ISO 20492-1:2008

INTERNATIONAL ISO
STANDARD 20492-1
First edition
2008-10-01
Glass in buildings — Insulating glass —
Part 1:
Durability of edge seals by climate tests
Verre dans la construction — Verre isolant —
Partie 1: Résistance des fermetures de côté par essais climatiques

Reference number
©
ISO 2008
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©  ISO 2008
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ii © ISO 2008 – All rights reserved

Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 Symbols and abbreviated terms .2
5 Requirements.3
6 Test methods .4
7 Methods of measurement.14
8 Test report.15
Annex A (normative) Reference method for frost/dew point temperature measurement.18
Annex B (normative) Moisture content measurement according to the 950 °C drying method.20
Annex C (normative) Moisture content measurement by the Karl Fischer method .24
Annex D (normative) Establishing the standard moisture adsorption capacity of desiccants.30
Bibliography.32

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 20492-1 was prepared by Technical Committee ISO/TC 160, Glass in building, Subcommittee SC 1,
Product considerations.
ISO 20492 consists of the following parts, under the general title Glass in buildings — Insulating glass:
⎯ Part 1: Durability of edge seals by climate tests
⎯ Part 2: Chemical fogging tests
⎯ Part 3: Gas concentration and gas leakage
⎯ Part 4: Test methods for the physical attributes of edge seals

iv © ISO 2008 – All rights reserved

Introduction
This part of ISO 20492 consists of a series of procedures for testing the performance of pre-assembled,
permanently sealed insulating glass units or insulating glass units with capillary tubes that have been
intentionally left open. This part of ISO 20492 is intended to help ensure that
⎯ energy savings are made, as the U-value and solar factor (solar-heat gain coefficient) do not change
significantly;
⎯ health is preserved, because sound-reduction and vision do not change significantly;
⎯ safety is provided, because mechanical resistance does not change significantly.
This part of ISO 20492 also covers additional characteristics that are important to the trade and includes the
marking of the product (i.e., the CE marking or markings of other regulatory groups).
It is necessary to consider distinct markets for insulating glass. As within each market there are technical
differences with respect to rebate sizes, vision lines and methods of application, two approaches are included
in this part of ISO 20492. Approach 1 addresses requirements for markets such as North America. Approach 2
addresses requirements for markets such as Europe. Each approach includes separate test methods and
specifications pertaining to minimum requirements for the durability of edge seals as determined by climate
tests.
This part of ISO 20492 does not cover physical requirements of sealed-glass insulating units such as
appearance, thermo-physical properties, heat and light transmission and glass displacement.
The main intended uses of the insulating glass units are installations in buildings and construction, such as in
windows, doors, curtain walling, skylights, roofs and partitions where protection against direct ultraviolet
radiation exists at the edges.
NOTE In cases where there is no protection against direct ultraviolet radiation at the edges, such as structural-
sealant glazing systems, it is still necessary to review factors such as sealant longevity when exposed to long term
ultraviolet light and the structural properties of the sealant for these applications. For more information on the requirements
[1] [2]
for structural-sealant glazing applications, reference can be made to ASTM C1369 , ASTM C1249 and
[3]
ASTM C1265 .
The test methods in this part of ISO 20492 are intended to provide a means for testing the performance of the
sealing system and construction of sealed, insulating glass units.
Sealed, insulating glass units tested in accordance with these method are not intended for long-term
immersion in water.
The options for testing apply only to sealed, insulating glass units that are constructed with glass.
The methods of this part of ISO 20492 might not be applicable in certain cases, such as for insulating glass
units containing spandrel glass or absorptive coatings, as these products can experience field temperatures
that exceed the temperature limitations of the sealant.

