ASTM E1827-11(2017)

Standard Test Methods for Determining Airtightness of Buildings Using an Orifice Blower Door

SIGNIFICANCE AND USE
5.1 Airtightness—Building airtightness is one factor that affects building air change rates under normal conditions of weather and building operation. These air change rates account for a significant portion of the space-conditioning load and affect occupant comfort, indoor air quality, and building durability. These test methods produce results that characterize the airtightness of the building envelope. These results can be used to compare the relative airtightness of similar buildings, determine airtightness improvements from retrofit measures applied to an existing building, and predict air leakage. Use of this standard in conjunction Practices E1186 permits the identification of leakage sources and rates of leakage from different components of the same building envelope. These test methods evolved from Test Method E779 to apply to orifice blower doors.  
5.1.1 Applicability to Natural Conditions—Pressures across building envelopes under normal conditions of weather and building operation vary substantially among various locations on the envelope and are generally much lower than the pressures during the test. Therefore, airtightness measurements using these test methods cannot be interpreted as direct measurements of natural infiltration or air change rates that would occur under natural conditions. However, airtightness measurements can be used to provide air leakage parameters for models of natural infiltration. Such models can estimate average annual ventilation rates and the associated energy costs. Test Method E741 measure natural air exchange rates using tracer gas dilution techniques.  
5.1.2 Relation to Test Method E779—These test methods are specific adaptations of Test Method E779 to orifice blower doors. For nonorifice blower doors or for buildings too large to use blower doors, use Test Method E779.  
5.2 Single-Point Method—Use this method to provide air leakage estimates for assessing improvements in airtightness.  
5.3 Two-Point Method—Use th...
SCOPE
1.1 These test methods describe two techniques for measuring air leakage rates through a building envelope in buildings that may be configured to a single zone. Both techniques use an orifice blower door to induce pressure differences across the building envelope and to measure those pressure differences and the resulting airflows. The measurements of pressure differences and airflows are used to determine airtightness and other leakage characteristics of the envelope.  
1.2 These test methods allow testing under depressurization and pressurization.  
1.3 These test methods are applicable to small indoor-outdoor temperature differentials and low wind pressure conditions; the uncertainty in the measured results increases with increasing wind speeds and temperature differentials.  
1.4 These test methods do not measure air change rate under normal conditions of weather and building operation. To measure air change rate directly, use Test Method E741.  
1.5 The text of these test methods reference notes and footnotes that provide explanatory material. These notes and footnotes, excluding those in tables and figures, shall not be considered as requirements of the standard.  
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.

General Information

• Status: Historical
• Publication Date: 31-Aug-2017
• ICS: 91.010.30 - Technical aspects
• Technical Committee: E06 - Performance of Buildings
• Drafting Committee: E06.41 - Air Leakage and Ventilation Performance

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E1827 −11 (Reapproved 2017)
Standard Test Methods for
Determining Airtightness of Buildings Using an Orifice
Blower Door
This standard is issued under the fixed designation E1827; 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 These test methods describe two techniques for measur- 2.1 ASTM Standards:
ing air leakage rates through a building envelope in buildings E456Terminology Relating to Quality and Statistics
thatmaybeconfiguredtoasinglezone.Bothtechniquesusean E631Terminology of Building Constructions
orifice blower door to induce pressure differences across the E741Test Method for Determining Air Change in a Single
building envelope and to measure those pressure differences Zone by Means of a Tracer Gas Dilution
and the resulting airflows. The measurements of pressure E779TestMethodforDeterminingAirLeakageRatebyFan
differences and airflows are used to determine airtightness and Pressurization
other leakage characteristics of the envelope. E1186Practices for Air Leakage Site Detection in Building
Envelopes and Air Barrier Systems
1.2 These test methods allow testing under depressurization
E1258Test Method for Airflow Calibration of Fan Pressur-
and pressurization.
ization Devices
1.3 These test methods are applicable to small indoor-
2.2 ISO International Standard:
outdoor temperature differentials and low wind pressure con-
ISO 9972Thermal Insulation—Determination of Building
ditions; the uncertainty in the measured results increases with
Airtightness—Fan Pressurization Method
increasing wind speeds and temperature differentials.
