ASTM C578-23

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: C578 − 22 C578 − 23
Standard Specification for
Rigid, Cellular Polystyrene Thermal Insulation
This standard is issued under the fixed designation C578; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 This specification covers the types, physical properties, and dimensions of cellular polystyrene boards with or without facings
or coatings made by molding (EPS) or extrusion (XPS) of expandable polystyrene. Products manufactured to this specification are
intended for use as thermal insulation for temperatures from –65 to +165°F (–53.9 to +73.9°C). This specification does not apply
to laminated products manufactured with any type of rigid board facer including fiberboard, perlite board, gypsum board, or
oriented strand board.
1.1.1 Additional requirements for Types IV and XIII for pipe, tank, and equipment thermal insulation for temperatures from –320
to +165°F (–196 to +73.9°C) are contained in Annex A1.
1.2 The use of thermal insulation materials covered by this specification is potentially regulated by codes that address fire
performance. For some end uses, specifiers need to also address the effect of moisture and wind pressure resistance. Guidelines
regarding these end use considerations are included in Appendix X1.
1.3 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.
1.4 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.
1.5 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:
C165 Test Method for Measuring Compressive Properties of Thermal Insulations
C168 Terminology Relating to Thermal Insulation
This specification is under the jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.22 on Organic and
Nonhomogeneous Inorganic Thermal Insulations.
Current edition approved Aug. 1, 2022Sept. 1, 2023. Published August 2022October 2023. Originally approved in 1965. Last previous edition approved in 20192022 as
C578 – 19.C578 – 22. DOI: 10.1520/C0578-22.10.1520/C0578-23.
This specification is similar to ISO 4898-1984, “Cellular Plastics–Specification for Rigid Cellular Materials Used in the Thermal Insulation of Buildings,” in title only.
The scope and technical content are significantly different.
ISO standards are available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
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
C578 − 23
C177 Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the
Guarded-Hot-Plate Apparatus
C203 Test Methods for Breaking Load and Flexural Properties of Block-Type Thermal Insulation
C272 Test Method for Water Absorption of Core Materials for Sandwich Constructions
C303 Test Method for Dimensions and Density of Preformed Block and Board–Type Thermal Insulation
C335 Test Method for Steady-State Heat Transfer Properties of Pipe Insulation
C390 Practice for Sampling and Acceptance of Thermal Insulation Lots
C518 Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus
C550 Test Method for Measuring Trueness and Squareness of Rigid Block and Board Thermal Insulation
C870 Practice for Conditioning of Thermal Insulating Materials
C1045 Practice for Calculating Thermal Transmission Properties Under Steady-State Conditions
C1058 Practice for Selecting Temperatures for Evaluating and Reporting Thermal Properties of Thermal Insulation
C1114 Test Method for Steady-State Thermal Transmission Properties by Means of the Thin-Heater Apparatus
C1303 Test Method for Predicting Long-Term Thermal Resistance of Closed-Cell Foam Insulation
C1363 Test Method for Thermal Performance of Building Materials and Envelope Assemblies by Means of a Hot Box Apparatus
C1512 Test Method for Characterizing the Effect of Exposure to Environmental Cycling on Thermal Performance of Insulation
Products
D1600 Terminology for Abbreviated Terms Relating to Plastics
D1621 Test Method for Compressive Properties of Rigid Cellular Plastics
D1622 Test Method for Apparent Density of Rigid Cellular Plastics
D2126 Test Method for Response of Rigid Cellular Plastics to Thermal and Humid Aging
D2863 Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics
(Oxygen Index)
E84 Test Method for Surface Burning Characteristics of Building Materials
E96/E96M Test Methods for Gravimetric Determination of Water Vapor Transmission Rate of Materials
E176 Terminology of Fire Standards
2.2 CAN/ULC Standard
CAN/ULC S770 Standard Test Method for the Determination of Long-Term Thermal Resistance of Closed-Cell Thermal
Insulating Foams
3. Terminology
3.1 Terms used in this specification are defined in Terminology C168.
3.2 Terms used in this specification that relate to fire standards are defined in Terminology E176.
3.3 Definitions of Terms Specific to This Standard:
3.3.1 EPS—letter designation for the molded expanded polystyrene thermal insulation classified by this specification. It is defined
as cellular plastic product manufactured from pre-expanded polystyrene beads subsequently molded into desired shapes and sizes
resulting in a product which is rigid with closed cellular structure.