INTERNATIONAL STANDARD ISO 20492-1:2008(E)

Glass in buildings — Insulating glass —
Part 1:
Durability of edge seals by climate tests
1 Scope
This part of ISO 20492 establishes two methods for testing the durability of edge seals of insulating glass units
by means of climate tests. The two methods are designated as Approach 1 for markets such as North
America and Approach 2 for markets such as Europe.
This part of ISO 20492 is applicable to pre-assembled, permanently sealed, insulating glass units with one or
two airspaces, and with capillary tubes that are intentionally left open to equalize pressure inside the unit with
the surrounding atmosphere.
This part of ISO 20492 is not applicable to sealed, insulating glass units that contain a spandrel glass coating.
This part of ISO 20492 does not apply to insulating glass (IG) units whose function is decorative only.
2 Normative references
The following reference documents are indispensable for the application of this document. For dated
references, only the cited edition applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 760, Determination of water — Karl Fischer method (General method)
EN 572-1, Glass in building — Basic soda lime silicate glass products — Definitions and general physical and
mechanical properties
EN 572-2, Glass in building — Basic soda lime silicate glass products — Float glass
EN 1279-1, Glass in building — Insulating glass units — Part 1: Generalities, dimensional tolerances and
rules for the system description
ASTM E546, Standard Test Method for Frost Dew Point of Sealed Insulating Glass Units
ASTM E631, Standard Terminology of Building Constructions
ASTM C1036, Standard Specification for Flat Glass
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 1279-1, ASTM E631 and the
following apply.
3.1
standard laboratory conditions
ambient temperature of (23 ± 2) °C and a relative humidity of (50 ± 5) %
3.2
standard moisture-adsorption capacity
capacity of a desiccant material to adsorb a quantity of moisture under controlled limit environmental
conditions
3.3
controlled limit environmental conditions
environment temperature of 10 °C with a dew-point temperature of − 5 °C, giving a relative humidity of 32,8 %
3.4
moisture penetration index
amount of drying capacity consumed after standardized ageing conditions
3.5
accuracy
accuracy of the test method itself within statistical confidence limits of 99 %
3.6
frost/dew point
temperature at which water, organic vapour or other chemicals begin to appear on the interior glass surface of
a sealed, insulating glass unit
3.7
sealed, insulating glass unit
pre-assembled unit consisting of panes of glass that are sealed at the edges and separated by dehydrated
space(s), intended for use in buildings
NOTE The unit is normally used for windows, window walls, picture windows, sliding doors, patio doors, or other
types of fenestration.
4 Symbols and abbreviated terms
For the purposes of this document, the following symbols and abbreviations apply.
I moisture penetration index (can be expressed in decimal or in percentage terms)
I average value of the moisture penetration index, I, based on five measurements
av
m mass of dish plus desiccant plus water adsorbed from 32 % r.h. air
c
m mass of dish plus desiccant plus water initially adsorbed plus water adsorbed when subjected to the
f
climate conditions in the chamber
m mass of dish plus desiccant plus water initially adsorbed
i
M mass of desiccant in mixtures with non-desiccant material
m
m mass of dish plus desiccant plus water adsorbed in equilibrium with a defined reference level of relative
r
humidity of air, or dish plus dried desiccant at high temperatures
M total mass of desiccant when, for the purpose of testing, in a mixture with non-desiccant material, the
t
non-desiccant material is replaced by the same volume of desiccant
m mass of dish when empty, clean and dry
o
2 © ISO 2008 – All rights reserved