2.3 Other Standard:
1.4 Thesetestmethodsdonotmeasureairchangerateunder
ANSI/ASME PTC 19.1–1985 Part 1: Measurement
normal conditions of weather and building operation. To
Uncertainty, Instruments, and Apparatus
measure air change rate directly, use Test Method E741.
3. Terminology
1.5 The text of these test methods reference notes and
footnotes that provide explanatory material. These notes and
3.1 Definitions:
footnotes, excluding those in tables and figures, shall not be
3.1.1 For definitions of general terms related to building
considered as requirements of the standard.
construction used in this test methods, refer to Terminology
1.6 This standard does not purport to address all of the E631andforgeneraltermsrelatedtoaccuracy,bias,precision,
and uncertainty refer to Terminology E456.
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 ACH ,n—the ratio of the air leakage rate at 50 Pa
priate safety, health, and environmental practices and deter-
(0.2 in. H O), corrected for a standard air density, to the
mine the applicability of regulatory limitations prior to use.
volume of the test zone (1/h).
For specific hazard statements see Section 7.
1.7 This international standard was developed in accor-
3.2.2 air leakage rate, Q ,n—the total volume of air
env
dance with internationally recognized principles on standard-
passing through the test zone envelope per unit of time (m /s,
ization established in the Decision on Principles for the
ft /min).
Development of International Standards, Guides and Recom-
3.2.3 airtightness, n—the degree to which a test zone
mendations issued by the World Trade Organization Technical
envelope resists the flow of air.
Barriers to Trade (TBT) Committee.
1 2
These test methods are under the jurisdiction of ASTM Committee E06 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Performance of Buildings and are the direct responsibility of Subcommittee E06.41 contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
on Air Leakage and Ventilation Performance. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Sept. 1, 2017. Published September 2017. Originally the ASTM website.
approved in 1996. Last previous edition approved in 2011 as E1827–11. DOI: Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/E1827-11R17. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1827−11 (2017)
NOTE 1—ACH , air leakage rate, and effective leakage area are
P = building pressure difference (see 3.2.5),
examples of measures of building airtightness.
¯
P = average pressure, P , at the primary pressure
1 sta
3.2.4 blower door, n—a fan pressurization device incorpo-
station, Pa (in. H O),
¯
rating a controllable fan and instruments for airflow measure-
P = averagepressure, P ,atthesecondarypressure
2 sta
ment and building pressure difference measurement that
station, Pa (in. H O),
mounts securely in a door or other opening. P = the reference pressure differential across the
ref
building envelope, Pa (in. H O),
3.2.5 building pressure difference, P, n—the pressure differ- 2
P = station pressure, Pa (in. H O),
sta 2
ence across the test zone envelope (Pa, in. H O).
P = test pressure, Pa (in. H O),
test 2
3.2.6 fan airflow rate, Q ,n—the volume of airflow
fan
P = zero-airflow pressure before test, Pa (in. H O),
zero1 2
3 3
through the blower door per unit of time (m /s, ft /min).
P = zero-airflow pressure after test, Pa (in. H O),
zero2 2
3 3
3.2.7 nominal airflow rate, Q ,n—the flow rate indicated Q = the air leakage rate, m /s (ft /min),
nom env
¯
Q = average air leakage rate, Q , at the primary
by the blower door using the manufacturer’s calibration
env1 env
3 3
3 3
pressure station, m /s (ft /min),
coefficients (m /s, ft /min).
¯
Q = average air leakage rate, Q , at the secondary
env2 env
3.2.8 orifice blower door, n—ablowerdoorinwhichairflow
3 3
pressure station, m /s (ft /min),
rate is determined by means of the pressure drop across an
Q = fan airflow rate (see 3.2.6),
fan
orifice or nozzle.
