ASTM E779-10(2018)
(Test Method)Standard Test Method for Determining Air Leakage Rate by Fan Pressurization
Standard Test Method for Determining Air Leakage Rate by Fan Pressurization
SIGNIFICANCE AND USE
5.1 Air leakage accounts for a significant portion of the thermal space conditioning load. In addition, it affects occupant comfort and indoor air quality.
5.2 In most commercial or industrial buildings, outdoor air is often introduced by design; however, air leakage is a significant addition to the designed outdoor airflow. In most residential buildings, indoor-outdoor air exchange is attributable primarily to air leakage through cracks and construction joints and is induced by pressure differences due to temperature differences, wind, operation of auxiliary fans (for example, kitchen and bathroom exhausts), and the operation of combustion equipment in the building.
5.3 The fan-pressurization method is simpler than tracer gas measurements and is intended to characterize the air tightness of the building envelope. It is used to compare the relative air tightness of several similar buildings to identify the leakage sources and rates of leakage from different components of the same building envelope, and to determine the air leakage reduction for individual retrofit measures applied incrementally to an existing building, and to determine ventilation rates when combined with weather and leak location information.
SCOPE
1.1 This test method measures 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 differential, therefore strong winds and large indoor-outdoor temperature differentials shall be avoided.
1.3 This test method is intended to quantify the air tightness of a building envelope. This test method does not measure air change rate or air leakage rate under normal weather conditions and building operation.
Note 1: See Test Method E741 to directly measure air-change rates using the tracer gas dilution method.
1.4 This test method is intended to be used for measuring the air tightness of building envelopes of single-zone buildings. For the purpose of this test method, many multi-zone buildings can be treated as single-zone buildings by opening interior doors or by inducing equal pressures in adjacent zones.
1.5 Only metric SI units of measurement are used in this standard. If a value for measurement is followed by a value in other units in parentheses, the second value may be approximate. The first stated value is the requirement.
1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements see Section 7.
1.7 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.
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Designation: E779 − 10 (Reapproved 2018)
Standard Test Method for
Determining Air Leakage Rate by Fan Pressurization
This standard is issued under the fixed designation E779; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This test method measures air-leakage rates through a 2.1 ASTM Standards:
building envelope under controlled pressurization and de- E631Terminology of Building Constructions
pressurization.
E741Test Method for Determining Air Change in a Single
Zone by Means of a Tracer Gas Dilution
1.2 This test method is applicable to small temperature
E1258Test Method for Airflow Calibration of Fan Pressur-
differentials and low-wind pressure differential, therefore
ization Devices
strong winds and large indoor-outdoor temperature differen-
tials shall be avoided.
3. Terminology
1.3 Thistestmethodisintendedtoquantifytheairtightness
3.1 Fordefinitionsoftermsusedinthistestmethod,referto
of a building envelope. This test method does not measure air
Terminology E631.
changerateorairleakagerateundernormalweatherconditions
and building operation.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 air-change rate, n—air-leakage rate in volume units/h
NOTE 1—See Test Method E741 to directly measure air-change rates
divided by the building space volume with identical volume
using the tracer gas dilution method.
units, normally expressed as air changes/h, ACH.
1.4 This test method is intended to be used for measuring
3.2.2 air-leakage, n—the movement/flow of air through the
theairtightnessofbuildingenvelopesofsingle-zonebuildings.
building envelope, which is driven by either or both positive
Forthepurposeofthistestmethod,manymulti-zonebuildings
(infiltration) and negative (exfiltration) pressure differences
can be treated as single-zone buildings by opening interior
across the envelope.
doors or by inducing equal pressures in adjacent zones.
3.2.3 air-leakage graph, n—the graph that shows the rela-
1.5 Only metric SI units of measurement are used in this
tionship of measured airflow rates to the corresponding mea-
standard. If a value for measurement is followed by a value in
sured pressure differences, plotted on a log-log scale.
other units in parentheses, the second value may be approxi-
mate. The first stated value is the requirement.
3.2.4 air-leakage rate, n—the volume of air movement/unit
time across the building envelope including airflow through
1.6 This standard does not purport to address all of the
joints, cracks, and porous surfaces, or a combination thereof
safety concerns, if any, associated with its use. It is the
driven by mechanical pressurization and de-pressurization,
responsibility of the user of this standard to establish appro-
naturalwindpressures,orairtemperaturedifferentialsbetween
priate safety, health, and environmental practices and deter-
the building interior and the outdoors, or a combination
mine the applicability of regulatory limitations prior to use.
thereof.
