ASTM C168-13

Standard Terminology Relating to Thermal Insulation

SCOPE
1.1 This standard provides definitions, symbols, units, and abbreviations of terms used in ASTM standards pertaining to thermal insulating materials, and to materials associated with them.  
1.2 This terminology is not intended to be used to classify insulation materials as having particular properties. Rather, classification of insulation materials is to be done by the material standards themselves.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Mar-2013
• ICS: 01.040.91 - Construction materials and building (Vocabularies)
• ICS: 91.100.60 - Thermal and sound insulating materials
• Technical Committee: C16 - Thermal Insulation
• Drafting Committee: C16.94 - Terminology

Relations

• Replaces: ASTM C168-10 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 01-Apr-2013
• Replaced By: ASTM C168-15 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 01-Jun-2015
• Referred By: ASTM C1199-22 - Standard Test Method for Measuring the Steady-State Thermal Transmittance of Fenestration Systems Using Hot Box Methods
• Effective Date: 01-Apr-2013
• Referred By: ASTM C1371-15(2022) - Standard Test Method for Determination of Emittance of Materials Near Room Temperature Using Portable Emissometers
• Effective Date: 01-Apr-2013
• Referred By: ASTM C419-20 - Standard Practice for Making and Curing Test Specimens of Mastic Thermal Insulation Coatings
• Effective Date: 01-Apr-2013
• Referred By: ASTM C1485-19 - Standard Test Method for Critical Radiant Flux of Exposed Attic Floor Insulation Using an Electric Radiant Heat Energy Source
• Effective Date: 01-Apr-2013
• Referred By: ASTM C1484-10(2018) - Standard Specification for Vacuum Insulation Panels
• Effective Date: 01-Apr-2013
• Referred By: ASTM C534/C534M-23 - Standard Specification for Preformed Flexible Elastomeric Cellular Thermal Insulation in Sheet and Tubular Form
• Effective Date: 01-Apr-2013
• Referred By: ASTM C755-20 - Standard Practice for Selection of Water Vapor Retarders for Thermal Insulation
• Effective Date: 01-Apr-2013
• Referred By: ASTM C1136-23 - Standard Specification for Flexible, Low Permeance Vapor Retarders for Thermal Insulation
• Effective Date: 01-Apr-2013
• Referred By: ASTM C1134-23 - Standard Test Method for Water Retention of Rigid Thermal Insulations Following Partial Immersion
• Effective Date: 01-Apr-2013
• Referred By: ASTM C1114-06(2019) - Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Thin-Heater Apparatus
• Effective Date: 01-Apr-2013
• Referred By: ASTM C518-21 - Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus
• Effective Date: 01-Apr-2013
• Referred By: ASTM C449-07(2019) - Standard Specification for Mineral Fiber Hydraulic-Setting Thermal Insulating and Finishing Cement
• Effective Date: 01-Apr-2013
• Referred By: ASTM C1549-16(2022) - Standard Test Method for Determination of Solar Reflectance Near Ambient Temperature Using a Portable Solar Reflectometer
• Effective Date: 01-Apr-2013

