ASTM E96/E96M-14

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Designation: E96/E96M − 13 E96/E96M − 14
Standard Test Methods for
Water Vapor Transmission 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 (WVT) of materials through which the passage of
water vapor may be of importance, such as paper, plastic films, other sheet materials, fiberboards, gypsum and plaster products,
wood products, and plastics. The test methods are limited to specimens not over 1 ⁄4 in. [32 mm] in thickness except as provided
in Section 9. Two basic methods, the Desiccant Method and the Water Method, are provided for the measurement of permeance,
and two variations include service conditions with one side wetted and service conditions with low humidity on one side and high
humidity on the other. Agreement should not be expected between results obtained by different methods. The method should be
selected that more nearly approaches the conditions of use.
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard. However, derived results can be 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 problems, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
C168 Terminology Relating to Thermal Insulation
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
D449 Specification for Asphalt Used in Dampproofing and Waterproofing
D2301 Specification for Vinyl Chloride Plastic Pressure-Sensitive Electrical Insulating Tape
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. 1, 2013Oct. 15, 2014. Published December 2013January 2015. Originally approved in 1953. Last previous edition approved in 20122013
as E96– 12.– 13. DOI: 10.1520/E0096_E0096M-13.10.1520/E0096_E0096M-14.
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.
A,B
TABLE 1 Metric Units and Conversion Factors
To Obtain (for the
Multiply by
same test condition)
WVT
2 2
g/h·m 1.43 grains/h·ft
2 2
grains/h·ft 0.697 g/h·m
Permeance
2 7
g/Pa·s·m 1.75 × 10 1 Perm (inch-pound)
−8 2
1 Perm (inch-pound) 5.72 × 10 g/Pa·s·m
Permeability
g/Pa·s·m 6.88 × 10 1 Perm inch
−9
1 Perm inch 1.45 × 10 g/Pa·s·m
A
These units are used in the construction trade. Other units may be used in other
standards.
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 − 14
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.
3.2 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 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 determine the rate of vapor movement through
the specimen from the water to the controlled atmosphere. The vapor pressure difference is nominally the same in both methods
except in the variation, with extremes of humidity on opposite sides.
5. Significance and Use
5.1 The purpose of these tests is to obtain, by means of simple apparatus, reliable values of water vapor transfer through
permeable and semipermeable materials, expressed in suitable units. These values are for use in design, manufacture, and
marketing. A permeance value obtained under one set of test conditions may not indicate the value under a different set of
conditions. For this reason, the test conditions should be selected that most closely approach the conditions of use. While any set
of conditions may be used and those conditions reported, standard conditions that have been useful are shown in Appendix X1.
6. Apparatus
6.1 Test Dish—The test dish shall be of any noncorroding material, impermeable to water or water vapor. It may be of any shape.
Light weight is desirable. A large, shallow dish is preferred, but its size and weight are limited when an analytical balance is chosen
2 2
to detect small weight changes. The mouth of the dish shall be as large as practical and at least 4.65 in. [3000 mm ]. The desiccant
or water area shall be not less than the mouth area except if a grid is used, as provided in 12.1, its effective area shall not exceed
10 % of the mouth area. An external flange or ledge around the mouth, to which the specimen may be attached, is useful when
shrinking or warping occurs. When the specimen area is larger than the mouth area, this overlay upon the ledge is a source of error,
particularly for thick specimens. This overlay material should be masked as described in 10.1 so that the mouth area defines the
test area. The overlay material results in a positive error, indicating excessive water vapor transmission. The magnitude of the error
is a complex function of the thickness, ledge width, mouth area, and possibly the permeability. This error is discussed by Joy and
Wilson (1) (see 13.4.3). This type of error should be limited to about 10 to 12 %. For a thick specimen the ledge should not exceed
3 1
⁄4 in. [19 mm] for a 10-in. [254-mm] or larger mouth (square or circular) or ⁄8 in. [3 mm] for a 5-in. [127-mm] mouth (square
or circular). For a 3-in. [76-mm] mouth (square or circular) the ledge should not exceed 0.11 in. [2.8 mm] wide. An allowable ledge
may be interpolated for intermediate sizes or calculated according to Joy and Wilson.(1) A rim around the ledge (Fig. X2.1) may
be useful. If a rim is provided, it shall be not more than ⁄4 in. [6 mm] higher than the specimen as attached. Different depths may
be used for the Desiccant Method and Water Method, but a ⁄4-in. [19-mm] depth (below the mouth) is satisfactory for either
method.
