ASTM C168-08a

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.

General Information

• Status: Historical
• Publication Date: 31-Aug-2008
• 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 C168-08 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 01-Sep-2008
• Replaced By: ASTM C168-08b - Standard Terminology Relating to Thermal Insulation
• Effective Date: 15-Dec-2008
• Referred By: ASTM E2988-17(2022) - Standard Practice for Specimen Preparation and Mounting of Flexible Fibrous Glass Insulation for Metal Buildings to Assess Surface Burning Characteristics
• Effective Date: 01-Sep-2008
• Referred By: ASTM E2599-22 - Standard Practice for Specimen Preparation and Mounting of Reflective Insulation, Radiant Barrier and Vinyl Stretch Ceiling Materials for Building Applications to Assess Surface Burning Characteristics
• Effective Date: 01-Sep-2008
• Referred By: ASTM C1155-95(2021) - Standard Practice for Determining Thermal Resistance of Building Envelope Components from the In-Situ Data
• Effective Date: 01-Sep-2008
• Referred By: ASTM C1321-15(2020) - Standard Practice for Installation and Use of Interior Radiation Control Coating Systems (IRCCS) in Building Construction
• Effective Date: 01-Sep-2008
• Referred By: ASTM C390-08(2019) - Standard Practice for Sampling and Acceptance of Thermal Insulation Lots
• Effective Date: 01-Sep-2008
• Referred By: ASTM C1153-10(2015) - Standard Practice for Location of Wet Insulation in Roofing Systems Using Infrared Imaging
• Effective Date: 01-Sep-2008
• Referred By: ASTM C1847-21 - Standard Specification for Direct Buried Pre-Insulated and Jacketed Polyurethane Bonded Low Temperature Hot Water Piping Systems
• Effective Date: 01-Sep-2008
• Referred By: ASTM C1558-19 - Standard Guide for Development of Standard Data Records for Computerization of Thermal Transmission Test Data for Thermal Insulation
• Effective Date: 01-Sep-2008
• Referred By: ASTM C991-23 - Standard Specification for Flexible Fibrous Glass Insulation for Metal Buildings
• Effective Date: 01-Sep-2008
• Referred By: ASTM C764-19 - Standard Specification for Mineral Fiber Loose-Fill Thermal Insulation
• Effective Date: 01-Sep-2008
• Referred By: ASTM C1290-16(2021) - Standard Specification for Flexible Fibrous Glass Blanket Insulation Used to Externally Insulate HVAC Ducts
• Effective Date: 01-Sep-2008
• Referred By: ASTM C1101/C1101M-06(2017) - Standard Test Methods for Classifying the Flexibility or Rigidity of Mineral Fiber Blanket and Board Insulation
• Effective Date: 01-Sep-2008
• Referred By: ASTM C835-06(2020) - Standard Test Method for Total Hemispherical Emittance of Surfaces up to 1400°C
• Effective Date: 01-Sep-2008

