part 3,Tests for Thermal Transmittance and Conductance, Sec-tion 3.1) Guarded Hot Box Method6

BS874 Part 3, Section 3.2, 1990, British Standard Methodsfor Determining Thermal Insulation Properties, Part 3,Tests for Thermal Transmittance and Conductance, Sec-tion 3.2 Calibrated Hot Box Method6

ASHRAE Fundamentals Handbook, 19977

3. Terminology3.1 Definitions Definitions and terms are in accordance

with definitions in Terminologies E 631 and C 168, from whichthe following have been selected and modified to apply tofenestration systems. See Fig. 1 for temperature locations.

3.2 Definitions of Terms Specific to This Standard:3.2.1 calibration transfer standard, n an insulation board

that is faced with glazing, and instrumented with temperature

sensors between the glazing and the insulation board core,which is used to calibrate the surface resistances and thesurround panel (see Annex A1 for design guidelines forcalibration transfer standards).

3.2.2 overall thermal resistance, RS, nthe temperaturedifference between the environments on the two sides of a bodyor assembly when a unit heat flow per unit area is establishedthrough the body or assembly under steady-state conditions. Itis defined as follows:

RS 5 1/U S (1)3.2.3 standardized thermal transmittance, U ST, nthe heat

transmission in unit time through unit area of a test specimenand standardized boundary air films, induced by unit tempera-ture difference between the environments on each side. It iscalculated using the CTS method as follows:

1/UST@CTS# 5 1/US1~1/hSTh 1/hh!1~1/hSTc 1/hc! (2)and using the area weighting (AW) method:

1/UST@AW#51/US1~AS/Ah!~1/h STh 1/hh!1~AS/Ac!~1/h STc 1/hc!(3)

where hSTh and hSTc are the standardized surface heat transfercoefficients on the room side and weather side, respectively.Their numerical values are specified in 8.2.9.1.

3.2.3.1 DiscussionThe calculation of the standardizedthermal transmittance, UST, assumes that only the surface heattransfer coefficients change from the calibrated standardizedvalues for the conditions of the test. This assumption may notbe valid if the surface temperature differentials for the stan-dardized calibration conditions are different from the surfacetemperature differential that existed for the fenestration productduring the test procedure. Therefore, the standardized thermaltransmittance should only be considered as an approximationfor use in comparing with calculated thermal transmittancevalues with standardized surface heat transfer coefficients.

3.2.4 surface resistance, nthe temperature difference be-tween an isothermal surface and its surroundings when a unitheat flow per unit area is established between the surface andthe surroundings under steady-state conditions by the com-bined effects of convection and radiation. Subscripts h and care used to differentiate between room side and weather sidesurface resistances, respectively. Surface resistances are calcu-lated as follows:

3 Annual Book of ASTM Standards, Vol 04.07.4 Available from American National Standards Institute, 11 West 42 nd St., 13th

Floor, New York, NY 10036.5 Available from National Fenestration Rating Council, 1300 Spring Street, Suite

120, Silver Spring, MD 20910.6 Available from British Standards Institution, British Standards House, 2 Park

Street, London W1A 2BS, England.7 Available from ASHRAE, 1791 Tullie Circle, N.E., Atlanta, GA 30329.

FIG. 1 Schematic Representation of Various Temperatures forFenestration Systems

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rh 5 1/hh (4)

rc 5 1/hc (5)3.2.5 surface heat transfer coeffcient, h, nthe time rate of

heat flow from a unit area of a surface to its surroundings,induced by a unit temperature difference between the surfaceand the environment. (This is sometimes called surface con-ductance or film coeffcient.)

3.2.5.1 DiscussionSubscripts are used to differentiate be-tween room side (1 or h) and weather side (2 or c) surfaceconditions (see Fig. 1). It should be recognized that due toradiation effects, the room side or weather side temperature (thand tc, respectively), may differ from the respective room sideor weather side baffle temperatures (tb1 and t b2, respectively).If there is a difference of more than 61 C (62.0 F), either onthe room side or weather side, the radiation effects shall beaccounted for to maintain accuracy in the calculated surfaceheat transfer coefficients. The areas used to calculate thesurface heat transfer coefficients (Eq 6 and 8) are differentdepending on which method of standardization is used. Whenthe CTS Method is used to standardize the thermal transmit-tance, the projected area, AS, is used to calculate the surfaceheat transfer coefficients, whereas when using the area weight-ing method, the actual wetted or heat transfer surface area,A

hor Ac, is used to determine the surface heat transfer

coefficients.The room side and weather side surface heat transfer coefficients are

calculated as follows:when:

th 5 tb1 ~61 C!, (6)hh 5 QS/@~AS or h!~th t1!#

when:th tb1 ~61 C!, (7)

hh 5 ~qr1 1 qc1!/~t h t1!when:

tc 5 t b2 ~61 C!,hc 5 Q S /@~AS or c! ~t2 tc!#

when:t c tb2 ~6 1C!, (8)

hc 5 ~qr2 1 qc2!/~t 2 tc! (9)3.2.5.2 DiscussionWhen testing inhomogeneous test

specimens, the test specimen surface temperatures and surfaceheat transfer coefficients will not be exactly the same as thoseobtained using the calibration transfer standard. As a conse-quence, the surface heat transfer coefficients obtained using thecalibration transfer standard cannot be unambiguously definedand hence a test specimen conductance cannot be defined andmeasured. For inhomogeneous test specimens, only the thermaltransmittance, US, can be defined and measured. It is thereforeessential to calibrate with surface heat transfer coefficients onthe Calibration Transfer Standard (CTS) which are as close aspossible to the conventionally accepted values for buildingdesign. Likewise, it would be desirable to have a surround

panel that closely duplicates the actual wall where the fenes-tration system would be installed. However, due to the widevariety of fenestration opening designs and constructions, thisis not feasible. Furthermore, for high resistance fenestrationsystems installed in fenestration opening designs and construc-tions that are thermal bridges, the large relative amount of heattransfer through the thermal bridge will cause the relativelysmall amount of heat transfer through the fenestration systemto have a larger than desirable error. As a result of the pointsstated above, the calculation of a specimen thermal conduc-tance or resistance (surface to surface) from a measuredthermal transmittance and the calculated surface heat transfercoefficients is not part of the basic measurement procedure.However, by using the CTS method or the area weighting(AW) method described in Section 8 it is possible to obtain astandardized thermal transmittance, UST, which is a ratheruseful tool for the evaluation and comparison of experimentalresults for fenestration systems with computer calculations ofthe thermal transmittance.

3.2.6 surround panel (sometimes called the mask, maskwall, or homogeneous wall), na homogeneous panel with anopening where the test specimen is installed (see 5.1.2 for adescription of a surround panel.)

3.2.7 test specimen, nthe fenestration system or productbeing tested.

3.2.8 test specimen thermal transmittance, U S (sometimescalled the overall coefficient of heat transfer or air-to-airU-factor), n the heat transfer in unit time through unit area ofa test specimen and its boundary air films, induced by unittemperature difference between the environments on each side.It is determined as follows:

US 5 QS/@AS~th tc!# (10)3.3 SymbolsThe symbols, terms, and units used in this

test method are as follows:

Ah = total heat transfer (or developed) surface areaof test specimen on room side, m2,

Ac = total heat transfer (or developed) surface areaof test specimen on weather side, m2,

Ab1 = area of room side baffle and all other surfacesin view of the test specimen, m2,

Ab2 = area of weather side baffle and all othersurfaces in view of the test specimen, m2,

AS = projected area of test specimen (same as openarea in surround panel), m2,

Asp = projected area of surround panel (does notinclude open area in surround panel), m2,

a = absorbtance of surface,C g = thermal conductance of glass or acceptable

transparent plastic facing on calibration trans-fer standard, W/(m2K),

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Csp = thermal conductance of surround panel (sur-face to surface), W/(m2K), determined bymeans of Test Method C 177 and PracticeC 1045, Test Method C 518 and PracticeC 1045, or Test Method C 1114 and PracticeC 1045,

Cts = thermal conductance of calibration transferstandard, W/(m2K), determined by means ofTest Method C 177 and Practice C 1045, TestMethod C 518 and Practice C 1045, or TestMethod C 1114 and Practice C 1045,

e = total hemispherical emittance of surface,F1b = room side radiative factor as defined after Eq

20,F 2b = weather side radiative factor as defined after

Eq 25,h STh = standardized surface heat transfer coefficient,

room side, (W/m2K),hSTc = standardized surface heat transfer coefficient,

weather side, (W/m2K),hh = surface heat transfer coefficient, room side,

W/(m2K),h c = surface heat transfer coefficient, weather side,

W/(m2K),Kc = convection coefficient, W/(m2K1.25),L = length of heat flow path, m,Q = time rate of heat flow through the total

surround panel/test specimen system, W,Qc = time rate of convective heat flow from test

specimen surface, W,Qfl = time rate of flanking loss heat flow around

surround panel, W,Qr = time rate of net radiative heat flow from test

specimen surface to the surroundings, W,QS = time rate of heat flow through the test speci-

men, W,Q sp = rime rate of heat flow through the surround

panel as determined from measured conduc-tance Cts and area weighted surround panelsurface temperatures, W,

q = heat flux (time rate of heat flow through unitarea), W/m2,

qS = heat flux through the test specimen, W/m2,q r1 = net radiative heat flux to the room side of the

test specimen, W/m2,qr2 = net radiative heat flux from the weather side

of the test specimen, W/m2,qc1 = convective heat flux to the room side of the

test specimen, W/m2,qc2 = convective heat flux from the weather side of

the test specimen, W/m2,r = reflectance of surface,r h = surface resistance, room side, m2K/W,rc = surface resistance, weather side, m2K/W,RS = overall thermal resistance of test specimen