3.3.2 RCPS—letter designations for the rigid cellular polystyrene thermal insulation classified by this specification that identifies
the product as rigid cellular polystyrene.
3.3.3 PS—used in this specification to represent polystyrene in accordance with Terminology D1600.
3.3.4 XPS—letter designation for the extruded expanded polystyrene thermal insulation classified by this specification. It is defined
as cellular plastic product manufactured in a one stage process by extrusion and expansion of the base polymer in the presence
of blowing agent(s) resulting in a product which is rigid with closed cellular structure.
4. Classification
4.1 This specification covers types of RCPS thermal insulations currently commercially available as described by the physical
property requirements in Table 1.
Available from Underwriters Laboratories (UL), 2600 N.W. Lake Rd., Camas, WA 98607-8542, http://www.ul.com.
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TABLE 1 Physical Property Requirements of RCPS Thermal Insulation
NOTE 1—It is possible that values for properties listed in this table will be affected by the presence of a surface skin which is a result of the
manufacturing process. The values for Type XIII properties listed in this table must be generated on material with the surface skin removed. Where
products are tested with skins-in-place, this condition shall be noted in the test report.
NOTE 2—Type III has been deleted because it is no longer available.
NOTE 3—In addition to the thermal resistance values in Table 1, values at mean temperatures of 25 ± 2°F (-4 ± 1°C), 40 ± 2°F (4 ± 1°C), and 110
± 2°F (43 ± 1°C) are provided in X1.7 for information purposes.
NOTE 4—Values quoted are maximum values for 1.00 in. (25.4 mm) thick samples with natural skins intact. Lower values will result for thicker
materials. Where water vapor permeance is a design issue, consult manufacturer.
NOTE 5—It is acceptable to determine the values for thermal resistance listed in this table on product at a thickness other than 1 in. (25.4 mm) in
accordance with 7.2.2.1. When tested at a thickness other than 1 in. (25.4 mm), the thermal resistance per inch shall meet the minimum requirement.
NOTE 6—Types XI, I, VIII, II, IX, XIV and XV are typically EPS insulation. Types XII, X, XIII, IV, VI, VII and V are typically XPS insulation.
Classification Type Type Type Type Type Type Type Type Type Type Type Type Type Type
XI I VIII II IX XIV XV XII X XIII IV VI VII V
Compressive resistance at 5.0 10.0 13.0 15.0 25.0 40.0 60.0 15.0 15.0 20.0 25.0 40.0 60.0 100.0
yield or 10 % deformation, (35) (69) (90) (104) (173) (276) (414) (104) (104) (138) (173) (276) (414) (690)
whichever occurs first
(with skins intact), min, psi
(kPa)
Thermal resistance of 1.00-in. 3.1 3.6 3.8 4.0 4.2 4.2 4.3 4.6 5.0 3.9 5.0 5.0 5.0 5.0
(25.4-mm) thickness, min, (0.55) (0.63) (0.67) (0.70) (0.74) (0.74) (0.76) (0.81) (0.88) (0.68) (0.88) (0.88) (0.88) (0.88)
2 2
F·ft ·h/Btu (K·m /W)
Mean temperature:
75 ± 2°F (24 ± 1°C)
Flexural strength, min, psi (kPa) 10 25 30 35 50 60 75 40 40 45 50 60 75 100
(70) (173) (208) (240) (345) (414) (517) (276) (276) (310) (345) (414) (517) (690)
Water vapor permeance of 5.0 5.0 3.5 3.5 2.5 2.5 2.5 1.5 1.5 2.0 1.5 1.1 1.1 1.1
1.00-in. (25.4-mm) thickness (287) (287) (201) (201) (143) (143) (143) (86) (86) (114) (86) (63) (63) (63)
(See Note 4.), max, perm
(ng/Pa·s·m )
Water absorption by total 4.0 4.0 3.0 3.0 2.0 2.0 2.0 0.3 0.3 1.0 0.3 0.3 0.3 0.3
immersion, max, volume %
Dimensional stability (change 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0
in dimensions), max,%
Oxygen index, min, volume % 24.0 24.0 24.0 24.0 24.0 24.0 24.0 24.0 24.0 24.0 24.0 24.0 24.0 24.0
3 3
Density, min, lb/ft (kg/m ) 0.70 0.90 1.15 1.35 1.80 2.40 3.00 1.20 1.30 1.60 1.45 1.80 2.20 3.00
(12) (15) (18) (22) (29) (38) (48) (19) (21) (26) (23) (29) (35) (48)
5. Ordering Information
5.1 Acquisition documents shall specify the following:
5.1.1 Title, number, and year of this specification,
5.1.2 Type (see Table 1),
5.1.3 R-value or thickness required (see Tables 1 and 2),
5.1.3.1 Thermal Resistance/Thickness Relationship—It is possible that the thermal resistance (R-value) and the thermal resistivity
(R-value/inch) of RCPS thermal insulation will vary with thickness. Therefore, when ordering, specify the R-value or the thickness,
or both. For additional information, see Practice C1045.
