ASTM E779-99
(Test Method)Standard Test Method for Determining Air Leakage Rate by Fan Pressurization
Standard Test Method for Determining Air Leakage Rate by Fan Pressurization
SCOPE
1.1 This test method describes a standardized technique for measuring air-leakage rates through a building envelope under controlled pressurization and de-pressurization.
1.2 This test method is applicable to small temperature differentials and low-wind pressure conditions. For tests conducted in the field, it must be recognized that field conditions may be less than ideal. Nevertheless, strong winds and large indoor-outdoor temperature differentials should be avoided.
1.3 The proper use of this test method requires a knowledge of the principles of air flow and pressure measurements.
1.4 This test method is intended to produce a measure of air tightness of a building envelope. Because of differences between natural load and test conditions, however, such measurements cannot be interpreted as direct measurements of air change rates that would occur under natural conditions.
1.5 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. For specific hazard statements see Section 7.
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Standards Content (Sample)
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Designation: E 779 – 99
Standard Test Method for
Determining Air Leakage Rate by Fan Pressurization
This standard is issued under the fixed designation E 779; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.2 air-leakage graph, n—the graph that shows the rela-
tionship of measured airflow rates to the corresponding mea-
1.1 This test method describes a standardized technique for
sured pressure differences, usually plotted on a log-log scale.
measuring air-leakage rates through a building envelope under
3.1.3 air-leakage rate, n—the volume of air movement/unit
controlled pressurization and de-pressurization.
time across the building envelope.
1.2 This test method is applicable to small temperature
3.1.3.1 Discussion—This movement includes flow through
differentials and low-wind pressure conditions. For tests con-
joints, cracks, and porous surfaces, or a combination thereof.
ducted in the field, it must be recognized that field conditions
The driving force for such an air leakage, in service can be
may be less than ideal. Nevertheless, strong winds and large
either mechanical pressurization and de-pressurization, natural
indoor-outdoor temperature differentials should be avoided.
wind pressures, or air temperature differentials between the
1.3 This test method is intended to produce a measure of air
building interior and the outdoors, or a combination thereof.
tightness of a building envelope. This test method does not
3.1.4 building envelope, n—the boundary or barrier sepa-
measure air leakage rates under normal conditions of weather
rating the interior volume of a building from the outside
and building operation. To measure air-change rate directly, use
environment.
the tracer gas dilution method (see Test Method E 741).
3.1.4.1 Discussion—For the purpose of this test method, the
1.4 This test method is intended for the measurement of the
interior volume is the deliberately conditioned space within a
airtightness of building envelopes of single-zone buildings. For
building, generally not including attics, basements, and at-
the purpose of this test method, many multi-zone buildings can
tached structures, for example, garages, unless such spaces are
be treated as single-zone buildings by opening interior doors or
connected to the heating and air conditioning system, such as
by inducing equal pressures in adjacent zones.
a crawl space plenum.
1.5 This standard does not purport to address all of the
3.1.5 single zone, n—a space in which the pressure differ-
safety concerns, if any, associated with its use. It is the
ences between any two places, differ by no more than 5 % of
responsibility of the user of this standard to establish appro-
the inside to outside pressure difference.
priate safety and health practices and determine the applica-
3.1.5.1 Discussion—A multi-room space that is intercon-
bility of regulatory limitations prior to use. For specific hazard
nected within itself with door-sized openings through any
statements see Section 7.
partitions or floors is likely to satisfy this criterion if the fan
3 3 3
2. Referenced Documents
airflow rate is less than 3 m /s 6 3 10 ft /min).
3.1.6 test pressure difference, n—the measured pressure
2.1 ASTM Standards:
difference across the building envelope, expressed in Pascals
E 741 Test Method for Determining Air Change in a Single
(in. of water or pounds-force/ft or in. of mercury).
Zone by Means of Tracer Gas Dilution.
3.2 Symbols and Units—See Table 1.
E 1258 Test Method for Airflow Calibration of Fan Pressur-
ization Devices
4. Summary of Test Method
3. Terminology 4.1 This test method consists of mechanical pressurization
or de-pressurization of a building and measurements of the
3.1 Definitions of Terms Specific to This Standard:
resulting airflow rates at given indoor-outdoor static pressure
3.1.1 air-change rate, n—air-leakage rate in volume units/h
differences. From the relationship between the airflow rates
divided by the building space volume with identical volume
and pressure differences, the air leakage characteristics of a
units, normally expressed as air changes/h, ACT–.
building envelope can be evaluated.