Q = nominal airflow rate (see 3.2.7),
nom
3.2.9 precisionindexoftheaverage,n—thesamplestandard
T = temperature, °C (°F),
deviationdividedbythesquarerootofthenumberofsamples.
t = value from a two-tailed student t table for the
95% confidence level,
3.2.10 pressure station, n—a specified induced change in
δn = measurement uncertainty of the envelope flow
the building pressure difference from the initial zero-flow
exponent (dimensionless),
building pressure difference (Pa, in. H O).
3 3
V = volume of the test zone, m (ft ),
zone
3.2.11 single zone, n—a space in which the pressure differ-
δQ = measurement uncertainty of the average air
env
3 3
ences between any two places, as indicated on a manometer,
leakage rate, m /s (ft /min),
3 3
differ by no more than 2.5 Pa (0.01 in. H O) during fan
δQ = the measurement uncertainty of Q ,m /s (ft /
50 50
pressurizationatabuildingpressuredifferenceof50Pa(0.2in.
min),
3 3
H O)andbynomorethan5%ofthehighestbuildingpressure
2 δQ = estimated bias of the flow rate, m /s (ft /min),
bias
difference achieved.
δQ = estimated bias of the flow rate at the primary
bias1
3 3
pressure station, m /s (ft /min),
NOTE 2—A multiroom space that is interconnected within itself with
δQ = estimated bias of the flow rate at the secondary
door-sizedopeningsthroughanypartitionsorfloorsislikelytosatisfythis bias2
3 3
3 3 3
criterionifthefanairflowrateislessthan3m /s(6×10 ft /min)andthe pressure station, m /s (ft /min),
test zone envelope is not extremely leaky.
δQ = precision index of the average measured flow
precision
3 3
rate, m /s (ft /min),
3.2.12 test zone, n—abuildingoraportionofabuildingthat
δQ = precision index of the average measured flow
is configured as a single zone for the purpose of this standard.
prec1
3 3
rate at the primary pressure station, m /s (ft /
NOTE 3—For detached dwellings, the test zone envelope normally
min),
comprises the thermal envelope.
δQ = precision index of the average measured flow
prec2
3.2.13 test zone envelope, n—thebarrierorseriesofbarriers 3
rate at the secondary pressure station, m /s
between a test zone and the outdoors. 3
(ft /min),
δP = measurement uncertainty of the average mea-
NOTE 4—The user establishes the test zone envelope at such places as
basements or neighboring rooms by choosing the level of resistance to
sured pressure differential across the building
airflowbetweenthetestzoneandoutdoorswithsuchmeasuresasopening
envelope, Pa (in. H O),
or closing windows and doors to, from, and within the adjacent spaces.
δP = estimatedbiasofthepressuredifferentialacross
bias
3.2.14 zero-flow building pressure difference, n—the natural
the building envelope, Pa (in. H O),
building pressure difference measured when there is no flow
δP = estimatedbiasofthepressuredifferentialacross
bias1
through the blower door. the building envelope at the primary pressure
station, Pa (in. H O),
3.3 Symbols—The following is a summary of the principal
δP = estimatedbiasofthepressuredifferentialacross
bias2
symbols used in these test methods:
the building envelope at the secondary pressure
Alt = altitude at site, m (ft), station, Pa (in. H O),
δP = precision index of the average measured pres-
C = flow coefficient at standard conditions, m /s
precision
n 3 n 4
(Pa)ft /min (in. H O ), sure differential across the building envelope,
L = effectiveleakageareaatstandardconditions,m Pa (in. H O),
(in. ), δP = precision index of the average measured pres-
prec1
n = envelope flow exponent (dimensionless), sure differential across the building envelope at
the primary pressure station, Pa (in. H O),
Historically, a variety of other units have been used.
E1827−11 (2017)
5.1.2 RelationtoTestMethodE779—Thesetestmethodsare
δP = precision index of the average measured pres-
prec2
specific adaptations of Test Method E779 to orifice blower
sure differential across the building envelope at
doors.Fornonorificeblowerdoorsorforbuildingstoolargeto
the secondary pressure station, Pa (in. H O),
use blower doors, use Test Method E779.
