Water vapour Transmission Rate
These test methods cover the determination of the
properties of flexible membranes to be used as vapor retarders
in contact with earth under concrete slabs, against walls, or as
ground cover in crawl spaces. The test methods are applicable
primarily to plastic films and other flexible sheets. The materials are not intended to be subjected to sustained hydrostatic
pressure. The procedures simulate conditions to which vapor
retarders may be subjected prior to and during installation, and
in service.
Terminology
Perm :- The time rate of water vapor migration
through a material or a construction of 1 grain/h·ft2
·in. mercury
(Hg) of vapor pressure difference.
Water-Vapor Permeability :- The time rate of water
vapor flow through unit area of unit thickness of a flat material
induced by unit vapor pressure difference between two parallel
specified surfaces under specific temperature and humidity
conditions.
water–vapor permeance :- —The time rate of water
vapor flow through unit area of the known thickness of a flat
material or a construction normal to two specific parallel
surfaces induced by unit vapor pressure difference between the
two surfaces under specific temperature and humidity conditions. While the SI unit is kg/s·m2
·Pa, the practical unit is the
perm.
water-vapor transmission (WVT) :- —the steady water
vapor flow in unit time through unit area of a flat material or a
construction normal to specific parallel surfaces induced by
specific temperatures, pressures, and humidities at each surface. Units in SI are kilogram per second, square metre,
(kg/s·m2
) [inch-pound, grain per hour, square foot, (grain/
h·ft2
)].
Test Specimen
The number and size of test specimens of each material
are specified in each test procedure. Great care is required to
protect the test areas of the specimens against damage or
contamination.
are specified in each test procedure. Great care is required to
protect the test areas of the specimens against damage or
contamination.
Water-Vapor Transmission of Material as Received
Significance and Use :- Since the water-vapor flow rate
through a material in service is significant in order for
comparisons to be made of performance after specific treatments of the material, the water-vapor flow rate of the material
as received is needed as a reference value. The as-received
material is presumed to be representative of the material that is
to be used on the purchaser’s project.
through a material in service is significant in order for
comparisons to be made of performance after specific treatments of the material, the water-vapor flow rate of the material
as received is needed as a reference value. The as-received
material is presumed to be representative of the material that is
to be used on the purchaser’s project.
Apparatus—The apparatus and test facilities are described in Test Methods E96/E96M and F1249.
Procedure:
Make water-vapor transmission tests on at least three
specimens of each material in accordance with Test Methods
E96/E96M or F1249. If the retarder material is coated or
treated on one surface to improve its water-vapor resistance,
make the test with this surface toward the water unless
otherwise specified.
specimens of each material in accordance with Test Methods
E96/E96M or F1249. If the retarder material is coated or
treated on one surface to improve its water-vapor resistance,
make the test with this surface toward the water unless
otherwise specified.
7.3.2 Where wax seals are used with the wet method, it is
good procedure to heat the test dishes uniformly to 45°C
[113°F] or slightly warmer before sealing the test sample to the
dish to avoid having the wax become too viscous for good
sealing.
good procedure to heat the test dishes uniformly to 45°C
[113°F] or slightly warmer before sealing the test sample to the
dish to avoid having the wax become too viscous for good
sealing.
Water-Vapor Transmission after Wetting and Drying
and after Long-Time Soaking
Significance and Use—After water-vapor retarders leave
the factory, they are exposed to many conditions of wetting and
drying and may be subjected to immersion or partial immersion
for various periods. To indicate the potential effect of wetting
and drying and relatively long-time exposure to soaking, the
data from these tests will be compared with those of the
material as received.
the factory, they are exposed to many conditions of wetting and
drying and may be subjected to immersion or partial immersion
for various periods. To indicate the potential effect of wetting
and drying and relatively long-time exposure to soaking, the
data from these tests will be compared with those of the
material as received.
