ASTM E1423-21

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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: E1423 − 14 E1423 − 21
Standard Practice for
Determining Steady State Thermal Transmittance of
Fenestration Systems
This standard is issued under the fixed designation E1423; 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.
1. Scope
1.1 This practice covers standard test specimen sizes and test conditions as well as the calculation and presentation of the thermal
transmittance and conductance data measured in accordance with Test Method C1199. The standard sizes and conditions are to be
used for fenestration product comparison purposes. The specifier may choose other sizes and conditions for product development
or research purposes.
1.2 This practice deals with the determination of the thermal properties of a fenestration system installed vertically without the
influences of solar heat gain and air leakage effects.
NOTE 1—To determine air leakage effects of fenestration systems, Test Method E283E283/E283M or E1424 should be referenced.
NOTE 2—See Appendix Appendix X1 regarding garage doors and rolling doors.
1.3 This practice specifies the procedure for determining the standardized thermal transmittance of a fenestration test specimen
using specified values of the room-side and weather-side surface heat transfer coefficients, h and h , respectively.
h c
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.after
SI units are provided for information only and are not considered standard.
1.5 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 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
C1199 Test Method for Measuring the Steady-State Thermal Transmittance of Fenestration Systems Using Hot Box Methods
This guidepractice is under the jurisdiction of ASTM Committee E06 on Performance of Buildings and is the direct responsibility of Subcommittee E06.51 on
Performance of Windows, Doors, Skylights and Curtain Walls.
Current edition approved April 1, 2014Aug. 1, 2021. Published May 2014August 2021. Originally approved in 1991. Last previous edition approved in 20062014 as
E1423 – 06.E1423 – 14. DOI: 10.1520/E1423-14.10.1520/E1423-21.
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’sstandard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1423 − 21
C1363 Test Method for Thermal Performance of Building Materials and Envelope Assemblies by Means of a Hot Box Apparatus
E283E283/E283M Test Method for Determining Rate of Air Leakage Through Exterior Windows, Skylights, Curtain Walls, and
Doors Under Specified Pressure Differences Across the Specimen
E631 Terminology of Building Constructions
E783 Test Method for Field Measurement of Air Leakage Through Installed Exterior Windows and Doors
E1424 Test Method for Determining the Rate of Air Leakage Through Exterior Windows, Curtain Walls, and Doors Under
Specified Pressure and Temperature Differences Across the Specimen
2.2 Other Documents:
ANSI/DASMA 105-1998105 Test Method for Thermal Transmittance and Air Infiltration of Garage Doors and Rolling Doors
NFRC 102-2002102 Procedure for Measuring the Steady-State Thermal Transmittance of Fenestration Systems
3. Terminology
3.1 Definitions—Definitions and terms are in accordance with Terminology E631 and C168, from which the following have
been selected and modified to apply specifically to fenestration systems. See Fig. 1 and Fig. 2 for variable identification. (For
further information on definitions and procedures, see Appendix X2 or Test Method C1199.)
3.1.1 surface heat transfer coeffıcient, h (sometimes called surface conductance or film coeffıcient)—the time rate of heat flow
from a unit area of a surface to its surroundings, induced by a unit temperature difference between the surface and the environment.
Subscripts are used to differentiate between room-side ( oror ) and weather-side ( or or ) surface heat transfer coefficients (see
1 h 2 c
Figs. 1 and 2).
3.1.2 thermal transmittance U (sometimes called overall coeffıcient of heat transfer)—the heat transfer in unit time through unit
s
area of a test specimen and its boundary air films, induced by unit temperature difference between the environments on each side.
3.2 Definitions of Terms Specific to This Standard:
FIG. 1 Window Mounted Flush with Climate Side of Surround Panel
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Available from National Fenestration Rating Council (NFRC), 6305 Ivy Lane,Ln., Suite 140, Greenbelt, MD 20770, http://www.nfrc.org.
E1423 − 21
FIG. 2 Door Mounted Flush with Climate Side of Surround Panel
3.2.1 standardized thermal transmittance, U —the heat transfer in unit time through unit area of a specimen (using standardized
ST
surface heat transfer coefficients) induced by unit temperature difference between the environments on each side. Test Method
C1199
3.2.2 surround panel (sometimes called the mask, mask wall,or homogeneous wall)—a panel with a homogeneous core that may
be faced with paint, plywood, or plastic in which the test specimen is mounted.
3.2.3 test specimen—the fenestration system or product being tested.