δV = measurement uncertainty of the zone volume,
zone
3 3
m (ft ),
5.2 Single-Point Method—Use this method to provide air
µ = dynamic viscosity, kg/m·s (lbm/ft·hr),
leakage estimates for assessing improvements in airtightness.
3 3
ρ = air density, kg/m (lbm/ft ), and
5.3 Two-Point Method—Use this method to provide air
ρ = air density at which the calibration values are
cal
3 3
leakage parameters for use as inputs to natural ventilation
valid, kg/m (lbm/ft ).
models.The two-point method uses more complex data analy-
4. Summary of Test Methods
sis techniques and requires more accurate measurements
(Tables X1.1 and X1.2) than the single-point method. It can be
4.1 Pressure versus Flow—These test methods consist of
usedtoestimatethebuildingleakagecharacteristicsatbuilding
mechanical depressurization or pressurization of a building
pressure differences as low as 4 Pa (0.016 in. H O).Avariety
zoneduringwhichmeasurementsoffanairflowratesaremade 2
of reference pressures for building envelope leaks has been
atoneormorepressurestations.Theairleakagecharacteristics
used or suggested for characterizing building airtightness.
of a building envelope are evaluated from the relationship
These pressures include 4 Pa (0.016 in. H O), 10 Pa (0.04 in.
between the building pressure differences and the resulting
H O), 30 Pa (0.12 in. H O), and 50 Pa (0.2 in. H O). The
airflow rates. Two alternative measurement and analysis pro- 2 2 2
ASHRAE Handbook of Fundamentals uses 4 Pa.
cedures are specified in this standard, the single-point method
and the two-point method.
5.4 Depressurization versus Pressurization—Depending on
4.1.1 Single-Point Method—This method provides air leak- the goals of the test method, the user may choose depressur-
age estimates by making multiple flow measurements near
ization or pressurization or both. This standard permits both
P =50 Pa (0.2 in. H O) and assuming a building flow depressurization and pressurization measurements to compen-
1 2
exponent of n =0.65.
sate for asymmetric flow in the two directions. Depressuriza-
4.1.2 Two-Point Method—This method provides air leakage
tionisappropriatefortestingthebuildingenvelopetightnessto
estimates by making multiple flow measurements near
include the tightness of such items as backdraft dampers that
P =50Pa (0.2 in. H O) and near P =12.5 Pa (0.05 in. H O)
inhibit infiltration but open during a pressurization test. Com-
1 2 2 2
that permit estimates of the building flow coefficient and flow
bining the results of depressurization and pressurization mea-
exponent.
surements can minimize wind and stack-pressure effects on
calculatingairtightnessbutmayoverestimateairleakagedueto
5. Significance and Use
backdraft dampers that open only under pressurization.
5.1 Airtightness—Building airtightness is one factor that
5.5 Effects of Wind and Temperature Differences—Calm
affects building air change rates under normal conditions of
winds and moderate temperatures during the test improve
weatherandbuildingoperation.Theseairchangeratesaccount
precisionandbias.Pressuregradientsovertheenvelopecaused
for a significant portion of the space-conditioning load and
by inside-outside temperature differences and wind cause bias
affect occupant comfort, indoor air quality, and building
in the measurement by changing the building pressure differ-
durability.Thesetestmethodsproduceresultsthatcharacterize
ences over the test envelope from what would occur in the
the airtightness of the building envelope. These results can be
absenceofthesefactors.Windalsocausespressurefluctuations
used to compare the relative airtightness of similar buildings,
that affect measurement precision and cause the data to be
determine airtightness improvements from retrofit measures
autocorrelated.
applied to an existing building, and predict air leakage. Use of
6. Apparatus
this standard in conjunction Practices E1186 permits the
identification of leakage sources and rates of leakage from
6.1 Blower Door—An orifice blower door (see Fig. 1).
differentcomponentsofthesamebuildingenvelope.Thesetest
6.2 Measurement Precision and Bias—Appendix X1 lists
methods evolved from Test Method E779 to apply to orifice
recommended values for the precision and bias of the mea-
blower doors.
surements of airflow, pressure difference, wind speed, and
5.1.1 Applicability to Natural Conditions—Pressures across
temperature to obtain the precision and bias for test results
building envelopes under normal conditions of weather and
described in 1
...

