ASTM C1373-98

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Designation: C 1373 – 98
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Practice for
Determination of Thermal Resistance of Attic Insulation
Systems Under Simulated Winter Conditions
This standard is issued under the fixed designation C 1373; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope units unless specified otherwise by the client.
1.8 This standard does not purport to address all of the
1.1 This practice presents a laboratory procedure to deter-
safety concerns, if any, associated with its use. It is the
mine the thermal resistance of attic insulation systems under
responsibility of the user of this standard to establish appro-
simulated steady-state winter conditions. The practice applies
priate safety and health practices and determine the applica-
only to attic insulation systems that face an open attic air space.
bility of regulatory limitations prior to use.
1.2 The thermal resistance of the insulation is inferred from
calculations based on measurements on a ceiling system
2. Referenced Documents
consisting of components consistent with the system being
2.1 ASTM Standards:
studied. For example, such a system might consist of a gypsum
C 167 Test Methods for Thickness and Density of Blanket
board or plywood ceiling, wood ceiling joists, and attic
or Batt Thermal Insulations
insulation with its top exposed to an open air space. The
C 168 Terminology Relating to Thermal Insulating Materi-
temperature applied to the gypsum board or plywood shall be
als
in the range of 18 to 24°C (64 to 75°F). The air temperature
C 177 Test Method for Steady-State Heat Flux Measure-
above the insulation shall correspond to winter conditions and
ments and Thermal Transmission Properties by Means of
may range from –46°C to 10°C (–51 to 50°F). The gypsum
the Guarded Hot Plate Apparatus
board or plywood ceiling shall be sealed to prevent direct
C 236 Test Method for Steady-State Thermal Performance
airflow between the warm and cold sides of the system.
of Building Assemblies by Means of a Guarded Hot Box
1.3 This practice applies to a wide variety of loose-fill or
C 518 Test Method for Steady-State Heat Flux Measure-
blanket thermal insulation products including fibrous glass,
ments and Thermal Transmission Properties by Means of
rock/slag wool, or cellulosic fiber materials; granular types
the Heat Flow Meter Apparatus
including vermiculite and perlite; pelletized products; and any
C 520 Test Methods for Density of Granular Loose-Fill
other insulation material that may be installed pneumatically or
Insulations
poured in place. The practice considers the effects on heat
C 549 Specification for Perlite Loose Fill Insulation
transfer of structures, specifically the ceiling joists, substrate,
C 665 Specification for Mineral-Fiber Blanket Thermal In-
for example, gypsum board, air films, and possible facings,
sulation for Light Frame Construction and Manufactured
films, or other materials that may be used in conjunction with
Housing
the insulation.
C 687 Practice for Determination of Thermal Resistance of
1.4 This practice measures the thermal resistance of the
Loose-Fill Building Insulation
attic/ceiling system in which the insulation material has been
C 739 Specification for Cellulosic Fiber (Wood Base)
preconditioned according to the material Specifications C 549,
Loose-Fill Thermal Insulation
C 665, C 739, and C 764.
C 764 Specification for Mineral Fiber Loose-Fill Thermal
1.5 The specimen preparation techniques outlined in this
Insulation
standard do not cover the characterization of loose-fill materi-
C 976 Test Method for Thermal Performance of Building
als intended for enclosed applications.
Assemblies by Means of a Calibrated Hot Box
1.6 This practice may be used to characterize material
C 1045 Practice for Calculating Thermal Transmission
behavior under controlled steady-state laboratory conditions
Properties from Steady-State Heat Flux Measurements
intended to simulate actual temperature conditions of use. The
C 1058 Practice for Selecting Temperatures for Evaluating
practice does not simulate forced air flow conditions.
and Reporting Thermal Properties of Thermal Insulation
1.7 All values shall be reported in both SI and inch-pound
C 1114 Test Method for Steady-State Thermal Transmission
Properties by Means of the Thin-Heater Apparatus
This practice is under the jurisdiction of ASTM Committee C-16 on Thermal
Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal
Measurements.
Current edition approved Nov. 10, 1998. Published May 1999. Annual Book of ASTM Standards, Vol 04.06.