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: C168 − 13
StandardTerminology Relating to
1
Thermal Insulation
This standard is issued under the fixed designation C168; 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 sion by several modes of heat transfer resulting in property
variation with specimen thickness, or surface emittance. See
1.1 This standard provides definitions, symbols, units, and
conductivity, thermal.
abbreviations of terms used in ASTM standards pertaining to
DISCUSSION—Thermal conductivity and resistivity are normally con-
thermal insulating materials, and to materials associated with
sidered to be intrinsic or specific properties of materials and, as such,
them.
should be independent of thickness. When nonconductive modes of
heat transfer are present within the specimen (radiation, free convec-
1.2 This terminology is not intended to be used to classify
tion) this may not be the case. To indicate the possible presence of this
insulation materials as having particular properties. Rather,
phenomena (for example, thickness effect) the modifier “apparent” is
classification of insulation materials is to be done by the
used, as in apparent thermal conductivity.
material standards themselves.
DISCUSSION—Test data using the “apparent” modifier must be quoted
1.3 This standard does not purport to address all of the
only for the conditions of the measurement. Values of thermal conduc-
safety concerns, if any, associated with its use. It is the
tance (material C) and thermal resistance (material R) calculated from
responsibility of the user of this standard to establish appro-
apparent thermal conductivity or resistivity, are valid only for the same
priate safety and health practices and determine the applica- conditions.
bility of regulatory limitations prior to use.
DISCUSSION—Test data labeled with “apparent” shall not include any
equipment related measurement errors induced due to measurement
2. Referenced Documents
attempts beyond an apparatus range or calibration.
2
2.1 ASTM Standards:
DISCUSSION—Useofthe“apparent”modifierwithsystem Corsystem
E456 Terminology Relating to Quality and Statistics
R measurements is not permitted.
E2282 Guide for Defining the Test Result of a Test Method
apparent thermal resistivity, r , n—a thermal resistivity
2.2 ISO Standard:
a
assigned to a material that exhibits thermal transmission by
ISO 7345 Thermal Insulation—Physical Quantities and
3
several modes of heat transfer resulting in property variation
Definitions
with specimen thickness, or surface emittance. See
3. Terminology
resistivity, thermal.
DISCUSSION—Seeentirediscussionunder apparent thermal conduc-
3.1 Definitions:
tivity.
absorptance, n—the ratio of the radiant flux absorbed by a
body to that incident upon it.
area weight, n—weight per unit area for a specified sample, in
2 2
units of lb/ft (kg/m ).
absorption, n—transformation of radiant energy to a different
form of energy by interaction with matter.
aerogel, n—a homogeneous, low-density solid phase material
derived from a gel, in which the liquid component of the gel
apparent thermal conductivity, λ , k , n—a thermal conduc-
a a
has been replaced with a gas.
tivity assigned to a material that exhibits thermal transmis-
DISCUSSION—The resulting material has a porous structure with an
average pore size below the mean free path of air molecules at standard
1
This terminology is under the jurisdiction of ASTM Committee C16 on atmospheric pressure and temperature.
Thermal Insulation and is the direct responsibility of Subcommittee C16.94 on
batt, n—blanket insulation manufactured to dimensions as
Terminology.
Current edition approved April 1, 2013. Published May 2013. Originally
required by a specific application.
approved in 1941. Last previous edition approved in 2010 as C 168 – 10.
DOI:101520/C0168–13.
blackbody, n—the ideal, perfect emitter and absorber of
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
thermal radiation. It emits radiant energy at each wavelength
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
at the maximum rate possible as a consequence of its
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. temperature, and absorbs all incident radiance.
3
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. blanket, n—flexible insulation product, supplied rolled or flat.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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This document is not an ASTM standard and is intended only to provide the user of an ASTM 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: C168 − 10 C168 − 13
Standard Terminology Relating to
1
Thermal Insulation
This standard is issued under the fixed designation C168; 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 standard provides definitions, symbols, units, and abbreviations of terms used in ASTM standards pertaining to thermal
insulating materials, and to materials associated with them.
1.2 This terminology is not intended to be used to classify insulation materials as having particular properties. Rather,
classification of insulation materials is to be done by the material standards themselves.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
E456 Terminology Relating to Quality and Statistics
E2282 Guide for Defining the Test Result of a Test Method
2.2 ISO Standard:
3
ISO 7345 Thermal Insulation—Physical Quantities and Definitions
3. Terminology
3.1 Definitions:
absorptance, n—the ratio of the radiant flux absorbed by a body to that incident upon it.
absorption, n—transformation of radiant energy to a different form of energy by interaction with matter.
apparent thermal conductivity, λ ,k ,n—a thermal conductivity assigned to a material that exhibits thermal transmission by
a a
several modes of heat transfer resulting in property variation with specimen thickness, or surface emittance. See conductivity,
thermal.
1
This terminology is under the jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.94 on Terminology.
Current edition approved Jan. 1, 2010April 1, 2013. Published February 2010May 2013. Originally approved in 1941. Last previous edition approved in 20082010 as
C 168 – 08a. DOI:101520/C0168–10.C 168 – 10. DOI:101520/C0168–13.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
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.
DISCUSSION—
Thermal conductivity and resistivity are normally considered to be intrinsic or specific properties of materials and, as such, should be independent of
thickness. When nonconductive modes of heat transfer are present within the specimen (radiation, free convection) this may not be the case. To indicate
the possible presence of this phenomena (for example, thickness effect) the modifier “apparent” is used, as in apparent thermal conductivity.
DISCUSSION—
Test data using the “apparent” modifier must be quoted only for the conditions of the measurement. Values of thermal conductance (material C) and
thermal resistance (material R) calculated from apparent thermal conductivity or resistivity, are valid only for the same conditions.
DISCUSSION—
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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C168 − 13
Test data labeled with “apparent” shall not include any equipment related measurement errors induced due to measurement attempts beyond an
apparatus range or calibration.
DISCUSSION—
Use of the “apparent” modifier with system C or system R measurements is not permitted.
apparent thermal resistivity, r ,n—a thermal resistivity assigned to a material that exhibits thermal transmission by several modes
a
of heat transfer resulting in property variation with specimen thickness, or surface emittance. See resistivity, thermal.
DISCUSSION—
See entire discussion under apparent thermal conductivity.
2 2
area weight, n—weight per unit area for a specified sample, in units of lb/ft (kg/m ).
aerogel, n—a homogeneous, low-density solid phase material derived from a gel, in which the liquid component of the gel has
been replaced with a gas.
DISCUSSION—
The resulting material has a porous structure with an average pore size below the mean free path of air molecules at standard atmos
...