For specific hazard statements see Section 7.
1.7 This international standard was developed in accor-
3.2.5 building envelope, n—the boundary or barrier separat-
dance with internationally recognized principles on standard-
ing different environmental conditions within a building and
ization established in the Decision on Principles for the
from the outside environment.
Development of International Standards, Guides and Recom-
3.2.6 effective leakage area, n—the area of a hole, with a
mendations issued by the World Trade Organization Technical
discharge coefficient of 1.0, which, witha4Pa pressure
Barriers to Trade (TBT) Committee.
difference, leaks the same as the building, also known as the
sum of the unintentional openings in the structure.
This test method is under the jurisdiction of ASTM Committee E06 on
Performance of Buildings and is the direct responsibility of Subcommittee E06.41
on Air Leakage and Ventilation Performance. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved July 15, 2018. Published July 2018. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1981. Last previous edition approved in 2010 as E779–10. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E0779-10R18. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E779 − 10 (2018)
3.2.7 height, building, n—the vertical distance from grade sources and rates of leakage from different components of the
plane to the average height of the highest ceiling surface. same building envelope, and to determine the air leakage
reductionforindividualretrofitmeasuresappliedincrementally
3.2.8 interior volume, n—deliberately conditioned space
toanexistingbuilding,andtodetermineventilationrateswhen
within a building, generally not including attics and attached
combined with weather and leak location information.
structures, for example, garages, unless such spaces are con-
nected to the heating and air conditioning system, such as a
6. Apparatus
crawl space plenum.
6.1 The following is a general description of the required
3.2.9 single zone, n—a space in which the pressure differ-
apparatus. Any arrangement of equipment using the same
ences between any two places, differ by no more than 5% of
principles and capable of performing the test procedure within
the inside to outside pressure difference including multi-room
the allowable tolerances shall be permitted.
space that is interconnected within itself with door-sized
6.2 Major Components:
openings through any partitions or floors where the fan airflow
3 3 3
6.2.1 Air-Moving Equipment—Fan, blower, HVAC air
rate is less than 3 m /s (6×10 ft /min).
movement component or blower door assembly that is capable
3.2.10 test pressure difference, n—the measured pressure
of moving air into and out of the conditioned space at required
difference across the building envelope, expressed in Pascals
2 flow rates under a range of test pressure differences. The
(in. of water or pounds-force/ft or in. of mercury).
system shall provide constant airflow at each incremental
3.3 Symbols and Units—See Table 1.
pressure difference at fixed pressure for the period required to
obtain readings of airflow rate.
4. Summary of Test Method
6.2.2 Pressure-Measuring Device—Manometer or pressure
4.1 This test method consists of mechanical pressurization
indicator to measure pressure difference with an accuracy of
or de-pressurization of a building and measurements of the
65% of the measured pressure or 0.25Pa (0.001in. H O),
resulting airflow rates at given indoor-outdoor static pressure
whichever is greater.
differences. From the relationship between the airflow rates
6.2.3 Airflow Measuring System—Device to measure air-
and pressure differences, the air leakage characteristics of a
flow with an accuracy of 65% of the measured flow. The
building envelope are determined.
airflow measuring system shall be calibrated in accordance
with Test Method E1258.
5. Significance and Use
6.2.4 Temperature-Measuring Device—Instrument to mea-
5.1 Air leakage accounts for a significant portion of the sure temperature with an accuracy of 61°C (2°F).
thermalspaceconditioningload.Inaddition,itaffectsoccupant
7. Hazards
comfort and indoor air quality.
