ISO 9972:2006

SLOVENSKI STANDARD
01-februar-2012
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Thermal performance of buildings - Determination of air permeability of buildings - Fan
pressurization method
Performance thermique des bâtiments - Détermination de la perméabilité à l'air des
bâtiments - Méthode de pressurisation par ventilateur
Ta slovenski standard je istoveten z: ISO 9972:2006
ICS:
91.120.10 Toplotna izolacija stavb Thermal insulation
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL ISO
STANDARD 9972
Second edition
2006-05-01
Thermal performance of buildings —
Determination of air permeability of
buildings — Fan pressurization method
Performance thermique des bâtiments — Détermination de la
perméabilité à l'air des bâtiments — Méthode de pressurisation par
ventilateur
Reference number
©
ISO 2006
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO 2006
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2006 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols. 1
4 Apparatus . 3
5 Measurement procedure . 4
6 Expression of results . 8
7 Test report . 12
8 Uncertainty . 13
Annex A (informative) Description of equipment used to pressurize buildings. 14
Annex B (informative) Dependence of air density on temperature, dew point and barometric
pressure. 16
Annex C (informative) Recommended procedure for estimating uncertainty in derived quantities. 17
Annex D (informative) Beaufort scale for wind force (extract) . 20

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 9972 was prepared by Technical Committee ISO/TC 163, Thermal performance and energy use in the
built environment, Subcommittee SC 1, Test and measurement methods.
This second edition cancels and replaces the first edition (ISO 9972:1996), which has been technically revised.
iv © ISO 2006 – All rights reserved

Introduction
The fan-pressurization method is intended to characterize the air permeability of the building envelope or parts
thereof. It can be used
a) to measure the air permeability of a building or part thereof for compliance with a design air-tightness
specification;
b) to compare the relative air permeability of several similar buildings or parts of buildings;
c) to identify the leakage sources;
d) to determine the air-leakage reduction resulting from individual retrofit measures applied incrementally to
an existing building or part of building.
The fan-pressurization method is suitable for the respective diagnostic purposes. Although the air infiltration
and exfiltration cannot be measured directly, the results of this method can also be used to estimate with
adequate precision by means of calculation both the mean infiltration through unintended leakages and the
mean air flow through intended air flow devices from outside, in relation to the pressure conditions to be
expected within the building.
This method does not measure the air-infiltration rate of a building. The results of the fan-pressurization test
can be used to estimate the air infiltration by means of calculation. Other methods are applicable when it is
desired to obtain a direct measurement of the air infiltration rate. It is better to use the fan-pressurization
method for diagnostic purposes and measure the actual infiltration rate with tracer gas methods. A single
tracer gas measurement gives limited information on the performance of ventilation and infiltration of buildings.
This method applies to measurements of air flow through the construction from outside to inside or vice versa.
It does not apply to air flow measurements from outside through the construction and from other places within
the construction back to outside.
The proper use of this International Standard requires a knowledge of the principles of air flow and pressure
measurements. Ideal conditions for the test described in this standard are small temperature differences and
low wind speeds. For tests conducted in the field, it needs to be recognized that field conditions can be less
than ideal. Nevertheless, strong winds and large indoor-outdoor temperature differences should be avoided.
INTERNATIONAL STANDARD ISO 9972:2006(E)