R ratio between the masses of desiccant M and M
m t
r.h. relative humidity
T standard moisture adsorption capacity of desiccant
c
T average standard moisture adsorption capacity of desiccant, T , obtained over two measurements
c,av c
T final moisture content of desiccant
f
T uncorrected final moisture content of desiccant
f,u
T initial moisture content of desiccant
i
T average initial moisture content of desiccant, T , obtained over four measurements
i,av i
T uncorrected initial moisture content of desiccant
i,u
Θ temperature of test specimens in test chamber
Θ temperature of the central test specimen in test chamber during constant temperature phase
c
Θ high temperature of the central test specimen in the test chamber during the high humidity/temperature
h
cycling phase
Θ low temperature of the central test specimen in the test chamber during the high humidity/temperature
l
cycling phase
Θ temperature of the central test specimen in the test chamber as the cycle moves between high
s
temperature and low temperature and vice versa
5 Requirements
5.1 Approach 1 — Final frost/dew point
The six test specimens that complete the weather cycle and high-humidity phases of the test in 6.1 shall be
unbroken and without deposits in the airspaces.
The final frost/dew points of all airspaces shall be − 40 °C or colder when measured in accordance with
ASTM E546 or equivalent.
5.2 Approach 2 — Moisture-penetration index
The following values shall be verified on test specimens that are submitted to the climate test.
⎯ The average moisture penetration index, I , over the five test specimens shall not exceed 0,20.
av
⎯ The average moisture penetration index, I , shall be the average over five test specimens. Where a test
av
specimen is broken, a spare test specimen shall be used instead.
NOTE Breakage of the glass in a test specimen does not constitute failure of the test specimen.
⎯ The specimen with the highest moisture penetration index, I, shall have an index value that does not
exceed 0,25.
6 Test methods
6.1 Approach 1
6.1.1 Principle
The frost/dew point of the test specimens is measured and the test specimens are then pre-conditioned for a
specified time in a high-humidity chamber with constant high temperature and high humidity. The test
specimens are then placed in a weather-cycling chamber where temperature, UV and moisture are varied to
specified parameters for a specified number of cycles. After cycling, the test specimens are then returned to
the high-humidity chamber for final conditioning. After final conditioning, the test specimens are evaluated for
the final frost/dew point.
6.1.2 Test specimens
Each test specimen shall measure (355 ± 6) mm wide by (505 ± 6) mm high and shall be composed of two or
three panes of clear, tinted or coated annealed, heat-strengthened, tempered or laminated glass.
The double-glazed test specimens shall be fabricated with at least one pane of clear, uncoated glass. The
triple-glazed test samples shall be fabricated with at least one outer pane of clear, uncoated glass. The other
outer pane shall be fabricated with a glass that allows easy viewing of the frost/dew point.
For double-glazed test specimens, the glass and airspace thicknesses of the test specimens shall be 4 mm
glass with 12 mm airspace, or 5 mm glass with 6 mm airspace.
For triple-glazed test specimens, 4 mm glass with 6 mm airspaces shall be used.
The tolerances of glass thickness shall be in accordance with ASTM C1036.
The airspace tolerances shall be ± 0,8 mm.
A minimum of six double-glazed test specimens shall be submitted for testing.
NOTE 1 However, it is recommended to submit an additional three test specimens in case of breakage.
Triple-glazed, sealed, insulating glass units that have a plastic film as the intermediate airspace divider shall
be acceptable as test specimens.
NOTE 2 The overall sealed, insulating glass unit thickness has some limits. Testing laboratories are usually able to
accommodate 30 mm overall thickness. If thicker sealed, insulating glass units are being tested, it is necessary to contact
the testing laboratory prior to manufacturing to ascertain their capabilities for testing thicker units.
Each test specimen shall be permanently and legibly marked with the designation of the manufacturer, the
date of fabrication (month or quarter and year) and orientation intended in the field (for units constructed with
coated glass).
During all stages of exposure and storage, the test specimens shall be held in a vertical position, with equal
support to all panes and no compression loading.
The selection of sealed, insulating, glass units for testing shall be made at random, except for sealed,
insulating, glass units that have been damaged in transit. Damaged sealed, insulating, glass units shall not be
tested.
Test specimens representing units that are gas-filled shall be fabricated using the same hole-sealing and gas-
filling techniques as those used for manufacturing. For example, if a gas-filling plug is used in manufacturing
the sealed insulating glass unit, then it should also be used in manufacturing the test specimens.
4 © ISO 2008 – All rights reserved

It is not necessary for the submitted test specimens to be filled with gas provided that the gas is classified as
inert. Test specimens that represent sealed, insulating, glass units that are normally filled with an inert gas
during manufacture may be submitted air-filled for testing, as long as the test specimens have been
manufactured with the same techniques as the sealed, insulating, glass units.
The test specimens representing sealed-glass insulating units that include tubes intended to be left open shall
be fabricated with one tube. This tube shall be left open during testing. Test specimens representing sealed,
insulating glass units that include tubes intended to be closed off after shipping shall be fabricated with one
tube. The exterior end of this tube shall be closed prior to testing.
For test specimens representing sealed-glass insulating units that include internal components in the airspace,
the grid formed by these components shall divide the test specimen into nine equal areas (3 × 3; see Figure 1).