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: E1827 − 11 E1827 − 11 (Reapproved 2017)
Standard Test Methods for
Determining Airtightness of Buildings Using an Orifice
Blower Door
This standard is issued under the fixed designation E1827; 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 These test methods describe two techniques for measuring air leakage rates through a building envelope in buildings that
may be configured to a single zone. Both techniques use an orifice blower door to induce pressure differences across the building
envelope and to measure those pressure differences and the resulting airflows. The measurements of pressure differences and
airflows are used to determine airtightness and other leakage characteristics of the envelope.
1.2 These test methods allow testing under depressurization and pressurization.
1.3 These test methods are applicable to small indoor-outdoor temperature differentials and low wind pressure conditions; the
uncertainty in the measured results increases with increasing wind speeds and temperature differentials.
1.4 These test methods do not measure air change rate under normal conditions of weather and building operation. To measure
air change rate directly, use Test MethodsMethod E741.
1.5 The text of these test methods reference notes and footnotes that provide explanatory material. These notes and footnotes,
excluding those in tables and figures, shall not be considered as requirements of the standard.
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:
E456 Terminology Relating to Quality and Statistics
E631 Terminology of Building Constructions
E741 Test Method for Determining Air Change in a Single Zone by Means of a Tracer Gas Dilution
E779 Test Method for Determining Air Leakage Rate by Fan Pressurization
E1186 Practices for Air Leakage Site Detection in Building Envelopes and Air Barrier Systems
E1258 Test Method for Airflow Calibration of Fan Pressurization Devices
2.2 ISO International Standards:Standard:
ISO 9972 Thermal Insulation—Determination of Building Airtightness—Fan Pressurization Method
2.3 Other Standards:Standard:
ANSI/ASME PTC 19.1–1985 Part 1: Measurement Uncertainty, Instruments, and Apparatus
3. Terminology
3.1 Definitions:
These test methods are under the jurisdiction of ASTM Committee E06 on Performance of Buildings and are the direct responsibility of Subcommittee E06.41 on Air
Leakage and Ventilation Performance.
Current edition approved Sept. 1, 2011Sept. 1, 2017. Published October 2011September 2017. Originally approved in 1996. Last previous edition approved in 20072011
as E1827 – 96 (2007).E1827 – 11. DOI: 10.1520/E1827-11.10.1520/E1827-11R17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1827 − 11 (2017)
3.1.1 For definitions of general terms related to building construction used in this test methods, refer to Terminology E631 and
for general terms related to accuracy, bias, precision, and uncertainty refer to Terminology E456.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 ACH , n—the ratio of the air leakage rate at 50 Pa (0.2 in. H O), corrected for a standard air density, to the volume of
50 2
the test zone (1/h).
3 3
3.2.2 air leakage rate, Q , n—the total volume of air passing through the test zone envelope per unit of time (m /s, ft /min).
env
3.2.3 airtightness, n—the degree to which a test zone envelope resists the flow of air.
E1827 − 11 (2017)
NOTE 1—ACH , air leakage rate, and effective leakage area are examples of measures of building airtightness.
3.2.4 blower door, n—a fan pressurization device incorporating a controllable fan and instruments for airflow measurement and
building pressure difference measurement that mounts securely in a door or other opening.
3.2.5 building pressure difference, P, n—the pressure difference across the test zone envelope (Pa, in. H O).
3 3
3.2.6 fan airflow rate, Q , n—the volume of airflow through the blower door per unit of time (m /s, ft /min).
fan
3.2.7 nominal airflow rate, Q , n—the flow rate indicated by the blower door using the manufacturer’s calibration coefficients
nom
3 3
(m /s, ft /min).
3.2.8 orifice blower door, n—a blower door in which airflow rate is determined by means of the pressure drop across an orifice
or nozzle.
3.2.9 precision index of the average, n—the sample standard deviation divided by the square root of the number of samples.
