ASTM C1340/C1340M-10
(Practice)Standard Practice for Estimation of Heat Gain or Loss Through Ceilings Under Attics Containing Radiant Barriers by Use of a Computer Program
Standard Practice for Estimation of Heat Gain or Loss Through Ceilings Under Attics Containing Radiant Barriers by Use of a Computer Program
SIGNIFICANCE AND USE
Manufacturers of radiant barriers express the performance of their products in terms of the total hemispherical emittance. The purpose of a radiant barrier is to decrease the radiation heat transfer across the attic air space, and hence, to decrease the heat loss or gain through the ceiling below the attic. The amount of decrease in heat flow will depend upon a number of factors, such as weather conditions, amount of mass or reflective insulation in the attic, solar absorptance of the roof, geometry of the attic and roof, and amount and type of attic ventilation. Because of the infinite combinations of these factors, it is not practical to publish data for each possible case.
The calculation of heat loss or gain of a system containing radiant barriers is mathematically complex, and because of the iterative nature of the method, it is best handled by computers.
Computers are now widely available to most producers and consumers of radiant barriers to permit the use of this practice.
The user of this practice may wish to modify the data input to represent accurately the structure. The computer program also may be modified to meet individual needs. Also, additional calculations may be desired, for example, to sum the hourly heat flows in some fashion to obtain estimates of seasonal or annual energy usages. This might be done using the hourly data as inputs to a whole-house model, and by choosing house balance points to use as cutoff points in the summations.
SCOPE
1.1 This practice covers the estimation of heat gain or loss through ceilings under attics containing radiant barriers by use of a computer program. The computer program included as an adjunct to this practice provides a calculational procedure for estimating the heat loss or gain through the ceiling under an attic containing a truss or rafter mounted radiant barrier. The program also is applicable to the estimation of heat loss or gain through ceilings under an attic without a radiant barrier. This procedure utilizes hour-by-hour weather data to estimate the hour-by-hour ceiling heat flows. The interior of the house below the ceiling is assumed to be maintained at a constant temperature. At present, the procedure is applicable to sloped-roof attics with rectangular floor plans having an unshaded gabled roof and a horizontal ceiling. It is not applicable to structures with flat roofs, vaulted ceilings, or cathedral ceilings. The calculational accuracy also is limited by the quality of physical property data for the construction materials, principally the insulation and the radiant barrier, and by the quality of the weather data.
1.2 Under some circumstances, interactions between radiant barriers and HVAC ducts in attics can have a significant effect on the thermal performance of a building. Ducts are included in an extension of the computer model given in the appendix.
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
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Designation: C1340/C1340M − 10
StandardPractice for
Estimation of Heat Gain or Loss Through Ceilings Under
Attics Containing Radiant Barriers by Use of a Computer
1
Program
This standard is issued under the fixed designation C1340/C1340M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2
1.1 This practice covers the estimation of heat gain or loss 2.1 ASTM Standards:
through ceilings under attics containing radiant barriers by use C168Terminology Relating to Thermal Insulation
of a computer program. The computer program included as an
2.2 ANSI Standards:
adjunct to this practice provides a calculational procedure for X3.5Flow Chart Symbols and Their Usage in Information
3
estimating the heat loss or gain through the ceiling under an
Processing
3
attic containing a truss or rafter mounted radiant barrier. The X3.9Standard for Fortran Programming Language
programalsoisapplicabletotheestimationofheatlossorgain
2.3 ASTM Adjuncts:
through ceilings under an attic without a radiant barrier. This
Computer Program for Estimation of Heat Gain or Loss
procedure utilizes hour-by-hour weather data to estimate the
through Ceilings Under Attics Containing Radiant Barri-
4
hour-by-hour ceiling heat flows. The interior of the house
ers
below the ceiling is assumed to be maintained at a constant
3. Terminology
temperature.At present, the procedure is applicable to sloped-
roof attics with rectangular floor plans having an unshaded
3.1 Definitions—For definitions of terms used in this
gabled roof and a horizontal ceiling. It is not applicable to
practice, refer to Terminology C168.
structureswithflatroofs,vaultedceilings,orcathedralceilings.
3.2 Symbols—Symbolswillbeintroducedanddefinedinthe
The calculational accuracy also is limited by the quality of
detailed description of the development.
physical property data for the construction materials, princi-
pally the insulation and the radiant barrier, and by the quality
4. Summary of Practice
of the weather data.
4.1 The procedures used in this practice are based on the
1.2 Undersomecircumstances,interactionsbetweenradiant
thermal response factor method for calculating dynamic heat
5
barriers and HVAC ducts in attics can have a significant effect
conductionthroughmultilayerslabs (1, 2), alongwithamodel
onthethermalperformanceofabuilding.Ductsareincludedin
for convective and radiative heat exchanges inside and outside
an extension of the computer model given in the appendix.
the attic.