Key
1 insulating glass spacer/edge seal
2 internal grids
Figure 1 — Test specimen with internal grids
Measures shall be taken to ensure that there is a clear view of the interior glass surface for the detection of
frost.
NOTE 3 Stains or scum that cannot be removed through cleaning are allowed to remain on the exterior glass surface
of the specimen after the accelerated weathering test. To counteract this, for example, place a mask of plastic tape 50 mm
by 50 mm (or larger) on the central region of both exterior glass surfaces before exposing the test specimen to weathering
conditions. Remove the mask for frost/dew point measurement.
The sealed insulating glass units should be sealed a minimum of 4 weeks from the date of manufacture to
allow for stabilization before testing.
Breakage of only two test specimens as a result of testing shall be permitted throughout the test. If more than
two test specimens are broken during the test, the relevant set of test specimens shall fail the test. Breakage
due to laboratory handling is not considered as test breakage. Units broken due to laboratory handling shall
be replaced and tested from the beginning.
6.1.3 Apparatus
6.1.3.1 High-humidity test chamber, capable of maintaining (60 ± 3) °C and 95 % ± 5 % r.h. The high-
humidity test chamber shall be protected from overheating with protective devices, including one or more
temperature sensors and a continuous temperature-recording device placed in an area in the chamber that
monitors the average temperature inside the chamber.
6.1.3.2 Weather-cycle test chamber, capable of providing the required test conditions specified in
6.1.4.6 to 6.1.4.16. (see Figures 2 to 4). Modifications to the weather-cycle test chamber shall be acceptable
as long as the required test conditions indicated in 6.1.4.2 are met. The chamber shall be protected from
overheating and from overcooling with protective devices. It shall be equipped with one or more temperature
sensors and a continuous temperature-recording device placed in an area that monitors the average
temperature inside the chamber.
Dimensions in millimetres
Key
1 fog or mist spray 6 polystyrene insulation 10 fan motor
2 cooling coil 7 rubber washer 11 air duct
3 fluorescent black light lamp F72T12BL/HO 8 clamping device 12 insulation
4 heating coil 9 test specimen 13 air flow
5 rubber pad
Figure 2 — Typical weather-cycle test chamber (Approach 1)
6 © ISO 2008 – All rights reserved

Dimensions in millimetres
Key
1 fluorescent black light lamps F72T12BL/HO
2 test specimen
Figure 3 — Location of fluorescent black-light lamp relative to the test specimen
NOTE The weather-cycle test apparatus is a modification of the device developed by the Institute for Research in
Construction (IRC) of the National Research Council of Canada. One modification is to expose each test specimen to two
black light lamps.
DANGER — Light from the ultraviolet sources used in this test method is harmful, especially to the
eyes. Appropriate protective measures should be implemented as prescribed by the light source
manufacturer.
6.1.3.3 Ultraviolet light source, consisting of two fluorescent black-light lamps, type F72T12BL/HO, for
each test specimen (see Figure 2). Each lamp shall be replaced when its ultraviolet light intensity falls below
2 2
10 W/m (1 000 µW/cm ) when measured with a long-wave ultraviolet meter that is in direct contact with the
lamp.
6.1.4 Procedure
6.1.4.1 In accordance with ASTM E546 or equivalent, determine the initial frost/dew point of all airspaces
on all test specimens that have been submitted.
6.1.4.2 Place six test specimens in the high-humidity test chamber and arrange the test specimens so
that each specimen has at least 6 mm (1/4 in) clearance all around.
6.1.4.3 Expose the six test specimens in the high-humidity test chamber to a temperature of (60 ± 3) °C
and 95 % ± 5 % r.h.
6.1.4.4 After 14 days, remove the test specimens. Allow the temperature of the test specimens to
equilibrate to (23 ± 3) °C for at least 24 h.
6.1.4.5 Determine the frost/dew point in accordance with ASTM E546 or equivalent. For triple-glazed,
sealed, insulating glass units, determine the frost/dew point for all airspaces. If liquid appears, record the
temperature of its appearance.
6.1.4.6 Place the six test specimens inside the weather-cycle chamber (see Figure 2), taking care that no
stress is induced in the test specimens by the method of fastening. The test specimens shall be oriented in the
weather-cycle chamber so that the glass surface that experiences weather changes in field exposure is the
same that faces the changes in the chamber. The other side of glass surface of each specimen shall be
exposed to room temperature [(23 ± 3) °C].