3.2.10 pressure station, n—a specified induced change in the building pressure difference from the initial zero-flow building
pressure difference (Pa, in. H O).
3.2.11 single zone, n—a space in which the pressure differences between any two places, as indicated on a manometer, differ
by no more than 2.5 Pa (0.01 in. H O) during fan pressurization at a building pressure difference of 50 Pa (0.2 in. H O) and by
2 2
no more than 5 % of the highest building pressure difference achieved.
NOTE 2—A multiroom space that is interconnected within itself with door-sized openings through any partitions or floors is likely to satisfy this criterion
3 3 3
if the fan airflow rate is less than 3 m /s (6 × 10 ft /min) and the test zone envelope is not extremely leaky.
3.2.12 test zone, n—a building or a portion of a building that is configured as a single zone for the purpose of this standard.
NOTE 3—For detached dwellings, the test zone envelope normally comprises the thermal envelope.
3.2.13 test zone envelope, n—the barrier or series of barriers between a test zone and the outdoors.
NOTE 4—The user establishes the test zone envelope at such places as basements or neighboring rooms by choosing the level of resistance to airflow
between the test zone and outdoors with such measures as opening or closing windows and doors to, from, and within the adjacent spaces.
3.2.14 zero-flow building pressure difference, n—the natural building pressure difference measured when there is no flow
through the blower door.
3.3 Symbols—The following is a summary of the principal symbols used in these test methods:
Alt = altitude at site, m (ft),
3 n 3 n 4
C = flow coefficient at standard conditions, m /s (Pa ) ft /min (in. H O ),
2 2
L = effective leakage area at standard conditions, m (in. ),
n = envelope flow exponent (dimensionless),
P = building pressure difference (see 3.2.5),
P = average pressure, P¯ , at the primary pressure station, Pa (in. H O),
1 sta 2
P = average pressure, P¯ , at the secondary pressure station, Pa (in. H O),
2 sta 2
P = the reference pressure differential across the building envelope, Pa (in. H O),
ref 2
P = station pressure, Pa (in. H O),
sta 2
P = test pressure, Pa (in. H O),
test 2
P = zero-airflow pressure before test, Pa (in. H O),
zero1 2
P = zero-airflow pressure after test, Pa (in. H O),
zero2 2
3 3
Q = the air leakage rate, m /s (ft /min),
env
3 3
Q = average air leakage rate, Q¯ , at the primary pressure station, m /s (ft /min),
env1 env
3 3
Q = average air leakage rate, Q¯ , at the secondary pressure station, m /s (ft /min),
env2 env
Q = fan airflow rate (see 3.2.6),
fan
Q = nominal airflow rate (see 3.2.7),
nom
T = temperature,° C (°F),
T = temperature, °C (°F),
t = value from a two-tailed student t table for the 95 % confidence level,
δn = measurement uncertainty of the envelope flow exponent (dimensionless),
3 3
V = volume of the test zone, m (ft ),
zone
3 3
δQ = measurement uncertainty of the average air leakage rate, m /s (ft /min),
env
3 3
δQ = the measurement uncertainty of Q , m /s (ft /min),
50 50
3 3
δQ = estimated bias of the flow rate, m /s (ft /min),
bias
3 3
δQ = estimated bias of the flow rate at the primary pressure station, m /s (ft /min),
bias1
3 3
δQ = estimated bias of the flow rate at the secondary pressure station, m /s (ft /min),
bias2
3 3
δQ = precision index of the average measured flow rate, m /s (ft /min),
precision
Historically, a variety of other units have been used.
