ASTM E96/E96M-24

Standard Test Methods for Gravimetric Determination of Water Vapor Transmission Rate of Materials

SIGNIFICANCE AND USE
5.1 The purpose of these tests is to determine water vapor transmission rate of materials by means of a simple gravimetric procedure.  
5.2 Test Conditions:  
5.2.1 A WVTR result obtained in one method under one set of test conditions cannot be used to predict the result that would be obtained using the same method with a different set of conditions, or using the other method. See Appendix X3 for discussion of determining dependency of WVTR on different relative humidity (at a given temperature).  
5.2.2 Test conditions that are commonly used or are considered standard in various industries or research applications are listed as Procedures A-E in Appendix X1, but use of these conditions is not mandatory in the methods herein.  
5.2.3 Given the caution in 5.2.1, the selection of test conditions that closely approach exposure conditions of material in actual use is advised when possible.  
5.2.4 Where tests are conducted for classification or compliance purposes, test conditions are typically defined in codes, specifications, and manufacturer’s technical literature.
SCOPE
1.1 These test methods cover the determination of water vapor transmission rate (WVTR) of materials, such as, but not limited to, paper, plastic films, other sheet materials, coatings, foams, fiberboards, gypsum and plaster products, wood products, and plastics. Two basic methods, the Desiccant Method and the Water Method, are provided for the measurement of WVTR. In these tests, the desired temperature and side-to-side humidity conditions, with resultant vapor drive through the specimen, are used. The test conditions employed are at the discretion of the user, but in all cases, are reported with the results.  
1.2 The values stated in either Inch-Pound or SI units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, each system shall be used independently of the other. Derived results are converted from one system to the other using appropriate conversion factors (see Table 1).  
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.

General Information

• Status: Published
• Publication Date: 29-Feb-2024
• ICS: 77.040.99 - Other methods of testing of metals
• Technical Committee: C16 - Thermal Insulation
• Drafting Committee: C16.33 - Insulation Finishes and Moisture

Relations

• Replaces: ASTM E96/E96M-23 - Standard Test Methods for Gravimetric Determination of Water Vapor Transmission Rate of Materials
• Effective Date: 01-Mar-2024
• Refers: ASTM C168-24 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 15-Apr-2024
• Refers: ASTM C168-22 - Standard Terminology Relating to Thermal Insulation
• Effective Date: 01-May-2022
• Referred By: ASTM C209-20 - Standard Test Methods for Cellulosic Fiber Insulating Board
• Effective Date: 01-Mar-2024
• Referred By: ASTM D4635-16 - Standard Specification for Plastic Films Made from Low-Density Polyethylene and Linear Low-Density Polyethylene for General Use and Packaging Applications
• Effective Date: 01-Mar-2024
• Referred By: ASTM E154/E154M-08a(2019) - Standard Test Methods for Water Vapor Retarders Used in Contact with Earth Under Concrete Slabs, on Walls, or as Ground Cover
• Effective Date: 01-Mar-2024
• Referred By: ASTM C647-19 - Standard Guide to Properties and Tests of Mastics and Coating Finishes for Thermal Insulation
• Effective Date: 01-Mar-2024
• Referred By: ASTM D4068-17(2022) - Standard Specification for Chlorinated Polyethylene (CPE) Sheeting for Concealed Water-Containment Membrane
• Effective Date: 01-Mar-2024
• Referred By: ASTM F3510-21 - Standard Guide for Characterizing Fiber-Based Constructs for Tissue-Engineered Medical Products
• Effective Date: 01-Mar-2024
• Referred By: ASTM C1423-21 - Standard Guide for Selecting Jacketing Materials for Thermal Insulation
• Effective Date: 01-Mar-2024
• Referred By: ASTM D6153-23 - Standard Specification for Materials for Bridge Deck Waterproofing Membrane Systems
• Effective Date: 01-Mar-2024
• Referred By: ASTM C1029-20 - Standard Specification for Spray-Applied Rigid Cellular Polyurethane Thermal Insulation
• Effective Date: 01-Mar-2024
• Referred By: ASTM D7230-06(2021) - Standard Guide for Evaluating Polymeric Lining Systems for Water Immersion in Coating Service Level III Safety-Related Applications on Metal Substrates
• Effective Date: 01-Mar-2024
• Referred By: ASTM C727-19(2024) - Standard Practice for Installation and Use of Reflective Insulation in Building Constructions
• Effective Date: 01-Mar-2024
• Referred By: ASTM B479-19 - Standard Specification for Annealed Aluminum and Aluminum-Alloy Foil for Flexible Barrier, Food Contact, and Other Applications
• Effective Date: 01-Mar-2024

Overview

ASTM E96/E96M-24 is the internationally recognized standard providing test methods for determining the water vapor transmission rate (WVTR) of materials through gravimetric procedures. Developed by ASTM International, these test methods are crucial for evaluating moisture barrier properties in a wide range of materials, including paper, plastic films, coatings, foams, fiberboards, gypsum and plaster products, wood, and plastics. Two primary methods are outlined: the Desiccant Method and the Water Method, both employing controlled temperature and humidity conditions to quantify WVTR.

Understanding water vapor transmission is essential for product performance, quality control, certification, and compliance in industries where moisture control directly impacts material durability, insulation, packaging, and construction.

Key Topics

• Water Vapor Transmission Rate (WVTR): Defines the steady flow of water vapor through a material under specific temperature and humidity conditions.
• Gravimetric Test Methods: WVTR is determined by measuring weight changes over time, either by absorbing water vapor into a desiccant or by allowing vapor to escape from water through the specimen.
• Test Methods Included:
  • Desiccant Method: Measures vapor passing from a high humidity environment through the material into a desiccant.
  • Water Method: Measures vapor passing from water through the material to a controlled, lower humidity environment.
• Selection of Test Conditions: Users are advised to select environmental conditions that most closely resemble the actual application environment, since results depend heavily on temperature and humidity.
• Reporting Requirements: Results must specify test conditions, method used, material details, and calculations to ensure data reproducibility and accuracy.
• Precision and Bias: The standard includes guidelines and references for interlaboratory precision, repeatability, and reproducibility based on established protocols.

Applications

ASTM E96/E96M-24 is widely adopted across multiple industries for its practical value in:

• Building Materials: Assessing moisture barrier properties of insulation, sheathing, wall panels, and vapor retarders to prevent condensation, mold growth, and thermal performance degradation.
• Packaging: Ensuring effective moisture barriers in flexible packaging films, containers, and wraps used for food, pharmaceuticals, and sensitive electronics.
• Coatings and Foams: Testing coatings, sealants, and insulation foams for suitability in damp environments or for compliance with building codes demanding specific vapor permeability thresholds.
• Wood and Gypsum Products: Evaluating construction materials that can be impacted by water vapor absorption, affecting structural integrity and indoor air quality.
• Research and Product Development: Providing a uniform method for R&D teams to benchmark and improve material formulations or validate manufacturer claims.

The use of standardized units (inch-pound or SI) and established calculation methods further aid in comparing material performance internationally and in regulatory compliance.

Related Standards

The following related ASTM standards are referenced for harmonized testing and terminology:

• ASTM C168 – Terminology Relating to Thermal Insulation
• ASTM C1809 – Practice for Preparation and Reporting of Specimens for Permeance Testing
• ASTM D449/D449M – Specification for Asphalt Used in Dampproofing and Waterproofing
• ASTM D2301 – Specification for Vinyl Chloride Plastic Pressure-Sensitive Electrical Insulating Tape
• ASTM E177 – Practice for Precision and Bias in ASTM Test Methods
• ASTM E691 – Practice for Conducting Interlaboratory Studies

Compliance with these additional standards enhances measurement accuracy and ensures consistent reporting across test laboratories and industry sectors.

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Keywords: ASTM E96, water vapor transmission rate, WVTR, gravimetric method, desiccant method, water method, permeance, building materials, packaging materials, moisture barrier testing, material compliance, laboratory testing standards.

Standards Content (Sample)