C 1373
densities will depend upon the product type, the installed
thickness, the installation equipment used, the installation
technique, and the geometry of the insulated space.
4.5 The onset of natural convection under winter conditions
may be a function of specimen thickness. For purposes of this
practice, the tests shall be carried out at thicknesses at which
the product is used.
4.6 Since this practice simulates winter conditions, the heat
flow direction shall be vertically upwards.
4.7 Specimens shall be prepared in a manner consistent with
the intended installation procedure. Products for pneumatic
installation shall be pneumatically-applied (blown), and prod-
ucts for pour-in-place installation shall be poured into place.
See 5.2.
5. Equipment
NOTE 1—A constant hot-side temperature (T, hot) is used for both tests
5.1 Thermal test apparatus used for this practice shall meet
and the temperature difference increases as the cold side temperature (T,
the following requirements:
cold) is decreased. See 5.1.6 for requirements on size of air space.
FIG. 1 Schematic of Thermal Resistance for a Permeable Attic 5.1.1 Conformance to Standards—The apparatus shall con-
Insulation Under Simulated Winter Conditions (Heat Flow Up)
form to all requirements of the ASTM thermal test method
used, except as required by 5.1.2-5.1.6.
C 1363 Test Method for the Thermal Performance of Build-
5.1.2 Size—The apparatus shall be capable of testing speci-
ing Assemblies by Means of a Hot Box Apparatus
mens at the thickness intended for product use. Length and
width of the metering area shall be at least twice the spacing of
3. Terminology
the wood joists or four times the specimen thickness, which-
3.1 Definitions— Unless otherwise stated, the definitions
ever is greater (see Fig. 2).
listed in Terminology C 168 are applicable herein.
5.1.3 Temperature— The apparatus shall be capable of
testing with the hot side surface maintained between 18 and
4. Significance and Use
24°C (64 and 75°F), and with the cold side air temperature
4.1 The thermal resistance of a ceiling system is used to
maintained near the winter condition for the particular climate
characterize its steady-state thermal performance.
being simulated, which may range from –46 to 10°C (–51 to
4.2 The thermal resistance of insulation is related to the
50°F). In the absence of specified temperatures, the ambient
density and thickness of the insulation. Test data on thermal
temperatures listed in Table 2 of C 1058 on Temperatures for
resistance are obtained at a thickness and density representative
Thermal Transmittance Evaluations may be used.
of the end use applications. In addition, the thermal resistance
NOTE 1—Only those with a hot ambient of 24°C (75°F) are applicable.
of the insulation system will be different from that of the
thermal insulation alone because of the system construction
5.1.4 Humidity—The absolute humidity on both sides of the
and materials.
test apparatus shall be maintained low enough to prevent
4.3 This practice is needed because the in-service thermal
condensation within the specimen. See 6.9.6 of Test Method
resistance of some permeable attic insulations under winter
C 1363 for humidity requirements for the hot box methods, 6.6
conditions may be different, lower or higher R, than that
of Test Method C 177 for the guarded hot plate method, and
measured at or close to simulated room temperature conditions
7.10 of Test Method C 518 for the heat flow meter apparatus.
utilizing small-scale tests in which the insulation is sandwiched
5.1.5 Orientation and Direction of Heat Flow—The thermal
between two isothermal impermeable plates that have a tem-
test specimen shall be oriented horizontally with heat flow up.
perature difference (DT) of 20 to 30°C (36 to 54°F). When such
insulation is installed in an attic, on top of a ceiling composed
of normal building materials such as gypsum board or ply-
wood, with an open top surface exposed to the attic air space,
the thermal resistance under winter conditions with heat flow
up and large temperature differences may be significantly less
because of additional heat transfer by natural convection. Fig.
1 illustrates the difference between results from small scale
tests and tests under the conditions of this practice. See Ref
(1-12) for discussions of this phenomenon.