TABLE 2 Common Dimensions of RCPS Thermal Insulation
Type XI, I, VIII, II, IX, XIV, XV X, IV, XII VI, VII V XIII
Width, in. (mm) 12 to 48 (305 to 1219) 16, 24, 48 (406, 610, 1219) 24 (610) 16 (406) 14 to 20 (356 to
508)
Length, in. (mm) 48 to 192 (1219 to 4877) 48, 96 108 (1219, 2438, 2743) 48, 96, (1219, 2438) 96 (2438) 36 to 112 (914 to
2845)
3 1
Thickness, in. (mm) ⁄8 to 24 (9.5 to 610) ⁄2 to 4 (13 to 102) 1 to 4 (25 to 102) 1 to 4 (25 to 102) 7 to 10 (178 to
254)
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5.1.4 Density, if other than specified in Table 1,
5.1.5 Tolerance, if other than specified (see 8.2),
5.1.6 Length and width required (see Table 2 and 8.1),
5.1.7 If other than straight edges are required (see 8.3),
5.1.8 If either ship-lap or tongue-and-groove edges are required (see 8.6),
5.1.9 Tapered Insulation—Special ordering information. In addition to other applicable requirements in Section 5 (Note 1),
acquisition documents for tapered RCPS thermal insulation shall specify the following:
5.1.9.1 Minimum starting thickness,
5.1.9.2 Slope, in./ft (mm/m),
5.1.9.3 Average R-value,
5.1.9.4 Minimum thickness,
5.1.9.5 Shop Drawings—The tapered insulation supplier shall provide shop drawings to illustrate installation patterns and
dimensions for each tapered module,
5.1.10 Sampling, if different (see 10.1),
5.1.11 If a certificate of compliance is required (see 14.1), and
5.1.12 If marking is other than specified (see 15.1).
NOTE 1—Physical properties of tapered insulation should be determined on blocks of RCPS thermal insulation before the insulation is tapered.
5.1.13 Type XIII—Special ordering information. In addition to other applicable requirements in Section 5, acquisition documents
for Type XIII thermal insulation shall specify if presence of surface skins is required.
6. Materials and Manufacture
6.1 RCPS thermal insulation shall be formed by the expansion of polystyrene resin beads or granules in a closed mold, or by the
expansion of polystyrene base resin in an extrusion process. RCPS thermal insulation shall be of uniform density and have
essentially closed cells. All RCPS thermal insulation shall contain sufficient flame retardants to meet the oxygen index
requirements of Table 1.
7. Physical Requirements
7.1 Inspection Requirements:
7.1.1 The physical requirements listed in this section are defined as inspection requirements (refer to Practice C390).
7.1.2 All dimensional requirements are described in Section 8.
7.1.3 All workmanship, finish, and appearance requirements are described in Section 9.
7.1.4 Density shall be in accordance with Table 1.
NOTE 2—For lots of 150 units or less, the tightened inspection sampling plan in Practice C390 will be followed.
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7.2 Qualification Requirements:
7.2.1 The physical properties listed in this section of the specification are defined as qualification requirements (refer to Practice
C390). Thermal resistance, compressive resistance, flexural strength, water vapor permeance, water absorption, dimensional
stability, and oxygen index shall be in accordance with Table 1. The average test value based upon testing the number of test
specimens required by the specified test method for each physical property or Section 11 of this specification shall be used to
determine compliance.
7.2.2 The mean thermal resistance of the material tested shall not be less than the minimum value identified in Table 1. The
thermal resistances of individual specimens tested shall not be less than 90 % of the minimum value identified in Table 1.