5. Significance and Use
This test method is under the jurisdiction of ASTM Committee E-6 on
5.1 Air leakage accounts for a significant portion of the
Performance of Buildings and is the direct responsibility of Subcommittee E06.41
on Air Leakage and Ventilation. thermal space conditioning load. In addition, it can affect
Current edition approved June 10, 1999. Published November 1999. Originally
occupant comfort and indoor air quality.
E1
published as E 779–81. Last previous edition E 779–87 (1992) .
5.2 In most commercial or industrial buildings, outdoor air
Annual Book of ASTM Standards, Vol 04.11.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 779
TABLE 1 Symbols and Units
practical. List the height above ground at which wind speed is
Symbol Quantity Unit measured.
E Elevation above sea level m [ft]
3 7. Hazards
Q Measured airflow rate m / s [cfm]
Q Air leakage rate m / s [cfm]
o
7.1 Eye Protection—Glass should not break at the building
3 n n
C Air leakage coefficient m /(s·Pa ) [cfm/ Pa ]
3 3 pressure differences normally applied to the test structure:
r Air density kg / m [lb/ ft ]
T Temperature ° C [°F]
however, for added safety, adequate precautions, such as the
n Pressure exponent . . .
use of eye protection should be taken to protect the personnel.
P Pressure Pa [lb/ft ]
2 7.2 Safety Clothing—Use safety equipment required for
dP Induced pressure difference Pa [lb/ ft ]
dP Reference pressure difference Pa [lb / ft ]
general field work, including safety shoes, and hard hats.
r
μ Dynamic air viscosity kg/(m·s) [lb / (ft·h)]
7.3 Equipment Guards—The air-moving equipment shall
2 2
A Area m [ft ]
have a proper guard or cage to house the fan or blower and to
prevent accidental access to any moving parts of the equip-
ment.
often is introduced by design; however, air leakage can be a
7.4 Noise Protection—Make hearing protection available
significant addition to the designed outdoor airflow. In most
for personnel who must be close to the noise that may be
residential buildings, indoor-outdoor air exchange is attribut-
generated by the fan.
able primarily to air leakage through cracks and construction
7.5 Debris and Fumes—The blower or fan forces a large
joints and can be induced by pressure differences due to
volume of air into or out of a building while operation.
temperature differences, wind, operation of auxiliary fans, for
Exercise care not to damage plants, pets, occupants, or internal
example, kitchen and bathroom exhausts, and the operation of
furnishings due to influx of cold or warm air. Exercise similar
combustion equipment in the building.
cautions against sucking debris or exhaust gases from fire-
5.3 The fan-pressurization method is simpler than tracer gas
places and flues into the interior of the building. Active
measurements and is intended to characterize the air tightness
combustion devices require a properly trained technician to
of the building envelope. It can be used to compare the relative
shut them off or to determine the safety of conducting the test.
air tightness of several similar buildings, to identify the leakage
8. Procedure
sources and rates of leakage from different components of the
same building envelope, and to determine the air leakage
8.1 To create a single zone for this test procedure, all
reduction for individual retrofit measures applied incrementally
interconnecting doors, except for closets, which should be
to an existing building, and to determine ventilation rates when
closed, in the conditioned space should be opened such that a
combined with weather and leak location information.
uniform pressure will be maintained within the conditioned
space to within 610 % of the measured inside/outside pressure
6. Apparatus
difference. Verify this condition by differential pressure mea-
6.1 The following is a general description of the required surements at the highest pressure used in the test. Make these
apparatus. Any arrangement of equipment using the same measurements at the highest and lowest level of the building
principles and capable of performing the test procedure within and on the windward and leeward sides.
the allowable tolerances is permitted. 8.2 HVAC balancing dampers and registers should not be
6.2 Major Components: adjusted. Fireplace and other operable dampers should be
6.2.1 Air-Moving Equipment—A fan, blower, or blower closed unless they are used to pass air to pressurize or
door assembly that is capable of moving air into and out of the de-pressurize the building.
conditioned space at required flow rates under a range of test 8.3 Make general observations of the condition of the
pressure differences. The system shall provide constant airflow building. Take notes on the windows, doors, opaque walls,
at each incremental pressure difference at fixed pressure for the roof, and floor.