7.1 EyeProtection—Glassbreakageatthebuildingpressure
5.2 In most commercial or industrial buildings, outdoor air
differencesnormallyappliedtotheteststructureisuncommon:
is often introduced by design; however, air leakage is a
however, for added safety, adequate precautions, such as the
significant addition to the designed outdoor airflow. In most
use of eye protection shall be taken to protect the personnel.
residential buildings, indoor-outdoor air exchange is attribut-
able primarily to air leakage through cracks and construction 7.2 Safety Clothing—Use safety equipment required for
jointsandisinducedbypressuredifferencesduetotemperature general field work, including safety shoes, and hard hats.
differences, wind, operation of auxiliary fans (for example,
7.3 Equipment Guards—The air-moving equipment shall
kitchen and bathroom exhausts), and the operation of combus-
have a proper guard or cage to house the fan or blower and to
tion equipment in the building.
prevent accidental access to any moving parts of the equip-
5.3 Thefan-pressurizationmethodissimplerthantracergas ment.
measurements and is intended to characterize the air tightness
7.4 NoiseProtection—Exposuretothenoiselevelgenerated
of the building envelope. It is used to compare the relative air
by fans can be hazardous to the hearing of involved personnel
tightness of several similar buildings to identify the leakage
and hearing protection is required.
7.5 Debris and Fumes—The blower or fan forces a large
TABLE 1 Symbols and Units
volume of air into or out of a building while in operation. Care
shall be exercised to not to damage plants, pets, occupants, or
Symbol Quantity Unit
E Elevation above sea level m [ft] internal furnishings due to influx of cold or warm air. Caution
Q Measured airflow rate m /s [cfm]
shallbeexercisedagainstsuckingdebrisorexhaustgasesfrom
Q Air leakage rate m /s [cfm]
o
fireplaces and flues into the interior of the building. Active
3 n n
C Air leakage coefficient m /(s · Pa ) [cfm/Pa ]
3 3
ρ Air density kg/m [lb/ft ] combustion devices shall be shut off or the safety determined
T Temperature °C [°F]
of conducting the test by a properly trained technician before
n Pressure exponent . . .
2 conducting the test.
P Pressure Pa [lb/ft ]
dP Induced pressure difference Pa [lb/ft ]
8. Procedure
dP Reference pressure difference Pa [lb/ft ]
r
µ Dynamic air viscosity kg/(m·s) [lb/(ft·h)]
2 2 8.1 To create a single zone for this test procedure, all
A Area m [ft ]
interconnecting doors in the conditioned space shall be open
E779 − 10 (2018)
such that a uniform pressure shall be maintained within the be close to the middle (horizontally) of the exterior wall.
conditioned space to within 610% of the measured inside/ Beware of direct sunlight hitting pressure tubing, especially
outside pressure difference. This condition shall be verified by
vertical sections.
differentialpressuremeasurementsatthehighestpressureused
8.8 Measure zero flow pressures with the fan opening
in the test. These measurements shall be taken at the highest
blocked.Thesezeroflowenvelopepressuresshallbemeasured
ceiling elevation and lowest floor elevation of the building and
before and after the flow measurements. The average over at
on the windward and leeward sides.
least a 10-s interval shall be used. These zero flow pressures
8.2 HVAC balancing dampers and registers shall not be
shall be subtracted from the envelope pressures measured
adjusted. Fireplace and other operable dampers shall be closed
during pressurization and depressurization.
unless they are used to pass air to pressurize or de-pressurize
the building. NOTE2—Someequipmentmayperformthisstep,oranequivalentstep,
automatically. Follow the manufacturer’s instructions accordingly.
8.3 General observations of the condition of the building
8.9 The range of the induced pressure difference shall be
shall be recorded, including appropriate observations of the
windows, doors, opaque walls, roof, and floor. from 10 to 60Pa (0.04 to 0.24in.H O), depending on the
capacity of the air-moving equipment. Because the capacity of
8.4 Measure and record the indoor and outdoor tempera-
theair-movingequipment,thelackoftightnessinthebuilding,
tures at the beginning and the end of the test and average the
and the weather conditions affect leakage measurements, the
values. If the product of the absolute value of the indoor/
full range of the higher values may not be achievable. In such
outdoor air temperature difference multiplied by the building
cases, substitute a partial range encompassing at least five data
height, gives a result greater than 200m °C (1180ft °F), the
points.
test shall not be performed, because the pressure difference
induced by the stack effect is too large to allow accurate
NOTE 3—It is advisable to check that the condition of the building
interpretation of the results.
envelope has not changed after each pressure reading, for example, that
sealed openings have not become unsealed or that doors, windows, or
8.5 Connect the air duct or blower door assembly to the
dampers have not been forced open by the induced pressure.
buildingenvelope,usingawindow,door,orventopening.Seal
8.10 Useincrementsof5to10Pa(0.02to0.04in.H O)for
or tape openings to avoid air leakage at these points.
the full range of induced pressure differences.