4.4 In normal use, the thickness of insulation products may
range from 75 mm (3 in.) to 500 mm (20 in.). Installed
The boldface numbers in parentheses refer to the list of references at the end of FIG. 2 Requirements on Dimensions of Test Specimen Metering
this standard. Area
C 1373
5.1.6 Thermal Test Specimen and Holder—The test assem- tions have been developed for use with mineral fiber and
bly shall be sized to match the test apparatus and shall be made cellulosic materials.
of construction materials representative of the intended appli- 5.2.1.1 A commercial blowing machine with a design ca-
cation. The substrate on which the insulation rests shall be pacity for delivering the subject material at a rate recom-
representative of the intended application, typically gypsum mended by the insulation manufacturer shall be used. The
board. The substrate shall be sealed to prevent direct airflow machine should utilize 46 m (150 ft) of flexible, internally
between the warm and cold sides of the system. Wood joists corrugated blowing hose with an appropriate sized diameter as
also shall be included. The test assembly shall be constructed specified by the machine manufacturer. At least 30 m (100 ft)
such that the top of the insulation is open to an air space having of the hose should be elevated between 3 and 6 m (10 and 20
a minimum thickness of 150 mm (6 in.). Test Methods C 236, ft) above the blowing machine to simulate typical installation
C 976, and C 1363 are preferred because of their ability to configuration. The hose should have no more than eight 90°
accommodate a large air space. Other apparatuses that can bends and no bends may be less than 1.2 m (4 ft) radius. It is
simulate in-service conditions also may be used, (for example, good practice to clean the hose periodically by mechanically
modifications of Test Methods C 177, C 518, or C 1114 with agitating it with the blower operating. This practice should
Practice C 1045). In all cases, the size requirements given in dislodge any pieces of old insulation that might be caught in
5.1.2 shall be met. Fig. 3 shows a schematic of an attic test the hose.
module that has been used for these types of tests. Other
6. Sampling
configurations without the roof structure are acceptable as long
as the minimum150 mm (6 in.) air space is maintained. 6.1 A sample of material shall be selected from a lot
5.2 Specimen Preparation Equipment: according to sampling plans given in the material specifica-
5.2.1 Blowing Apparatus—A blowing apparatus is required tions, regulations, or other appropriate documents when appli-
when pneumatically-applied specimens are to be tested. cable. In the absence of such directions, material from at least
Choose the combination of hopper, blower, hose size and two randomly chosen packages shall be combined in equal
length that is representative of common use for the application portions (mass) so as to combine materials as uniformly as
of the material to be tested. The following machine specifica- practicable.
FIG. 3 Schematic of Attic Test Module and Large Scale Climate Simulator Used for Tests on Attic Insulation Under Simulated Winter
Conditions
C 1373
6.2 The insulation material should be preconditioned to a representative density. Some bag labels utilize multiple densi-
moisture content in equilibrium with the laboratory conditions ties to reflect the fact that greater thickness installations usually
prior to the specimen installation. Preconditioning of materials result in higher installed densities. The use of multiple densi-
not only ensures controlled installation conditions but may ties can be detected from the bag label by calculating the label
reduce the time required to condition the prepared specimen density for several different R-value levels. Label densities for
prior to thermal testing. For conditioning requirements, see the a given R-value can be calculated from the bag label by
applicable materials Specifications C 520, C 549, C 665, dividing the minimum mass/unit area by the minimum thick-
C 739, and C 764. ness. If the calculated densities are significantly different, the
multiple density label has been used. When applicable speci-
7. Specimen Preparation
fications or codes do not specify the density to be used for
7.1 General Instructions:
comparison purposes, the recommended practice is to use the
7.1.1 All specimens shall be prepared to a thickness and unit 2
R-30 label density ( R(SI) – 5.3 m · K/W). If the density is not
area mass that are given for the label R-value specification of
available from the bag label, a density for test purposes can be
interest for the material under test.
established by the procedures outlined in Test Method C 520 or
7.1.2 Specimens shall be prepared in a manner consistent
Specification C 739.
with the intended installation procedure. All materials shall be
7.2.3 Calculate the target mass of insulation required to fill
installed carefully using the manufacturer’s recommended
the sample frame to the target thickness and density from the
installation practice. Batts shall be cut, as required, to fit the
equation:
available specimen holder. Products for pneumatic installation
m5r@~L 3 A ! – V # (1)
ins joist
shall be pneumatically-applied (blown), and products for
pour-in-place installation shall be poured into the specimen
where:
h
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