NOTE This figure represents the ideal cycle described in 6.1.4.2. Any temperature variation within the tolerance zone
shown is acceptable.
Key
X time, expressed in hours
Y1 temperature, expressed in degrees Celsius
Y2 temperature, expressed in degrees Fahrenheit
1 temperature of the chamber
2 exposure to ultraviolet light
3 fog or mist spray
Figure 4 — Schematic drawing of each cycle for weather-cycle test chamber
8 © ISO 2008 – All rights reserved

6.1.4.7 Decrease the temperature inside the weather-cycling chamber from (23 ± 3) °C to (− 29 ± 3) °C
over a period of (60 ± 5) min.
6.1.4.8 Maintain the temperature inside the weather cycling chamber at (− 29 ± 3) °C for (60 ± 5) min.
6.1.4.9 Increase the temperature inside the weather cycling chamber to (23 ± 3) °C over a period of
(60 ± 5) min.
6.1.4.10 Switch on the ultraviolet light source, and over a period of (60 ± 5) min increase the temperature
in the weather cycling chamber to (60 ± 3) °C.
6.1.4.11 At the beginning of this same 60 min period, turn on the water or mist supply to the weather-
cycling chamber. Ensure that the interior of the chamber around the test specimens reaches a minimum of
90 % r.h. within this (60 ± 5) min time period. Turn off the water or mist supply after (60 ± 5) min.
6.1.4.12 Maintain the temperature in the weather-cycling chamber at (60 ± 3) °C, and continue ultraviolet
exposure for a period of (60 ± 5) min.
6.1.4.13 Over a period of (60 ± 5) min, decrease the temperature inside the weather-cycling chamber from
(60 ± 3) °C to room temperature, and continue the test specimens' exposure to the ultraviolet light source. At
the end of this period of (60 ± 5) min, turn off ultraviolet light source.
6.1.4.14 Repeat 6.1.4.7 to 6.1.4.13, 252 times (cycles) over a period of 63 days. Each cycle shall be
6 h ± 5 min (see Figure 4). Remove the test specimens from the weather-cycling chamber and allow the test
specimens to equilibrate to a temperature of (23 ± 3) °C for at least 24 h.
6.1.4.15 Determine the frost/dew point of the test specimens in accordance with ASTM E546 or equivalent.
For triple-glazed, sealed, insulating glass units, determine the frost/dew point for all airspaces. If liquid
appears, record the occurrence.
6.1.4.16 Repeat the steps outlined in 6.1.4.1 to 6.1.4.4, except continue the exposure time indicated in
6.1.4.4 for 28 days instead of 14 days.
6.1.4.17 Determine the final frost/dew point in accordance with ASTM E546 or equivalent. For triple-glazed,
sealed, insulating glass units, determine the frost/dew point for all airspaces. If liquid appears, record the
occurrence. Final frost/dew points shall be determined at least 24 h after the test, but no later than 7 days
after the test.
6.2 Approach 2
6.2.1 Principle
Sets of sealed, insulating glass units are exposed to a climate test. The initial and final dew point and the
initial and final moisture content, as applicable to the specific insulating-glass system being tested, are
measured and the moisture penetration index is calculated.
6.2.2 Apparatus
6.2.2.1 Weather cycling chamber, capable of providing the following required test conditions.
The climate condition in the chamber(s) shall include two parts, with the first part consisting of 56 temperature
cycles of 12 h from − 18 °C to + 53 °C with rates of temperature change of 14 °C/h, followed by a second part
consisting of a constant temperature of + 58 °C for seven weeks. High humidity shall be as described.
The exact specifications of the temperature, humidity and time and their tolerances shall be in accordance
with Figures 5 and 6.
Key
1 56 temperature cycles of 12 h (four weeks' total duration)
2 interval of 2 h to 4 h for moving test pieces, if necessary
3 (1 176 ± 4) h (seven weeks' total duration ) at a constant temperature and a relative humidity of r.h. W 95 %
Θ glass temperature
a
Temperature cycles start with the cooling segment.
b
The two parts of the process, items 1 and 3, may be carried out in a single chamber or in two separate chambers. If
two chambers are used, allow up to 4 h for moving the test specimens from one to the other for the second period.
c
Condensation on test specimen is allowed.
Figure 5 — Overview of climate conditions in chamber of the centrally located test specimen
10 © ISO 2008 – All rights reserved