8.6 If a damper is used to control airflow, it shall be in a
fully closed position for the zero flow pressure measurements.
8.11 At each pressure difference, measure the airflow rate
and the pressure differences across the envelope.After the fan
8.7 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.
10-s interval shall be used.
Where possible, locate the pressure tap at the bottom of the
leeward wall. When wind causes adverse pressure fluctuations
8.12 For each test, collect data for both pressurization and
it may be advantageous to average the pressures measured at
de-pressurization.
multiple locations, for example, one across each facade. Fig. 1
illustrates preferred locations that avoid extremes of exterior 8.13 Determine the elevation of the measurement site, E (m
pressures. A good location avoids exterior corners and should or ft), above mean sea level within 100m (330ft).
FIG. 1 Recommended Locations for Exterior Pressures (Plan Views of Buildings—“X” Within Circles Mark Pressure Tap Locations)
E779 − 10 (2018)
n
9. Data Analysis and Calculations Q 5 C dP (3)
~ !
9.1 Unless the airflow measuring system gives volumetric
9.5.1 Use an unweighted log-linearized linear regression
flowsatthebarometricpressureandthetemperaturesoftheair 3 3
technique,whereQistheairflowrate,inm /s(ft /min),anddP
flowing through the flowmeter during the test, these readings
is the differential pressure in Pa. In determining the fit of the
shall be converted using information obtained from the manu-
above equation, the confidence intervals of the derived air
facturer for the change in calibrati
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
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: E779 − 10 E779 − 10 (Reapproved 2018)
Standard Test Method for
Determining Air Leakage Rate by Fan Pressurization
This standard is issued under the fixed designation E779; 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 test method measures 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 differential, therefore strong winds
and large indoor-outdoor temperature differentials shall be avoided.
1.3 This test method is intended to quantify the air tightness of a building envelope. This test method does not measure air
change rate or air leakage rate under normal weather conditions and building operation.
NOTE 1—See Test Method E741 to directly measure air-change rates using the tracer gas dilution method.
1.4 This test method is intended to be used for measuring the air tightness of building envelopes of single-zone buildings. For
the purpose of this test method, many multi-zone buildings can be treated as single-zone buildings by opening interior doors or
by inducing equal pressures in adjacent zones.
1.5 Only metric SI units of measurement are used in this standard. If a value for measurement is followed by a value in other
units in parentheses, the second value may be approximate. The first stated value is the requirement.
1.6 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. For specific hazard statements see Section 7.
1.7 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:
E631 Terminology of Building Constructions
E741 Test Method for Determining Air Change in a Single Zone by Means of a Tracer Gas Dilution
E1258 Test Method for Airflow Calibration of Fan Pressurization Devices
3. Terminology
3.1 For definitions of terms used in this test method, refer to Terminology E631.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 air-change rate, n—air-leakage rate in volume units/h divided by the building space volume with identical volume units,
normally expressed as air changes/h, ACH.
3.2.2 air-leakage, n—the movement/flow of air through the building envelope, which is driven by either or both positive
(infiltration) and negative (exfiltration) pressure differences across the envelope.
3.2.3 air-leakage graph, n—the graph that shows the relationship of measured airflow rates to the corresponding measured
pressure differences, plotted on a log-log scale.
This test method is under the jurisdiction of ASTM Committee E06 on Performance of Buildings and is the direct responsibility of Subcommittee E06.41 on Air Leakage
and Ventilation Performance.
Current edition approved Jan. 15, 2010July 15, 2018. Published April 2010July 2018. Originally approved in 1981. Last previous edition approved in 20032010 as
E779 – 03.E779 – 10. DOI: 10.1520/E0779-10.10.1520/E0779-10R18.
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
E779 − 10 (2018)
3.2.4 air-leakage rate, n—the volume of air movement/unit time across the building envelope including airflow through joints,
cracks, and porous surfaces, or a combination thereof driven by mechanical pressurization and de-pressurization, natural wind
pressures, or air temperature differentials between the building interior and the outdoors, or a combination thereof.
3.2.5 building envelope, n—the boundary or barrier separating different environmental conditions within a building and from
the outside environment.