(air to air under test conditions), m2K/W,tb1 = equivalent radiative baffle surface tempera-

ture, room side, K or C,tb2 = equivalent radiative baffle surface tempera-

ture, weather side, K or C,

th = average temperature of room side air, C,tc = average temperature of weather side air, C,t1 = average area weighted temperature of test

specimen room side surface, K or C,t2 = average area weighted temperature of test

specimen weather side surface, K or C,t18 = average area weighted temperature of room

side glass/core interface of calibration trans-fer standard, K or C,

t 28 = average area weighted temperature of weatherside glass/core interface of calibration trans-fer standard, K or C,

US = thermal transmittance of test specimen (air toair under test conditions), W/(m2K),

UST = standardized thermal transmittance of testspecimen, W/(m2K),

UST[AW] = standardized thermal transmittance of testspecimen determined using measured areaweighted [AW] surface temperatures (air toair), W/(m2K), and

UST[CTS] = standardized thermal transmittance of testspecimen determined using calibration trans-fer standard [CTS] surface heat transfer coef-ficients (air to air), W/(m2K).

4. Significance and Use4.1 This test method details the calibration and testing

procedures and necessary additional temperature instrumenta-tion required in applying Test Methods C 236, C 976, orC 1363 to measure the thermal transmittance of fenestrationsystems mounted vertically in the thermal chamber.

4.2 Since both temperature and surface heat transfer coef-ficient conditions affect results, use of recommended condi-tions will assist in reducing confusion caused by comparingresults of tests performed under dissimilar conditions. Stan-dardized test conditions for determining the thermal transmit-tance of fenestration systems are specified in Practice E 1423and Section 5.3. However, this procedure can be used withother conditions for research purposes or product development.

4.3 It should be recognized that the only true experimentalmeasurement is the thermal transmittance, US, value deter-mined in Section 7. The standardized thermal transmittancevalue, UST, obtained by either the Calibration Transfer Stan-dard (CTS) or area weighting (AW) methods described inSection 8 include adjustments to the US value that are madebecause the current computer calculation methods (NFRC100-97) for determining the thermal transmittance are notcapable of applying the actual surface heat transfer coefficientsthat exist on the test specimen while testing at standardizedconditions. The current computer calculation methods assumethat uniform standardized surface heat transfer coefficientsexist on the indoor and outdoor fenestration product surfaces,which is not the case. Until such a time that the computercalculation methods are upgraded to have the actual surfaceheat transfer coefficients applied to the actual fenestrationproduct geometry, the modification of the true tested thermaltransmittance value, US, to a standardized value UST, isnecessary for rating and comparison (measured with calcu-lated) purposes.

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4.3.1 It should be noted that the standardized surface heattransfer coefficients, hh and hs, as calibrated prior to testing afenestration product using an appropriately sized CalibrationTransfer Standard (CTS) may differ from the surface heattransfer coefficients that exist during a hot box test on a specifictest specimen. Fenestration systems usually have frame andsash surfaces that introduce two- and three-dimensional con-vective heat transfer effects which result in variable surfaceheat transfer coefficients, which differ from the standardizedvalues. As a result of this, the test specimen surface heattransfer coefficients will differ from those obtained with thenon-framed, essentially flat Calibration Transfer Standardtested under the same conditions. In this standardizing proce-dure, it is assumed that the differences are small enough so thatthe calibration surface heat transfer coefficients can be used tocalculate equivalent test specimen average surfaces tempera-tures, t1 and t2, in order to estimate the actual test specimensurface heat transfer coefficients. It should be recognized thatthis assumption will not be accurate for all fenestrationproducts, especially for high thermal transmittance productswhere the surface heat transfer coefficients are a major portionof the overall thermal resistance and also for fenestrationproducts with significant surface projections (for example,skylights, roof windows, garden windows) where the surfaceheat transfer coefficients are quite different from the standard-ized values.

4.3.2 In these situations, an attempt should be made tomeasure the test specimen surface temperature distributionsand then calculate directly the test specimen average areaweighted surfaces temperatures, t1 and t2. This area weighting(AW) method also has problems in that the placement oftemperature sensors to get an accurate area weighting is notknown, especially on high conductivity horizontal surfaces thatact as heat transfer extended surfaces (that is, fins). In addition,the placement of many temperature sensors on the test speci-men surfaces will affect the velocity fields in the vicinity ofthese surfaces which will affect the surface temperatures andsurface heat transfer coefficients.

4.3.3 Guidelines for determining which standardizing pro-cedure to follow are given in 8.2.

4.4 The thermal transmittance of a test specimen is affectedby its size and three-dimensional geometry. Care must beexercised when extrapolating to product sizes smaller or largerthan the test specimen. Therefore, it is recommended thatfenestration systems be tested at the recommended sizesspecified in Practice E 1423 or NFRC 100-97.

NOTE 3This test method does not include procedures to determine theheat flow due to either air movement through the specimen or solarradiation effects. As a consequence, the thermal transmittance resultsobtained do not reflect performances that may be expected from fieldinstallations due to not accounting for solar radiation, air leakage effects,and the thermal bridge effects that may occur due to the specific designand construction of the fenestration system opening. Since there is such awide variety of fenestration system openings in North American residen-tial, commercial and industrial buildings, it is not feasible to select atypical surround panel construction for installing the fenestration systemtest specimen. This situation allows the selection of a relatively highthermal resistance surround panel which places the focus of the test on thefenestration system thermal performance alone. Therefore, it should berecognized that the thermal transmittance results obtained from this test

method are for ideal laboratory conditions in a highly insulative surroundpanel, and should only be used for fenestration product comparisons andas input to thermal performance analyses which also include solar, airleakage, and thermal ridge effects due to the surrounding buildingstructure. To determine air leakage for windows and doors, refer to TestMethods E 283 and E 783.

5. Calibration5.1 General:5.1.1 Calibration requirementsA minimum of two cali-

bration test procedures shall be performed to determine thesurround panel flanking loss and to characterize the surfaceheat transfer coefficients on a Calibration Transfer Standardbefore testing actual fenestration products. The first calibrationtest requires that a continuous surround panel (with the testspecimen aperture filled with the same material as the rest ofthe surround panel) be tested at standard test conditions inorder to determine the surround panel flanking heat transferand the metering box wall heat transfer. In the second set ofcalibration tests, a Calibration Transfer Standard with itsweather side face located 25 mm in from the weather side edgeof the surround panel opening shall be mounted in the surroundpanel and tested at standardized conditions. The fans in thethermal chamber may have to be adjusted so that the surfaceheat transfer coefficients measured on both sides of theCalibration Transfer Standard are within a set tolerance of thestandardized surface heat transfer coefficients (see 5.3).

5.1.2 Surround Panel As explained in Notes 2 and 4,there may be a strong interaction between the heat flow in anactual surrounding wall and the frame of the fenestrationsystem. If the surrounding wall construction contains highlyconductive materials, the heat flow through the fenestrationsystem frame could be significantly changed. Since it is notfeasible to select a typical wall to use as a surround panel, it isdesirable to have a relatively high-resistance surround panel tominimize this shorting interaction so that the heat flowthrough the fenestration system itself can be measured asaccurately as possible. This is especially true for the highlyresistive superwindows currently being developed.

5.1.2.1 A surround panel, consisting of a stable homoge-neous thermal insulation material with a thermal conductivityat 24 C not in excess of 0.04 W/(mK) and having a very lowgas permeance, shall be provided for mounting the testspecimen (see Fig. 2). For structural integrity, the homoge-neous insulation core may be sandwiched between two sheetsof a support material having a very low gas (air and watervapor) permeance and stable thermal and dimensional proper-ties. The opening in the central homogeneous insulation boardcore may be covered with a nonreflecting tape to minimizesurface damage. The thickness of the homogeneous insulationcore of the surround panel (see Fig. 2) shall be at least themaximum thickness of the test specimen (usually one part ofthe test specimen frame) and shall be in no circumstances lessthan 100 mm. The maximum thickness of the homogeneousinsulation core of the surround panel should be no more than25 mm greater than the maximum thickness of the testspecimen. That is, for test specimen maximum thicknesses lessthan or equal to 100 mm, the surround panel core thicknessshould be 100 mm. For test specimen maximum thicknessesgreater than 100 mm and up to 125 mm, the surround panel

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core thickness should be 125 mm. For test specimen maximumthicknesses greater than 125 mm and up to 150 mm, thesurround panel core thickness should be 150 mm and so on forlarger test specimens. Unless specifically required for testspecimen mounting purposes (very high mass test specimenslike patio doors or large curtain walls), no thermal anomalies(that is, thermal bridges like wood or metal) shall exist in thesurround panel. In those specific situations where the surroundpanel is not homogeneous, a detailed drawing describing thesurround panel and the thermal anomaly materials and themodified surround panel construction, along with the measuredthermal conductances (using Test Methods C 177 or C 518) ofall materials used shall be included with the test report. It isrequired that the thermal conductance (Csp surface to surfaceincluding facing and core materials) of a sample of thesurround panel be measured in a guarded hot place (TestMethod C 177) or a heat flow meter (Test Method C 518) at aminimum of three temperatures over the range of conditions atwhich the surround panel will be used.