3.2.4 thermal resistance, R —the temperature difference between the environments on the two sides of a body or assembly when
S
a unit heat flow per unit time per unit area is established through the body or assembly under steady-state conditions. It is defined
as follows:
R 5 (1)
S
U
S
where:
2 2
R = overall thermal resistance of specimen (air to air under test conditions), (m ·K)/W ((ft ·hr·°F)/Btu).
S
3.3 Symbols—The symbols, terms, and units used in this test method are as follows:
A total heat transfer surface area of test specimen on weather side, m
c
A total heat transfer surface area of test specimen on room side, m
h
A projected area of test specimen, (same as open area in surround panel), m
s
E1423 − 21
h surface heat transfer coefficient, weather side, W/(m ·K)
c
h surface heat transfer coefficient, room side, W/(m ·K)
h
h surface heat transfer coefficient, combined room and weather side, W/(m ·K)
h+c
h standardized surface heat transfer coefficient, weather side, W/(m ·K)
STc
h standardized surface heat transfer coefficient, room side, W/(m ·K)
STh
R overall thermal resistance of test specimen (air to air under test conditions), (m ·K)/W
S
t average temperature of weather side air, °C
c
t average temperature of room side air, °C
h
t average temperature of test specimen, room side surface, K or °C
t average temperature of test specimen, weather side surface, K or °C
U thermal transmittance of test specimen (air to air under test conditions), W/(m ·K)
S
U standardized thermal transmittance of test specimen, W/(m ·K)
ST
4. Significance and Use
4.1 This practice details the test specimen sizes and test conditions, namely, the room-side and weather-side air temperatures, and
the surface heat transfer coefficients for both sides of the test specimen, when testing fenestration products in accordance with Test
Method C1199.
4.2 The thermal transmittance and conductance of a specimen are affected by its size and three-dimensional geometry. Tests should
therefore be conducted using the specimen sizes recommended in 5.1. Should the specimen size differ from those given in 5.1, the
actual size shall be reported in the test report.
4.3 Many factors can affect the thermal performance of a fenestration system, including deflections of sealed glazing units. Care
should be exercised to maintain the original physical condition of the fenestration system and while installing it in the surround
panel.
4.4 The thermal transmittance and conductance results obtained do not, and are not intended, to reflect performances expected
from field installations since they do not account for solar radiation and air leakage effects. The thermal transmittance and
conductance results are taken from specified laboratory conditions and are to be used only for fenestration product comparisons
and as input to thermal performance analyses that also include solar and air leakage effects.
5. Test Specimen
5.1 Specimen Sizes—The specimen sizes given in Table 1 for different types of fenestration systems shall be used when testing
fenestration products. For test specimens not manufactured at the exact sizes given in Table 1, choose the product with dimensions
that produces the smallest value of deviation, D, calculated by Eq 2. For non-rectangular products, choose the product with an area
closest to the area of the product in Table 1.
2 2
D 5= W 2 W 1 H 2 H (2)
@~ ! ~ ! #
p m p m
where:
D = deviation, mm (in.)
W , H = width and height of production size, mm (in.)
p p
W , H = width and height of model size, mm (in.)
m m
6. Test Conditions
6.1 General—A single set of test conditions does not necessarily define the thermal characteristics of a fenestration system.
However, a single set of test conditions is specified to permit comparison of the thermal transmittance of different fenestration
products. Thermal transmittance values obtained under this set of test conditions have been shown to be valid for the range of
weather conditions typical of the North American climate [weather-side temperatures between 4343 °C and −30°C (110−30 °C
(110 °F and −22°F)−22 °F) and wind speeds up to 6.7 m/s (15 mph)].
6.2 Test Conditions for U-Values for Comparison Purposes—The test specimen shall be tested in accordance with Test Method
C1199. For comparison purposes, the following set of conditions shall be used (see Fig. 1):
t 5 21.0°C60.3°C 69.8°F60.5°F (3)
~ !
h
E1423 − 21
A
TABLE 1 Specimen Size Dimensions
B
Window Type Configuration Test Specimen Model Size, mm. (in.)