3.2.6 effective leakage area, n—the area of a hole, with a discharge coefficient of 1.0, which, with a 4 Pa pressure difference,
leaks the same as the building, also known as the sum of the unintentional openings in the structure.
3.2.7 height, building, n—the vertical distance from grade plane to the average height of the highest ceiling surface.
3.2.8 interior volume, n—deliberately conditioned space within a building, generally not including attics and attached structures,
for example, garages, unless such spaces are connected to the heating and air conditioning system, such as a crawl space plenum.
3.2.9 single zone, n—a space in which the pressure differences between any two places, differ by no more than 5 % of the inside
to outside pressure difference including multi-room space that is interconnected within itself with door-sized openings through any
3 3 3
partitions or floors where the fan airflow rate is less than 3 m /s (6 × 10 ft /min).
3.2.10 test pressure difference, n—the measured pressure difference across the building envelope, expressed in Pascals (in. of
water or pounds-force/ft or in. of mercury).
3.3 Symbols and Units—See Table 1.
4. Summary of Test Method
4.1 This test method consists of mechanical pressurization or de-pressurization of a building and measurements of the resulting
airflow rates at given indoor-outdoor static pressure differences. From the relationship between the airflow rates and pressure
differences, the air leakage characteristics of a building envelope are determined.
5. Significance and Use
5.1 Air leakage accounts for a significant portion of the thermal space conditioning load. In addition, it affects occupant comfort
and indoor air quality.
5.2 In most commercial or industrial buildings, outdoor air is often introduced by design; however, air leakage is a significant
addition to the designed outdoor airflow. In most residential buildings, indoor-outdoor air exchange is attributable primarily to air
leakage through cracks and construction joints and is induced by pressure differences due to temperature differences, wind,
operation of auxiliary fans (for example, kitchen and bathroom exhausts), and the operation of combustion equipment in the
building.
5.3 The fan-pressurization method is simpler than tracer gas measurements and is intended to characterize the air tightness of
the building envelope. It is used to compare the relative air tightness of several similar buildings to identify the leakage sources
and rates of leakage from different components of the same building envelope, and to determine the air leakage reduction for
individual retrofit measures applied incrementally to an existing building, and to determine ventilation rates when combined with
weather and leak location information.
6. Apparatus
6.1 The following is a general description of the required apparatus. Any arrangement of equipment using the same principles
and capable of performing the test procedure within the allowable tolerances shall be permitted.
6.2 Major Components:
TABLE 1 Symbols and Units
Symbol Quantity Unit
E Elevation above sea level m [ft]
Q Measured airflow rate m /s [cfm]
Q Air leakage rate m /s [cfm]
o
3 n n
C Air leakage coefficient m /(s · Pa ) [cfm/Pa ]
3 3
ρ Air density kg/m [lb/ft ]
T Temperature ° C [°F]
T Temperature °C [°F]
n Pressure exponent . . .
P Pressure Pa [lb/ft ]
dP Induced pressure difference Pa [lb/ft ]
dP Reference pressure difference Pa [lb/ft ]
r
μ Dynamic air viscosity kg/(m·s) [lb/(ft·h)]
2 2
A Area m [ft ]
E779 − 10 (2018)
6.2.1 Air-Moving Equipment—Fan, blower, HVAC air movement component or blower door assembly that is capable of moving
air into and out of the conditioned space at required flow rates under a range of test pressure differences. The system shall provide
constant airflow at each incremental pressure difference at fixed pressure for the period required to obtain readings of airflow rate.
6.2.2 Pressure-Measuring Device—Manometer or pressure indicator to measure pressure difference with an accuracy of
6 5 %65 % of the measured pressure or 0.25 Pa (0.001 in. H O), whichever is greater.
6.2.3 Airflow Measuring System—Device to measure airflow with an accuracy of 6 5 %65 % of the measured flow. The airflow
measuring system shall be calibrated in accordance with Test Method E1258.
6.2.4 Temperature-Measuring Device—Instrument to measure temperature with an accuracy of 6 1°C (2°F).61 °C (2 °F).
7. Hazards
7.1 Eye Protection—Glass breakage at the building pressure differences normally applied to the test structure is uncommon:
however, for added safety, adequate precautions, such as the use of eye protection shall be taken to protect the personnel.