E1827 − 11 (2017)
3 3
δQ = precision index of the average measured flow rate at the primary pressure station, m /s (ft /min),
prec1
3 3
δQ = precision index of the average measured flow rate at the secondary pressure station, m /s (ft /min),
prec2
δP = measurement uncertainty of the average measured pressure differential across the building envelope, Pa (in. H O),
δP = estimated bias of the pressure differential across the building envelope, Pa (in. H O),
bias 2
δP = estimated bias of the pressure differential across the building envelope at the primary pressure station, Pa (in. H O),
bias1 2
δP = estimated bias of the pressure differential across the building envelope at the secondary pressure station, Pa (in.
bias2
H O),
δP = precision index of the average measured pressure differential across the building envelope, Pa (in. H O),
precision 2
δP = precision index of the average measured pressure differential across the building envelope at the primary pressure
prec1
station, Pa (in. H O),
δP = precision index of the average measured pressure differential across the building envelope at the secondary pressure
prec2
station, Pa (in. H O),
3 3
δV = measurement uncertainty of the zone volume, m (ft ),
zone
μ = dynamic viscosity, kg/m·s (lbm/ft·hr),
3 3
ρ = air density, kg/m (lbm/ft ), and
3 3
ρ = air density at which the calibration values are valid, kg/m (lbm/ft ).
cal
4. Summary of Test Methods
4.1 Pressure versus Flow—These test methods consist of mechanical depressurization or pressurization of a building zone
during which measurements of fan airflow rates are made at one or more pressure stations. The air leakage characteristics of a
building envelope are evaluated from the relationship between the building pressure differences and the resulting airflow rates. Two
alternative measurement and analysis procedures are specified in this standard, the single-point method and the two-point method.
4.1.1 Single-Point Method—This method provides air leakage estimates by making multiple flow measurements near P = 50
Pa (0.2 in. H O) and assuming a building flow exponent of n = 0.65.
4.1.2 Two-Point Method—This method provides air leakage estimates by making multiple flow measurements near P = 50 Pa
= 50 Pa (0.2 in. H O) and near P = 12.5 Pa (0.05 in. H O) that permit estimates of the building flow coefficient and flow
2 2 2
exponent.
5. Significance and Use
5.1 Airtightness—Building airtightness is one factor that affects building air change rates under normal conditions of weather
and building operation. These air change rates account for a significant portion of the space-conditioning load and affect occupant
comfort, indoor air quality, and building durability. These test methods produce results that characterize the airtightness of the
building envelope. These results can be used to compare the relative airtightness of similar buildings, determine airtightness
improvements from retrofit measures applied to an existing building, and predict air leakage. Use of this standard in conjunction
PracticePractices E1186 permits the identification of leakage sources and rates of leakage from different components of the same
building envelope. These test methods evolved from Test Method E779 to apply to orifice blower doors.
5.1.1 Applicability to Natural Conditions—Pressures across building envelopes under normal conditions of weather and
building operation vary substantially among various locations on the envelope and are generally much lower than the pressures
during the test. Therefore, airtightness measurements using these test methods cannot be interpreted as direct measurements of
natural infiltration or air change rates that would occur under natural conditions. However, airtightness measurements can be used
to provide air leakage parameters for models of natural infiltration. Such models can estimate average annual ventilation rates and
the associated energy costs. Test MethodsMethod E741 measure natural air exchange rates using tracer gas dilution techniques.
5.1.2 Relation to Test Method E779—These test methods are specific adaptations of Test Method E779 to orifice blower doors.
For nonorifice blower doors or for buildings too large to use blower doors, use Test Method E779.
5.2 Single-Point Method—Use this method to provide air leakage estimates for assessing improvements in airtightness.
5.3 Two-Point Method—Use this method to provide air leakage parameters for use as inputs to natural ventilation models. The
two-point method uses more complex data analysis techniques and requires more accurate measurements (Tables X1.1 and X1.2)
than the single-point method. It can be used to estimate the building leakage characteristics at building pressure differences as low
as 4 Pa (0.016 in. H O). A variety of reference pressures for building envelope leaks has been used or suggested for characterizing
building airtightness. These pressures include 4 Pa (0.016 in. H O), 10 Pa (0.04 in. H O), 30 Pa (0.12 in. H O), and 50 Pa (0.2
2 2 2
in. H O). The ASHRAE Handbook of Fundamentals uses 4 Pa.
5.4 Depressurization versus Pressurization—Depending on the goals of the test method, the user may choose depressurization
or pressuri
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