Key
X time, expressed in hours
Y1 relative humidity, expressed in percent
Y2 temperature, expressed in degrees Celsius
1 relative humidity during temperature cycle
2 relative humidity interrupted during the cold part of the cycle
3 high temperature, Θ , for the centrally located test specimen during the cycle, equal to (53,0 ± 1,0) °C
h
4 low temperature, Θ , for the centrally located test specimen during the cycle, equal to (18,0 ± 1,0) °C
l
5 temperature, Θ , of the centrally located test specimen during the cycle during a temperature change of (14 ± 2) °C/h
s
a
Maximum value of W 95 %.
b
Condensation on test specimen from time to time is allowed.
c
Time intervals: t = 5 h ± 1 min; t = 1 h ± 1 min; t = 5 h ± 1 min; t = 1 h ± 1 min; t = 12 h ± 1 min (total cycle time).
1 2 3 4 5
Figure 6 — Temperature/time and humidity/time relations in cycling stage
The temperatures and temperature tolerances indicated in Figures 5 and 6 shall be valid for the glass of the
unit that is centrally located in the chamber(s). The temperature of that centrally located test specimen shall
be recorded continuously. The relative humidity and air temperature, measured at the most suitable location in
the test chamber(s) shall also be recorded continuously. Any deviations in temperature and in relative
humidity shall be noted in the test report.
The glass temperatures of the other test specimens in the chamber shall be the following:
a) during cycling:
high temperature: (Θ ± 1,0) °C,
h
low temperature: (Θ ± 2,0) °C,
l
changing temperature: (Θ ± 2,0) °C for a rate of temperature change of (14 ± 2) °C/h;
s
b) during constant temperature: (Θ ± 0,5) °C.
c
In order to maximize uniform climate conditions throughout the chamber(s), the distance between the
vertically placed test specimens shall not be less than 15 mm.
6.2.3 Test specimens
A set of sealed, insulating glass units shall consist of 15 test pieces. The test specimens shall be
representative of the system description (see EN 1279-1) and shall consist of two panes of 4 mm clear float
glass manufactured in accordance with EN 572-1 and EN 572-2. The length of each pane shall be
(502 ± 2) mm, and the width (352 ± 2) mm. The gap between the panes shall be 12 mm ± 1 mm, or if a 12 mm
gap cannot be made by the manufacturer, a gap shall be made between the panes that is as near to 12 mm
as possible.
The cavity is preferably air filled, but other gases may also be used.
Construction details of the edges and corners of the test specimens shall correspond to the edge and corner
details in sealed insulating glass units that are supplied to the market.
When the system description contains curved, sealed, insulating glass units with a bending radius u 1 m, the
test pieces shall be curved as described in EN 1279-1.
When the system provides a mixture of desiccant and non-desiccant material that is incapable of resisting
1 000 °C, ISO 760 (Karl Fischer method) shall be used for determining the moisture contents (after verifying
the method for applicability), or the non-desiccant material shall be replaced by the same volume of desiccant.
When the system provides a mixture of desiccant and non-desiccant material that is incapable of withstanding
220 °C, the non-desiccant material shall be replaced by the same volume of desiccant.
6.2.4 Procedure
6.2.4.1 Condition 15 test specimens for a minimum of two weeks at standard laboratory conditions.
6.2.4.2 Measure the initial dew point temperatures of all 15 test specimens in accordance with 7.1.2,
These shall be within a range of ± 10 °C of the maximum dew-point temperature as stated in, or derived from,
information in the manufacturer's product/type description. Dew-point temperature measurements that are
less than − 60 °C shall be considered and recorded as − 60 °C.
6.2.4.3 Rank the test specimens in order of dew-point value, commencing with the highest dew point
value as number 1 and ending with the lowest dew point as number 15. Number units with dew point values
below − 60 °C at random. The sealed, insulating glass units shall be selected in accordance with Table 1.
Table 1 — Designation of insulating glass units in climate tests
Unit number Designated units
7, 8, 9 and 10 Measurement of initial moisture content of desiccant, T
i
4, 5, 6,11 and 12 Climate testing and measurement of final moisture content of desiccant, T
f
2, 3, 13 and 14 Spare units to replace broken units for measurement of final moisture content of desiccant, T ,
f
(after climate testing)
1 and 15 Rejection or measurement of standard moisture adsorption capacity of desiccant, T , as
c
required
6.2.4.4 When starting the climate test, measure the initial moisture content, T , of the desiccant (if any) on
i
the four selected test specimens (see Table 1), in accordance with 7.2. For sealed insulating glass units
without desiccant, determine an equivalent value for initial moisture content, T, in accordance with 7.2.4.
i
using the dew-point temperature from 6.2.4.2.
12 © ISO 2008 – All rights reserved