Thermal performance of buildings — Determination of air
permeability of buildings — Fan pressurization method
1 Scope
This International Standard is intended for the measurement of the air permeability of buildings or parts of
buildings in the field. It specifies the use of mechanical pressurization or depressurization of a building or part
of a building. It describes the measurement of the resulting air flow rates over a range of indoor-outdoor static
pressure differences.
This International Standard is intended for the measurement of the air leakage of building envelopes of
single-zone buildings. For the purpose of this International Standard, many multi-zone buildings can be
treated as single-zone buildings by opening interior doors or by inducing equal pressures in adjacent zones.
It does not address evaluation of air permeability through individual components.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 6781, Thermal Insulation — Qualitative detection of thermal irregularities in building envelopes — Infrared
method
ISO 7345, Thermal Insulation — Physical quantities and definitions
ISO 13790:2004, Thermal performance of buildings — Calculation of energy use for space heating and
cooling
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7345 and the following apply.
3.1.1
air leakage rate
air flow rate across the building envelope
NOTE This movement includes flow through joints, cracks and porous surfaces, or a combination thereof, induced by
the air-moving equipment used in this standard (see Clause 4).
3.1.2
internal volume
deliberately heated, cooled or mechanically ventilated space within a building or part of a building subject to
the measurement, generally not including the attic space, basement space and attached structures
3.1.3
building envelope
boundary or barrier separating the internal volume subject to the test from the outside environment or another
part of the building
3.1.4
air change rate at reference pressure
air leakage rate per internal volume at the reference pressure difference across the building envelope
NOTE The reference pressure is usually 50 Pa.
3.1.5
air permeability
air leakage rate per envelope area at the reference pressure difference across the building envelope
NOTE The reference pressure is usually 50 Pa.
3.1.6
specific leakage rate
air leakage rate per net floor area at the reference pressure difference across the building envelope
NOTE A pressure difference of 50 Pa is the most common.
3.1.7
leakage area
area corresponding to air leakage rate at the reference pressure difference across the building envelope
NOTE A pressure difference of 10 Pa is the most common.
3.1.8
specific leakage area
leakage area per net floor area or envelope area at the test reference pressure difference across the building
envelope
3.2 Symbols
Symbol Quantity Unit
2 2
a specific leakage area at 10 Pa m /m
A envelope area m
E
A floor area m
F
A leakage area m
L
3 n
C air flow coefficient m /(h⋅Pa )
env
3 n
C air leakage coefficient m /(h⋅Pa )
L
–1
n air change rate at 50 Pa h
p pressure Pa
p uncorrected barometric pressure Pa
bar
p partial vapour pressure of water Pa
v
p saturation vapour pressure of water Pa
vs
Q tracer gas injection rate m /h
q air permeability at 50 Pa m /h
q air permeability
a50
2 © ISO 2006 – All rights reserved

Symbol Quantity Unit
q air flow rate through the building envelope m /h
env
q air flow rate through the building envelope m /s
env,s
q air leakage rate at 50 Pa m /h
L50
q measured air flow rate m /h
m
3 2
q air permeability at 50 Pa m /(h⋅m )
p50
q air leakage rate at a specified reference pressure m /h
pr
difference
q readings of air flow rate m /h
r
V internal volume m
3 2
w specific leakage rate at 50 Pa m /(h⋅m )
∆p induced pressure difference Pa
∆p zero flow pressure difference (average) Pa
∆p ; ∆p zero-flow pressure difference before and after the Pa
0,1 0,2
test (air moving equipment closed)
∆p measured pressure difference Pa
m
∆p reference pressure Pa
r
Φ relative humidity –
Τ absolute temperature K
Τ external air absolute temperature K
e
Τ internal air absolute temperature K
int
ρ air density kg/m
ρ external air density kg/m
e
ρ internal air density kg/m
int
4 Apparatus
4.1 General
The following description of apparatus is general in nature. Any arrangement of equipment using the same
principles and capable of performing the test procedure within the allowable tolerances is permitted. Examples
of equipment configurations commonly used are indicated in Annex A.
Periodic calibration of the measurement system, used in this test method, according to manufacturer
specifications or to standardized quality insurance systems is required.
4.2 Equipment
4.2.1 Air-moving equipment
This includes any device that is capable of inducing a specific range of positive and negative pressure
differences across the building envelope or part thereof. The system shall provide a constant air flow at each
pressure difference for the period required to obtain readings of air flow rate.
4.2.2 Pressure-measuring device
This includes any instrument capable of measuring pressure differences with an accuracy of ± 2 Pa in the
range of 0 Pa to 100 Pa.
4.2.3 Air flow rate measuring system
This includes any device capable of measuring air flow rate within ± 7 % of the reading.
Care shall be taken if the principle underlying the measurement of volumetric flow rate is an orifice. The
reading of the air flow rate shall be corrected according to air density (see manufacturers' specifications).
4.2.4 Temperature-measuring device
This includes any instrument capable of measuring temperature to an accuracy of ± 1 K.
5 Measurement procedure
5.1 Measurement conditions
5.1.1 General
There are two methods for this measurement procedure: depressurization or pressurization of a building or
part of a building. Regardless of which method is used, the air leakage of building envelope can be measured.
The accuracy of this measurement procedure is largely dependent on the instrumentation and apparatus used
and on the ambient conditions under which the data are taken.
NOTE In general, the measurement result of the depressurization method is larger than that for the pressurization
method. However, when air-tightness in the building is high, the test results of both methods are almost equal.
5.1.2 Measured extent
The extent of the building or part of the building measured is defined as follows.
a) Normally, the part of the building measured includes all deliberately conditioned rooms.
b) In special cases, the extent of the part of the building actually to be tested can be defined in agreement
with the client.
c) If the aim of the measurement is compliance with the air-tightness specification of a building code or
standard and the measured extent is not defined in this code or by a standard, the measured extent is
defined as in a).
Individual parts of a building can be measured separately; e.g. in apartment buildings, each apartment can be
measured individually. However, interpretation of results shall consider that air leakage measured in this way
can include flow through leaks to adjacent parts of the building.
NOTE 1 It is possible that an apartment building meets air-tightness requirements, but that one or more individual
apartments do not.
NOTE 2 Good practice requires measuring pressures induced in adjoining spaces, such as the attic and basement or
adjacent apartments, since air flow into or out of these spaces can be induced by the test method.
5.1.3 Time of measurement
The measurement can take place only after the completion of the envelope of the building or part of the
building to be tested.
NOTE A preliminary air permeability measurement of the air barrier of the building under construction can allow
leakages to be repaired more easily than after the building has been completed.
4 © ISO 2006 – All rights reserved