1.3 The values stated in either SI units or inch-pound units
4.2 The operation of the computer program involves the
are to be regarded separately as standard. The values stated in
following steps:
each system may not be exact equivalents; therefore, each
system shall be used independently of the other. Combining
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
values from the two systems may result in non-conformance
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
with the standard.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
1 3
This practice is under the jurisdiction of ASTM Committee C16 on Thermal Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
Insulation and is the direct responsibility of Subcommittee C16.21 on Reflective 4th Floor, New York, NY 10036, http://www.ansi.org.
4
Insulation. Available from ASTM International Headquarters. Order Adjunct No.
CurrenteditionapprovedJune1,2010.PublishedJuly2010.Originallyapproved ADJC1340.
5
in 1999. Last previous edition approved in 2004 as C1340–04. DOI: 10.1520/ Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
C1340_C1340M-10. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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C1340/C1340M − 10
4.2.1 Response Factors—A separate computer program additionalcalculationsmaybedesired,forexample,tosumthe
must be used to calculate the thermal response factors of the hourly heat flows in some fashion to obtain estimates of
solid materials surrounding the attic. Input to this program seasonalorannualenergyusages.Thismightbedoneusingthe
would consist of the thermal conductivity, specific heat, hourlydataasinputstoawhole-housemodel,andbychoosing
density,andthicknessofeachlayer,orthethermalresistanceof house balance points to use as cutoff points in the summations.
the layer if it has negligible density, and the fraction of the
6. Method of Ca
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:C1340–04 Designation: C1340/C1340M – 10
Standard Practice for
Estimation of Heat Gain or Loss Through Ceilings Under
Attics Containing Radiant Barriers by Use of a Computer
1
Program
This standard is issued under the fixed designation C1340/C1340M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers the estimation of heat gain or loss through ceilings under attics containing radiant barriers by use of
a computer program. The computer program included as an adjunct to this practice provides a calculational procedure for
estimatingtheheatlossorgainthroughtheceilingunderanatticcontainingatrussorraftermountedradiantbarrier.Theprogram
also is applicable to the estimation of heat loss or gain through ceilings under an attic without a radiant barrier. This procedure
utilizes hour-by-hour weather data to estimate the hour-by-hour ceiling heat flows. The interior of the house below the ceiling is
assumed to be maintained at a constant temperature.At present, the procedure is applicable to sloped-roof attics with rectangular
floor plans having an unshaded gabled roof and a horizontal ceiling. It is not applicable to structures with flat roofs, vaulted
ceilings, or cathedral ceilings. The calculational accuracy also is limited by the quality of physical property data for the
construction materials, principally the insulation and the radiant barrier, and by the quality of the weather data.
1.2 Under some circumstances, interactions between radiant barriers and HVAC ducts in attics can have a significant effect on
the thermal performance of a building. Ducts are included in an extension of the computer model given in the appendix.
1.3The values stated in inch-pound units are to be regarded as the standard.The values given in parentheses are for information
only.
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard.The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
2. Referenced Documents
2
2.1 ASTM Standards:
C168 Terminology Relating to Thermal Insulation
2.2 ANSI Standards:
3
X3.5 Flow Chart Symbols and Their Usage in Information Processing
3
X3.9 Standard for Fortran Programming Language
2.3 ASTM Adjuncts:
4
Computer Program for Estimation of Heat Gain or Loss through Ceilings Under Attics Containing Radiant Barriers
3. Terminology
3.1 Definitions—For definitions of terms used in this practice, refer to Terminology C168.
3.2 Symbols—Symbols will be introduced and defined in the detailed description of the development.
4. Summary of Practice
4.1 The procedures used in this practice are based on the thermal response factor method for calculating dynamic heat
1
This practice is under the jurisdiction ofASTM Committee C16 onThermal Insulation and is the direct responsibility of Subcommittee C16.21 on Reflective Insulation.
Current edition approved Sept. 1, 2004. Published October 2004. Originally approved in 1999. Last previous edition approved in 1999 as C1340–99.
Current edition approved June 1, 2010. Published July 2010. Originally approved in 1999. Last previous edition approved in 2004 as C1340–04. DOI:
10.1520/C1340_C1340M-10.
2
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.ForAnnualBookofASTMStandards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
4
Available from ASTM Headquarters. Request Adjunct: ADJC1340.
4
Available from ASTM International Headquarters. Order Adjunct No. ADJC1340.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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C1340/C1340M – 10
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conductionthroughmultilayerslabs (1, 2), alongwithamodelforconvectiveandradiativeheatexchangesinsideandoutsidethe
attic.
4.2 The operation of the computer program involves the following steps:
4.2.1 Response Factors—A separate computer program must be used to calculate the thermal respons
...
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