ASTM C1668-24

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Designation: C1668 − 20 C1668 − 24
Standard Specification for
Externally Applied Reflective Insulation Systems on Rigid
Duct in Heating, Ventilation, and Air Conditioning (HVAC)
Systems
This standard is issued under the fixed designation C1668; 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 specification covers the requirements and physical properties of reflective insulation systems applied externally to Rigid
Heating, Ventilation, and Air Conditioning (HVAC) duct systems operating at or below 250°F (121.1°C). These insulation systems
consist of one or more low-emittance surfaces, such as metallic foil or metallic deposits, mounted on substrates to produce
reflective air spaces. Reflective insulation systems derive thermal performance from surfaces with an emittance of no greater than
0.1 facing enclosed air spaces.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
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, health, and environmental 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
2.1 ASTM Standards:
C168 Terminology Relating to Thermal Insulation
C335 Test Method for Steady-State Heat Transfer Properties of Pipe Insulation
C390 Practice for Sampling and Acceptance of Thermal Insulation Lots
C411 Test Method for Hot-Surface Performance of High-Temperature Thermal Insulation
C1045 Practice for Calculating Thermal Transmission Properties Under Steady-State Conditions
C1258 Test Method for Elevated Temperature and Humidity Resistance of Vapor Retarders for Insulation
C1338 Test Method for Determining Fungi Resistance of Insulation Materials and Facings
C1371 Test Method for Determination of Emittance of Materials Near Room Temperature Using Portable Emissometers
E84 Test Method for Surface Burning Characteristics of Building Materials
E96/E96M Test Methods for Gravimetric Determination of Water Vapor Transmission Rate of Materials
This specification is under the jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.21 on Reflective
Insulation.
Current edition approved May 1, 2020March 1, 2024. Published June 2020March 2024. Originally approved in 2009. Last previous edition approved in 20192020 as
C1668 – 19.C1668 – 20. DOI: 10.1520/C1668-20.10.1520/C1668-24.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1668 − 24
E2599 Practice for Specimen Preparation and Mounting of Reflective Insulation, Radiant Barrier and Vinyl Stretch Ceiling
Materials for Building Applications to Assess Surface Burning Characteristics
2.2 Other Test Method:
TAPPI Standard T-512 sp-02 Creasing of Flexible Packaging Material Paper Specimens for Testing
3. Terminology
3.1 Definitions:
3.1.1 Unless otherwise noted, the terms used in this specification conform to Terminology C168.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 HVAC ducts—as pertaining to this standard, ducts having rigid rectangular or circular cross-section used to transfer air from
the air handling equipment to the conditioned space and return.
3.2.2 insulation spacers—material used to form enclosed air spaces that are interior to the reflective insulation system.
3.2.3 reflective insulation—thermal insulation consisting of one or more low emittance surfaces, bounding one or more enclosed
air space(s). C168
4. Classification
4.1 Products covered by this specification are classified according to the substrate material and have the physical properties as
listed in Table 1.
4.1.1 Type A—Product with polyethylene foam substrate.
4.1.2 Type B—Product with polyethylene bubble pack substrate.
4.1.3 Type C—Product with fiberglass substrate.
4.1.4 Type D—Product with polyester fiber substrate.
4.1.5 Type E—Product with kraft paper substrate.
5. Ordering Information
5.1 Specify the required thermal resistance.
5.2 Specify the number of layers of insulation, width, thickness of the insulation system and the configuration of the duct(s) to
be insulated.
5.3 Special markings, when required, shall be specified.
TABLE 1 Classification Criteria
Type Type Type Type Type
Property
A B C D E
Emittance # # # # #
0.10 0.10 0.10 0.10 0.10
Max. Flame Spread Index 25 25 25 25 25
Max. Smoke Developed Index 50 50 50 50 50
Hot Surface Performance Min. Min. Min. Min. Min.
250ºF 250ºF 250ºF 250ºF 250ºF
Water Vapor Permeance 0.02 0.02 0.02 0.02 0.02
(perms) or less or less or less or less or less
Available from Technical Association of the Pulp and Paper Industry (TAPPI), 15 Technology Parkway South, Norcross, GA 30092, http://www.tappi.org.
C1668 − 24
5.4 Special performance requirements, when required.
6. Materials and Manufacture
6.1 Reflective insulation shall consist of low-emittance surface(s) with substrates and adhesives required to meet the specified
thermal performance and physical properties. Air spaces shall be maintained by use of insulation spacers.
6.2 Multiple layer reflective insulation shall be designed to attain the intended separation of layers. The design separation shall
be maintained by the use of proper size, location and method of securing the insulation spacers to the duct system.
6.3 Dimensions—Insulation and properly sized insulation spacers shall be furnished in dimensions specifically agreed upon
between the producer and the buyer.
7. Physical Properties
7.1 Emittance—Low-emittance surfaces used for this insulation shall have a surface emittance of 0.1 or less, as determined in
accordance with 10.1.
7.2 Water Vapor Permeance—The water vapor permeance shall be determined in accordance with 10.2 and shall meet the
requirements of Table 1.
7.3 Surface Burning Characteristics—Surface Burning Characteristics shall be determined in accordance with 10.3. The
maximum flame spread index shall not exceed 25 and the maximum smoke developed index shall not exceed 50.
7.4 Aging Resistance—The laminates of the reflective insulation shall be tested for aging resistance in accordance with 10.4. Three
specimens shall be tested. The test specimens shall be shielded from condensate that drips from the ceiling of the humidity chamber
during the test.
7.4.1 After exposure the specimens shall be evaluated for visible corrosion and delamination. For purposes of corrosion
evaluation, disregard the outer 0.25 in. (6 mm) perimeter. No tested specimen shall exhibit visible corrosion or unaided
delamination of layers.
7.4.2 After exposure re-measure the emittance of the samples. No test specimen shall have greater than 0.04 deviation from the
original emittance measurement and must remain under 0.1.
7.5 Adhesive Performance—Adhesives when used shall show no sign of bleeding when tested in accordance with the test
procedure in 10.5. Disregard bleeding at cut edges. Bleeding or delamination, shall be cause for rejection.
7.6 Pliability—Specimens tested in accordance with the procedure in 10.6 shall not show cracking or delamination.
7.7 Fungi Resistance—Specimens shall not have growth greater than the comparative item (southern yellow pine) when tested in
accordance with 10.7. Use interpretation of results in 7.2 of Test Method C1338.
7.8 Thermal Resistance—Determine the thermal resistance in accordance with procedures in 10.8. The surface-to-surface R-value
of a test assembly shall not be less than 95 % of the label value when tested in accordance with 10.8.
7.9 Hot-Surface Performance—Determine the Hot-Surface performance in accordance with procedures in 10.9. The minimum
temperature requirement is 250ºF (121.1°C).
8. Workmanship, Finish, and Appearance
8.1 The insulation system shall be manufactured, packaged and shipped in such a manner that, when received, it shall be suitable
for installation.
C1668 − 24
9. Sampling
9.1 Sampling shall be performed in accordance with Practice C390.
10. Test Methods
10.1 Emittance—The emittance of the product shall be tested in accordance with Test Method C1371.
10.2 Water Vapor Permeance—The permeance of the insulation product shall be tested in accordance with Test Method E96/E96M
(Desiccant Method).
10.3 Surface Burning Characteristics—The surface burning characteristics shall be determined in accordance w
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