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: E96/E96M − 24
Standard Test Methods for
Gravimetric Determination of Water Vapor Transmission
Rate of Materials
This standard is issued under the fixed designation E96/E96M; 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 2. Referenced Documents
2.1 ASTM Standards:
1.1 These test methods cover the determination of water
C168 Terminology Relating to Thermal Insulation
vapor transmission rate (WVTR) of materials, such as, but not
C1809 Practice for Preparation of Specimens and Reporting
limited to, paper, plastic films, other sheet materials, coatings,
of Results for Permeance Testing of Pressure Sensitive
foams, fiberboards, gypsum and plaster products, wood
Adhesive Sealed Joints in Insulation Vapor Retarders
products, and plastics. Two basic methods, the Desiccant
D449/D449M Specification for Asphalt Used in Dampproof-
Method and the Water Method, are provided for the measure-
ing and Waterproofing
ment of WVTR. In these tests, the desired temperature and
D2301 Specification for Vinyl Chloride Plastic Pressure-
side-to-side humidity conditions, with resultant vapor drive
Sensitive Electrical Insulating Tape
through the specimen, are used. The test conditions employed
E177 Practice for Use of the Terms Precision and Bias in
are at the discretion of the user, but in all cases, are reported
ASTM Test Methods
with the results.
E691 Practice for Conducting an Interlaboratory Study to
1.2 The values stated in either Inch-Pound or SI units are to Determine the Precision of a Test Method
be regarded separately as standard. The values stated in each
3. Terminology
system are not necessarily exact equivalents; therefore, each
3.1 Definitions of terms used in this standard will be found
system shall be used independently of the other. Derived
in Terminology C168, from which the following is quoted:
results are converted from one system to the other using
“water vapor permeability—the time rate of water vapor
appropriate conversion factors (see Table 1).
transmission through unit area of flat material of unit thickness
1.3 This standard does not purport to address all of the
induced by unit vapor pressure difference between two specific
safety concerns, if any, associated with its use. It is the
surfaces, under specified temperature and humidity conditions.
responsibility of the user of this standard to establish appro-
Discussion—Permeability is a property of a material, but the
priate safety, health, and environmental practices and deter-
permeability of a body that performs like a material may be
mine the applicability of regulatory limitations prior to use.
used. Permeability is the arithmetic product of permeance and
1.4 This international standard was developed in accor- thickness.
dance with internationally recognized principles on standard- water vapor permeance—the time rate of water vapor
ization established in the Decision on Principles for the transmission through unit area of flat material or construction
induced by unit vapor pressure difference between two specific
Development of International Standards, Guides and Recom-
surfaces, under specified temperature and humidity conditions.
mendations issued by the World Trade Organization Technical
Discussion—Permeance is a performance evaluation and not
Barriers to Trade (TBT) Committee.
a property of a material.
water vapor transmission rate—the steady water vapor flow
in unit time through unit area of a body, normal to specific
These test methods are under the jurisdiction of ASTM Committee C16 on
Thermal Insulation and are the direct responsibility of Subcommittee C16.33 on
Insulation Finishes and Moisture. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved March 1, 2024. Published March 2024. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1953. Last previous edition approved in 2023 as E96/E96M – 23. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E0096_E0096M-24. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E96/E96M − 24
A,B
TABLE 1 Units and Conversion Factors
5.2.4 Where tests are conducted for classification or com-
To Obtain (for the
pliance purposes, test conditions are typically defined in codes,
Multiply by
same test condition)
specifications, and manufacturer’s technical literature.
WVTR
2 2
g/h·m 1.43 grains/h·ft
6. Apparatus
2 2
grains/h·ft 0.697 g/h·m
6.1 Test Dish—The test dish shall be of any noncorroding
Water Vapor Permeance (WVP)
2 –2
material, impermeable to water or water vapor. There is no
ng/Pa·s·m 1.75 × 10 perm
2 7
g/Pa·s·m 1.75 × 10 perm specified shape or maximum size for the test dish. Light weight
perm 57.2 ng/Pa·s·m
is desirable. A shallow dish is preferred, but its size and weight
–8 2
perm 5.72 × 10 g/Pa·s·m
are limited when an analytical balance is chosen to detect small
Permeability weight changes. The mouth of the dish shall be as large as
2 2
ng/Pa·s·m 0.688 perm-inch
practical and at least 4.65 in. [3000 mm ] in area. The
g/Pa·s·m 6.88 × 10 perm-inch
desiccant or water area shall not be less than the mouth area
perm-inch 1.45 ng/Pa·s·m
–9
perm-inch 1.45 × 10 g/Pa·s·m
except when a grid is used, as provided in 13.1, with its
A
effective area not exceeding 10 % of the mouth area. A flange
These units are commonly used in the construction and building materials
industries. Additional units are used in other industries, such as packaging.
or ledge around the mouth, on which the specimen rests is
B
All conversions of mm Hg to Pa are made at a temperature of 0°C.
commonly used to ensure sealing, but other configurations are
allowed.
6.1.1 When the specimen area is larger than the mouth area,
this overlay upon the ledge is a source of error. The magnitude
parallel surfaces, under specific conditions of temperature and
of this error increases with the width of the overlay upon the
humidity at each surface.”
ledge. The overlay material results in a positive error, indicat-
ing excessive water vapor transmission. To minimize this error,
4. Summary of Test Methods
this overlay material is to be masked as described in 11.1 so
4.1 In the Desiccant Method the test specimen is sealed to
that the mouth area defines the test area. The magnitude of the
the open mouth of a test dish containing a desiccant, and the
edge mask error is a complex function of the specimen
assembly placed in a controlled atmosphere. Periodic weigh-
thickness, ledge width, mouth area, and in some cases the
ings are used to determine the rate of water vapor movement
specimen permeability. This error is discussed by Joy and
through the specimen into the desiccant.
Wilson (1) (see 14.4.3). This type of error is to be limited to
4.2 In the Water Method, the dish contains distilled water,
no more than 12 %. For a thick specimen the ledge width shall
and the weighings are used to determine the rate of vapor
not exceed ⁄4 in. [19 mm] for a 10-in. [254-mm] or larger span
movement through the specimen from the water to the con-
mouth (square or circular) or ⁄8 in. [3 mm] for a 5-in.
trolled atmosphere.
[127-mm] span mouth (square or circular). For a 3-in. [76-mm]
span mouth (square or circular) the ledge shall not exceed 0.11
4.3 Given a common controlled atmosphere, the vapor
in. [2.8 mm] wide. An allowable ledge that limits error to 12%
pressure difference is nominally the same in both methods, but
shall be determined by interpolation for intermediate sizes. Per
the water method exposes the specimen to higher humidity,
Joy and Wilson (1), using Equation 7, it is possible to solve for
which potentially affects the water vapor transmission through
the ledge width that results in a specific or lower error rate. To
the material. The controlled atmosphere temperature and hu-
achieve a lower error rate or to calculate specific intermediate
midity levels are selected by the user.
ledge widths, the ledge width is solved for using Equation 7.
5. Significance and Use When a rim is incorporated, it shall not be more than ⁄4 in. [6
mm] higher than the specimen as attached. See sections 12.1
5.1 The purpose of these tests is to determine water vapor
and 13.1 for requirements for the clearance for the test dishes
transmission rate of materials by means of a simple gravimetric
for the Desiccant Method and Water Method, respectively.
procedure.
6.2 Test Chamber—The room or cabinet where the as-
5.2 Test Conditions:
sembled test dishes are to be placed shall have a controlled
5.2.1 A WVTR result obtained in one method under one set
temperature and relative humidity. Common test conditions are
of test conditions cannot be used to predict the result that
listed in Appendix X1. If not listed among these, temperature
would be obtained using the same method with a different set
and relative humidity corresponding to the intended application
of conditions, or using the other method. See Appendix X3 for
of, or specification for, the material to be tested (see Appendix
discussion of determining dependency of WVTR on different
X1) are used. Refer to product standard specification for test
relative humidity (at a given temperature).
conditions for classification or compliance purposes. Tempera-
5.2.2 Test conditions that are commonly used or are consid-
ture shall be maintained at 6 5 °F [2.8 °C] at a given
ered standard in various industries or research applications are
measurement point, with the average at the end of the test
listed as Procedures A-E in Appendix X1, but use of these
period being within 6 2 °F [1.1°C] of the specified test
conditions is not mandatory in the methods herein.
5.2.3 Given the caution in 5.2.1, the selection of test
conditions that closely approach exposure conditions of mate-
The boldface numbers in parentheses refer to the list of references at the end of
rial in actual use is advised when possible. this standard.
E96/E96M − 24
condition. Relative humidity shall be maintained at 6 5 % at a 7.1.1 Material with sieve size not specified, or classified as
given measurement point, with the average at the end of the larger than No. 8 (2.36 mm), shall be passed through a No. 8
test period being within 6 2% of the specified test condition. (2.36 mm) sieve prior to use.
Provisions shall be made to prevent water from dripping onto 7.1.2 Virgin desiccant that has been in a tightly sealed
the surface of a specimen when tested at high humidity, when container does not have to be dried before use. Material near
condensation on the chamber walls is possible. Both tempera- the bottom of the container with visible powdery fines present
ture and relative humidity shall be measured and recorded at a shall not be used.
frequency of at least once every 15 min for the duration of the 7.1.3 Desiccant to be re-used shall be dried at 400°F