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:C168–08a
Standard Terminology Relating to
1
Thermal Insulation
This standard is issued under the fixed designation C 168; 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.
phenomena (for example, thickness effect) the modifier “apparent” is
1. Scope
used, as in apparent thermal conductivity.
1.1 This standard provides definitions, symbols, units, and
DISCUSSION—Test data using the “apparent” modifier must be quoted
abbreviations of terms used in ASTM standards pertaining to
only for the conditions of the measurement. Values of thermal conduc-
thermal insulating materials, and to materials associated with
tance (material C) and thermal resistance (material R) calculated from
them. apparent thermal conductivity or resistivity, are valid only for the same
conditions.
1.2 This terminology is not intended to be used to classify
DISCUSSION—Test data labeled with “apparent” shall not include any
insulation materials as having particular properties. Rather,
equipment related measurement errors induced due to measurement
classification of insulation materials is to be done by the
attempts beyond an apparatus range or calibration.
material standards themselves.
DISCUSSION—Useofthe“apparent”modifierwithsystem Corsystem
R measurements is not permitted.
2. Referenced Documents
apparent thermal resistivity, r , n—a thermal resistivity
a
2.1 ASTM Standards:
assigned to a material that exhibits thermal transmission by
E 456 Terminology Relating to Quality and Statistics
several modes of heat transfer resulting in property variation
E 2282 Guide for Defining the Test Result of a Test Method
with specimen thickness, or surface emittance. See resistiv-
2.2 ISO Standard:
ity, thermal.
ISO 7345 Thermal Insulation—Physical Quantities and
2
Definitions
DISCUSSION—Seeentirediscussionunder apparent thermal conduc-
tivity.
3. Terminology
area weight, n—weight per unit area for a specified sample, in
3.1 Definitions:
2 2
units of lb/ft (kg/m ).
absorptance, n—the ratio of the radiant flux absorbed by a
aerogel, n—a homogeneous, low-density solid phase material
body to that incident upon it. derived from a gel, in which the liquid component of the gel
absorption, n—transformation of radiant energy to a different
has been replaced with a gas.
form of energy by interaction with matter.
DISCUSSION—The resulting material has a porous structure with an
apparent thermal conductivity, l , k , n—a thermal con-
a a
average pore size below the mean free path of air molecules at standard
ductivity assigned to a material that exhibits thermal trans-
atmospheric pressure and temperature.
mission by several modes of heat transfer resulting in
batt, n—blanket insulation manufactured to dimensions as
property variation with specimen thickness, or surface emit-
required by a specific application.
tance. See conductivity, thermal.
blackbody, n—the ideal, perfect emitter and absorber of
DISCUSSION—Thermal conductivity and resistivity are normally con-
thermal radiation. It emits radiant energy at each wavelength
sidered to be intrinsic or specific properties of materials and, as such,
at the maximum rate possible as a consequence of its
should be independent of thickness. When nonconductive modes of
temperature, and absorbs all incident radiance.
heat transfer are present within the specimen (radiation, free convec-
blanket, n—flexible insulation product, supplied rolled or flat.
tion) this may not be the case. To indicate the possible presence of this
blanket insulation, n—a relatively flat and flexible insulation
in coherent sheet form furnished in units of substantial area.
1
This terminology is under the jurisdiction of ASTM Committee C16 on
blanket insulation, metal mesh, n— blanket insulation cov-
Thermal Insulation and is the direct responsibility of Subcommittee C16.94 on
ered by flexible metal-mesh facings attached on one or both
Terminology.
sides.
Current edition approved Sept. 1, 2008. Published September 2008. Originally
approved in 1941. Last previous edition approved in 2008 as C 168 – 08.
block insulation, n—rigid insulation preformed into rectangu-
2
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
lar units.
4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

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C168–08a
board insulation, n—semirigid insulation preformed into A conductance (C) associated with a material shall be
rectangular units having a degree of suppleness particular
...

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:C168–08 Designation: C 168 – 08a
Standard Terminology Relating to
1
Thermal Insulation
This standard is issued under the fixed designation C 168; 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 Thisstandardprovidesdefinitions,symbols,units,andabbreviationsoftermsusedinASTMstandardspertainingtothermal
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.
2. Referenced Documents
2.1 ASTM Standards:
E 456 Terminology Relating to Quality and Statistics
E 2282 Guide for Defining the Test Result of a Test Method
2.2 ISO Standard:
2
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, l , 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.
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—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
a
modes 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
atmospheric pressure and temperature.
batt, n—blanket insulation manufactured to dimensions as required by a specific application.
blackbody, n—the ideal, perfect emitter and absorber of thermal radiation. It emits radiant energy at each wavelength at the
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 JuneSept. 1, 2008. Published JulySeptember 2008. Originally approved in 1941. Last previous edition approved in 20052008 as
C168–05a.C 168 – 08.
2
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

---------------------- Page: 1 ----------------------
C 168 – 08a
maximum rate possible as a consequence of its temperature, and absorbs all incident radiance.
blanket, n—flexible insulation product, supplied rolled or flat.
blanket insulation, n—a relatively flat and flexible insulation in coherent sheet form furnished in units of substantial area.
blanket insulation, metal mesh, n— blanket insulation cove
...