period required to obtain readings of airflow rate. Where 8.4 Measure and record the indoor and outdoor tempera-
applicable, the HVAC system of the building may be used in tures at the beginning and the end of the test so that their
place of the fan or blower. average values can be estimated. If the product of the absolute
6.2.2 Pressure-Measuring Device—A manometer or pres- value of the indoor/outdoor air temperature difference multi-
sure indicator to measure pressure difference with an accuracy plied by the building height, gives a result greater than 200
of 65 % of measured pressure.
m°C (1180 ft°F), do not perform the test, because the pressure
6.2.3 Airflow Measuring System—A device to measure difference induced by the stack effect is too large to allow
airflow with an accuracy of 65 % of the measured flow. The
accurate interpretation of the results.
airflow measuring system shall be calibrated in accordance 8.5 If the wind speed is to be part of the measurement
with Test Method E 1258 record, use a wind-measuring device or obtain readings from a
6.2.4 Temperature-Measuring Device—An instrument to nearby weather bureau. Preferred test conditions are wind
measure temperature with an accuracy of 61°C (2°F). speed of 0 to 2 m/s (0 to 4 mph) and an outside temperature
6.2.5 Wind Speed-Measuring Device (Optional)—A device from 5 to 35°C (41 to 95°F).
to give an accuracy within 60.25 m/s (0.56 mph) at 2.5 m/s 8.6 Connect the air duct or blower door assembly to the
(5.6 mph). Perform wind speed measurements at a distance building envelope, using a window, door, or vent opening. Seal
three to five building heights away from the buildings, where or tape openings to avoid leakage at these points.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 779
8.7 If a damper is used to control airflow, it should be in a 8.12 At each pressure difference, measure the airflow rate
fully closed position for the zero flow pressure measurements. and the pressure differences across the envelope. After the fan
8.8 Installing the Envelope Pressure Sensor(s)—Install the and instrumentation have stabilized, the average over at least a
pressure measuring device across the building envelope. It is 10-s interval should be used.
good practice to use more than one location across the building 8.13 For each test, collect data for both pressurization and
envelope for pressure measurement, for example, one across de-pressurization.
each facade. Fig. 1 illustrates preferred locations for exterior 8.14 Determine the elevation of the measurement site, E (m
pressure measurement locations that avoid extremes of exterior or ft), above mean sea level within 100 m (330 ft).
pressures (at exterior corners). A good location avoids exterior
9. Data Analysis and Calculations
corners and complex architectural features and should be close
9.1 Unless the airflow measuring system gives volumetric
to the middle of the exterior wall. In addition, buildings more
flows at the pressure and the temperatures of the air flowing
than three stories, or 7.5 m (25.5 ft), high shall have exterior
through the flowmeter during the test, these readings must be
pressures measured at more than one height on the exterior
converted using information obtained from the manufacturer
walls. The pressures from each location should be averaged,
for the change in calibration with these parameters.
typically using a manifold. Average the pressures over at least
9.2 Convert the readings of the airflow measuring system
a 10-s time period.
(corrected as in 9.1, if necessary) to volumetric air flows at the
8.9 Measure zero flow pressures with the fan opening
temperature and barometric pressure, due to elevation changes
blocked. These zero flow envelope pressures are measured
only, of the outside air for depressurization tests or of the inside
before and after the flow measurements. These zero flow
air for pressurization tests (see Appendix X1). To convert the
pressures are to be subtracted from the envelope pressures
airflow rate to air leakage rate for depressurization, use the
measured during pressurization and depressurization.
following equation:
NOTE 1—Some equipment may perform this step, or an equivalent step,
r
in
automatically. Follow the manufacturer’s instructions accordingly.
Q 5 Q (1)
S D
o
r
out
8.10 The range of the induced pressure difference shall be
where:
from 10 to 60 Pa (0.04 to 0.24 in. H O) depending on the
3 3
r 5 the indoor air density, in kg/m (lb/ft ), and
capacity of the air-handling equipment. Because the capacity
in
3 3
p 5 the outdoor air density, in kg/m (lb/ft ).
of the air handling equipment, the tightness of the building, and out
9.2.1 To convert the airflow rate to air leakage rate for
the weather conditions affect leakage measurements, the full
pressurization, use the following equation:
range of the higher values may not be achievable. In such
cases, substitute a partial range encompassing at least five data
r
out
Q 5 Q (2)
S D
o
points. r
in
9.3 Average the zero flow envelope pressures measured
NOTE 2—It is advisable to check that the condition of the building
envelope has not changed after each pressure reading, f
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