test. Air shall be continuously circulated throughout the [200°C] for 4 h per inch, or any fraction thereof, of desiccant
chamber, with a velocity sufficient to maintain uniform condi- depth in vessel. Re-dried desiccant shall be stored in a sealed
tions within the chamber. Test dishes shall be placed in the container and be at room temperature before use. Prior to use,
chamber in such a way that air flow is not restricted over the it shall be sieved over No. 30 (600 μm) mesh.
top of the specimen. Barometric pressure shall be measured
NOTE 3—Calcium chloride sold in 4-8 mesh size is commonly available
and recorded at every weighing for use in the still air
through chemical/lab supply houses.
correction. See 15.6.1.1.
7.2 Water—For the Water Method, distilled water shall be
6.3 Balance—Weighing shall be performed using an elec-
used in the test dish (Note 6).
tronic analytical balance of suitable capability (See Note 1).
7.3 Sealant—The sealant used for attaching the specimen to
the dish must be impervious to the passage of water vapor (and
NOTE 1—Various aspects of balance specifications and performance
other than capacity and resolution should be considered in choosing
water). Seals of molten asphalt or wax are required for tests
-2 -1 -1
equipment suitable for the weighing demands of these tests. In use, best
producing results below 4 perms [230 ng·m ·s ·Pa ]. Sealing
laboratory practices for verification of balance performance, along with
methods are discussed in Appendix X2.
proper care and maintenance should be followed.
6.3.1 The balance shall have sufficient capacity to accom-
8. Sampling
modate the assembled dish mass and, in the case of desiccant
8.1 The material shall be sampled in accordance with
method tests, added mass of any moisture gained.
standard methods of sampling applicable to the material or
6.3.2 Resolution (or readability) of the balance shall be no
product under test. For homogenous materials, the sample shall
more than 1 % of the assembled dish assembly weight change
be of uniform thickness. When the opposing faces of a product
during the span of six or more consecutive steady state
are dissimilar, the two faces shall be designated by distinguish-
weighings utilized per 14.3.
ing identification (for example, on a one-side-coated sample,
6.3.2.1 If the resolution does not meet the requirement of
“I” for the coated side and “II” for the uncoated side).
6.3.2, weighing shall be extended until such a point that the
weight change is at least 100 times the resolution of the balance
9. Test Specimens
(See Note 2).
9.1 Test specimens shall be representative of the material
NOTE 2—Example: The following table lists the days at steady state
tested. When a product is designed for use in only one position,
required at various balance resolutions less than that of the balance used
three specimens shall be tested by the same method with the
for the hypothetical specimen shown.
vapor flow in the designated direction. When the faces of a
Balance Resolution = 0.1 mg (0.0001 g)
product are indistinguishable, three specimens shall be tested
Weighed once every 24 h
Steady state observed, six points chosen (five days)
by the same method. When the faces of a product are different,
Weight gain over steady state span = 0.7815 g
and the location of the vapor source is independent of the
Balance Number
installation, six specimens shall be tested by the same method,
Resolution of Days
three being tested with the vapor flow in each direction and so
0.1 mg 5
0.001 g 5 reported. A blank specimen for both orientations is required
0.01 g 7
(see 9.6).
0.1 g 64
1.0 g 640
9.2 Materials of homogeneous composition and physical
structure shall be tested at any thickness to determine water
6.3.2.2 In cases where WVTR is near zero and weight gain
vapor permeance (WVP). When determining permeability, the
or loss is so small that the requirements of this section cannot
specimen must be a minimum of ⁄2 in. [12.5 mm] thick.
be fulfilled regardless of test duration, the report shall make
note of such.
9.3 A slab of a singular material that varies in physical
structure by layer (such as a foamed plastic or rubber with
6.4 Thickness-Measuring Gage—The gage shall have an
natural “skins”) shall be tested at the thickness of use.
accuracy of 61 % of the reading or 0.0001 in. [0.0025 mm],
whichever is greater.
9.4 When a material has a pitted or textured surface, the
tested overall thickness, if less than that of use, shall be at least
7. Materials
five times the sum of the maximum pit depths in both its faces.
7.1 Desiccant—For the Desiccant Method, anhydrous cal- 9.5 When testing pressure sensitive adhesive sealed joints
cium chloride in the form of pellets that will pass a No. 8 used in insulation vapor retarder systems, prepare the speci-
[2.36-mm] sieve (Note 3) shall be used. mens according to Practice C1809.
E96/E96M − 24
9.6 Use of a Blank Specimen: from the controlled environment, but if removal is necessary,
the time outside of the test environment shall be kept to a
9.6.1 All tests require an additional blank specimen to be
minimum.
tested exactly like the others, except that no desiccant or water
is put in the dish. Failure to use this blank specimen to establish
12.4 Terminate the test or change the desiccant before the
modified dish weights may significantly increase the time
water absorbed by the desiccant exceeds 10 % of its starting
required to complete the test. The time to reach equilibrium of
weight. The desiccant gain is isolated using the blank specimen
water vapor transmission increases as the square of thickness.
to adjust for moisture content change of the specimen.
Some thick, particularly hygroscopic, materials take as long as
12.5 Analyze the results as prescribed in 14.1.
60 days to reach equilibrium conditions.
NOTE 4—The WVTR of some materials (especially of wood and paper)
9.6.2 The blank specimen is used to cancel out the effects of
is influenced by the ambient relative humidity immediately before the test.
barometric pressure changes eliminating the need for buoyancy A hysteresis results in higher WVTR when the relative humidity to which
the specimen is exposed prior to testing is above the test condition or vice
corrections, moisture changes of hygroscopic materials, and
versa. Conditioning specimens of wood, paper, or other materials having
mass changes of uncured specimens. This enables simpler,
significant moisture content to constant weight in a 50 % relative humidity
more accurate calculations and reduces the time to establish
atmosphere prior to testing can reduce the time needed to reach a steady
steady state mass change.
state weight gain.
9.6.3 The blank specimen becomes the fourth specimen of a
13. Procedure for Water Method
standard three dish test set.
3 1
13.1 Fill the test dish with distilled water to a level ⁄4 6 ⁄4
in. [19 6 6 mm] from the specimen. The air space thus allowed
10. Specimen Thickness Measurement
has a small vapor resistance, but it is necessary in order to
10.1 When testing permeability of homogeneous materials,
reduce the risk of water touching the specimen when the dish
the overall thickness of each specimen shall be measured.
is handled. Such contact invalidates a test on some materials
Divide the specimen into quadrants and measure each quadrant
such as paper, wood, or other hygroscopic materials. The water
with a gage meeting the requirements of 6.4, and average the
depth shall be not less than ⁄8 in. [3 mm] to ensure coverage of
results.
the dish bottom throughout the test. When using a glass dish,
its bottom must be visibly covered at all times but no specific
11. Attachment of Specimen to Test Dish
depth is required. Reduce water surges by placing a grid of
light non-corroding material in the dish to break the water
11.1 Attach the specimen to the dish by sealing in such a
surface. This grid shall be at least ⁄4 in. [6 mm] below the
manner that the dish mouth defines the area of the specimen
specimen, and it shall not reduce the water surface by more
exposed to the vapor pressure in the dish. If necessary, mask
than 10 %.
the specimen top surface that is exposed to conditioned air so
that its exposure duplicates the mouth shape and size and is
NOTE 5—When it is desirable to reuse an assembled specimen for a
directly above it. A template is useful for locating the mask.
subsequent test series It is acceptable to add water through a small sealable
Thoroughly seal the edges of the specimen to prevent the hole in the dish above the water line.
passage of vapor into, out of, or around the specimen edges or
13.2 Attach the specimen to the dish (see 11.1) and place it
any portion thereof. Suggested methods of attachment are
in the controlled environment on a horizontal surface. Follow
described in Appendix X2.
the procedure given in 12.3 through 12.5.
NOTE 6—When preparing specimens, to avoid possible formation of
11.2 It is possible that some specimens will warp and break
condensation on the interior surface of the specimen, it is advisable to
the seal during the test. The risk is reduced by preconditioning
bring the temperature of the prepared specimen dish to within 62°F [1°C]
the specimen to the controlled environmental conditions of the
of the test temperature prior to placing into controlled test environment.
NOTE 7—When weighing water method test specimens, if the specimen
test for 24 hours, while mechanically restraining it to the dish.
is exposed to an environment that is below the temperature of the
controlled environment and the inside surface of the specimen could reach
12. Procedure for Desiccant Method
dew point for the air inside the dish, condensation might form on that
1 surface. Instruction in 12.3 addresses avoidance of this.
12.1 Fill the test dish with desiccant within ⁄4 in. [6 mm] of
the specimen. Weigh the amount of desiccant placed in each 13.3 Where water is expected to be in contact with the
dish. Leave enough space so that shaking of the dish, to be
barrier in service, proceed as in 13.2 except place the dish in an
done at each weighing, will mix the desiccant. inverted position. The dish must be sufficiently level so that
water covers the inner surface of the specimen despite any
12.2 Attach the specimen to the dish (see 11.1) and place it
distortion of the specimen due to the weight of the water.
in the controlled environment room or chamber.
Locate the test dish so that air circulates over the exposed
12.3 Weigh the dish assembly periodically, often enough to
surface. Place the test dishes on the balance in the upright
obtain at least six data points at steady state. A data point is the
position for weighing, but keep the period during which the