5.1.2.2 For added confidence in establishing the heat flowthrough the actual surround panel used in a test, it is requiredthat it be installed in the hot box where the test specimenmounting hole(s) are completely filled with the same thicknessmaterials (core and facers) used in constructing the homoge-neous surround panel, and Test Methods C 236, C 976, orC 1363 tests at the temperature conditions above be made todetermine the time rate of heat flow through a complete[without mounting hole(s)] or homogeneous surround panel.The surround panel time rate of flanking loss heat flow (QFL)should then be determined by subtracting the calculatedone-dimensional surround panel time rate of heat flow [calcu-lated by multiplying the measured surround panel thermalconductance ( Csp) times the total homogeneous surround panelprojected surface area times the average area weighted surface

temperature difference across the surround panel] from themeasured time rate of heat flow through the homogeneoussurround panel (see 5.2.1 and Test Method C 1363).

NOTE 4A recommended surround panel core material is expandedpolystyrene (beadboard) having a density in excess of 20 kg/m3 which hasbeen aged unfaced in the laboratory for a minimum of 90 days. Suitablefacing materials are approximately 3 to 4 mm thick heat-resistant rigidABS (a plastic material containing acrylonitrile, butadiene, and styrene)thermoplastic sheets with smooth or matte finish faces or similar thicknessHi-Impact Polystyrene plastic sheets (like the material used on the insideof refrigerators). The surround panel may have to have some horizontaland vertical saw cuts made in the cold side facing material to minimize theeffects of differential thermal expansion between the cold and hot sidefaces. The thin cuts should be covered with similar emittance tape stripsto provide a smooth surface to the weather and room side air flows.

5.1.3 Calibration transfer standardThe test facility sur-face heat transfer coefficients shall be calibrated using a heatflux transducer Calibration Transfer Standard constructed asdescribed in Annex A1 and illustrated in Fig. 3a and 3b. TheCalibration Transfer Standard has a core material of knowncharacteristics traceable to primary standards such as theguarded hot plate of a national standard laboratory. Theprojected area of the Calibration Transfer Standard shouldcover the same range as the test specimen model size andtolerances as specified in Practice E 1423 or NFRC 100-97.See 5.3 for the values of the standardized surface heat transfercoefficients required for using this test method for ratingpurposes.

NOTE 5It is recommended that a minimum of three CalibrationTransfer Standards be used that cover the range of test specimen modelsizes that a laboratory plans to test. A minimum of three CalibrationTransfer Standards should be used: one approximately the smallest modelsize to be tested, one approximately the average model size to be tested,and one approximately the largest model size to be tested.

5.1.4 Temperature measurementsIn addition to the air andsurface area weighted temperature measurements specified inTest Methods C 236, C 976, or C 1363, the following tempera-ture measurements are required:

5.1.4.1 Radiating surface temperaturesThe temperatureof all surfaces (baffles, surround panel opening, box surfaces,shields, etc) exchanging radiation heat transfer with the testspecimen using the same area weighing criteria as specified inTest Methods C 236, C 976, or C 1363.

5.1.4.2 Air temperatures The room side and weather sideair stream temperatures in a horizontal plane parrallel to thesurround panel surfaces shall be measured as specified inSection 6.10.3.1 of Test Method C 1363. As a minimumrequirement, these should be the mean of measurements atthree equidistant locations on the centerline of each glazing ortest specimen surface. However, it is strongly recommendedthat at least nine air temperature sensors in a 3 x 3 array beused.

NOTE 6The temperature sensor requirements given in 5.1.4, 5.1.4.1,and 5.1.4.2 are minimum requirements. Section 6.5.2 on temperaturemeasurements requires additional temperature sensors which are depen-dent on the test specimen type. More temperature sensors may be used ifthey provide more accurate average temperature (air and surface) values.

5.1.5 Air leakage For sealing procedures, see PracticeE 1423.

FIG. 2 Surround Panel With CTS

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5.2 Calibration Tests:5.2.1 Flanking Loss Test Procedure:5.2.1.1 Install a continuous surround panel (one without the

test specimen aperture cut in it) in the thermal chamber andattach temperature sensors to both sides at the density de-scribed in Test Methods C 236, C 976, or C 1363. Seal thesurround panel as per section of 7.14 of Test method C 1363.The heat flow through the continuous surround panel asdetermined by its area, the surface temperature difference onboth sides of the surround panel, and the thermal conductivityof the surround panels materials (as determined by TestMethods C 177, C 518, or C 1114) is compared to the metered

heat flow that is input into the metering chamber (after it iscorrected for the heat flow through the metering chamber wallsdetermined as per Annex A1 and Annex A2 of Test MethodC 1363) to determine the surround panel flanking loss. Aseparate surround panel flanking loss shall be determined foreach combination of materials and thicknesses of surroundpanels used for testing;as per Annex A3 of Test MethodC 1363.

NOTE 7It is convenient to measure the time constant of the thermalchamber and the surround panel at this time. The time constant is used todetermine when a particular test has achieved steady-state conditions, andis determined using the process described in Section A5 of Test MethodC 1363. A continuous surround panel (i.e., with the test specimen aperturefilled with surround panel material) can be used as a conservative estimateof the time constant of most window test specimens, which have a thermalcapacity and diffusivity less than an equivalent sized surround panelmaterial. Therefore it is useful to determine the time constant of a thermalchamber and surround panel at the same time that the flanking loss isdetermined.

5.2.1.2 Establish, as per Test Methods C 236, C 976, orC 1363, steady-state temperature conditions for which thesurround panel is to be calibrated, and record measurements ofpower, temperatures, and velocity.

5.2.2 Flanking Loss Data Analysis:5.2.2.1 Surround panel flanking loss, QFL, is determined by

performing a Test Methods C 236, C 976, or C 1363 test on acontinuous surround panel (with the test specimen mountinghole completely filled with the same thickness materials usedin constructing the homogeneous surround panel) at the tem-perature ranges expected during a test. The following equationis used to determine the surround panel flanking loss:

QFL 5 Q Qsp (11)

where:Q = power delivered to the metering chamber by the

heaters, fans, etc., which is corrected for the heatflow through the metering box walls, W,

Qsp = Csp Asp (t sp1 t sp2), W,Csp = conductance of surround panel, W/(m2 K),Asp = area of surround panel, m2,tsp1 = area weighted average room side surround panel

surface temperature, C, andtsp2 = area weighted average weather side surround panel

surface temperature, C.5.2.3 Calibration Transfer Standard Test Procedure:5.2.3.1 Install the Calibration Transfer Standard with the

weather side surface 25 mm (1 in.) in from the surround panelweather side surface (see Fig. 2). Seal the cracks around theperimeter of the Calibration Transfer Standard with nonmetal-lic tape or caulking, or both, to prevent air leakage. Each of thesurface temperature thermocouples in the Calibration TransferStandard should be individually measured, but if the thermo-couples are to be electrically averaged, the thermocouple leadswithin an averaged group must be the same length and eachaveraged group must be confined to individual horizontal rows.

5.2.3.2 Establish, as per Test Method C 1363 steady-statethermal conditions for which the surround panel and Calibra-tion Transfer Standard are to be calibrated and record measure-ments of power, temperature, and velocity.

5.2.4 Calibration Transfer Standard Data Analysis:

FIG. 3 (a) Example Calibration Transfer Standard Design Information

FIG. 3 (b) Minimum Temperature Sensors Array for Typical CTS

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5.2.4.1 Total heat flow The time rate of heat flow throughthe test assembly (surround panel and Calibration TransferStandard), Q, is determined by the procedures specified in TestMethods C 236, C 976, or C 1363.

5.2.4.2 Calibration Transfer Standard Heat Flow, Qs, iscalculated as follows:

QS 5 CtsAS ~t18 t28! (12)

where:Cts = conductance of Calibration Transfer Standard core,

W/(m2 K), as determined by either Test MethodsC 177, C 518, or C 1114 and Practice C 1045,

A S = area of Calibration Transfer Standard, m2,t18 = average equal area weighted temperature of room

side glass/core interface of calibration standard, C(see Fig. 1), and

t28 = average equal area weighted temperature of weatherside glass/core interface of calibration standard, C(see Fig. 1).

5.2.4.3 Surround panel heat flow, Q sp, is then:Qsp 5 Csp Asp ~tsp1 tsp2! (13)

where:Asp = surround panel area, m2,tsp 1 = area weighted room side surround panel surface

temperature, C, andtsp2 = area weighted weather side surround panel surface

temperature, C.NOTE 8If a mean temperature correction for the surround panel is

required, conduct calibration tests at three different mean temperatureconditions as required in 5.1.2.

