ASTM C168-17

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.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Historical
• Publication Date: 31-May-2017
• 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 C168-15a - Standard Terminology Relating to Thermal Insulation
• Effective Date: 01-Jun-2017
• Replaced By: ASTM C168-18 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 15-Apr-2018
• Referred By: ASTM C1335-23 - Standard Test Method for Measuring Non-Fibrous Content of Man-Made Rock and Slag Mineral Fiber Insulation
• Effective Date: 01-Jun-2017
• Referred By: ASTM C667-17(2022) - Standard Specification for Prefabricated Reflective Insulation Systems for Equipment and Pipe Operating at Temperatures above Ambient Air
• Effective Date: 01-Jun-2017
• Referred By: ASTM C163-05(2023) - Standard Practice for Mixing Thermal Insulating Cement Samples
• Effective Date: 01-Jun-2017
• Referred By: ASTM C390-08(2019) - Standard Practice for Sampling and Acceptance of Thermal Insulation Lots
• Effective Date: 01-Jun-2017
• 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-Jun-2017
• Referred By: ASTM E1423-21 - Standard Practice for Determining Steady State Thermal Transmittance of Fenestration Systems
• Effective Date: 01-Jun-2017
• Referred By: ASTM C916-20 - Standard Specification for Adhesives for Duct Thermal Insulation
• Effective Date: 01-Jun-2017
• Referred By: ASTM C1902-22a - Standard Specification for Cellular Glass Insulation Used in Building and Roof Applications
• Effective Date: 01-Jun-2017
• Referred By: ASTM C656-17(2023) - Standard Specification for Structural Insulating Board, Calcium Silicate
• Effective Date: 01-Jun-2017
• Referred By: ASTM C1729M-21 - Standard Specification for Aluminum Jacketing for Insulation
• Effective Date: 01-Jun-2017
• Referred By: ASTM C592-22a - Standard Specification for Mineral Fiber Blanket Insulation and Blanket-Type Pipe Insulation (Metal-Mesh Covered) (Industrial Type)
• Effective Date: 01-Jun-2017
• Referred By: ASTM C727-19 - Standard Practice for Installation and Use of Reflective Insulation in Building Constructions
• Effective Date: 01-Jun-2017
• Referred By: ASTM C1263-95(2021) - Standard Test Method for Thermal Integrity of Flexible Water Vapor Retarders
• Effective Date: 01-Jun-2017

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 − 17
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 3. Terminology
1.1 This standard provides definitions, symbols, units, and 3.1 Definitions:
absorptance, n—the ratio of the radiant flux absorbed by a
abbreviations of terms used in ASTM standards pertaining to
body to that incident upon it.
thermal insulating materials, and to materials associated with
them.
absorption, n—transformation of radiant energy to a different
1.2 This terminology is not intended to be used to classify form of energy by interaction with matter.
insulation materials as having particular properties. Rather,
apparent thermal conductivity, λ , k , n—a thermal conduc-
a a
classification of insulation materials is to be done by the
tivity assigned to a material that exhibits thermal transmis-
material standards themselves.
sion by several modes of heat transfer resulting in property
1.3 This standard does not purport to address all of the
variation with specimen thickness, or surface emittance. See
safety concerns, if any, associated with its use. It is the
conductivity, thermal.
responsibility of the user of this standard to establish appro- DISCUSSION—Thermal conductivity and resistivity are normally con-
sidered to be intrinsic or specific properties of materials and, as such,
priate safety and health practices and determine the applica-
should be independent of thickness. When nonconductive modes of
bility of regulatory limitations prior to use.
heat transfer are present within the specimen (radiation, free convec-
1.4 This international standard was developed in accor-
tion) this may not be the case. To indicate the possible presence of this
dance with internationally recognized principles on standard- phenomena (for example, thickness effect) the modifier “apparent” is
used, as in apparent thermal conductivity.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
DISCUSSION—Test data using the “apparent” modifier must be quoted
mendations issued by the World Trade Organization Technical
only for the conditions of the measurement. Values of thermal conduc-
Barriers to Trade (TBT) Committee. tance (material C) and thermal resistance (material R) calculated from
apparent thermal conductivity or resistivity, are valid only for the same
conditions.
2. Referenced Documents
2 DISCUSSION—Test data labeled with “apparent” shall not include any
2.1 ASTM Standards:
equipment related measurement errors induced due to measurement
D3574 Test Methods for Flexible Cellular Materials—Slab,
attempts beyond an apparatus range or calibration.
Bonded, and Molded Urethane Foams
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
a
2.2 ISO Standard:
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
resistivity, thermal.
DISCUSSION—Seeentirediscussionunder apparent thermal conduc-
1
This terminology is under the jurisdiction of ASTM Committee C16 on
tivity.
Thermal Insulation and is the direct responsibility of Subcommittee C16.94 on
Terminology. area weight, n—weight per unit area for a specified sample, in
2 2
Current edition approved June 1, 2017. Published June 2017. Originally
units of lb/ft (kg/m ).
approved in 1941. Last previous edition approved in 2015 as C168 – 15a.
DOI:101520/C0168-17.
aerogel, n—a homogeneous, low-density solid phase material
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
derived from a gel, in which the liquid component of the gel
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
has been replaced with a gas.
Standards volume information, refer to the standard’s Document Summary page on
DISCUSSION—The resulting material has a porous structure with an
the ASTM website.
3
average pore size below the mean free path of air molecules at standard
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. atmospheric pressure and temperature.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohock
...

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 − 15a C168 − 17
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.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 ASTM Standards:
D3574 Test Methods for Flexible Cellular Materials—Slab, Bonded, and Molded Urethane Foams
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 Oct. 15, 2015June 1, 2017. Published October 2015June 2017. Originally approved in 1941. Last previous edition approved in 2015 as
C168 – 15.C168 – 15a. DOI:101520/C0168–15A.DOI:101520/C0168-17.
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—
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
C168 − 17
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 modes
a
of heat transfer resulting in property variation with specimen thickness, or surface emittance. See resistivity, thermal.
DISCUSSION—
See entire discussion under appar
...