6.2.4.5 Calculate the average initial moisture content of the desiccant from Equation (1):
T
i,n
T = (1)
1,av ∑
n=1
6.2.4.6 Submit the five selected test specimens (see Table 1) to the climate conditions in accordance
with 6.2.2 and run through the required number of cycles.
NOTE For reasons of time saving and cost aspects of this test, the manufacturer or his agent can decide whether to
submit the spare units to climate conditions from the beginning or only when a unit under climate conditions breaks.
6.2.4.7 After cycling the five test specimens, store them for a minimum of two weeks under standard
laboratory conditions.
Measure the final moisture content, T , of the desiccant (if any) of the five test specimens in accordance with
f
7.2.
6.2.4.8 When the amount of desiccant in the test specimen differs from the sealed insulating glass units
on the market, the final moisture content, T , shall be corrected using Equation (2):
f
Q
desiccant_as_per_system_description
k = (2)
Q
desiccant_unit_in_test
where Q is the amount of desiccant, expressed as either mass (in grams) or as volume (cubic centimetres).
When there are technical reasons that the quantity of desiccant in the test pieces cannot be representative of
the system description, the test may be performed with a different quantity, however test results should be
corrected in order to obtain a true value.
6.2.4.9 For units without desiccant, measure the final dew-point temperatures of the five test specimens
in accordance with 7.1.2. Using these dew-point temperatures, determine an equivalent value for T for each
f
specimen in accordance with 7.2.4.
6.2.4.10 Establish the standard moisture adsorption capacity, T , in accordance with Annex D.
c
6.2.4.11 If a measurement of T is required in Annex D, use the measured values of the two specimens to
c
calculate T from Equation (3):
c,av
T
c,n
T = (3)
c,av ∑
n=1
6.2.4.12 Calculate the moisture penetration index, I, expressed as a fraction or as a percentage, of each of
the five selected or designated test specimens subjected to the climate conditions, as given in Equations (4)
and (5), respectively:
TT−
fi,av
I = (4)
TT−
c,av i,av
TT−
fi,av
I = 100 (5)
TT−
c,av i,av
6.2.4.13 Calculate the average moisture penetration index from Equation (6):
I
n
I = (6)
av ∑
n=1
6.2.4.14 Ensure that the manufacturers of sealed, insulating glass units are aware of the accuracy of the
climate test, using the results from proficiency testing.
NOTE A proficiency test involving 10 laboratories, using Approach 2 in this International Standard, demonstrated that
an accuracy, as defined in 3.5, of ± 0,10 can be achieved when the moisture penetration index, I, is expressed as a ratio,
or ± 10 % absolute can be achieved when I is expressed as a percentage.
7 Methods of measurement
7.1 Measurement of frost/dew point temperature
7.1.1 For Approach 1, the measurement method described in ASTM E546 shall be used to determine the
frost/dew point. Any visible deposit in the airspace shall be observed and recorded.
7.1.2 For Approach 2, any measurement method that is applicable shall be checked against the reference
method in Annex A.
7.2 Measurement of moisture content for Approach 2
7.2.1 General
Use the moisture-content measurement method, of those described in 7.2.2, 7.2.3 or 7.2.4, that corresponds
to the appropriate insulating glass design: bulk desiccant, incorporated in sealant desiccant or no desiccant.
Ensure that moisture content values from different measurement methods are not mixed.
NOTE Although the final moisture penetration index, I, is independent of the method used, the moisture content
values are not.
7.2.2 Moisture content of desiccant in bulk
When the desiccant in the test specimens is loose and not incorporated into a sealant, use the method in
Annex B to measure the initial moisture content, T , or the final moisture content, T .
i f
7.2.3 Moisture content of desiccant incorporated in organic spacer
When the desiccant in the test specimens is incorporated in an organic spacer, use the method in Annex C to
measure the initial moisture content, T , or the final moisture content, T . Prepare and collect four samples of
i f
organic spacer material containing desiccant; one from each side in accordance with C.4.2.3, of each test
specimen.
NOTE The method determines directly the moisture contents, T and T .
i f
7.2.4 Moisture content in insulating glass units without desiccant
When the dew point temperature is measured in accordance with 7.1.2, determine the corresponding water
vapour partial pressure using Table 2. Designate the value obtained as T in the case of initial moisture
i
content, and T in the case of the final moisture content.
f
The value of the water vapour partial pressure obtained for the controlled limit environmental conditions
defined in 3.3 shall be designated T , and is equal to 402 Pa (dew point − 5 °C).
c
14 © ISO 2008 – All rights reserved