5.2.4.4 If t b1 = th 61C (62F) and tb2 = tc 61C (62F)see 5.2.4.6 to determine the surface heat transfer coefficients. Ifcalculated values of the surface temperatures are to be used inthe calculation procedure specified in Section 8, Calculation ofStandardized Thermal Transmittance, then the calculation pro-cedures specified in 5.2.2.5 also should be carried out todetermine the convection coefficient, Kc.

5.2.4.5 If t b1 > th +1C (2F) or tb1 < th 1C (2F) and tb2> t c +1C (2F) or tb2 < tc 1C (2F), after calculating t1 andt2 from Eq 17 and 18, respectively, see 5.2.4.7 to determine thesurface heat transfer coefficients.

5.2.4.6 Surface heat transfer coefficients, hh and hc, when tb1= th 61C (62F) and tb2 = tc 61C (62F), are calculated asfollows:

hh 5 @QS/A S ~th t1# (14)

where:th = average room side air temperature, C, andt1 = equal area weighted average room side Calibration

Transfer Standard surface temperature, C, which iscalculated from the following:

t1 5 t18 1 Cts~t18 t28!/C g (15)

where:Cg = conductance of facing on calibration transfer stan-

dard, W/(m2K).NOTE 9The conductance of the glazing layer is the thermal conduc-

tivity of the glazing material divided by the glazing layer thickness. A

value of 1 W/(mK) for the thermal conductivity of float glass isrecommended if the actual value is not provided by the manufacturer. Inother cases, such as laminated or plastic glazing, the glazing manufacturershould provide the measured thermal conductivity of the glazing material.

hc 5 Qs/~A S~t2 tc!! (16)

where:tc = average weather side air temperature, C, andt2 = equal area weighted average weather side calibration

transfer standard surface temperature, C, which iscalculated from the following:

t2 5 t28 Cts ~t18 t28!/C g (17)5.2.4.7 Surface heat transfer coefficients, hh and hc when tb1

> th +1C (2F) or tb1 < th 1C (2F) and t b2 > tc +1C (2F)or tb2 < tc 1C (2F), are calculated as follows:

5.2.4.7(1) Room side radiative heat transfer, Qr1When theroom side baffle or box wall is close to the test specimen,parallel plate radiative heat transfer can be assumed. Then:

qr1 5 Qr1/AS 5 F1b s @~t b11273.16!4~t11273.16!4! (18)

where:F 1b = 1.0/[1/e 1 + 1/eb1) 1], assuming a view factor of 1.0

between infinite parallel plates,e 1 = emittance of glass Calibration Transfer Standard

facing sheet (glass or plastic),eb1 = radiant average emittance of the baffle/shield/

surround panel opening/box wall and all othersurfaces in view of the test specimen,

tb1 = area weighted radiant average baffle/shield/boxwall/surround panel opening surface temperature inview of the test specimen, C, and

s = Stefan-Boltzmann constant = 5.67 3 10 8,W/(m2K4).

NOTE 10If the view factor between the test specimen surface and thebaffle/shield/box wall/surround panel opening surfaces is not equal to 1.0or if the baffle/shield/box wall/surround panel opening is not isothermal towithin 61C (62F) then the radiative heat transfer calculation procedurein Annex A2 is required. Isothermal to within 61C (62F) is determinedby comparing each of the individual baffle/shield/box wall/surround paneltemperature measurements to the mean of all the baffle/shield/boxwall/surround panel opening temperature measurements. If any of theindividual baffle/shield/box wall/surround panel opening temperaturemeasurements differ from the mean by more than 61C (62F), then theradiative heat transfer calculation procedure in Annex A2 is required. Hotbox operators should recognize that the radiative calculation procedure inAnnex A2 adds to the complexity of the tests being conducted. For manyhot boxes, additional baffle/shield/box wall/surround panel opening andother surrounding surfaces have to have their temperatures accuratelymeasured and recorded, and the more complex radiative heat transferanalysis specified in Annex A2 may have to be added to the data analysis.To circumvent this, hot box operators should make the necessarymodifications to their facilities so that the surrounding baffle/shield/boxwall/surround panel opening temperatures are isothermal to within 61C(62F) and the mean baffle/shield/box wall/surround panel openingtemperature is within 61C (62F) of the respective air temperature. Asimple solution for many hot box designs would be to add a large, flatbaffle that is parallel to the surround panel. If a large isothermal baffle islocated close enough to the surround panel so that the test specimen (orcalibration transfer standard) sees only the baffle and the surround panelopening surfaces, the experimental data analysis does not have to includethe more complex radiative heat transfer calculation procedure specified in

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Annex A2. This greatly simplifies the test procedure and the experimentaldata analysis.

5.2.4.7(2) Room side convective heat transfer, Qc:Qc1 5 QS Qr1 (19)

and:qc1 5 Q c1/As (20)

Also, using Eq 20, the convection constant Kc in thefollowing equation for the convective heat transfer to the testspecimen can be determined.

Kc 5 qc1/~th t1! 1.25 (21)NOTE 11The convective heat transfer calculation assumes natural

convection on the room side of the Calibration Transfer Standard. Toensure that a single convection coefficient, Kc, can be used for fenestrationsystem tests, its behavior should be investigated, using the calibrationtransfer standard, over the range of heat flows expected. The hot boxoperator may use a convective correlation different from Eq 21 if it ismore appropriate for the convective heat transfer situation that exists forthat operators hot box. However, the test report should include thealternative form of Eq 21 used and the alternative value of the convectionconstant Kc obtained.

5.2.4.7(3) Room side surface heat transfer coefficient, hhFrom Eq 18 and 20:

hh 5 ~qr1 1 qc1!/~th t1! (22)where t1 is calculated in accordance with Eq 15.5.2.4.7(4) Weather side radiative heat transfer, Qr2When

the weather side baffle or box wall is close to the test specimen,parallel plate radiative heat transfer can be assumed. Then:

qr2 5 Qr2/AS 5 F2b s @~t21273.16!4 ~tb21273.16! 4# (23)

where:F 2b = 1.0/[1/e 2+1/eb2 1], assuming a view factor of 1.0

between infinite parallel plates,e2 = emittance of Calibration Transfer Standard facing

sheet (glass or plastic),e b2 = radiant average emittance of the baffle/shield/

surround panel opening/box wall and all othersurfaces in view of the test specimen,

tb2 = area weighted radiant average baffle/shield/boxwall/surround panel opening surface temperature inview of the test specimen, C, and

s = Stefan-Boltzmann constant = 5.67 3 10 8,W/(m2K4).

NOTE 12If the view factor between the test specimen surface and thebaffle/shield/surround panel opening/box wall surface is not equal to 1.0or if the baffle/shield/surround panel opening/box wall is not isothermal towithin 61C (62F), then the radiative heat transfer calculation proce-dure in Annex A2 is required. Isothermal to within 61C (62F) isdetermined by comparing each of the individual baffle/shield/surroundpanel opening/box wall temperature measurements to the mean of all thebaffle/shield/surround panel opening/box wall temperature measurements.If any of the individual baffle/shield/surround panel opening/box walltemperature measurements differ from the mean by more than 61C(62F), then the radiative heat transfer calculation procedure in Annex A2is required.

5.2.4.7(5) Weather side convective heat transfer, Qc2:Qc2 5 QS Qr2 (24)

and

qc2 5 Qc2/AS (25)5.2.4.7(6) Weather side surface heat transfer coefficient,

hcFrom Eq 23 and 25:hc 5 ~qr2 1 qc2!/~tc t2! (26)

where t2 is calculated in accordance with Eq 17.5.3 Standardized Surface Heat Transfer Coeffcients:5.3.1 Thermal chamber velocity adjustmentsThe results

from the Calibration Transfer Standard tests are used for twopurposes. The primary objective is to adjust the air velocities inthe room and weather side of the thermal chamber so that theyproduce standardized surface heat transfer coefficients, withinthe tolerances specified below, on both sides of each Calibra-tion Transfer Standard used. The second objective is todetermine the convection coefficient, Kc, and the weather sidesurface heat transfer coefficient, hc, for use in the CTS methodof calculating the standardized thermal transmittance (see8.2.1).

5.3.2 The impinging air flow (for perpendicular and parallelair flow directions) on the Calibration Transfer Standard shouldbe as uniform as possible. After the calibration tests have beenperformed, the test laboratory shall compare the surface heattransfer coefficients measured on each Calibration TransferStandard with the standardized heat transfer coefficients speci-fied in 5.3.3 and 5.3.4. If the surface heat transfer coefficientsmeasured on a Calibration Transfer Standard are outside of thetolerance specified in 5.3.3 and 5.3.4, then the laboratory shalladjust the fan speeds, plenums, or thermal chamber configu-ration to meet the specified tolerance before running tests onfenestration products. If the surface heat transfer coefficientsgenerated on the Calibration Transfer Standard are not withinthe tolerances specified in 5.3.3 and 5.3.4, then the actualCalibration Transfer Standard surface heat transfer coefficientsshall be clearly identified in the test report, and only thethermal transmittance, US, shall be reported. The standardizedthermal transmittance shall not be reported unless the surfaceheat transfer coefficients generated on the Calibration TransferStandard are within the tolerance specified in 5.3.3 and 5.3.4.

