1、Designation: C 1155 95 (Reapproved 2007)Standard Practice forDetermining Thermal Resistance of Building EnvelopeComponents from the In-Situ Data1This standard is issued under the fixed designation C 1155; the number immediately following the designation indicates the year oforiginal adoption or, in
2、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 practice covers how to obtain and use data fromin-situ measurement of temperat
3、ures and heat fluxes on build-ing envelopes to compute thermal resistance. Thermal resis-tance is defined in Terminology C 168 in terms of steady-stateconditions only. This practice provides an estimate of thatvalue for the range of temperatures encountered during themeasurement of temperatures and
4、heat flux.1.2 This practice presents two specific techniques, thesummation technique and the sum of least squares technique,and permits the use of other techniques that have been properlyvalidated. This practice provides a means for estimating themean temperature of the building component for estima
5、ting thedependence of measured R-value on temperature for thesummation technique. The sum of least squares techniqueproduces a calculation of thermal resistance which is a functionof mean temperature.1.3 Each thermal resistance calculation applies to a subsec-tion of the building envelope component
6、that was instru-mented. Each calculation applies to temperature conditionssimilar to those of the measurement. The calculation of thermalresistance from in-situ data represents in-service conditions.However, field measurements of temperature and heat flux maynot achieve the accuracy obtainable in la
7、boratory apparatuses.1.4 This practice permits calculation of thermal resistanceon portions of a building envelope that have been properlyinstrumented with temperature and heat flux sensing instru-ments. The size of sensors and construction of the buildingcomponent determine how many sensors shall b
8、e used andwhere they should be placed. Because of the variety of possibleconstruction types, sensor placement and subsequent dataanalysis require the demonstrated good judgement of the user.1.5 Each calculation pertains only to a defined subsection ofthe building envelope. Combining results from dif
9、ferent sub-sections to characterize overall thermal resistance is beyond thescope of this practice.1.6 This practice sets criteria for the data-collection tech-niques necessary for the calculation of thermal properties (seeNote 1). Any valid technique may provide the data for thispractice, but the r
10、esults of this practice shall not be consideredto be from an ASTM standard, unless the instrumentationtechnique itself is an ASTM standard.NOTE 1Currently only Practice C 1046 can provide the data for thispractice. It also offers guidance on how to place sensors in a mannerrepresentative of more tha
11、n just the instrumented portions of the buildingcomponents.1.7 This practice pertains to light-through medium-weightconstruction as defined by example in 5.8. The calculationsapply to the range of indoor and outdoor temperatures ob-served.1.8 The values stated in SI units are to be regarded as thest
12、andard. The values given in parentheses are for informationonly.1.9 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 appli
13、ca-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 168 Terminology Relating to Thermal InsulationC 1046 Practice for In-Situ Measurement of Heat Flux andTemperature on Building Envelope ComponentsC 1060 Practice for Thermographic Inspection of InsulationIns
14、tallations in Envelope Cavities of Frame BuildingsC 1130 Practice for Calibrating Thin Heat Flux TransducersC 1153 Practice for Location of Wet Insulation in RoofingSystems Using Infrared Imaging3. Terminology3.1 DefinitionsFor definitions of terms relating to thermalinsulating materials, see Termin
15、ology C 168.1This practice is under the jurisdiction of ASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.30 on ThermalMeasurement.Current edition approved May 1, 2007. Published May 2007. Originallyapproved in 1990. Last previous edition approved in 2001 a
16、s C 1155 95(2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Har
17、bor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2 Definitions of Terms Specific to This Standard:3.2.1 building envelope componentthe portion of thebuilding envelope, such as a wall, roof, floor, window, or door,that has consistent construction. For example, an exteriorstud
18、 wall would be a building envelope component, whereas alayer thereof would not be.3.2.2 convergence factor for thermal resistance, CRnthedifference between Reat time, t, and Reat time, tn, divided byReat time, t, where n is a time interval chosen by the usermaking the calculation of thermal resistan
