ASTM C1338-19(2022)

• Abstract:

  SIGNIFICANCE AND USE; 2.1 The type of materials used in the manufacture of insulation products and the type of membrane used to face these products can sometimes affect fungi sustenance in the presence of high humidity. ; 2.2 This test method is used to determine the relative ability of an insulation and its facing to resist fungal growth under conditions favorable for their development. ; 2.3 This test method uses a comparative material to determine the relative ability of a material to resist fungal growth. In some specialized product areas, it is required that no growth take place. In such cases, the use of the comparative material is omitted and the pass/fail criterion is based upon growth.; SCOPE; 1.1 This test method covers the determination of the ability of new insulation materials and their facings to resist fungal growth. ; 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.

• Status: Published
• Publication Date: 31-Aug-2022
• ICS: 91.100.60 - Thermal and sound insulating materials
• Technical Committee: C16 - Thermal Insulation
• Drafting Committee: C16.31 - Chemical and Physical Properties

Overview

ASTM C1338-19(2022) is the internationally recognized standard test method developed by ASTM International for determining the fungi resistance of insulation materials and their facings. This standard provides a comparative laboratory procedure to evaluate how well insulation products and their facings resist the growth of common fungi under high humidity conditions. The document is critical for manufacturers, product testing labs, and regulatory compliance professionals to ensure insulation is suitable for use in environments where moisture and microbial contamination are primary concerns.

By utilizing this method, industry stakeholders can demonstrate the microbial resistance of insulation boards, batts, blankets, loose-fill, mineral fiber, cellulose, and foam products. This helps promote better indoor air quality, enhance building durability, and support compliance with building codes and health standards.

Key Topics

• Material Performance Evaluation: Examines insulation and facing materials to assess their susceptibility to fungal growth under controlled, high-humidity laboratory conditions.
• Test Methodology: Provides a standard procedure involving environmental chambers, control samples, and specific fungi species to evaluate the relative resistance of materials.
• Comparative Assessment: Employs a comparative item (such as birch tongue depressor or pine strip) to gauge fungal growth and to determine pass/fail status.
• Result Interpretation: Specifies that materials failing to outperform the comparative item, or exhibiting any fungal growth where zero tolerance is required, are considered non-compliant.
• Reporting Requirements: Details necessary documentation steps including material identification, test conditions, evaluation criteria, and results.

Applications

The ASTM C1338-19(2022) standard has broad practical applications across multiple sectors:

• Building and Construction: Assists architects, engineers, and contractors in selecting mold-resistant insulation materials for commercial, institutional, and residential projects, particularly in humid climates.
• HVAC Systems: Enables manufacturers and service providers to specify insulation with proven fungi resistance for duct linings and building envelope assemblies where moisture ingress is a risk.
• Product Manufacturing and R&D: Supports the development and qualification of new insulation products and facings for enhanced durability, safety, and compliance.
• Compliance and Certification: Provides a scientific, repeatable basis for regulatory bodies and certification agencies to validate claims of fungal resistance in insulation products, aiding in specification writing and procurement.
• Environmental Health: Helps ensure indoor air quality by reducing the potential for mold growth in insulation, supporting healthy building initiatives and occupant well-being.

Related Standards

To further support the fungi resistance of insulation and ensure comprehensive product assurance, consideration of the following related standards is recommended:

• ASTM C518: Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus
• ASTM C665: Standard Specification for Mineral-Fiber Blanket Thermal Insulation for Light Frame Construction and Manufactured Housing
• ASTM C411: Standard Test Method for Hot-Surface Performance of High-Temperature Thermal Insulation
• UL 181: Standard for Safety - Factory-Made Air Ducts and Air Connectors
• ISO 846: Plastics - Evaluation of the action of microorganisms

Summary

ASTM C1338-19(2022) remains a key reference for ensuring the quality, safety, and fungal resistance of insulation materials and facings used in the built environment. Following this standard helps professionals minimize the risk of mold-related issues, extend the life of building systems, and safeguard occupant health. For additional best practices, consult related ASTM and international standards as part of a comprehensive product assessment and specification process.