5.3.3 Room side standardized surface heat transfercoeffcientThe standardized surface heat transfer coefficientmeasured on the room side of each Calibration TransferStandard shall be:

hSTh 5 7.7 W/~m2K! 65 %~Allowed CTS calibration range of 7.3 to 8.0 W/~m2K!!.

(27)Since 7.0 W/(m2K) is the natural convection lower limit of

the indoor side overall surface heat transfer coefficient, a 65 %variation is allowed to accommodate some forced convectiondue to small room side air circulation fans that provide a moreuniform flow distribution on the indoor side of the CTS.

NOTE 13Using the 1997 ASHRAE Fundamentals Handbook, Fenes-tration Chapter 29, Table 3, the indoor side of the overall combined naturalconvection, radiation surface heat transfer coefficient for a 1.22 m (4 ft)high, 12.7 mm (0.5 in.) wide cavity, double glazed, low emittance glazingunit is 6.98 W/(m2K). For a 1.22 m (4 ft) high, 12.7 mm (0.5 in.) thickhigh-density expanded polystyrene (EPS) foam core Calibration TransferStandard (CTS) with two 4 mm glass faces, the indoor side calculatedoverall combined natural convection, radiation surface heat transfercoefficient is 7.02 W/(m 2K) using the same methods and equations that

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were used to obtain the ASHRAE Chapter 29, Table 3 results. Roundingoff these two results gives a nominal standardized surface heat transfercoefficient of 7 W/(m2K) (1.23 Btu/(hrft2F)), which is the naturalconvection lower limit for this size CTS. The room side standardizedsurface heat transfer coefficient has been set slightly above this level toallow a small amount of forced convection.

5.3.4 Weather side standardized heat transfercoeffcientThe standardized surface heat transfer coefficientmeasured on the weather side of each Calibration TransferStandard shall be:

hSTc 5 29 W/~m2K! 6 10 %~Allowed CTS calibration range of 26 to 32 W/~m2K!!.

(28)Again, referring to the 1997 ASHRAE Fundamentals Hand-

book, Fenestration Chapter 29, the recommended design valuefor the weather side overall combined forced convection,radiation surface heat transfer coefficient for a nominal 24km/h (15 mile per hour) wind speed is hc = 29 W/(m2K) (5.1Btu/(hrft 2F)).

NOTE 14Since the ASHRAE value of 29 W/(m2K) comes from heattransfer experiments on a 0.3 m by 0.3 m (1 ft by 1 ft) flat plate, for alarger 1.22 m (4 ft) high CTS, the forced convection heat transfercoefficient will tend to be lower due to the continued growth of theboundary layer, thus reducing the weather side overall combined forcedconvection, radiation surface heat transfer coefficient. The degree of thisreduction depends on a number of factors, including the flow conditioningbefore it reaches the surface of the CTS, the initial flow direction (parallelor perpendicular), the flow regimen along the CTS surface (completelylaminar or turbulent over a portion of the CTS) and the depth that the CTSis recessed in the surround panel opening. Therefore, to account for thisand to also allow lower nominal weather side wind speeds to be used toadjust the weather side overall combined forced convection, radiationsurface heat transfer coefficient, a 610 % variation in the weather sidestandardized value is allowed.

6. Experimental Procedure6.1 Detailed written operating procedures for each test

apparatus shall be developed and shall be available to ensurethat the tests are conducted in accordance with the require-ments of this test method.

6.2 Installation of Fenestration System:6.2.1 The fenestration system to be tested should be in-

stalled in the surround panel with a configuration that simulatesthe actual installation as closely as possible. That is, thecomplete assembly including all frame elements should be inplace during the test. The surround panel requirements speci-fied in 5.1.2 and the sealing requirements specified in 5.1.5 (forthe calibration transfer standard) also apply to the test speci-men. See 7.2 of Practice E 1423 for further guidance oninstallation.

6.3 Test Conditions:6.3.1 Wherever the temperatures and standard heat transfer

coefficients are not otherwise specified, 5.3 and PracticeF 1423 should be used as guides for selecting the appropriatetest temperature conditions.

6.4 Stabilization and Test Times:6.4.1 Establish, as per 10.9 of Test Method C 1363, steady-

state temperature and power conditions for which the testspecimen is to be tested and record measurements of power,temperatures, and velocity at the specified test intervals.

6.5 Recorded Test Measurements:6.5.1 Power measurementsthe total net heat transfer or

average power transferred through the test specimen during ameasurement interval. The energy balance to determine thisshould account for all metering box heating and cooling, powerto fans or blowers, any significant power to transducers,corrections for the metering box wall heat transfer and sur-round panel and test frame flanking heat transfer, any otherextraneous heat flows, and corrections for the energy flow(enthalpy difference times air leakage mass flow rate) associ-ated with any air leakage entering and leaving the meteringchamber.

6.5.2 Temperature measurementsall measurements speci-fied in Test Methods C 236, C 976, or C 1363. The temperaturesensors used should be special limit (premium) thermocouples(24 gage may be used; 30 gage or smaller are recommended forthe test specimen surface temperatures), or appropriate sizethermistors or RTDs (resistance temperature detectors).

6.5.2.1 Additional temperature measurements shall be madeon the surround panel wall (see 6.5.2 of Test Method C 236, 5.7of Test Method C 976, or 6.10.2 of Test Method C 1363, for theminimum number of area weighted surround panel temperaturesensors to use).

6.5.2.2 For determining the thermal transmittance, US, andthe standardized thermal transmittance, UST, it will be neces-sary to make additional temperature measurements on thefenestration test specimen frame, glazing (center and nearedges) and on any other surfaces (sills, muntins, etc.) in orderto provide a representative area weighted value of the surfacetemperatures of the specimen. It must be recognized that thereis such a wide range of fenestration system designs that it is notpossible to specify the locations of the temperature sensors toprovide a correct area weighted determination of the varioussurface temperatures for all configurations. See PracticeE 1423 for additional guidance on the location of test specimensurface temperature sensors for different fenestration systems.The weighted heat transfer surface areas used with the frame/sash temperature measurements shall add up to the total surfacearea of the frame/sash in contact with the surrounding air. Also,any area weighted surface temperatures determined in thismanner shall be compared with the calculated equivalent roomside and weather side surface temperatures specified in 8.2.1and 8.2.2. If a discrepancy exists, it may be due to either thetemperature calculation process or the placing of the areaweighted temperature sensors. The technique of area weightedtemperature measurements may be necessary (see 3.1) whenthe frame and glazing conductances are dissimilar or thesurface geometry is complicated or projects out into theweather side chamber, or both. If this is the case, excessive useof temperature sensors may cause the measured surface heattransfer coefficients, hh and hc to differ from the actual heattransfer coefficients, introducing further uncertainty in theresults. The temperature sensors used should be special limit(premium) thermocouples (24 gage (0.02010 in., 0.5106 mm),30 gage (0.01003 in., 0.2546 mm) or smaller are recommendedfor the surface temperatures), thermistors or resistance tem-perature detectors (RTDs), and shall be placed so as to

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minimize the disturbance of the air flows on the surfaces of thetest specimen.

6.5.2.3 Temperature measurements should also be made inthe room side and weather side air streams in the same quantityand spacing as the surface temperature sensors (see 6.5.2 ofTest Method C 236, 5.7 of Test Method C 976; and 6.10.3.1 ofTest Method C 1363.). This will allow for a more accuratemeasurement of the room side and weather side surface heattransfer coefficients.

6.5.3 Radiation effectsTo minimize the effect of radiation-induced error on the temperature sensors, the temperatures ofall surfaces exchanging radiation heat transfer with the fenes-tration system (test specimen or calibration transfer standard)shall be measured. This includes: (1) room side and weatherside shields and baffles, (2) air distribution system components,and (3) hot box walls and portions of the surround panel thatare in view of the test specimen. Any heating and coolingdevices must be shielded from the surround panel/fenestrationsystem and the surface temperature of the shield should bemeasured. The temperature sensors must be applied to thesesurfaces with tape or adhesive that has an emissivity similar tothat of the surface. The air temperature sensors should either beshielded or be as small as possible so that they are notsignificantly affected by surfaces with which they are exchang-ing radiation (see 6.5.2 of Test Method C 236; 5.7 of TestMethod C 976; or 6.10.3.1 of Test Method C 1363).

6.5.4 Wind speed measurementsThe weather side windspeed shall be measured at a location that represents the freestream condition. For both perpendicular and parallel flowpatterns, it is required that this location be a distance out in theair stream such that the wind speed sensor is not in the testspecimen surface boundary layers or wakes. A minimumdistance of 75 mm (3 in.) out from the test specimen centerpoint is recommended. The hot box operators experience andknowledge of the air distribution system and hot box designshould be drawn upon to determine the proper location.

6.5.4.1 Mapping the velocity fields on both the room andweather sides by periodic traversing of the air flow field todetermine the air velocity distribution is recommended at everycalibration interval to verify that a uniform air flow is directedat or across the face of the test specimen.

6.5.4.2 On the room side, where natural convection condi-tions are desired, it is required to mount a velocity sensor at alocation that represents the average velocity so that naturalconvection conditions can be verified and the room sideaverage air velocity can be measured during the test.

6.5.4.3 The types of acceptable air speed sensors are notspecified within this test method. However, an accuracy of65 % of the reading is required and a sensor whose signal canbe converted to a digital form for automated data recording isrecommended.