weight at a particular time. The time of weighing shall be
wetted surface of the specimen is not covered with water to a
recorded to a precision of approximately 1 % of the time span
minimum.
between successive weighing. Thus, if weighings are made
14. Determination and Utilization of Steady State
every hour, record the time to the nearest 30 s; if recordings are
made every day, a time to the nearest 15 min is acceptable. 14.1 The rate of weight change of a specimen is at steady
Ideally, weighing is done without removal of the test dishes state when that rate is essentially constant over a period that is
E96/E96M − 24
a minimum of six consecutive weighings. However, additional In SI units:
weighings increase the confidence in the measurement.
G = steady state weight change (from the straight line),
g,
14.2 The data from the beginning or the end, or both, of the
t = time, h,
weighing sequence is not always part of the steady state portion
G/t = slope of the straight line, g/h,
of the test due to internal moisture content changes or loss of
A = test area (cup mouth area), m , and
desiccant efficiency or excess water loss. Analysis of the data
WVTR = water vapor transmission rate, g/h·m .
per 14.3 is needed to ensure only steady state portions of the
test are used for calculating WVTR. 15.3.2 Water Vapor Permeance:
WVTR WVTR
14.3 The steady state portion of the test is most easily
WVP 5 5 (2)
Δp S· R 2 R
~ !
identified graphically.
1 2
14.3.1 Plot the weight, modified by the blank specimen,
where:
against elapsed time.
In inch-pound units:
14.3.2 Where a straight line adequately fits the plot of at
Δp = vapor pressure difference, in. Hg,
least six properly spaced points (periodic weight changes
S = saturation vapor pressure at test temperature, in. Hg,
matching, or exceeding 20 % of the multiple of 100 times the
R = relative humidity at the source expressed as a fraction
scale sensitivity), steady state is assumed.
(the test chamber for desiccant method; in the dish for
14.3.3 The slope of that fitted line is the water vapor
water method), and
transmission rate. See Appendix X4 for additional discussion
R = relative humidity at the vapor sink expressed as a
regarding measurements of materials of zero or near-zero water
fraction.
vapor permeance (WVP).
In SI units:
Δp = vapor pressure difference, Pa,
15. Calculation and Analysis of Results
S = saturation vapor pressure at test temperature, Pa,
15.1 Blank Specimen—The blank specimen is used to com-
R = relative humidity at the source expressed as a fraction
pensate for variability in test conditions due to temperature
(the test chamber for desiccant method; in the dish for
and/or barometric pressure fluctuations. The test specimen
water method), and
recorded weights are adjusted by calculating the weight change
R = relative humidity at the vapor sink expressed as a
of the blank specimen from the beginning of the test to time of
fraction.
weighing. This adjustment is made by subtracting the weight
15.4 In the controlled room or chamber the relative humid-
change of the blank specimen from the weight change of the
ity and temperature are the average of values actually measured
test dish at the time of weighing of both. This permits earlier
during the test. In the dish the relative humidity is nominally
recognition of steady state conditions.
0 % for the desiccant and 100 % for the water. These values are
15.2 A mathematical least squares regression analysis of the
usually within 3 % relative humidity of the actual relative
-1 -1 -2
weight, modified by the blank specimen, as a function of time
humidity for specimens below 4 perms [230 ng·Pa ·s ·m ]
will give the water vapor transmission rate.
when the required conditions are maintained (no more than
15.2.1 For materials with very low water vapor permeance,
10 % moisture in CaCl and no more than 1 in. [25 mm] air
this method is used to determine the results after 30 to 60 days
space above water).
when using an analytical balance, with a sensitivity of ≈1 mg,
15.5 Perform the calculation of permeability only when the
even if the weight change does not meet the 100 times the
test specimen is homogeneous and not less than ⁄2 in. [12.5
sensitivity requirement of 6.3. These specimens must be clearly
mm] thick, as follows:
identified in the report. Reference Appendix X4 for discussion
Permeability 5 WVP·thickness (3)
regarding measurements of near zero or zero water vapor
permeance (WVP) materials.
15.6 Corrections—It is important that all applicable correc-
tions be made to all measurements, with the exception of still
15.3 Calculate the water vapor transmission rate, WVTR,
and WVP as follows: air and surface resistance corrections for materials with WVP
-1 -1 -2
measurements of 2 perms [114 ng·Pa ·s ·m ] or less, which
15.3.1 Water Vapor Transmission Rate:
are insignificant and need not be applied (2). Background and
G G / t
~ !
discussion of the various corrections are found in the literature
WVTR 5 5 (1)
t·A A
(2, 3, 4, 5, 6). Fig. 1 contains a diagram of the corrections
where: referenced in this section.
In inch-pound units:
15.6.1 Corrections for Resistance due to Still Air and
G = steady state weight change, grains (from the Specimen Surface:
straight line),
15.6.1.1 When the material is highly permeable, these
t = time during which G occurred, h,
corrections become more significant. With known thickness of
G/t = slope of the straight line, grains/h,
the still air layer in the cup, the corresponding vapor resistance
A = test area (cup mouth area), ft , and
is calculated using the following equations (Eq 4 and Eq 5) for
WVTR = water vapor transmission rate, grains/h·ft .
permeability.
E96/E96M − 24
FIG. 1 Referenced Corrections in 15.6
6 1.81
5.3081 × 10 P T 16.1.1 Identification of the material tested, including prod-
o
δ 5 · · (4)
S D S D
a
R T P 491.67 uct thickness for homogeneous materials tested for permeabil-
v
ity.
where:
16.1.2 The side of each specimen on which the higher
δ = permeability of still air, Perm in.,
a
humidity was applied. The surfaces shall be clearly identified
T = temperature, °R,
when there is a difference between the two sides. The orienta-
P = ambient barometric pressure, in Hg,
tion of the specimen shall be described.
P = standard barometric pressure, that is, 29.92 in. Hg, and
o
16.1.3 Method used (desiccant or water).
R = ideal gas constant for water, that is, 85.780
v
-1 -1 16.1.4 Average test temperature.
ft·lbf·lb ·°R .
16.1.5 Average relative humidity in the test chamber.
25 1.81
2.306 × 10 ·P T
16.1.6 WVTR, WVP, and permeability when calculated, of
o
δ 5 (5)
S D
a
R ·T·P 273.15
each specimen in appropriate units.
v
16.1.7 The average WVTR, WVP, and permeability of all
where:
specimens tested.
-1 -1 -1
δ = permeability of still air, kg·m ·s ·Pa ,
a
16.1.7.1 When reporting in Inch-Pound units, for results 1.0
T = temperature, K,
perm and greater, report the results to two significant figures.
P = ambient barometric pressure, Pa,
For results less than 1.0 perm report the result to two decimals.
P = standard barometric pressure, that is, 101325 Pa, and
o
-
-1 -1 16.1.7.2 When reporting in SI units, for results 57.2 ng·m
R = ideal gas constant for water, that is, 461.5 J·K ·kg .
v
-1 -1
2·s ·Pa and greater, round to the nearest whole unit. For perm
-2 -1 -1
15.6.1.2 In the absence of any measured data, the surface
results less than 57.2 ng·m ·s ·Pa round to one decimal
resistances (that is, inside and outside surfaces of the speci-
place.
men) is approximated by using Lewis’ relation (5). For cup
16.1.8 Portion of the plot indicating the section of the curve
methods that follow this standard, the total surface resistance
used to calculate WVP
-3 2 -1
(Hansen and Lund (6)) is ≈ 2.29 × 10 h·ft ·in.Hg·grains (4
16.1.9 Description of cup and type or composition of
-5 2 -1
× 10 Pa·s·m ·ng ).
sealant.
15.6.2 Edge Mask Correction—The following equation (Joy
16.1.10 Corrections applied, if any.
and Wilson (1)) is to be used to correct the excess effect due to
edge masking during specimen preparation: 17. Precision and Bias
17.1 Precision—Table 2 is based on interlaboratory tests
400·t 2
Percent excess WVT 5 log (6)
e 2·π·b
S D
π·S 2 conducted in 1988 and 1991. In 1988 four materials (A, B, C,
~ !
11e t
D) were tested using the desiccant method and the water
where:
method in triplicate. Fifteen laboratories contributed data, with
In inch-pound units:
full results secured from four laboratories. In 1991 ten labora-
t = specimen thickness, ft,
tories contributed data for material E, using triplicate
b = width of masked edge, ft, and
specimens, again using both the desiccant method and the
S = four times the test area divided by the perimeter, ft.
1 water method. Tables 3 and 4 are based on another interlabo-
ratory test conducted in 1995–96. (7) One material at a nominal
where:
thickness of 1 in. (25 mm) was tested by ten participating
In SI units:
laboratories. Results from only nine laboratories were used in
t = specimen thickness, m,
the analyses because of the presence of severe outliers (see
b = width of masked edge, m, and
Practice E691) in the observation of tenth laboratory.
S = four times the test area divided by the perimeter, m.
17.1.1 Test results were analyzed using Practice E691.
15.6.2.1 If the cup assembly includes any edge masking this
17.2 Additional precision data and analysis for this test
correction shall be made.
method is based on an interlaboratory study (#512) conducted
15.7 Example calculations are presented in Appendix X5.
Supporting data have been filed at ASTM International Headquarters and may
16. Report
be obtained by requesting Research Report RR:C16-1014. Contact ASTM Customer
16.1 The report shall include the following: Service at [e-mail].
E96/E96M − 24
TABLE 2 Results on Precision from Interlaboratory Testing
For Desiccant Method at 23°C Repeatability Reproducibility
Mean
Thickness s CV LSD s CV LSD
Material Permeance
A -2 -1 -1 B -2 -1 -1 B -2 -1 -1 B -2 -1 -1 B
(mm) (ng·m ·s ·Pa ) (%) (ng·m ·s ·Pa ) (ng·m ·s ·Pa ) (%) (ng·m ·s ·Pa )
-2 -1 -1 B
(ng·m ·s ·Pa )
A 0.0254 34.7 0.95 2.7 2.7 5.6 16.2 15.9
B 0.1397 0.74 0.16 21.7 0.46 0.31 42.6 0.92
C 12.7 3.51 0.25 7.2 0.69 1.06 30.2 2.8
D 25.4 44.8 1.5 3.3 4.2 3.5 7.8 10.0
E 0.3556 2.64 0.13 5.0 0.40 0.31 11.7 0.86
For Water Method at 23°C Repeatability Reproducibility
Mean
Thickness s CV LSD s CV LSD
Material Permeance
A -2 -1 -1 B -2 -1 -1 B -2 -1 -1 B -2 -1 -1 B
(mm) (ng·m ·s ·Pa ) (%) (ng·m ·s ·Pa ) (ng·m ·s ·Pa ) (%) (ng·m ·s ·Pa )
-2 -1 -1 B
(ng·m ·s ·Pa )
A 0.0254 40.91 0.77 1.9 2.2 8.9 21.8 25.2
B 0.1397 0.90 0.13 14.0 0.35 0.12 13.4 0.34
C 12.7 5.55 0.31 5.7 0.92 1.1 20.1 3.1
D 25.4 59.5 1.1 1.8 3.1 12.4 20.9 35.5
E 0.3556 3.40 0.19 5.7 0.57 0.47 13.8 1.3
A
1 in.
...