Apparatus:
Controlled-Temperature Vessels, of suitable size for
soaking specimens and equipped with a temperature controller
actuated by a thermostat. The controller shall be of a type that
E154/E154M − 08a (2013)´1
2
will maintain temperature in the vessels between 22 and 24°C
[72 and 75°F]. If space permits, the test chamber used for the
water-vapor transmission tests may be used to hold soaking
pans in place of the thermostatically controlled vessel.
soaking specimens and equipped with a temperature controller
actuated by a thermostat. The controller shall be of a type that
E154/E154M − 08a (2013)´1
2
will maintain temperature in the vessels between 22 and 24°C
[72 and 75°F]. If space permits, the test chamber used for the
water-vapor transmission tests may be used to hold soaking
pans in place of the thermostatically controlled vessel.
Oven or Drying Chamber, for drying test specimens,
thermostatically controlled at a temperature between 60 and
62°C [140 and 144°F].
thermostatically controlled at a temperature between 60 and
62°C [140 and 144°F].
Water-Vapor Transmission Apparatus, as prescribed in
Test Methods E96/E96M and F1249.
8.2.4 Mandrel—A round metal bar or rod 25 mm [1 in.] in
diameter and approximately 460 mm [18 in.] long.
Test Methods E96/E96M and F1249.
8.2.4 Mandrel—A round metal bar or rod 25 mm [1 in.] in
diameter and approximately 460 mm [18 in.] long.
Procedure:
Cut three specimens, 305 by 305 mm [12 by 12 in.] of
the material to be tested.
the material to be tested.
Immerse the specimens in potable water kept at a
temperature between 22 and 24°C [72 and 75°F] for 16 h
(overnight). Then dry the specimens in an oven kept between
60 and 62°C [140 and 144°F] for 8 h. Repeat the wetting and
drying cycle for a total of five cycles (Monday through Friday)
to be followed by immersing the specimens in water over the
weekend (64 h). Repeat the wetting and drying cycle five more
days and immerse the specimens in water for a period of 161⁄2
days (weekend plus two weeks). Dry the specimens between
60 and 62°C [140 and 144°F] and then condition to a constant
weight in the chamber where water-vapor transmission tests
are made.
temperature between 22 and 24°C [72 and 75°F] for 16 h
(overnight). Then dry the specimens in an oven kept between
60 and 62°C [140 and 144°F] for 8 h. Repeat the wetting and
drying cycle for a total of five cycles (Monday through Friday)
to be followed by immersing the specimens in water over the
weekend (64 h). Repeat the wetting and drying cycle five more
days and immerse the specimens in water for a period of 161⁄2
days (weekend plus two weeks). Dry the specimens between
60 and 62°C [140 and 144°F] and then condition to a constant
weight in the chamber where water-vapor transmission tests
are made.
Cut the specimens into halves parallel to the machine
direction (the long direction as taken from the roll or package).
Bend one of the halves of each specimen with one surface up
and the other specimen with the opposite surface up at an angle
of 90° over a 25-mm [1-in.] diameter mandrel in a period of 2
s or less at a temperature between 22 and 24°C [72 and 75°F].
Record evidence of cracking or delamination.
direction (the long direction as taken from the roll or package).
Bend one of the halves of each specimen with one surface up
and the other specimen with the opposite surface up at an angle
of 90° over a 25-mm [1-in.] diameter mandrel in a period of 2
s or less at a temperature between 22 and 24°C [72 and 75°F].
Record evidence of cracking or delamination.
Cut specimens for the water-vapor transmission test so
that the full bent portion is installed in the center of the pan
with the surface that was concave at the time of bending facing
the water. Determine water-vapor transmission in accordance
with Section 7.
that the full bent portion is installed in the center of the pan
with the surface that was concave at the time of bending facing
the water. Determine water-vapor transmission in accordance
with Section 7.
Precision and Bias—The statements regarding precision
and bias in Test Methods E96/E96M and F1249 shall also
apply to this test method.
and bias in Test Methods E96/E96M and F1249 shall also
apply to this test method.