6.5.5 Glazing deflectionGlazing deflection measurementsshall be reported for each test specimen as specified in PracticeE 1423.

7. Calculation of Thermal Transmittance7.1 General CalculationsThe following shall be calcu-

lated for each test:7.1.1 Total heat flow, QThe time rate of heat input into the

metering box corrected for the metering box wall heat transfer,as determined using procedures specified in Test MethodsC 236, C 976, or C 1363.

7.1.2 Surround panel heat flow, Qsp,Qsp 5 Csp Asp ~tsp1 tsp2! (29)

where Csp is the thermal conductance of the surround panelas specified in 5.1.2 using Test Methods C 177, C 518, orC 1114.

7.1.3 Test specimen heat flow, QS,QS 5 Q Qsp QFL (30)

where the surround panel flanking loss, QFL, is determinedas specified in 5.2.1 and 5.2.2

7.1.4 Test specimen thermal transmittance, US,US 5 QS/@AS ~th tc!# (31)

8. Calculation of Standardized Thermal Transmittance8.1 The thermal transmittance results measured using this

test method can be standardized for rating and comparisonpurposes. The standardization process attempts to determinethe actual surface heat transfer coefficients on the room andweather side surfaces on the test specimen during the test, andreplace them with standard surface heat transfer coefficientswhen determining the standardized thermal transmittance. Thestandardized thermal transmittance is useful when comparingresults from different thermal chamber configurations (that is,parallel versus perpendicular weather side air flow), and whencomparing test results with computer calculated thermal trans-mittance (U-factor) values.

8.2 The following sections offer two methods of calculatingthe standardized thermal transmittance. The procedure thatutilizes the calculation of the equivalent surface temperaturesto compute the test specimen thermal conductance (CTSmethod) is described in 8.2.1-8.2.3, 8.2.5, and 8.2.7, and themethod that uses the area weighted surface temperature mea-surements to compute the standardized thermal transmittanceof the test specimen (area weighting method) is described in8.2.4, 8.2.6, and 8.2.8. The area weighting method shall beused if the measured thermal transmittance, US, is greater than3.4 W/(m2K) (0.60 Btu/(hrft2F)) or the ratio of the testspecimen projected area to wetted (heat transfer) area on eitherside of the test specimen is less than 0.80. The test laboratoryshall indicate in the test report which method was used tocalculate the final standardized thermal transmittance.

NOTE 15It should be noted that the surface heat transfer coefficients,hh and hc, determined from the appropriately sized calibration transferstandard may differ from the surface heat transfer coefficients that existduring a hot box test on a specific test specimen. Actual fenestrationsystems usually have frame and sash surfaces that introduce three-dimensional convective heat transfer effects in the surface heat transfercoefficients. As a result of this, the test specimen surface heat transfercoefficients will differ from those obtained with the nonframed, essentiallytwo-dimensional calibration transfer standard tested under the sameconditions. In this test method, it is either assumed that the differences aresmall enough so that the calibration surface heat transfer coefficients canbe used to calculate equivalent test specimen average surfaces tempera-tures, t1 and t2, in order to estimate the actual test specimen surface heattransfer coefficients. It should be recognized that this assumption will notbe accurate for all fenestration products, especially for high thermaltransmittance products where the surface heat transfer coefficients are a

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major portion of the overall thermal transmittance and also for projectingfenestration products (for example, skylights, roof windows, gardenwindows) where the surface heat transfer coefficients are quite differentfrom the standardized values. In these situations, an attempt should bemade to measure the test specimen surface temperature distributions andthen calculate directly the test specimen average surfaces temperatures, t1 and t2. This area weighting (AW) method also has problems in that theplacement of temperature sensors to get an accurate area weighting is notknown, especially on high conductivity horizontal surfaces which act asheat transfer extended surfaces (that is, fins). In addition, the placement ofmany temperature sensors on the test specimen surfaces will affect thevelocity fields in the vicinity of these surfaces which will effect the surfacetemperatures and surface heat transfer coefficients. Since neither of thesetwo methods correctly reproduces the actual thermal performance of thefenestration product, it is important that the current computer calculationmodels be improved so that future measured versus calculated compari-sons of the thermal transmittance are made with the actual thermaltransmittance, US:

8.2.1 CTS methodEquivalent room side surface tempera-ture of test specimen, t 1, is calculated by solving the followingthree equations for Qr1, Qc1 and t 1:

QS 5 Q1 1 Qc1 (32)

Qr1 5 Ah F1b s @~tb11273.16!4 ~t11273.16! 4# (33)

Q c1 5 Ah Kc ~th t1!1.25 (34)where Kc is determined during the calibration tests, and F1 b

is calculated as shown in 5.2.4.7( 1).NOTE 16One way to solve these equations is by iteration. Assume a

value for t1 in Eq 33, calculate Qr1, determine Qc1 from Eq 32, thencalculate a new t1 from Eq 34. If this new value is different from theassumed value, then use the average of the two t1 values in Eq 33 andrepeat the calculation until the t1 values agree to within 0.1C.

8.2.2 CTS methodEquivalent weather side surface tem-perature, t2,

t2 5 QS/~hc Ac! 1 th (35)where hc is determined from the procedures specified in

5.2.3.8.2.3 CTS methodRoom side surface conductance, hh,

hh 5 QS/@AS ~th t1!# (36)where t1, the room side surface temperature, is the calculated

equivalent value as determined in 8.2.1.8.2.4 Area weighting methodRoom side surface heat

transfer coefficient, h h:hh 5 Q S/@Ah ~th t1!# (37)

where the room side surface temperature, t1, used is the areaweighted average value that was measured on the surface of thetest specimen with temperature sensors.

8.2.5 CTS methodWeather side surface heat transfer co-efficient, hc:

hc 5 QS/@AS ~t2 tc!# (38)where t2, the weather side surface temperature, is the

calculated equivalent value as determined in 8.2.2.8.2.6 Area weighting methodWeather side surface heat

transfer coefficient, h c:h c 5 QS/@Ac ~t2 tc!# (39)

where the weather side surface temperature, t2, used is thearea weighted average value that was measured on the surfaceof the test specimen with temperature sensors.

8.2.7 CTS methodTest specimen standardized thermaltransmittance, UST[CTS],

UST@CTS# 5 1/@1/US 1 ~1/hSTh 1/hh!! 1 ~1/h STc 1/hc!# (40)where hSTh and hSTc are the standardized surface heat transfer

coefficients on the room side and weather side, as defined in8.2.9.

8.2.8 Area weighting methodTest specimen standardizedthermal transmittance, UST[AW]:

UST@AW# 5 1.0/@~1/US! 1~AS/Ah!~1/~hSTh1/hh! 1 ~AS/Ac!~1/hSTc1/hc!#(41)

where hSTh and hSTc are the standardized surface heat transfercoefficients on the room side and weather side, as defined in8.2.9.

8.2.9 Standardized Surface Heat Transfer Coeffcients:8.2.9.1 The nominal values of the standardized surface heat

transfer coefficients as specified in 5.3.3 and 5.3.4 are:hSTh5 7.7 W/~m2 K! ~1.36 Btu/~h ft2 F!! (42)

h STc 5 29 W/~m2 K! ~5.1 Btu/~h ft2 F!! (43)

9. Report9.1 Report the following information:9.1.1 All of the information specified in Test Methods

C 236, Section 10; C 976, Section 11; or C 1363, Section 12.The test specimen size, design drawing(s), and a detaileddescription of all the test specimen components (that is, frame,glazing, hardware weather-stripping, etc.) also shall be re-ported. Any nonstandard test specimen size and nonstandardtest conditions used shall be explained.

9.1.2 The time rate of heat flow through the total surroundpanel/test specimen, Q.

9.1.3 The surround panel calculated time rate of heat flow,QSP.

9.1.4 The time rate of flanking loss heat flow for thesurround panel, QFL.

9.1.5 The net test specimen heat flow rate, QS.9.1.6 The weather side and room side average baffle tem-

peratures, tb1 and tb2.9.1.7 The test specimen room side and weather side heat

transfer surface areas, Ah and Ac.9.1.8 The surround panel area, A sp.9.1.9 The room side and weather side baffle areas, Ab1 and

Ab2.9.1.10 The measured thermal transmittance, US.9.1.11 If determined, the values of and the method used to

determine:9.1.11.1 The calculated room and weather side surface heat

transfer coefficients, hh and hc.9.1.11.2 The average test specimen room side and weather

side surface temperatures, t1 and t2.9.1.11.3 The calculated standardized thermal transmittance,

UST (CTS or AW).9.1.12 Also, the following information should be provided:

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9.1.12.1 Diagrams documenting all surface temperature lo-cations (baffles, surround panel, and test specimen) and thecorresponding temperatures at each location.

9.1.12.2 The values of, and method used to determine, theglass deflections as required in 6.5.5.1.

9.1.13 See Test Method C 1363 for measurement uncertain-ties required.

9.1.14 The following statement shall be included in the testreport directly after the above results are reported. This testmethod does not include procedures to determine the heat flowdue to either air movement through the specimen or solarradiation effects. As a consequence, the thermal transmittanceresults obtained do not reflect performances which may beexpected from field installations due to not accounting for solarradiation, air leakage effects, and the thermal bridge effects thatmay occur due to the specific design and construction of thefenestration system opening. The latter can only be determinedby in-situ measurements. Therefore, it should be recognizedthat the thermal transmittance results obtained from this testmethod are for ideal laboratory conditions and should only beused for fenestration product comparisons and as input tothermal performance analyses which also include solar, airleakage and thermal bridge effects.