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: E96/E96M − 23 E96/E96M − 24
Standard Test Methods for
Gravimetric Determination of Water Vapor Transmission
Rate of Materials
This standard is issued under the fixed designation E96/E96M; 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 These test methods cover the determination of water vapor transmission rate (WVTR) of materials, such as, but not limited
to, paper, plastic films, other sheet materials, coatings, foams, fiberboards, gypsum and plaster products, wood products, and
plastics. Two basic methods, the Desiccant Method and the Water Method, are provided for the measurement of WVTR. In these
tests, the desired temperature and side-to-side humidity conditions, with resultant vapor drive through the specimen, are used. The
test conditions employed are at the discretion of the user, but in all cases, are reported with the results.
1.2 The values stated in either Inch-Pound or SI units are to be regarded separately as standard. The values stated in each system
are not necessarily exact equivalents; therefore, each system shall be used independently of the other. Derived results are converted
from one system to the other using appropriate conversion factors (see Table 1).
These test methods are under the jurisdiction of ASTM Committee C16 on Thermal Insulation and are the direct responsibility of Subcommittee C16.33 on Insulation
Finishes and Moisture.
Current edition approved Nov. 15, 2023March 1, 2024. Published January 2024March 2024. Originally approved in 1953. Last previous edition approved in 20222023
ε1
as E96/E96M – 22aE96/E96M – 23. . DOI: 10.1520/E0096_E0096M-23.10.1520/E0096_E0096M-24.
A,B
TABLE 1 Units and Conversion Factors
To Obtain (for the
Multiply by
same test condition)
WVTR
2 2
g/h·m 1.43 grains/h·ft
2 2
grains/h·ft 0.697 g/h·m
Water Vapor Permeance (WVP)
2 –2
ng/Pa·s·m 1.75 × 10 perm
2 7
g/Pa·s·m 1.75 × 10 perm
perm 57.2 ng/Pa·s·m
–8 2
perm 5.72 × 10 g/Pa·s·m
Permeability
ng/Pa·s·m 0.688 perm-inch
g/Pa·s·m 6.88 × 10 perm-inch
perm-inch 1.45 ng/Pa·s·m
–9
perm-inch 1.45 × 10 g/Pa·s·m
A
These units are commonly used in the construction and building materials
industries. Additional units are used in other industries, such as packaging.
B
All conversions of mm Hg to Pa are made at a temperature of 0°C.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E96/E96M − 24
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
C1809 Practice for Preparation of Specimens and Reporting of Results for Permeance Testing of Pressure Sensitive Adhesive
Sealed Joints in Insulation Vapor Retarders
D449/D449M Specification for Asphalt Used in Dampproofing and Waterproofing
D2301 Specification for Vinyl Chloride Plastic Pressure-Sensitive Electrical Insulating Tape
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions of terms used in this standard will be found in Terminology C168, from which the following is quoted:
“water vapor permeability—the time rate of water vapor transmission through unit area of flat material of unit thickness induced
by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions.
Discussion—Permeability is a property of a material, but the permeability of a body that performs like a material may be used.
Permeability is the arithmetic product of permeance and thickness.
water vapor permeance—the time rate of water vapor transmission through unit area of flat material or construction induced by
unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions.
Discussion—Permeance is a performance evaluation and not a property of a material.
water vapor transmission rate—the steady water vapor flow in unit time through unit area of a body, normal to specific parallel
surfaces, under specific conditions of temperature and humidity at each surface.”
4. Summary of Test Methods
4.1 In the Desiccant Method the test specimen is sealed to the open mouth of a test dish containing a desiccant, and the assembly
placed in a controlled atmosphere. Periodic weighings are used to determine the rate of water vapor movement through the
specimen into the desiccant.
4.2 In the Water Method, the dish contains distilled water, and the weighings are used to determine the rate of vapor movement
through the specimen from the water to the controlled atmosphere.
4.3 Given a common controlled atmosphere, the vapor pressure difference is nominally the same in both methods, but the water
method exposes the specimen to higher humidity, which potentially affects the water vapor transmission through the material. The
controlled atmosphere temperature and humidity levels are selected by the user.
5. Significance and Use
5.1 The purpose of these tests is to determine water vapor transmission rate of materials by means of a simple gravimetric
procedure.
5.2 Test Conditions:
5.2.1 A WVTR result obtained in one method under one set of test conditions cannot be used to predict the result that would be
obtained using the same method with a different set of conditions, or using the other method. See Appendix X3 for discussion of
determining dependency of WVTR on different relative humidity (at a given temperature).
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.
E96/E96M − 24
5.2.2 Test conditions that are commonly used or are considered standard in various industries or research applications are listed
as Procedures A-E in Appendix X1, but use of these conditions is not mandatory in the methods herein.
5.2.3 Given the caution in 5.2.1, the selection of test conditions that closely approach exposure conditions of material in actual
use is advised when possible.
5.2.4 Where tests are conducted for classification or compliance purposes, test conditions are typically defined in codes,
specifications, and manufacturer’s technical literature.
6. Apparatus
6.1 Test Dish—The test dish shall be of any noncorroding material, impermeable to water or water vapor. There is no specified
shape or maximum size for the test dish. Light weight is desirable. A shallow dish is preferred, but its size and weight are limited
when an analytical balance is chosen to detect small weight changes. The mouth of the dish shall be as large as practical and at
2 2
least 4.65 in. [3000 mm ] in area. The desiccant or water area shall not be less than the mouth area except when a grid is used,
as provided in 13.1, with its effective area not exceeding 10 % of the mouth area. A flange or ledge around the mouth, on which
the specimen rests is commonly used to ensure sealing, but other configurations are allowed.
6.1.1 When the specimen area is larger than the mouth area, this overlay upon the ledge is a source of error. The magnitude of
this error increases with the width of the overlay upon the ledge. The overlay material results in a positive error, indicating
excessive water vapor transmission. To minimize this error, this overlay material is to be masked as described in 11.1 so that the
mouth area defines the test area. The magnitude of the edge mask error is a complex function of the specimen thickness, ledge
width, mouth area, and in some cases the specimen permeability. This error is discussed by Joy and Wilson (1) (see 14.4.3). This
type of error is to be limited to no more than 12 %. For a thick specimen the ledge width shall not exceed ⁄4 in. [19 mm] for a
10-in. [254-mm] or larger span mouth (square or circular) or ⁄8 in. [3 mm] for a 5-in. [127-mm] span mouth (square or circular).
For a 3-in. [76-mm] span mouth (square or circular) the ledge shall not exceed 0.11 in. [2.8 mm] wide. An allowable ledge that
limits error to 12% shall be determined by interpolation for intermediate sizes. Per Joy and Wilson (1), using Equation 7, it is
possible to solve for the ledge width that results in a specific or lower error rate. To achieve a lower error rate or to calculate specific
intermediate ledge widths, the ledge width is solved for using Equation 7. When a rim is incorporated, it shall not be more than
⁄4 in. [6 mm] higher than the specimen as attached. See sections 12.1 and 13.1 for requirements for the clearance for the test dishes
for the Desiccant Method and Water Method, respectively.
6.2 Test Chamber—The room or cabinet where the assembled test dishes are to be placed shall have a controlled temperature and
relative humidity. Common test conditions are listed in Appendix X1. If not listed among these, temperature and relative humidity
corresponding to the intended application of, or specification for, the material to be tested (see Appendix X1) are used. Refer to
product standard specification for test conditions for classification or compliance purposes. Temperature shall be maintained at 6
5 °F [2.8 °C] at a given measurement point, with the average at the end of the test period being within 6 2 °F [1.1°C] of the
specified test condition. Relative humidity shall be maintained at 6 5 % at a given measurement point, with the average at the end
of the test period being within 6 2% of the specified test condition. Provisions shall be made to prevent water from dripping onto
the surface of a specimen when tested at high humidity, when condensation on the chamber walls is possible. Both temperature
and relative humidity shall be measured and recorded at a frequency of at least once every 15 min for the duration of the test. Air
shall be continuously circulated throughout the chamber, with a velocity sufficient to maintain uniform conditions within the
chamber. Test dishes shall be placed in the chamber in such a way that air flow is not restricted over the top of the specimen.
Barometric pressure shall be measured and recorded at every weighing for use in the still air correction. See 15.6.1.1.
6.3 Balance—Weighing shall be performed using an electronic analytical balance of suitable capability (See Note 1).
NOTE 1—Various aspects of balance specifications and performance other than capacity and resolution should be considered in choosing equipment
suitable for the weighing demands of these tests. In use, best laboratory practices for verification of balance performance, along with proper care and
maintenance should be followed.
6.3.1 The balance shall have sufficient capacity to accommodate the assembled dish mass and, in the case of desiccant method
tests, added mass of any moisture gained.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
E96/E96M − 24
6.3.2 Resolution (or readability) of the balance shall be no more than 1 % of the assembled dish assembly weight change during