Table 2 — The water vapour partial pressure as function of the temperature
Dew point Partial water Dew point Partial water Dew point Partial water Dew point Partial water
vapour vapour vapour vapour
pressure pressure pressure pressure
°C Pa °C Pa °C Pa °C Pa
20 2 335 − 1 563 − 21 94 − 41 11,5
19 2 201 − 2 518 − 22 85 − 42 10,3
18 2 055 − 3 476 − 23 77 − 43 9,12
17 1 935 − 4 438 − 24 70 − 44 8,13
16 1 814 − 5 402 − 25 64 − 45 7,21
15 1 694 − 6 369 − 26 57,4 − 46 6,40
14 1 601 − 7 343 − 27 51,9 − 47 5,68
13 1 494 − 8 310 − 28 46,8 − 48 5,04
12 1 401 − 9 284 − 29 42,3 − 49 4,46
11 1 307 − 10 260 − 30 38,1 − 50 3,94
10 1 227 − 11 238 − 31 34,3 − 51 3,48
9 1 147 − 12 218 − 32 30,9 − 52 3,07
8 1 067 − 13 199 − 33 27,8 − 53 2,70
7 1 001 − 14 182 − 34 25,0 − 54 2,37
6 934 − 15 166 − 35 22,4 − 55 2,09
5 876 − 16 151 − 36 20,1 − 56 1,84
4 814 − 17 138 − 37 18,0 − 57 1,61
3 760 − 18 125 − 38 16,1 − 58 1,41
2 707 − 19 114 − 39 14,4 − 59 1,24
1 656 − 20 104 − 40 12,9 − 60 1,08
0 610
8 Test report
8.1 Approach 1
The test report shall contain the following items:
a) reference to this part of ISO 20492;
b) dimensions of the test specimen (width by height) and overall thickness;
c) type and thickness of glass;
d) glass coatings and surface locations if applicable;
e) airspace thickness;
f) description of the spacer composition(s) and configuration;
g) description of the corner construction, including the type and number of corner keys;
h) desiccant type and quantity, if provided;
i) presence and type of tube, if applicable;
j) presence and composition (if known) of muntin bars;
k) sealant type(s) and dimensions, if provided;
l) manufacturer and manufactured date (month or quarter, if known, and year);
m) date testing was started;
n) glass breakage, if observed;
o) final frost/dew point of each unit after testing according to 6.1.4.3;
p) any visible deposit(s) in the airspace.
8.2 Approach 2
The test report shall evaluate the test in detail and shall include the summary shown in Figure 7:
16 © ISO 2008 – All rights reserved

Name of test house, its address and logo.
o
Summary of report n . Date .
Insulating glass units — Moisture penetration results in accordance with ISO 20492–1, Approach 2
For details, see the test report
Company: Name: .
Address: .
.......................................................................................................................................................
.......................................................................................................................................................
.......................................................................................................................................................
.......................................................................................................................................................
Plant: Name: .
Address: .
.......................................................................................................................................................
.......................................................................................................................................................
.......................................................................................................................................................
.......................................................................................................................................................
System description, file number: .
Product name: .

System conforms: YES NO (Delete whichever is not applicable)
NOTE Comparisons of moisture penetration indices of different insulati
...