I - Window Assemblies
Vertical slider XO or XX 1200 × 1500 (47 × 59)
Horizontal slider XO or XX 1500 × 1200 (59 × 47)
Casement - Double XX 1200 × 1550 (47 × 59)
Casement - Single X 1200 × 1500 (47 × 59)
Projecting (Awning - Double) XX 1500 × 1200 (59 × 47)
Projected (Awning - Single) X 1500 × 600 (59 × 24)
Fixed (includes non-standard shapes) O 1200 × 1500 (47 × 59)
Sloped Glazing OO 2000 × 2000 (79 × 79)
Skylights/roof window X 1200 × 1200 (47 × 47)
Greenhouse/Garden X 1500 × 1200 (59 × 47)
Dual Action X 1200 × 1500 (47 × 59)
Pivoted X 1200 × 1500 (47 × 59)
Sidelites X 600 × 1200 (24 × 79)
Transoms X 1200 × 600 (79 × 24)
Basement O Rated at the appropriate product type
Bay or Bow Rated at the appropriate product type
Composite - Fixed beside operable 1200 × 1500 (47 × 59)
Composite - Fixed over operable 1200 × 1500 (47 × 59)
Hinged Escape X 1500 × 1200 (59 × 47)
Jal/Jal Awning X 1200 × 1500 (47 × 59)
Tropical Awning X 1500 × 1200 (59 × 47)
II - Door Assemblies
B
Swinging door(s) with frame X, OX or XX 1000 × 2000 (39 × 82)
C
or 2000 × 2000 (79 × 79)
Sliding Patio doors with frame XO or XX 2000 × 2000 (79 × 79)
A
Select size type based on the manufacturer’s average standard size and intended use of the product.
B
Typical of a single door.
C
Typical of a double door.
t 5218.0°C60.3°C 20.40°F60.5°F (4)
~ !
c
6.2.1 Room Side (Natural Convection)—The air velocity should be less than 0.3 m/s (60 ft/min). For comparison purposes, the
standard surface heat transfer coefficient measured on the room side of each calibration transfer standard (CTS) during calibration
shall be:
2 2
h 5 7.67 W/m ·K65% ~1.35 Btu/hr·ft ·°F65%! (5)
STc
@Allowed CTS calibration range of:
2 2
7.29 to 8.05 W/m ·K ~1.28 to 1.42 Btu/hr·ft ·°F!]
Since this is the natural convection lower limit of the indoor side overall surface heat transfer coefficient, a 65 % variation in
this value is allowed to accommodate some forced convection due to small room side air circulation fans that provide a more
uniform flow distribution on the indoor side of the CTS.
NOTE 3—Using the 1997 American Society for Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) Fundamentals Handbook (1),
Fenestration Chapter 29, Table 3, the indoor side of the overall combined natural convection, radiation heat transfer coefficient for a 1.22-m (4-ft) high,
2 2
13-mm (0.5-in.)1.22 m (4 ft) high, 13 mm (0.5 in.) wide cavity, double glazed, low emittance glazing unit is 6.98 W/(m ·K) (1.23 Btu/(hr·ft ·°F)). For
a 1.22-m (4-ft) high, 12.7-mm (0.5-in.)1.22 m (4 ft) high, 12.7 mm (0.5 in.) thick high density expanded polystyrene (EPS) foam core CTS with two 4-mm
(0.16-in.)4 mm (0.16 in.) glass faces, the indoor side calculated overall combined natural convection, radiation heat transfer coefficient is 7.02 W/(m ·K)
(1.24 Btu/(hr·ft ·°F)), using the same methods and equations that were used to obtain the ASHRAE Chapter 27, Table 3 results. Rounding off these two
2 2
results gives a nominal standardized surface heat transfer coefficient of 7.0 W/(m ·K) (1.23 Btu/(hr·ft ·°F)), which is the below the limit for natural
convection for this size of CTS.
6.2.2 Weather-side—For comparison purposes, the standard surface heat transfer coefficient measured on the weather side of each
CTS shall be (perpendicular or parallel):
2 2
h 5 30.0 W/m ·K610% ~5.28 Btu/hr·ft ·°F610%! (6)
STc
Allowed CTS calibration range of:
@
2 2
27.0 to 33.0 W/m ·K ~4.75 to 5.81 Btu/hr·ft ·°F!]
Available from American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. (ASHRAE), 1791 Tullie Circle, NE, Atlanta, GA 30329,
http://www.ashrae.org.
E1423 − 21
NOTE 4—Again, referring to the 1997 ASHRAE Fundamentals Handbook (1), Fenestration Chapter 29, the recommended design value for the weather
side overall combined forced convection, radiation heat transfer coefficient for a nominal 24 km/h (15 mph) wind speed is h = 29.0 W/(m ·K) (5.1
c
Btu/(hr·ft ·°F)).
6.2.3 Combined Room and Weather Side—For comparison purposes, the combined standard surface heat transfer coefficient
measured simultaneously on both the room and weather side of each calibration transfer standard (CTS) during calibration shall
be:
2 2
h 5 6.11W/m ·K65% ~1.08 Btu/hr·ft ·°F65%! (7)
h1c
Allowed CTS calibration range of:
@
2 2
5.80 to 6.72 W/m ·K ~1.03 to 1.13 Btu/hr·ft ·°F!]
where:
1 1
h = 1/( ⁄hh + ⁄hc)
h+c
6.2.4 Relative Humidity on the Warm Side—Condensation on the test specimen may influence the temperature measurements of
the surface and shall be avoided. The relative humidity in the metering chamber shall be maintained at or below 15 %.