the span of six or more consecutive steady state weighings utilized per 14.3.
6.3.2.1 If the resolution does not meet the requirement of 6.3.2, weighing shall be extended until such a point that the weight
change is at least 100 times the resolution of the balance (See Note 2).
NOTE 2—Example: The following table lists the days at steady state required at various balance resolutions less than that of the balance used for the
hypothetical specimen shown.
Balance Resolution = 0.1 mg (0.0001 g)
Weighed once every 24 h
Steady state observed, six points chosen (five days)
Weight gain over steady state span = 0.7815 g
Balance Number
Resolution of Days
0.1 mg 5
0.001 g 5
0.01 g 7
0.1 g 64
1.0 g 640
6.3.2.2 In cases where WVTR is near zero and weight gain or loss is so small that the requirements of this section cannot be
fulfilled regardless of test duration, the report shall make note of such.
6.4 Thickness-Measuring Gage—The gage shall have an accuracy of 61 % of the reading or 0.0001 in. [0.0025 mm], whichever
is greater.
7. Materials
7.1 Desiccant—For the Desiccant Method, anhydrous calcium chloride in the form of small pellets that will pass a No. 8
[2.36-mm] sieve, andsieve (Note 3 free of fines that will pass a No. 30 [600-μm] sieve, ) shall be used.
7.1.1 Material with sieve size not specified, or classified as larger than No. 8 (2.36 mm), shall be passed through a No. 8 (2.36
mm) sieve prior to use.
7.1.2 Virgin desiccant that has been in a tightly sealed container does not have to be dried before use. Material near the bottom
of the container with visible powdery fines present shall not be used.
7.1.3 Desiccant to be re-used shall be dried at 400°F [200°C] for 4 hoursh per inch, or any fraction thereof, of desiccant depth
in vessel. Re-dried desiccant shall be stored in a sealed container and be at room temperature before use. Prior to use, it shall be
sieved over No. 30 (600 μm) mesh.
NOTE 3—Calcium chloride sold in 4-8 mesh size is commonly available through chemical/lab supply houses.
7.1.2 Virgin material that has been in a sealed container does not have to be dried before use.
7.2 Water—For the Water Method, distilled water shall be used in the test dish (Note 56).
7.3 Sealant—The sealant used for attaching the specimen to the dish must be impervious to the passage of water vapor (and water).
-2 -1 -1
Seals of molten asphalt or wax are required for tests producing results below 4 perms [230 ng·m ·s ·Pa ]. Sealing methods are
discussed in Appendix X2.
8. Sampling
8.1 The material shall be sampled in accordance with standard methods of sampling applicable to the material or product under
E96/E96M − 24
test. For homogenous materials, the sample shall be of uniform thickness. When the opposing faces of a product are dissimilar,
the two faces shall be designated by distinguishing identification (for example, on a one-side-coated sample, “I” for the coated side
and “II” for the uncoated side).
9. Test Specimens
9.1 Test specimens shall be representative of the material tested. When a product is designed for use in only one position, three
specimens shall be tested by the same method with the vapor flow in the designated direction. When the faces of a product are
indistinguishable, three specimens shall be tested by the same method. When the faces of a product are different, and the location
of the vapor source is independent of the installation, six specimens shall be tested by the same method, three being tested with
the vapor flow in each direction and so reported. A blank specimen for both orientations is required (see 9.6).
9.2 Materials of homogeneous composition and physical structure shall be tested at any thickness to determine water vapor
permeance (WVP). When determining permeability, the specimen must be a minimum of ⁄2 in. [12.5 mm] thick.
9.3 A slab of a singular material that varies in physical structure by layer (such as a foamed plastic or rubber with natural “skins”)
shall be tested at the thickness of use.
9.4 When a material has a pitted or textured surface, the tested overall thickness, if less than that of use, shall be at least five times
the sum of the maximum pit depths in both its faces.
9.5 When testing pressure sensitive adhesive sealed joints used in insulation vapor retarder systems, prepare the specimens
according to Practice C1809.
9.6 Use of a Blank Specimen:
9.6.1 All tests require an additional blank specimen to be tested exactly like the others, except that no desiccant or water is put
in the dish. Failure to use this blank specimen to establish modified dish weights may significantly increase the time required to
complete the test. The time to reach equilibrium of water vapor transmission increases as the square of thickness. Some thick,
particularly hygroscopic, materials take as long as 60 days to reach equilibrium conditions.
9.6.2 The blank specimen is used to cancel out the effects of barometric pressure changes eliminating the need for buoyancy
corrections, moisture changes of hygroscopic materials, and mass changes of uncured specimens. This enables simpler, more
accurate calculations and reduces the time to establish steady state mass change.
9.6.3 The blank specimen becomes the fourth specimen of a standard three dish test set.
10. Specimen Thickness Measurement
10.1 When testing permeability of homogeneous materials, the overall thickness of each specimen shall be measured. Divide the
specimen into quadrants and measure each quadrant with a gage meeting the requirements of 6.4, and average the results.
11. Attachment of Specimen to Test Dish
11.1 Attach the specimen to the dish by sealing in such a manner that the dish mouth defines the area of the specimen exposed
to the vapor pressure in the dish. If necessary, mask the specimen top surface that is exposed to conditioned air so that its exposure
duplicates the mouth shape and size and is directly above it. A template is useful for locating the mask. Thoroughly seal the edges
of the specimen to prevent the passage of vapor into, out of, or around the specimen edges or any portion thereof. Suggested
methods of attachment are described in Appendix X2.
11.2 It is possible that some specimens will warp and break the seal during the test. The risk is reduced by preconditioning the
specimen to the controlled environmental conditions of the test for 24 hours, while mechanically restraining it to the dish.
12. Procedure for Desiccant Method
12.1 Fill the test dish with desiccant within ⁄4 in. [6 mm] of the specimen. Weigh the amount of desiccant placed in each dish.
Leave enough space so that shaking of the dish, to be done at each weighing, will mix the desiccant.
E96/E96M − 24
12.2 Attach the specimen to the dish (see 11.1) and place it in the controlled environment room or chamber.
12.3 Weigh the dish assembly periodically, often enough to obtain at least six data points at steady state. A data point is the weight
at a particular time. The time of weighing shall be recorded to a precision of approximately 1 % of the time span between
successive weighing. Thus, if weighings are made every hour, record the time to the nearest 30 s; if recordings are made every
day, a time to the nearest 15 min is acceptable. Ideally, weighing is done without removal of the test dishes from the controlled
environment, but if removal is necessary, the time outside of the test environment shall be kept to a minimum.
12.4 Terminate the test or change the desiccant before the water absorbed by the desiccant exceeds 10 % of its starting weight.
The desiccant gain is isolated using the blank specimen to adjust for moisture content change of the specimen.
12.5 Analyze the results as prescribed in 14.1.
NOTE 4—The WVTR of some materials (especially of wood and paper) is influenced by the ambient relative humidity immediately before the test. A
hysteresis results in higher WVTR when the relative humidity to which the specimen is exposed prior to testing is above the test condition or vice versa.
Conditioning specimens of wood, paper, or other materials having significant moisture content to constant weight in a 50 % relative humidity atmosphere
prior to testing can reduce the time needed to reach a steady state weight gain.
13. Procedure for Water Method
3 1
13.1 Fill the test dish with distilled water to a level ⁄4 6 ⁄4 in. [19 6 6 mm] from the specimen. The air space thus allowed has
a small vapor resistance, but it is necessary in order to reduce the risk of water touching the specimen when the dish is handled.
Such contact invalidates a test on some materials such as paper, wood, or other hygroscopic materials. The water depth shall be
not less than ⁄8 in. [3 mm] to ensure coverage of the dish bottom throughout the test. When using a glass dish, its bottom must
be visibly covered at all times but no specific depth is required. Reduce water surges by placing a grid of light non-corroding
material in the dish to break the water surface. This grid shall be at least ⁄4 in. [6 mm] below the specimen, and it shall not reduce
the water surface by more than 10 %.
NOTE 5—When it is desirable to reuse an assembled specimen for a subsequent test series It is acceptable to add water through a small sealable hole in
the dish above the water line.
13.2 Attach the specimen to the dish (see 11.1) and place it in the controlled environment on a horizontal surface. Follow the
procedure given in 12.3 through 12.5.
NOTE 6—When preparing specimens, to avoid possible formation of condensation on the interior surface of the specimen, it is advisable to bring the
temperature of the prepared specimen dish to within 62°F [1°C] of the test temperature prior to placing into controlled test environment.
NOTE 7—When weighing water method test specimens, if the specimen is exposed to an environment that is below the temperature of the controlled
environment and the inside surface of the specimen could reach dew point for the air inside the dish, condensation might form on that surface. Instruction
in 12.3 addresses avoidance of this.
13.3 Where water is expected to be in contact with the barrier in service, proceed as in 13.2 except place the dish in an inverted
position. The dish must be sufficiently level so that water covers the inner surface of the specimen despite any distortion of the
specimen due to the weight of the water. Locate the test dish so that air circulates over the exposed surface. Place the test dishes
on the balance in the upright position for weighing, but keep the period during which the wetted surface of the specimen is not