19、ce.3.2.3 corresponding mean temperaturearithmetic averageof the two boundary temperatures on a building envelopecomponent, weighted to account for non-steady-state heat flux.3.2.4 estimate of thermal resistance, Rethe working cal-culation of thermal resistance from in-situ data at any onesensor site
20、. This does not contribute to the thermal resistancecalculated in this practice until criteria for sufficient data andfor variance of Reare met.3.2.5 heat flow sensorany device that produces a continu-ous output which is a function of heat flux or heat flow, forexample, heat flux transducer (HFT) or
21、 portable calorimeter.3.2.6 temperature sensorany device that produces a con-tinuous output which is a function of temperature, for example,thermocouple, thermistor, or resistance device.3.3 Symbols Applied to the Terms Used in This Standard:3.3.1 Variables for the Summation Technique:A = area assoc
22、iated with a single set of temperature and heatflux sensors,C = thermal conductance, W/m2K (Btu/hft2R),CR = convergence factor (dimensionless),e = error of measurement of heat flux, W/m2(Btu/hft2),M = number of values of DT and q in the source data,N = number of sensor sites,n = test for convergence
23、 interval, h,q = heat flux, W/m2(Btu/hft2),R = thermal resistance, m2K/W (hft2R/Btu),s(x) = standard deviation of x, based on N1 degrees offreedom,T = temperature, K (R, C, F),t = time, h,V(x) = coefficient of variation of x,DT = difference in temperature between indoors and out-doors, K (R, C, F),l
24、 = apparent thermal conductivity, W/mK (Btu/hftR), andx = position coordinate (from 0 to distance L in incrementsof Dx),r = material density, kg/m3(lb/ft3).3.3.2 Subscripts for the Summation Technique:a = air,e = estimate,i = indoor,j = counter for summation of sensor sites,k = counter for summation
25、 of time-series data,m = area coverage,n = test for convergence value.o = outdoor, ands = surface,3.3.3 Variables for the Sum of Least Squares Technique:Cr= material specific heat, J/kgK (Btu/lbF),Ymi= measured temperature at indoor node m for time i K(R, C, F),Fni= measured heat flux at interior no
26、de n for time i W/m2(Btu/hft2),l = apparent thermal conductivity, W/mK (Btu/hftF),Tmi= calculated temperature at indoor node m for time i K(R, C, F),qni= calculated heat flux at interior node n for time i W/m2(Btu/hft2),WTm= weighting factor to normalize temperature contribu-tion to G,Wqn= weighting
27、 factor to normalize heat flux contribution toG, andG = weighted sum of squares function.3.3.4 Subscripts for the Sum of Least Squares Technique:s = specific heat of value, “s,” J/kgK (Btu/lbF)4. Summary of Practice4.1 This practice presents two mathematical procedures forcalculating the thermal res
28、istance of a building envelopesubsection from measured in-situ temperature and heat fluxdata. The procedures are the summation technique (1)3and thesum of least squares technique (2, 3). Proper validation of othertechniques is required.4.2 The results of each calculation pertain only to a particu-la
29、r subsection that was instrumented appropriately.Appropriateinstrumentation implies that heat flow can be substantiallyaccounted for by the placement of sensors within the definedsubsection. Since data obtained from in-situ measurements areunlikely to represent steady-state conditions, a calculation
30、 ofthermal resistance is possible only when certain criteria aremet. The data also provide an estimate of whether the collec-tion process has run long enough to satisfy an accuracycriterion for the calculation of thermal resistance. An estimateof error is also possible.4.3 This practice provides a m
31、eans for estimating the meantemperature of the building component (see 6.5.1.4) for esti-mating the dependence of measured R-value on temperature forthe summation technique by weighting the recorded tempera-tures such that they correspond to the observed heat fluxes. Thesum of least squares techniqu
32、e has its own means for estimat-ing thermal resistance as a function of temperature.5. Significance and Use5.1 Significance of Thermal Resistance MeasurementsKnowledge of the thermal resistance of new buildings isimportant to determine whether the quality of constructionsatisfies criteria set by the
33、 designer, by the owner, or by aregulatory agency. Differences in quality of materials orworkmanship may cause building components not to achievedesign performance.5.1.1 For Existing BuildingsKnowledge of thermal resis-tance is important to the owners of older buildings to determinewhether the build
34、ings should receive insulation or other3The boldface numbers in parentheses refer to the list of references at the end ofthis practice.C 1155 95 (2007)2energy-conserving improvements. Inadequate knowledge ofthe thermal properties of materials or heat flow paths within theconstruction or degradation