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.
Designation: C1338 − 19 (Reapproved 2022)
Standard Test Method for
Determining Fungi Resistance of Insulation Materials and
Facings
This standard is issued under the fixed designation C1338; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Apparatus
3.1 Glassware—Sterile disposable petri dishes, 4in. or 6 in.
1.1 This test method covers the determination of the ability
(100mm or 150 mm) by 0.6in. or 0.75 in. (15mm or 20 mm)
of new insulation materials and their facings to resist fungal
insizearepreferred.Forlargerspecimens,traysofborosilicate
growth.
glass or baking dishes up to 16in. by 20 in. (400mm by 600
1.2 The values stated in inch-pound units are to be regarded
mm) in size may be used.
as standard. The values given in parentheses are mathematical
3.2 Environmental Chamber or Cabinet—Equipment for
conversions to SI units that are provided for information only
this test method shall maintain a temperature of 82.4°F to
and are not considered standard.
86°F (28°C to 30°C) and a relative humidity of 95%
1.3 This standard does not purport to address all of the
(64%). Provisions shall be made to prevent condensation
safety concerns, if any, associated with its use. It is the
from dripping on the test specimen. There shall be free
responsibility of the user of this standard to establish appro-
circulation of air around the test chamber.
priate safety, health, and environmental practices and deter-
3.3 Atomizer—A chromatography atomizer capable of pro-
mine the applicability of regulatory limitations prior to use.
2 2
viding 100000spores⁄in. 6 20000 spores/in. (15000spo-
1.4 This international standard was developed in accor-
2 2
res⁄cm 6 3000 spores/cm ) shall be used for inoculation.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
3.4 Autoclavable Biohazard Bags, or metal pan able to
Development of International Standards, Guides and Recom-
withstand autoclaving.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. 4. Reagents and Materials
4.1 Purity of Water—Unless otherwise specified, references
2. Significance and Use
to water shall be understood to mean sterile distilled water or
water of equal purity.
2.1 The type of materials used in the manufacture of
insulation products and the type of membrane used to face
4.2 Inoculum:
these products can sometimes affect fungi sustenance in the
Fungi ATCC
presence of high humidity.
Aspergillus niger 9642
Aspergillus versicolor 11 730
2.2 Thistestmethodisusedtodeterminetherelativeability
Penicillium funiculosum 11 797
Chaetomium globosum 6205
of an insulation and its facing to resist fungal growth under
Aspergillus flavus 9643
conditions favorable for their development.
4.3 Cultures—Maintain cultures of the Aspergillus fungi
2.3 This test method uses a comparative material to deter-
separately on Czapek Dox agar (see Note 1). Culture the
minetherelativeabilityofamaterialtoresistfungalgrowth.In
Chaetomiumglobosumonstripsofcellulosefilterpaperonthe
some specialized product areas, it is required that no growth
surfaceofCzapekDoxagar.MaintainthePenicilliumfungion
take place. In such cases, the use of the comparative material
Sabouraud Dextrose agar. The stock cultures may be kept for
is omitted and the pass/fail criterion is based upon growth.
notmorethan4monthsat43°F 67°F(6°C 64°C)atwhich
time subcultures shall be made, and new stocks selected from
ThistestmethodisunderthejurisdictionofASTMCommitteeC16onThermal
InsulationandisthedirectresponsibilityofSubcommitteeC16.31onChemicaland The sole source of supply of the cultures known to the committee at this time
Physical Properties. is American Type Culture Collection (ATCC), 12301 Parklawn Drive, Rockville,
Current edition approved Sept. 1, 2022. Published October 2022. Originally MD20852.Ifyouareawareofalternativesuppliers,pleaseprovidethisinformation
approved in 1996. Last previous edition approved in 2019 as C1338–19. DOI: to ASTM International Headquarters. Your comments will receive careful consid-
10.1520/C1338-19R22. erationatameetingoftheresponsibletechnicalcommittee, whichyoumayattend.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1338 − 19 (2022)
the subcultures. If genetic or physiological changes occur, throughatleasta0.24in.(6mm)layerofglasswoolcontained
obtain new cultures. Incubate subcultures used for preparing inaglassfunnel,intoasterileflask.Thisprocessisintendedto
new stock cultures or the spore suspension at 86°F 6 4°F removelargemycelialfragmentsandclumpsofagarthatcould
(30°C 6 2°C) for five days or longer. interfere with the spraying process. Centrifuge the filtered
spore suspension. Remove all the supernatant down to the
NOTE 1—This media is readily available from any science/
surfaceofthesporepellet,takingcarenottoremoveordisturb
microbiological supply house.
the spore pellet. Resuspend the residue in 50 mL of sterile
5. Specimens
water and centrifuge. (It may be necessary to add a small
quantity of nontoxic wetting agent, not to exceed 0.10 g/L, to
5.1 Viability Specimens—Determine the viability of the
prevent clumping of the spores.) Wash the spores obtained
spore suspension during incubation with these controls: with
from each of the fungi in this manner three times. Dilute the
each daily group of tests, place one piece of sterilized What-
2 2
final washed residue with distilled water in such a manner that
man 500 filter paper, 1 in. (6.4 cm ) on each of two prepared
the resultant spore suspension shall contain 1000000spores
hardened Czapek Dox agar specimens in separate petri dishes.
per mL 6200000 spores per mL as determined with a
Prepare a third petri dish with Sabouraud Dextrose agar.
counting chamber. Repeat the operation for each organism
5.2 ComparativeMaterial—Awhitebirchtonguedepressor,
used in the test and blend equal volumes of the resultant spore
0.75in. by 6 in. (20mm by 150 mm) or southern yellow pine
suspensions to obtain the final mixed
...