9.1.15 If the thermal chamber is set up to test at environ-mental conditions that are not within the tolerances specifiedfor the room side and weather side standardized surface heattransfer coefficients in 5.3 and the nominal ASHRAE environ-mental temperatures of 21C (70F) and 18C (0F), then thefollowing additional information from Section 5 must bereported for each test specimen: the size, construction, materialthermal properties, and measured thermal transmittance of therelevant Calibration Transfer Standard, the test conditions, airand surface temperatures, and surface heat transfer coefficientsmeasured on that Calibration Transfer Standard; any calibra-tion coefficients used in calculating the test specimen standard-ized thermal transmittance from the relevant calibration orCalibration Transfer Standard tests; and an explanation of anyother conditions that are outside of the requirements specifiedin this test method.

9.2 Uncertainty Estimation:9.2.1 The individual laboratory measurement uncertainty of

this test method depends upon the test equipment and operatingprocedures, and upon the test conditions and specimen prop-erties. For this reason, no simple quantitative statement can bemade that will apply to all tests; however, in order to complywith the requirements of 9.1.13, it is necessary to estimate theuncertainty of the results for each test to be reported. Suchestimates of uncertainty can be based upon an analysis usingthe propagation of errors theory (often called uncertaintyanalysis) discussed in textbooks on engineering experimenta-tion and statistical analysis (see, for example, Schenck8). Theseuncertainty estimates can be augmented by the results ofintralaboratory test comparisons, by the results of experimentsdesigned to determine repeatability of the effect of deviationsfrom design test conditions, and by measurements of reference

specimens from appropriate standards laboratories. In general,the best overall accuracy will be obtained in an apparatus withlow metering box wall heat transfer, low surround panel heattransfer, and low flanking (surround panel and surround panelframe) heat transfer relative to the test specimen heat transfer.Low metering box wall heat transfer can be achieved by usinghighly insulated walls subjected to small temperature differ-ences. Low surround panel heat transfer can be achieved withhighly insulated surround panels that have a small exposedsurface area in relation to the metering chamber aperture area.Low surround panel and surround panel frame flanking heattransfer, in relation to metering box heat input, can be achievedby using homogeneous and highly insulated surround panelsand surround panel frames with no thermal bridges. Also ingeneral, for a particular apparatus, the uncertainty will decreaseas the heat transfer through the specimen increases.

NOTE 17As an example, an outline of the procedure for an uncer-tainty analysis for thermal transmittance, US, is as follows:

From 7.1.4, US = Q S/(AS(t1 t2)) where the heat transfer through thespecimen, QS, is determined from the electrical power input (heatingelements and fans) to the metering box, QE, the heat into or out of themetering box through its walls, QBW, the heat transfer through thesurround panel, Qsp, and the flanking (surround panel and surround panelframe) heat transfer, QFL; such that QS = Q E 6 QBW Qsp QFL. (Otherterms such as air cooling or air leakage also should be accounted for ifthey occur.)

Combining these equations, the relation for the thermal transmittance isUS = (QE 6 QBW QSP Q FL)/(AS( t1 t2)). The individual uncertaintyfor each quantity in this equation must be estimated. Such estimates maybe made from the knowledge of how each of these quantities isdetermined. This should include an uncertainty analysis of each quantityby taking the appropriate partial derivatives with respect to the variablesthat are used to determine that quantity until an individual instrument(temperature, power, etc.) with a known measurement uncertainty or fromthe results of calibration experiments designed to investigate suchuncertainties are determined. Then, following the propagation of errorstheory which assumes the errors to be independent, the uncertainties arecombined by determining the square root of the sum of the squares of allof the contributing uncertainties. Relative uncertainties (fractional orpercentage of a the variable whose uncertainty is being estimated) can alsobe obtained. One ad hoc estimate by Elmahdy9 for a fenestration hot boxgave an uncertainty estimate of 6 %.

10. Precision and Bias10.1 Interlaboratory Comparison Results:10.1.1 BackgroundSeven interlaboratory comparisons for

this procedure have been conducted by the National Fenestra-tion Rating Council (NFRC) from 1994 to 1998 using bothguarded and calibrated hot boxes. These interlaboratory com-parisons had between seven and nine laboratories participating,with some laboratories having parallel weather side air flow,and others having perpendicular weather side air flow in thethermal chamber. All of the laboratories were expected to testthe specimens at the following nominal conditions:

10.1.1.1 Weather side average air temperature of 18C,10.1.1.2 Room side average air temperature of 21C,10.1.1.3 Standardized weather side surface heat transfer

coefficient of 29 W/(m2K), and

8 Schenck, H., Theory of Engineering Experimentation, McGraw Hill, NewYork, NY Third Edition, 1979, p. 53.

9 Elmahdy, A. H., Heat Transmission and R-value of Fenestration SystemsUsing IRC Hot Box: Procedure and Uncertainty Analysis, ASHRAE Transactions98(2): 630637.

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10.1.1.4 Standardized room side surface heat transfer coef-ficient of 8.3 W/(m2K).

10.1.2 See Table 1 for a summary of the seven interlabora-tory comparison results described below.

10.1.2.1 1994 interlaboratory comparison Number 1Thedesign of the first interlaboratory comparison is described byWise and Mathis.10 Nine laboratories participated in thisinterlaboratory comparison, which was conducted betweenMarch and August 1994. Data were reported for a 182 cm 3121 cm horizontal sliding window with a non-thermally brokenaluminum frame and 19 mm double glazed clear insulatingglazing units filled with air.

10.1.2.2 1994 Interlaboratory Comparison Number2Seven testing laboratories participated in this interlabora-tory comparison, which was conducted between July andOctober 1994. The test specimen in this interlaboratory com-parison was a 183 cm 3 122 cm Calibration Transfer Standardmade from a 13.5 mm EPS core, which was faced with 3.86mm polycarbonate. This interlaboratory comparison only re-quested that the test laboratories report the standardizedthermal transmittance calculated by the CTS method, andthermocouples were not placed on the outside of the testspecimen. In addition, the polycarbonate was scored on bothsides to minimize thermal expansion.

10.1.2.3 1995 Interlaboratory Comparison Number3Eight testing laboratories participated in the third interlabo-ratory comparison between April and December 1995. Resultswere reported for a 122 cm 3 183 cm double hung windowwith a reinforced vinyl frame, and 19 mm double glazed,argon-filled glazing units with a low-e coating of emittance0.09 on surface number 3.

10.1.2.4 1995 Interlaboratory Comparison Number4Eight testing laboratories participated in the fourth inter-laboratory comparison, which was conducted between June1995 and August 1996. The test specimen in this interlabora-tory comparison was a 183 cm 3 122 cm calibration panel with13.5 mm EPS core faced with 4.76 mm glass. This interlabo-ratory comparison only requested that the test laboratoriesreport the standardized thermal transmittance calculated by theCTS method even though thermocouples were placed on theoutside of the test specimen.

10.1.2.5 1996 Interlaboratory Comparison Number5Eight testing laboratories participated in the fifth interlabo-

ratory comparison between May and November 1996. Resultswere reported for a 122 cm 3 122 cm fixed window with analuminum clad wood frame, which was quadruple glazed withtwo suspended films having a low-e coating of emittance of0.11, and the glazing cavity was filled with krypton.

10.1.2.6 1997 Interlaboratory Comparison Number 6Nine testing laboratories participated in the sixth interlabora-tory comparison between March and August 1997. Resultswere reported for a 122 cm x 122 cm fixed window with analuminum clad wood frame, which was dual glazed, consistingof nominal 25.4 cm thick insulating glass fabricated from twonominal 5 mm sheets of glass, nominal 16 mm air space, noinert gas fill and a reported 0.04 emittance Low E coating.The spacer was specified to be a dual-sealed, U-shaped rolledspacer system.

10.1.2.7 1998 Interlaboratory Comparison Number 7Nine testing laboratories participated in the seventh interlabo-ratory comparison between March and August 1998. Resultswere reported for a 122 cm x 122 cm fixed window with analuminum clad wood frame, which was dual glazed, consistingof niminal 25.4 cm thick insulating glass fabricated from twoniminal 5 mm sheets of glass, nominal 16 mm air space, noinert gas fill and a reported 0.04 emittance Low E coating.The spacer was specified to be a dual-sealed, U-shaped rolledspacer system. Same test sample was used for the 1997Interlaboratory Comparison Number 6.

10.1.3 PrecisionTable 1 presents a summary of theseven above described interlaboratory comparisons. The year,test specimen, and number of laboratories participation isgiven, along with the following results:

US = average thermal transmittance, W/(m2K)UST = average standardized thermal transmittance, W/(m

2K)R = reproducibility limit [for 95 % confidence limits,

2.8 times the standard deviation], W/(m2K)R % = reproducibility limit percent [reproducibility lim-

mit divided by the mean], %10.1.4 Bias To give some idea of the bias associated

with the above described interlaboratory comparisons, thecalibration standard used in the comparison 2 had a calculatedtheoretical thermal transmittance of 1.65 W/(m2K), and thecaliabration transfer standard used in comparison 4 had acalculated theoretical thermal transmittance of 1.75 W/(m2K).The calculated theoretical values have an associated uncer-taincy which is not known.