35、of materials may cause inaccurateassumptions in calculations that use published data.5.2 Advantage of In-Situ DataThis practice provides in-formation about thermal performance that is based on mea-sured data. This may determine the quality of new constructionfor acceptance by the owner or occupant o
36、r it may providejustification for an energy conservation investment that couldnot be made based on calculations using published design data.5.3 Heat Flow PathsThis practice assumes that net heatflow is perpendicular to the surface of the building envelopecomponent within a given subsection. Knowledg
37、e of surfacetemperature in the area subject to measurement is required forplacing sensors appropriately. Appropriate use of infraredthermography is often used to obtain such information. Ther-mography reveals nonuniform surface temperatures caused bystructural members, convection currents, air leaka
38、ge, andmoisture in insulation. Practices C 1060 and C 1153 detail theappropriate use of infrared thermography. Note that thermog-raphy as a basis for extrapolating the results obtained at ameasurement site to other similar parts of the same building isbeyond the scope of this practice.5.4 User Knowl
39、edge RequiredThis practice requires thatthe user have knowledge that the data employed represent anadequate sample of locations to describe the thermal perfor-mance of the construction. Sources for this knowledge includethe referenced literature in Practice C 1046 and related workslisted in Appendix
40、 X2. The accuracy of the calculation isstrongly dependent on the history of the temperature differ-ences across the envelope component. The sensing and datacollection apparatuses shall have been used properly. Factorssuch as convection and moisture migration affect interpretationof the field data.5.
41、5 Indoor-Outdoor Temperature DifferenceThe speed ofconvergence of the summation technique described in thispractice improves with the size of the average indoor-outdoortemperature difference across the building envelope. The sumof least squares technique is insensitive to indoor-outdoortemperature d
42、ifference, to small and drifting temperature dif-ferences, and to small accumulated heat fluxes.5.6 Time-Varying Thermal ConditionsThe field data rep-resent varying thermal conditions. Therefore, obtain time-series data at least five times more frequently than the mostfrequent cyclical heat input, s
43、uch as a furnace cycle. Obtain thedata for a long enough period such that two sets of data that enda user-chosen time period apart do not cause the calculation ofthermal resistance to be different by more than 10 %, asdiscussed in 6.4.5.6.1 Gather the data over an adequate range of thermalconditions
44、 to represent the thermal resistance under the condi-tions to be characterized.NOTE 2The construction of some building components includesmaterials whose thermal performance is dependent on the direction of heatflow, for example, switching modes between convection and stablestratification in horizon
45、tal air spaces.5.7 Lateral Heat FlowAvoid areas with significant lateralheat flow. Report the location of each source of temperatureand heat flux data. Identify possible sources of lateral heat flow,including a highly conductive surface, thermal bridges beneaththe surface, convection cells, etc., th
46、at may violate the assump-tion of heat flow perpendicular to the building envelopecomponent.NOTE 3Appropriate choice of heat flow sensors and placement ofthose sensors can sometimes provide meaningful results in the presence oflateral heat flow in building components. Metal surfaces and certainconcr
47、ete or masonry components may create severe difficulties formeasurement due to lateral heat flow.5.8 Light- to Medium-Weight ConstructionThis practiceis limited to light- to medium-weight construction that has anindoor temperature that varies by less than 3 K (5F). Theheaviest construction to which
48、this practice applies wouldweigh 440 kg/m2(90 lb/ft2), assuming that the massiveelements in building construction all have a specific heat ofabout 0.9 kJ/kg K (0.2 Btu/lbF). Examples of the heaviestconstruction include: (1) a 390-kg/m2(80-lb/ft2) wall with abrick veneer, a layer of insulation, and c
49、oncrete blocks on theinside layer or (2) a 76-mm (3-in.) concrete slab with insulatedbuilt-up roofing of 240 kg/m2(50 lb/ft2). Insufficient knowl-edge and experience exists to extend the practice to heavierconstruction.5.9 Heat Flow ModesThe mode of heat flow is a signifi-cant factor determining R-value in construction that containsair spaces. In horizontal construction, air stratifies or convects,depending on whether heat flow is downwards or upwards. Invertical construction, such as walls with cavities, convectioncells af