covered with water to a minimum.
14. Determination and Utilization of Steady State
14.1 The rate of weight change of a specimen is at steady state when that rate is essentially constant over a period that is a
minimum of six consecutive weighings. However, additional weighings increase the confidence in the measurement.
14.2 The data from the beginning or the end, or both, of the weighing sequence is not always part of the steady state portion of
the test due to internal moisture content changes or loss of desiccant efficiency or excess water loss. Analysis of the data per 14.3
is needed to ensure only steady state portions of the test are used for calculating WVTR.
14.3 The steady state portion of the test is most easily identified graphically.
E96/E96M − 24
14.3.1 Plot the weight, modified by the blank specimen, against elapsed time.
14.3.2 Where a straight line adequately fits the plot of at least six properly spaced points (periodic weight changes matching, or
exceeding 20 % of the multiple of 100 times the scale sensitivity), steady state is assumed.
14.3.3 The slope of that fitted line is the water vapor transmission rate. See Appendix X4 for additional discussion regarding
measurements of materials of zero or near-zero water vapor permeance (WVP).
15. Calculation and Analysis of Results
15.1 Blank Specimen—The blank specimen is used to compensate for variability in test conditions due to temperature and/or
barometric pressure fluctuations. The test specimen recorded weights are adjusted by calculating the weight change of the blank
specimen from the beginning of the test to time of weighing. This adjustment is made by subtracting the weight change of the blank
specimen from the weight change of the test dish at the time of weighing of both. This permits earlier recognition of steady state
conditions.
15.2 A mathematical least squares regression analysis of the weight, modified by the blank specimen, as a function of time will
give the water vapor transmission rate.
15.2.1 For materials with very low water vapor permeance, this method is used to determine the results after 30 to 60 days when
using an analytical balance, with a sensitivity of ≈1 mg, even if the weight change does not meet the 100 times the sensitivity
requirement of 6.3. These specimens must be clearly identified in the report. Reference Appendix X4 for discussion regarding
measurements of near zero or zero water vapor permeance (WVP) materials.
15.3 Calculate the water vapor transmission rate, WVTR, and WVP as follows:
15.3.1 Water Vapor Transmission Rate:
G G / t
~ !
WVTR 5 5 (1)
t·A A
where:
In inch-pound units:
G = steady state weight change, grains (from the straight line),
t = time during which G occurred, h,
G/t = slope of the straight line, grains/h,
A = test area (cup mouth area), ft , and
WVTR = water vapor transmission rate, grains/h·ft .
In SI units:
G = steady state weight change (from the straight line), g,
t = time, h,
G/t = slope of the straight line, g/h,
A = test area (cup mouth area), m , and
WVTR = water vapor transmission rate, g/h·m .
15.3.2 Water Vapor Permeance:
WVTR WVTR
WVP 5 5 (2)
Δp S· R 2 R
~ !
1 2
where:
In inch-pound units:
Δp = vapor pressure difference, in. Hg,
S = saturation vapor pressure at test temperature, in. Hg,
E96/E96M − 24
FIG. 1 Referenced Corrections in 15.6
R = relative humidity at the source expressed as a fraction (the test chamber for desiccant method; in the dish for water
method), and
R = relative humidity at the vapor sink expressed as a fraction.
In SI units:
Δp = vapor pressure difference, Pa,
S = saturation vapor pressure at test temperature, Pa,
R = relative humidity at the source expressed as a fraction (the test chamber for desiccant method; in the dish for water
method), and
R = relative humidity at the vapor sink expressed as a fraction.
15.4 In the controlled room or chamber the relative humidity and temperature are the average of values actually measured during
the test. In the dish the relative humidity is nominally 0 % for the desiccant and 100 % for the water. These values are usually
-1 -1 -2
within 3 % relative humidity of the actual relative humidity for specimens below 4 perms [230 ng·Pa ·s ·m ] when the required
conditions are maintained (no more than 10 % moisture in CaCl and no more than 1 in. [25 mm] air space above water).
15.5 Perform the calculation of permeability only when the test specimen is homogeneous and not less than ⁄2 in. [12.5 mm] thick,
as follows:
Permeability 5 WVP·thickness (3)
15.6 Corrections—It is important that all applicable corrections be made to all measurements that result in WVP value more than
-1 -1 -2
2 perms [114 ng·Pameasurements, with the exception of still air and surface resistance corrections ·s ·m ]. Corrections for
-1 -1 -2
materials with WVP value measurements of 2 perms [114 ng·Pa ·s ·m ] or less less, which are insignificant and need not be
applied (2). The procedures for making various corrections, as summarized below, Background and discussion of the various
corrections are found in the literature (2, 3, 4, 5, 6).Fig. 1 contains a diagram of the corrections referenced in this section.
15.6.1 Corrections for Resistance due to Still Air and Specimen Surface:
15.6.1.1 When the material is highly permeable, these corrections become more significant. With known thickness of the still air
layer in the cup, the corresponding vapor resistance is calculated using the following equations (Eq 4 and Eq 5) for permeability.
6 1.81
5.3081 ×10 P T
o
δ 5 · · (4)
S D S D
a
R T P 491.67
v
where:
δ = permeability of still air, Perm in.,
a
T = temperature, °R,
P = ambient barometric pressure, in Hg,
P = standard barometric pressure, that is, 29.92 in. Hg, and
o
-1 -1
R = ideal gas constant for water, that is, 85.780 ft·lbf·lb ·°R .
v
25 1.81
2.306 ×10 ·P T
o
δ 5 (5)
S D
a
R ·T·P 273.15
v
where:
-1 -1 -1
δ = permeability of still air, kg·m ·s ·Pa ,
a
E96/E96M − 24
T = temperature, K,
P = ambient barometric pressure, Pa,
P = standard barometric pressure, that is, 101325 Pa, and
o
-1 -1
R = ideal gas constant for water, that is, 461.5 J·K ·kg .
v
15.6.1.2 In the absence of any measured data, the surface resistances (that is, inside and outside surfaces of the specimen) is
approximated by using Lewis’ relation (5). For cup methods that follow this standard, the total surface resistance (Hansen and Lund
-3 2 -1 -5 2 -1
(6)) is ≈ 2.29 × 10 h·ft ·in.Hg·grains (4 × 10 Pa·s·m ·ng ).
15.6.2 Edge Mask Correction—The following equation (Joy and Wilson (1)) is to be used to correct the excess effect due to edge
masking during specimen preparation:
400·t 2
Percent excess WVT 5 log (6)
e 2·π·b
S D
π·S 2~ !
11e t
where:
In inch-pound units:
t = specimen thickness, ft,
b = width of masked edge, ft, and
S = four times the test area divided by the perimeter, ft.
where:
In SI units:
t = specimen thickness, m,
b = width of masked edge, m, and
S = four times the test area divided by the perimeter, m.
15.6.2.1 If the cup assembly includes any edge masking this correction shall be made.
15.7 Example calculations are presented in Appendix X5.
16. Report
16.1 The report shall include the following:
16.1.1 Identification of the material tested, including product thickness for homogeneous materials tested for permeability.
16.1.2 The side of each specimen on which the higher humidity was applied. The surfaces shall be clearly identified when there
is a difference between the two sides. The orientation of the specimen shall be described.
16.1.3 Method used (desiccant or water).
16.1.4 Average test temperature.
16.1.5 Average relative humidity in the test chamber.
16.1.6 WVTR, WVP, and permeability when calculated, of each specimen in appropriate units.
16.1.7 The average WVTR, WVP, and permeability of all specimens tested.
16.1.7.1 When reporting in Inch-Pound units, for results 1.0 perm and greater, report the results to two significant figures. For
results less than 1.0 perm report the result to two decimals.
-2 -1 -1
16.1.7.2 When reporting in SI units, for results 57.2 ng·m ·s ·Pa and greater, round to the nearest whole unit. For perm results
-2 -1 -1
less than 57.2 ng·m ·s ·Pa round to one decimal place.
16.1.8 Portion of the plot indicating the section of the curve used to calculate WVP
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TABLE 2 Results on Precision from Interlaboratory Testing
For Desiccant Method at 23°C Repeatability Reproducibility
Mean
Thickness s CV LSD s CV LSD
Material Permeance
A -2 -1 -1 B -2 -1 -1 B -2 -1 -1 B -2 -1 -1 B
(mm) (ng·m ·s ·Pa ) (%) (ng·m ·s ·Pa ) (ng·m ·s ·Pa ) (%) (ng·m ·s ·Pa )
-2 -1 -1 B
(ng·m ·s ·Pa )
A 0.0254 34.7 0.95 2.7 2.7 5.6 16.2 15.9
B 0.1397 0.74 0.16 21.7 0.46 0.31 42.6 0.92
C 12.7 3.51 0.25 7.2 0.69 1.06 30.2 2.8
D 25.4 44.8 1.5 3.3 4.2 3.5 7.8 10.0
E 0.3556 2.64 0.13 5.0 0.40 0.31 11.7 0.86
For Water Method at 23°C Repeatability Reproducibility
Mean
Thickness s CV LSD s CV LSD
Material Permeance
A -2 -1 -1 B -2 -1 -1 B -2 -1 -1 B -2 -1 -1 B
(mm) (ng·m ·s ·Pa ) (%) (ng·m ·s ·Pa ) (ng·m ·s ·Pa ) (%) (ng·m ·s ·Pa )
-2 -1 -1 B
(ng·m ·s ·Pa )
A 0.0254 40.91 0.77 1.9 2.2 8.9 21.8 25.2
B 0.1397 0.90 0.13 14.0 0.35 0.12 13.4 0.34
C 12.7 5.55 0.31 5.7 0.92 1.1 20.1 3.1
D 25.4 59.5 1.1 1.8 3.1 12.4 20.9 35.5
E 0.3556 3.40 0.19 5.7 0.57 0.47 13.8 1.3
A
1 in. = 25.4 mm
B -2 -1 -1
1 perm (inch-pound) = 57.2 ng·m ·s ·Pa
Legend:
s = standard deviation
CV = percent coefficient of variation (s × 100/ Mean)
LSD = least significant difference between two individual test results based on a 95 % confidence level = 2=2s
NOTE 1—Material B was Teflon PTFE fluorocarbon resin brand of tetrafluoroethylene. It was extremely difficult to provide a seal to this sample, which
accounts for the poor repeatability.
16.1.9 Description of cup and type or composition of sealant.
16.1.10 Corrections applied, if any.
17. Precision and Bias
17.1 Precision—Table 2 is based on interlaboratory tests conducted in 1988 and 1991. In 1988 four materials (A, B, C, D) were
tested using the desiccant method and the water method in triplicate. Fifteen laboratories contributed data, with full results secured
from four laboratories. In 1991 ten laboratories contributed data for material E, using triplicate specimens, again using both the
desiccant method and the water method. Tables 3 and 4 are based on another interlaboratory test conducted in 1995–96. (7) One