7.2.2.1 Test 1 in. (25.4 mm) thick specimens for determination of compliance with thermal resistance, compressive resistance,
water vapor permeance, water absorption, dimensional stability and density property requirements in Table 1. If 1 in. (25.4 mm)
thickness product is not produced the next available commercially manufactured product thickness greater than 1 in. (25.4 mm)
thickness shall be tested and reported.
7.2.3 Compliance with qualification requirements shall be in accordance with Practice C390.
7.3 Long Term Thermal Resistance (LTTR)—Determine and report values in accordance with Test Method C1303 or CAN/ULC
S770. LTTR shall apply to types IV, V, VI, VII, and X only. The composition of the test stacks used for the test measurements
shall be reported.
7.4 Table 1 describes types of RCPS thermal insulation. However, it does not cover all available products on the market. The
values stated in Table 1 are not intended to be used as design values. It is the buyer’s responsibility to specify design requirements
and obtain supporting documentation from the material supplier.
7.5 Combustibility Characteristics—RCPS thermal insulation is an organic material and is, therefore, combustible. It shall not be
exposed to flames or other ignition sources. The values obtained by the oxygen index test (see Table 1 and 11.10) do not necessarily
indicate or describe the fire risk of the materials and are used in this specification primarily to distinguish between insulations
formulated with flame retardants and those not so formulated.
8. Dimensions and Permissible Variations
8.1 The materials covered by this specification are commonly available in the sizes shown in Table 2. Other sizes shall be agreed
upon between the supplier and the user.
8.2 Dimensional Tolerances—Unless otherwise specified, the length tolerance shall not exceed 60.03 in./ft (62.5 mm/m) of
length; the width tolerance shall not exceed 60.06 in./ft (65.0 mm/m) of width; and the thickness tolerance shall not exceed 60.06
in./in. (659.5 mm/m) of thickness. For products less than 1.00 in. (25.4 mm) in thickness, the thickness tolerance shall not exceed
60.06 in. (1.5 mm).
8.2.1 Dimensional Tolerances for RCPS Type XIII—The length tolerance shall not exceed +1, −0 in (+25.4, −0 mm); the width
tolerance shall not exceed +0.5, −0 in (+12.7, −0 mm); and the thickness tolerance shall not exceed +0.5, −0 in (+12.7, −0 mm).
8.3 Edge Trueness—Unless otherwise specified, RCPS thermal insulation shall be furnished with true edges. Edges shall not
deviate more than 0.03 in./ft (2.5 mm/m) of length or width.
8.4 Face Trueness—RCPS thermal insulation shall not deviate from absolute trueness by more than 0.03 in./ft (2.5 mm ⁄m) of
length or width.
8.5 Squareness—RCPS thermal insulation shall not deviate from squareness by more than 0.06 in./ft (5.0 mm/m) of length or
width.
Supporting data can be found in Oak Ridge National Lab Report number ORNL/TM-2012/214. Evaluation of Experimental Parameters in the Accelerated Aging of
Closed-Cell Foam Insulation, December 2012.
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8.6 Ship-Lap and Tongue-and-Groove Edges—When specified, RCPS thermal insulation shall be furnished with either ship-lap or
tongue-and-groove edges.
8.6.1 For RCPS thermal insulation manufactured with ship-lap edges, the depth of the ship-lap cut shall be one half the board
thickness +0.06, −0 in. ( +1.5, −0 mm). The minimum width of the cut for RCPS thermal insulation of 1.00-in. (25.4-mm)
thickness or greater shall be 0.50 6 0.06 in. (12.7 6 1.5 mm). For RCPS thermal insulation less than 1.00 in. (25.4 mm) in
thickness, the minimum width of the cut shall be 0.25 6 0.06 in. (6.4 6 1.5 mm). The ship-lap cut shall be made on opposite faces
of the board for both length and width. The resulting joint shall be smooth and uniform.
8.6.2 For RCPS thermal insulation manufactured with tongue-and-groove edges, the tongue of one shall fit snugly into the groove
of a second. The resulting joint shall be smooth and uniform.
9. Workmanship, Finish, and Appearance
9.1 Defects—RCPS thermal insulation shall have no defects that will adversely affect its service qualities. RCPS thermal insulation
shall be of uniform texture and
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