6.2 Test Chamber—The room or cabinet where the assembled test dishes are to be placed shall have a controlled temperature
(see Note 1) and relative humidity. Some standard test conditions that have been useful are given in Appendix X1. The temperature
chosen shall be determined according to the desired application of the material to be tested (see Appendix X1). The relative
humidity shall be maintained at 50 6 2 %, except where extremes of humidities are desired, when the conditions shall be 100 6
1.8°F [38 6 1°C] and 90 6 2 % relative humidity. Both temperature and relative humidity shall be measured frequently or
preferably recorded continuously. Air shall be continuously circulated throughout the chamber, with a velocity sufficient to
maintain uniform conditions at all test locations. The air velocity over the specimen shall be between 0.066 and 1 ft/s [0.02 and
-1
0.3 m·s ]. Suitable racks shall be provided on which to place the test dishes within the test chamber.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
The minimum acceptable is to perform this measurement each time the sample is weighed.
E96/E96M − 14
NOTE 1—Simple temperature control by heating alone is usually made possible at 90°F [32°C]. However, it is very desirable to enter the controlled
space, and a comfortable temperature is more satisfactory for that arrangement. Temperatures of 73.4°F [23°C] and 80°F [26.7°C] are in use and are
satisfactory for this purpose. With cyclic control, the average test temperature may be obtained from a sensitive thermometer in a mass of dry sand. The
temperature of the chamber walls facing a specimen over water should not be cooler than the water to avoid condensation on the test specimen.
6.3 Balance and Weights—The balance shall be sensitive to a change smaller than 1 % of the weight change during the period
when a steady state is considered to exist. The weights used shall be accurate to 1 % of the weight change during the steady-state
period (Note 2). A light wire sling may be substituted for the usual pan to accommodate a larger and heavier load.
6.4 Thickness-Measuring Gage—The nominal thickness of the specimen shall be determined using a thickness-measuring gage
with an accuracy of 61 % of the reading or 0.0001 in. [0.0025 mm], whichever is greater.
-1 -1 -2
NOTE 2—For example: 1-perm [57 ng·Pa ·s ·m ] specimen 10 in. [254 mm] square at 80°F [26.7°C] passes 8.6 grains or 0.56 g/day. In 18 days of
steady state, the transfer is 10 g. For this usage, the balance must have a sensitivity of 1 % of 10 g or 0.1 g and the weights must be accurate to 0.1 g.
If, however, the balance has a sensitivity of 0.2 g or the weights are no better than 0.2 g, the requirements of this paragraph can be met by continuing
the steady state for 36 days. An analytical balance that is much more sensitive will permit more rapid results on specimens below 1 perm [57
-1 -1 -2
ng·Pa ·s ·m ] when the assembled dish is not excessively heavy.
7. Materials
7.1 Desiccant and Water:
7.1.1 For the Desiccant Method, anhydrous calcium chloride in the form of small lumps that will pass a No. 8 [2.36-mm] sieve,
and free of fines that will pass a No. 30 [600-μm] sieve, shall be used (Note 3). It shall be dried at 400°F [200°C] before use.
NOTE 3—If CaCl will react chemically on the specimen, an adsorbing desiccant such as silica gel, activated at 400°F [200°C], may be used; but the
moisture gain by this desiccant during the test must be limited to 4 %.
7.1.2 For the Water Method, distilled water shall be used in the test dish.
7.2 Sealant—The sealant used for attaching the specimen to the dish, in order to be suitable for this purpose, must be highly
resistant to the passage of water vapor (and water). It must not lose weight to, or gain weight from, the atmosphere in an amount,
over the required period of time, that would affect the test result by more than 2 %. It must not affect the vapor pressure in a
-2 -1 -1
water-filled dish. Molten asphalt or wax is required for permeance tests 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 under test. The
sample shall be of uniform thickness. If the material is of nonsymmetrical construction, the two faces shall be designated by
distinguishing marks (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 sides of a product are
indistinguishable, three specimens shall be tested by the same method. When the sides of a product are different and either side
may face the vapor source, four specimens shall be tested by the same method, two being tested with the vapor flow in each
direction and so reported.
9.2 A slab, produced and used as a laminate (such as a foamed plastic with natural “skins”) may be tested in the thickness of
use. Alternatively, it may be sliced into two or more sheets, each being separately tested and so reported as provided in 9.4,
provided also, that the “overlay upon the cup ledge” (6.1) of any laminate shall not exceed ⁄8 in. [3 mm].
9.3 When the material as used has a pitted or textured surface, the tested thickness shall be that of use. When it is homogeneous,
however, a thinner slice of the slab may be tested as provided in 9.4.
9.4 In either case (9.2 or 9.3), the tested overall thickness, if less than that of use, shall be at least five times the sum of the
-2 -1 -1
maximum pit depths in both its faces, and its tested permeance shall be not greater than 5 perms [≈ 300 ng·m ·s ·Pa ].
9.5 For homogeneous (not laminated) materials with thickness greater than ⁄2 in., the overall nominal thickness of each
specimen shall be measured with an accuracy of 61 % of the reading at the center of each quadrant and the results averaged.
-2 -1 -1
9.6 When testing any material with a permeance less than 0.05 perms [3 ng·m ·s ·
...