10 Wise, D. J., Mathis, R. C., An Assessment of Interlaboratory Repeatability inFenestration Energy RatingsPart 2: Interlaboratory Comparison of Test Results,Thermal Performance of the Exterior Envelopes of Buildings VI: ConferenceProceedings, December 4-8, 1995, p. 535540.

TABLE 1 Summary of Interlaboratory Comparison ResultsComparison

Number Year Test Specimen LabsUS

W/m2KUST

W/m2KUS

R (W/m2K)US

R (%)UST

R (W/m2K)UST

R (%)1 1994 Aluminum frame slider window 9 4.01 3.80 60.98 24.4 60.58 15.42 1994 Calibration transfer standard 7 1.69 1.65 60.57 33.9 60.34 20.33 1995 Vinyl frame double hung window 8 2.16 2.09 60.38 17.8 60.30 14.34 1995/1996 Calibration transfer standard 8 1.74 1.70 60.22 11.7 60.20 12.75 1996 Aluminum clad wood frame fixed window 8 1.47 1.43 60.30 20.4 60.23 16.36 1997 Aluminum clad wood frame fixed window 9 1.91 1.88 60.37 19.5 60.23 12.37 1998 Aluminum clad wood frame fixed window 9 1.84 1.79 60.24 13.0 60.16 9.0

Note: R = Reproducibility Limit W/(m2K), R % = Percent Reproducibility limit

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11. Keywords11.1 doors; fenestration; heat; hot box; R-value; steady-

state; testing; thermal transmission; U-factor; U-value; win-dows

ANNEXES

(Mandatory Information)

A1. CALIBRATION TRANSFER STANDARD DESIGN

A1.1 This large heat flux transducer is used in the calibra-tion of the surface heat transfer coefficients. Fig. 3a is aschematic diagram of a calibration transfer standard whichconsists of a homogeneous, well characterized, core calibrationmaterial made from an insulation board that has a knownthermal conductivity measured by Test Methods C 177 orC 518. A recommended calibration transfer standard corematerial is 12.7 mm nominal thickness expanded polystyrene(beadboard) having a density in excess of 20 kg/m3 that hasbeen aged unfaced in the laboratory for a minimum of 90 days.(Expanded polystyrene with a nominal density of 50 kg/m3 anda nominal thermal conductivity of 0.033 W/(m K) has beenused with success. Machining the surfaces of the expandedpolystyrene to ensure flatness is also recommended.) Suitablefacing materials are 3 to 6 mm tempered float glass (glasssheets of thickness 4 mm, with a nominal thermal conductivityof 1.0 W/(m K) and a nominal surface hemispherical emittanceof 0.84 have been used with success) or 3 to 6 mm clearpolycarbonate sheet. (It should be recognized that the surfaceemittance of the polycarbonate has to be precisely measuredand used where appropriate in calculations requiring thecalibration transfer standards surface emittance. Polycarbon-ate sheets of thickness 4 mm, with a nominal thermal conduc-tivity of 0.2 W/(m K) and a nominal surface hemisphericalemittance of 0.90 have been used with success). It is required,

prior to assembly of the calibration transfer standard, that thethermal conductivity of the material used for the core of thecalibration transfer standard be measured in a guarded hot plate(see Test Method C 177) or a heat flow meter (see Test MethodC 518) at a minimum of three temperatures over the range ofuse (10C, 0C, and 10C are recommended).

A1.2 The temperature sensors are area-weighted and lo-cated in the manner shown in Fig. 3a and 3b. The minimumnumber of temperature sensors per side for a wide range ofcalibration transfer standard sizes is given in Table A1.1. Alsoincluded in Table A1.1 are the recommended number ofsensors per side along with a recommended array to meet theminimum required sensor densities. The temperature sensorsshould be laid out equal areas to simplify the area weightingcalculation (that is, the average row, column, or overall areaweighted temperature becomes the average temperature of therow, column, or total sensors for a side). The temperaturesensors should be able to measure accurately the temperaturedifference across the core material of the calibration transferstandard. It has been found satisfactory to use 30-gage (0.3mm) or smaller diameter copper-constantan insulated thermo-couple wire from the same wire lot for both sides of thecalibration transfer standard to obtain an accurate core tem-perature difference. The small diameter wire pair should have

TABLE A1.1 Calibration Transfer Standard (CTS) Temperature Sensor RequirementsCTS SizeA

in.3 in.(m 3 m)

CTS AreaBft2

(m2)Minimum Number ofSensors Per SideC

Recommended Number ofSensors Per Side

RecommendedArrays

Recommended SensorDensitiesD Sensors/ft2

(Sensors/m2)24 3 48 8 12 12 3 3 4 1.5 (16.1)

(0.61 3 1.22) (0.74) 18 3 3 6 2.25 (24.3)36 3 60 15 18 18 3 3 6 1.2 (12.9)

(0.91 3 1.52) (1.39) 24 4 3 6 1.6 (17.3)48 3 72 24 24 24 4 3 6 1.0 (10.8)

(1.22 3 1.83) (2.23) 32 4 3 8 1.33 (14.3)48 3 84 28 28 28 4 3 7 1.0 (10.8)

(1.22 3 2.13) (2.60) 42 6 3 7 1.5 (16.2)72 3 80 40 40 42 6 3 7 1.05 (11.3)

(1.83 3 2.03) (3.72) 48 6 3 8 1.2 (12.9)80 3 80 44.4 45 49 7 3 7 1.10 (12.2)

(2.03 3 2.03) (4.13) 64 8 3 8 1.44 (15.5)72 3 96 48 48 48 6 3 8 1.0 (10.8)

(1.83 3 2.44) (4.46) 64 8 3 8 1.33 (14.3)96 3 96 64 64 64 8 3 8 1.0 (10.8)

(2.44 3 2.44) (5.95) 72 8 3 9 1.13 (12.1)AThe minimum Calibration Transfer Standard (CTS) size is 24 in. 3 48 in. (0.61m 3 1.22m) or 8 ft2 (0.74 m2).BThe temperature sensors must be laid out in an equal area array. See Fig. 2 for recommended arrays for typical CTS.CTo minimize disturbing the room side and weather side air flows on the CTS surface, all sensors are to be located between the CTS faces and the CTS core material.DHigher temperature sensor densities are recommended for research purposes.

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the insulation stripped off to expose approximately 10 mm ofbare wire and then each wire is separately soldered to one sideof a thin (3 mil [0.003 in (0.08 mm)] nominal thickness) coppershim material approximately 20 by 20 mm in size. Theconstantan wire should be soldered to the center of the coppershim and the copper thermocouple wire should be separatelysoldered to the copper shim approximately 6 mm in distancefrom the constantan-shim solder point. The recommendedsolder is resin core, lead 60/40, 6 mm nominal diameter, andthe resulting solder joints should be cleaned with alcohol toremove excess solder material and resin residue. The reversesmooth side of the shim material is then adhered with a thinfilm of two part epoxy (Loctite Minute Bond 312 has beenfound satisfactory.) to the glazing facing inner surfaces. Afterthe epoxy has dried and all epoxy removed from the surround-ing glazing surface, the glazing facing inner surfaces and theexpanded polystyrene core material faces are coated with a thin

film of a polystyrene compatible water-based contact adhesive(HB Fuller XR-1377-24-LT Blue Contact adhesive has beenfound satisfactory). After allowing the contact adhesive to dry(A minimum of 24 h at room temperature with a relativehumidity less than 50 % is recommended; when dry, thecontact adhesive will not stick to the touch.), the expandedpolystyrene is adhered to the glazing facings by applying anample uniform pressure to the glazing outer faces for anamount of time to allow the glazing faces to permanently bondto the expanded polystyrene.

A1.2.1 Since the thermal conductivity of the core material isknown (previously measured by Test Methods C 177, C 518, orC 1114), and it is possible to accurately measure its thickness,the conductance of the core material can be calculated. Thisallows the heat flux through the calibration transfer standard tobe determined from measurement of the temperature differenceacross the core material.

A2. RADIATION HEAT TRANSFER CALCULATION PROCEDURE

A2.1 This calculation procedure is to be used when theassumption that the fenestration system and baffle surfaces areparallel surfaces and the fenestration system only exchangesradiation heat transfer with the isothermal baffles is not true. Inmany situations, the fenestration system also exchanges radia-tion heat transfer with the surround panel opening surfaces andwith nonisothermal baffle and other surfaces. In those situa-tions, the radiation calculation procedure described in thisannex is required. Before using the calculation proceduredescribed in this annex, it is recommended the section onradiation heat transfer found in Chapter 3 of the 1997 (or themost recent version) ASHRAE Fundamentals Handbook bestudied. The material in the following sections of this annexclosely follows the radiation heat transfer material given in the1997 ASHRAE Fundamentals Handbook.

A2.2 Radiation Heat Transfer in An Enclosure:A2.2.1 In addition to heat transfer by convection (mass

motion plus conduction), there is radiation heat tr