7. Test Specimen Installation and Instrumentation
7.1 Test Specimen Installation:
7.1.1 Surround Panel—A surround panel shall be provided for installation of the test specimen similar to that shown in Figs. 1
and 2 (see the description in Test Methods C1199 and C1363).
7.1.2 Test Specimen—The fenestration system to be tested shall be installed in the surround panel as shown in Figs. 1 and 2 for
windows and doors. That is, the complete assembly, including all frame elements and operating hardware, shall be in place during
the test. Accessory interior or exterior devices, such as trim or insect screens, shall be removed before testing. The test specimen
shall be mounted so that it is centered in the metering area of the surround panel, and the frame on the cold side of the fenestration
product shall be flush with the weather side of the surround panel. The specimen shall be fixed securely in a plane parallel to the
surround panel surfaces, suitable for any wind loads experienced during testing. The installation shall also allow space to
accommodate all sash or operating members, or both. If the fenestration system does not fill the opening in the surround panel
completely, the space between the surround panel and the fenestration system shall be filled with material of similar thermal
conductance and thickness to that of the surround panel. Perimeter joints between the specimen and the surround panel shall be
sealed on both sides of the wall. In no case shall the tape or caulk cover more than 13 mm (0.50 in.) of the test specimen frame
or edge.
7.1.2.1 Projecting Fenestration Products—Skylights shall be tested in a configuration that is as close to the actual installation as
possible (without integral flashing) with the following conditions:
(1) Curb-mounted skylights that do not have an integral curb attached shall be installed on a nominal 40 mm × 90 mm (1 ⁄2
in. × 3 ⁄2 in.) wood curb made from Douglas fir with no knots.
(2) Skylights shall be tested and reported in the vertical orientation.
(3) Skylights installed inside the rafter opening that have the bottom of the curb touching the finish facing material may extend
the surround panel material to the inside of the curb, or the inside of the finished opening material, whichever comes first. The
surround panel material shall not extend beyond the inside of the skylight curb.
(4) The skylight size listed in Table 1 is based on a center of the rafter to the center of the rafter dimension. Thereby, the
standard size references a median size between a skylight mounted between the rafters and a skylight mounted on top of the rafters.
(5) The U-factor for skylights is based on the projected fenestration area. For skylights installed between the rafters, the outside
dimension of the curb is considered to be the projected area. For skylights installed on top of the rafters, the inside dimension of
the curb is considered to be the projected area.
7.1.3 Air Leakage—All potential air leakage sites on the test specimen, on the surround panel, and at the interface between the
surround panel and the test specimen must be sealed with nonmetallic tape or caulking, or both, as close to the warm side as
possible to minimize or eliminate air leakage between the room side and weather side chambers. The thermal performance can be
affected by the method and placement of the test specimen air seal. Therefore, the test specimen is to be sealed at the warm side
of the test specimen with tape, caulking, or other material of similar surface emissivity (60.1) to that of the adhering surface.
Minimize the use of tape or caulking, as excessive application of these materials can affect the thermal performance of the test
specimen.
E1423 − 21
7.1.3.1 A test specimen with primary and secondary components (such as a storm window) shall be sealed at the warm side of
each component.
7.1.3.2 Weep holes/slots located on the cold side shall be sealed on the cold side.
7.1.3.3 Perimeter joints between the test specimen and the surround panel shall be sealed on both sides of the wall. In no case shall
the tape or caulk cover more than 13 mm (0.50 in.) of the test specimen frame or edge.
7.1.3.4 As an additional precaution to minimize the potential for leakage of air through and around the sealed test specimen, means
mayshall be provided to measure and equalizemonitor the pressure difference across the test specimen. For hot boxes that have
a perpendicular (to the test specimen weather side surface) wind direction, this is accomplished by balancing the the pressure
difference between the weather side total pressure withand the room side static pressure to 0 shall be no greater than 0 Pa 6 10
2 2
Pa (0(0 lbf ⁄ft 6 0.21 Lbf/ftlbf/ft ). For hot boxes that have a parallel (to the test specimen weather side surface) wind direction,
this is accomplished by balancing the the pressure difference between the weather side static pressure withand the room side static
2 2
pressure to 0 shall be no greater than 0 Pa 6 10 Pa (0(0
...