material at a nominal thickness of 1 in. (25 mm) was tested by ten participating laboratories. Results from only nine laboratories
were used in the analyses because of the presence of severe outliers (see Practice E691) in the observation of tenth laboratory.
17.1.1 Test results were analyzed using Practice E691.
17.2 Additional precision data and analysis for this test method is based on an interlaboratory study (#512) conducted in 2010.
Six laboratories participated in this study, analyzing four different extremely low WVP materials. Procedure A, desiccant method
at 73°F/50 % RH, was used. Each “test result” reported represents an individual determination, and all participants reported three
replicate test results for every material. Practice E691 was followed for the design and analysis of the data; the details are given
in ASTM Research Report No. C16-1040.
17.2.1 Repeatability limit (r)—Two test results obtained within one laboratory shall be judged not equivalent if they differ by more
than the “r” value for that material; “r” is the interval representing the critical difference between two test results for the same
material, obtained by the same operator using the same equipment on the same day in the same laboratory.
17.2.1.1 Repeatability limits are listed in Table 5.
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:C16-1014. Contact ASTM Customer
Service at [e-mail].
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:C16-1040. Contact ASTM Customer
Service at [e-mail].
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TABLE 3 Results on Precision from Interlaboratory Testing—Dry Cup Measurements on Expanded Polystyrene
-1 -1 -1 A
Permeability (ng·m ·s ·Pa )
Lab x¯ s d h k
Spec #1 Spec #2 Spec #3
1 2.54 2.46 2.21 2.40 1.72E-01 -7.01E-01 -1.50 1.06
2 2.65 2.87 2.68 2.73 1.19E-01 -3.71E-01 -0.79 0.73
3 3.79 3.49 3.65 3.64 1.50E-01 5.39E-01 1.15 0.92
4 2.77 2.73 2.69 2.73 4.00E-02 -3.74E-01 -0.80 0.25
5 2.67 2.66 2.79 2.71 7.23E-02 -3.98E-01 -0.85 0.44
6 3.26 3.38 3.29 3.31 6.24E-02 2.06E-01 0.44 0.38
7 3.05 3.72 3.33 3.37 3.37E-01 2.62E-01 0.56 2.07
8 3.76 3.53 3.87 3.72 1.73E-01 6.16E-01 1.31 1.07
9 3.24 3.48 3.26 3.33 1.33E-01 2.22E-01 0.47 0.82
=
x s s s
r x¯ R
3.10 1.63E-01 4.69E-01 4.87E-01
A -1 -1 -1
1 perm in. = 1.45 (ng·m ·s ·Pa )
NOTE 1—The average of the cell averages gives the permeability for the round robin material, according to the dry cup measurements, as
-1 -1 -1
3.10 ng·m ·s ·Pa .
-1 -1 -1 -1
NOTE 2—The repeatability standard deviation is 1.6 × 10 ng·m ·s ·Pa .
-1 -1 -1 -1
NOTE 3—The reproducibility standard deviation is 4.9 × 10 ng·m ·s ·Pa .
TABLE 4 Results on Precision from Interlaboratory Testing—Wet Cup Measurements on Expanded Polystyrene
-1 -1 -1 A
Permeability (ng·m ·s ·Pa )
Lab x¯ s d h k
Spec #1 Spec #2 Spec #3
1 2.90 3.14 2.94 2.99 1.29E-01 -3.58E-01 -0.94 0.77
2 3.50 3.46 3.52 3.49 3.06E-02 1.43E-01 0.37 0.18
3 4.23 3.76 3.65 3.88 3.08E-01 5.29E-01 1.39 1.84
5 3.32 3.29 2.97 3.19 1.94E-01 -1.58E-01 -0.41 1.16
6 2.61 2.82 2.80 2.74 1.16E-01 -6.08E-01 -1.59 0.69
7 3.53 3.18 3.41 3.37 1.77E-01 1.92E-02 0.05 1.06
8 3.30 3.42 3.29 3.34 7.23E-02 -1.42E-02 -0.04 0.43
9 3.75 3.97 3.67 3.80 1.55E-01 4.46E-01 1.17 0.93
=
x s s s
r x¯ R
3.35 1.67E-01 3.82E-01 4.06E-01
A -1 -1 -1
1 perm in. = 1.45 ng·m ·s ·Pa
Legend:
x¯ = Cell average or the average from one laboratory
s = Cell standard deviation, or the standard deviation for one laboratory
=
x = Average of the Cell averages
=
d = Cell deviation or the difference (x¯ − x)
s = Repeatability standard deviation (within a laboratory)
r
s = Reproducibility standard deviation (between the laboratories)
R
h = the between-laboratory consistency statistic
k = the within-laboratory consistency statistic
NOTE 1—The average of the cell averages gives the permeability for the round robin material, according to the wet cup measurements,
-1 -1 -1
as 3.35 ng·m ·s ·Pa .
-01 -1 -1 -1
NOTE 2—The repeatability standard deviation is 1.7 × 10 ng·m ·s ·Pa .
-01 -1 -1 -1
NOTE 3—The reproducibility standard deviation is 4.1 × 10 ng·m ·s ·Pa .
17.2.2 Reproducibility limit (R)—Two test results shall be judged not equivalent if they differ by more than the “R” value for that
material; “R” is the interval representing the critical difference between two test results for the same material, obtained by different
operators using different equipment in different laboratories.
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TABLE 5 Water Vapor Transmission (perms) ILS #512
A
Material Average Repeatability Standard Reproducibility Standard Repeatability Limit Reproducibility Limit
Deviation Deviation
x¯ s s r R
r R
A 0.00877 0.00166 0.00336 0.00465 0.00940
B 0.00843 0.01067 0.01067 0.02988 0.02988
C 0.02028 0.01698 0.01698 0.04756 0.04756
D 0.00567 0.00938 0.00967 0.02626 0.02706
A
The average of the laboratories’ calculated averages
17.2.2.1 Reproducibility limits are listed in Table 5.
17.2.3 The above terms (repeatability limit and reproducibility limit) are used as specified in Practice E177.
17.2.4 Any judgment in accordance with statements 16.2.1 and 16.2.2 would have an approximate 95% probability of being
correct.
17.3 The precision statement was determined through statistical examination of 72 test results, submitted by six laboratories, for
four materials. The four materials were described as:
Material A: 6 mil high barrier PVdC-based film
Material B: 10 mil high barrier PVdC-based film
Material C: 15 mil high barrier HDPE-based film
Material D: PET film/1 mil aluminum foil/PET film lamination
17.4 To judge the equivalency of two test results, choose the material that is closest in characteristics to the test material.
17.5 Using information from this ILS, Appendix section X3 discusses the testing of extremely low WVP materials.
17.6 An additional interlaboratory study employing very low WVP materials, ILS no. 607, was conducted by committee F02 in
2012.
18. Keywords
18.1 desiccant method; perm; permeability; perm-inch; steady-state; water method; water vapor permeance (WVP); water vapor
transmission rate (WVTR)
APPENDIXES
(Nonmandatory Information)
X1. COMMON TEST CONDITIONS
X1.1 Commonly used test conditions are:
X1.1.1 Procedure A—Desiccant Method at 73.4°F [23°C], 50% RH.
X1.1.2 Procedure B—Water Method at 73.4°F [23°C], 50% RH.
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:C16-1045. Contact ASTM Customer
Service at [e-mail].
E96/E96M − 24
X1.1.3 Procedure BW—Inverted Water Method at 73.4°F [23°C], 50% RH.
X1.1.4 Procedure C—Desiccant Method at 90°F [32.2°C], 50% RH.
X1.1.5 Procedure D—Water Method at 90°F [32.2°C], 50% RH.
X1.1.6 Procedure E—Desiccant Method at 100°F [37.8°C], 90% RH.
X1.2 Per test method instructions, unless otherwise prescribed by regulation, specification, ASTM standard, or other governing
document, select test conditions similar to those to which the material will be exposed to actual use.
X2. CUP DESIGN AND SEALING METHODS
X2.1 An ideal sealing material has the following properties:
X2.1.1 Impermeability to water in either vapor or liquid form.
X2.1.2 No gain or loss of weight from or to the environment (evaporation, oxidation, hygroscopicity, and water solubility being
undesirable).
X2.1.3 Good adhesion to any specimen and to the dish (even when wet).
X2.1.4 Complete conformity to a rough surface.
X2.1.5 Compatibility with the specimen and no excessive penetration into it.
X2.1.6 Ability to withstand normal handling without cracking or separating from dish or specimen once solidified.
X2.1.7 Workable viscosity and melting point for handling when making seals. Caution shall be taken so that the molten sealant
does not damage the specimen.
-2 -1 -1
X2.1.8 Molten asphalt or wax is required for WVP tests below 4 perms [240 ng·m ·s ·Pa ].
X2.1.9 A test to determine sealant behavior is done using an impervious specimen (metal) normally sealed to the dish and so
tested.
E96/E96M − 24
X2.2 The following materials are commonly used molten sealants:
X2.2.1 Asphalt, meeting the requirements of Specification D449/D449M, Type III.
X2.2.2 Beeswax and rosin (equal weights).
X2.2.3 Microcrystalline wax (60 %), mixed with refined crystalline paraffin wax (40 %).
X2.3 For thick materials with porous edges, it is necessary to guard the edges to prevent penetration of the sealant into the
specimen. See Fig. X2.1.
X2.3.1 Materials:
X2.3.1.1 Aluminum foil, 0.005 in. [0.125 mm] minimum thickness.
X2.3.1.2 Tape, meeting the requirements of Specification D2301, vinyl chloride plastic pressure-sensitive, electrical insulating
tape.
X2.3.1.3 Cement, contact bond, preferably rubber base.
X2.3.2 Procedure:
2 2
X2.3.2.1 Step 1—Seal aluminum foil around edges of specimen, leaving a 100-in. [0.0654-m ] exposed test area on each side.
Use contact bond cement as directed by the manufacturer.
X2.3.2.2 Step 2—Spread sealant on inside of rim and ledge. Place desiccant (dry), or water and surge control material (wet) in
pan. Press specimen in place. Avoid squeezing compound into the test area.
X2.3.2.3 Step 3—Coat outside of rim and bottom of ledge with contact bond cement, and place foil strips from edge of template,
around rim, and bottom of ledge.
X2.4 A method of using hot asphalt, as applied to a 10-in. [254-mm] square-mouth dish with ledge and rim, is as follows:
X2.4.1 Apparatus:
3 3 3
X2.4.1.1 Template—A square frame of brass or steel, ⁄16 in. [5 mm] thick and ⁄4 in. [19 mm] deep. The ⁄16-in. [5-mm] thickness
is tapered to zero at the bottom of the frame where it will touch the test specimen and maintain a 10-in. [254-mm] square test area.
E96/E96M − 24
X2.4.1.2 Sealant—Asphalt (see X2.3.1 used at the proper pouring consistency of 375 to 450°F [179 to 232°C].
X2.4.1.3 Melting Pot, for the asphalt, electrically heated, with one dimension greater than 11 ⁄8 in. [289 mm].
X2.4.1.4 Small Ladle, for pouring.
X2.4.2 Procedure—Mark the 11 ⁄8-in. [289-mm] square specimen with a line at an equal distance from each edge, so that the area
enclosed by the lines is as nearly as possible a 10-in. [254-mm] square. The template may be used for marking. Dip each edge
of the specimen in molten asphalt up to the line, so that the test area is defined and all edges are coated with a heavy layer of
asphalt. Place the specimen over the pan containing water or desiccant. Lightly oil the template or coat with petroleum jelly on
its outer side, and place on the specimen. Pour molten asphalt into the space between the template and the rim of the pan. After
the asphalt has cooled for a few minutes, the template should be easily remova
...