7.2 Safety Clothing—Use safety equipment required for general field work, including safety shoes, and hard hats.
7.3 Equipment Guards—The air-moving equipment shall have a proper guard or cage to house the fan or blower and to prevent
accidental access to any moving parts of the equipment.
7.4 Noise Protection—Exposure to the noise level generated by fans can be hazardous to the hearing of involved personnel and
hearing protection is required.
7.5 Debris and Fumes—The blower or fan forces a large volume of air into or out of a building while in operation. Care shall
be exercised to not to damage plants, pets, occupants, or internal furnishings due to influx of cold or warm air. Caution shall be
exercised against sucking debris or exhaust gases from fireplaces and flues into the interior of the building. Active combustion
devices shall be shut off or the safety determined of conducting the test by a properly trained technician before conducting the test.
8. Procedure
8.1 To create a single zone for this test procedure, all interconnecting doors in the conditioned space shall be open such that
a uniform pressure shall be maintained within the conditioned space to within 610 % of the measured inside/outside pressure
difference. This condition shall be verified by differential pressure measurements at the highest pressure used in the test. These
measurements shall be taken at the highest ceiling elevation and lowest floor elevation of the building and on the windward and
leeward sides.
8.2 HVAC balancing dampers and registers shall not be adjusted. Fireplace and other operable dampers shall be closed unless
they are used to pass air to pressurize or de-pressurize the building.
8.3 General observations of the condition of the building shall be recorded, including appropriate observations of the windows,
doors, opaque walls, roof, and floor.
8.4 Measure and record the indoor and outdoor temperatures at the beginning and the end of the test and average the values.
If the product of the absolute value of the indoor/outdoor air temperature difference multiplied by the building height, gives a result
greater than 200 m °C (1180 ft °F), the test shall not be performed, because the pressure difference induced by the stack effect is
too large to allow accurate interpretation of the results.
8.5 Connect the air duct or blower door assembly to the building envelope, using a window, door, or vent opening. Seal or tape
openings to avoid air leakage at these points.
8.6 If a damper is used to control airflow, it shall be in a fully closed position for the zero flow pressure measurements.
8.7 Installing the Envelope Pressure Sensor(s)—Install the pressure measuring device across the building envelope. Where
possible, locate the pressure tap at the bottom of the leeward wall. When wind causes adverse pressure fluctuations it may be
advantageous to average the pressures measured at multiple locations, for example, one across each facade. Fig. 1 illustrates
preferred locations that avoid extremes of exterior pressures. A good location avoids exterior corners and should be close to the
middle (horizontally) of the exterior wall. Beware of direct sunlight hitting pressure tubing, especially vertical sections.
8.8 Measure zero flow pressures with the fan opening blocked. These zero flow envelope pressures shall be measured before
and after the flow measurements. The average over at least a 10-s interval shall be used. These zero flow pressures shall be
subtracted from the envelope pressures measured during pressurization and depressurization.
NOTE 2—Some equipment may perform this step, or an equivalent step, automatically. Follow the manufacturer’s instructions accordingly.
8.9 The range of the induced pressure difference shall be from 10 to 60 Pa (0.04 to 0.24 in. H O), depending on the capacity
of the air-moving equipment. Because the capacity of the air-moving equipment, the lack of tightness in the building, and the
weather conditions affect leakage measurements, the full range of the higher values may not be achievable. In such cases, substitute
a partial range encompassing at least five data points.
NOTE 3—It is advisable to check that the condition of the building envelope has not changed after each pressure reading, for example, that sealed
openings have not become unsealed or that doors, windows, or dampers have not been forced open by the induced pressure.
E779 − 10 (2018)
FIG. 1 Recommended Locations for Exterior Pressures (Plan Views of Buildings—“X” Within Circles Mark Pressure Tap Locations)
8.10 Use increments of 5 to 10 Pa (0.02 to 0.04 in. H O) for the full range of induced pressure differences.
8.11 At each pressure difference, measure the airflow rate and the pressure differences across the envelope. After the fan and
instrumentation have stabilized, the average over at least a 10-s interval shall be used.
8.12 For each test, collect data for both pressurization and de-pressurization.
8.13 Determine the elevation of the measurement site, E (m or ft), above mean sea level within
...
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