5.1.4 Meteorological conditions
If the product of the indoor/outdoor air temperature difference, expressed in Kelvin, multiplied by the height,
expressed in metres, of the building or measured part of the building gives a result greater than 250 m⋅K, it is
unlikely that a satisfactory zero-flow pressure difference can be obtained (see 5.3.3).
If the wind speed near the ground exceeds 3 m/s or the meteorological wind speed exceeds 6 m/s or reaches
3 on the Beaufort scale, it is unlikely that a satisfactory zero-flow pressure difference can be obtained (see
5.3.3).
5.2 Preparation
5.2.1 General
This International Standard describes three types of test methods depending on the purpose. The preparation
of the building depends on the test method selected:
⎯ Method A (test of a building in use):
The condition of the building envelope should represent its condition during the season in which heating
or cooling systems are used.
⎯ Method B (test of the building envelope):
Any intentional opening in the building envelope shall be closed or sealed as specified in 5.2.2 and 5.2.3.
⎯ Method C (test of the building in use):
Automatically regulating, externally mounted air transfer devices are sealed, other openings are handled
in the same way as for method A.
5.2.2 Building components
Close all intentional exterior openings of the building or part of the building to be tested (windows, doors,
fireguard).
For the purpose of methods A and C (building in use), do not take any further measures to improve the
air-tightness of the building components (however, see also 5.2.3). For the purpose of method C, all
automatically regulating externally mounted air transfer devices are sealed. This is valid for natural supply and
exhaust systems, as well as for natural supply and mechanical exhaust systems.
For the purpose of method B (building envelope), all adjustable openings shall be closed and remaining
intentional openings shall be sealed.
The entire building or part of the building to be tested shall be configured to respond to pressurization as a
single zone.
All interconnecting doors (except for cupboards and closets, which should be closed) in the part of the building
to be tested shall be opened so that a uniform pressure is maintained within a range of less than 10 % of the
measured inside/outside pressure difference.
NOTE When testing large or complex buildings, this condition becomes increasingly important and can be verified by
selected differential pressure measurements between different rooms at the highest pressure contemplated.
Make general observations of the condition of the building. Take notes on the windows, doors, opaque walls,
roof and floor, position of adjustable openings and any sealings applied to intentional openings.
5.2.3 Heating, ventilation and air conditioning systems
Heating systems with indoor air intake shall be turned off. Open fireplaces shall be cleared of ashes.
Mechanical ventilation and air conditioning systems shall be turned off.
Air terminal devices of mechanical ventilation or air conditioning systems shall be sealed. Other ventilation
openings (for example, openings for natural ventilation) shall be closed for purposes of method A and sealed
for method B.
Take measures to avoid exhaust hazards from heating systems. Take into account heating sources in
adjacent apartments.
If there is an intention to estimate the infiltration/exfiltration air change rate in accordance with
ISO 13790:2004, natural system openings are kept open for the purpose of the pressurization test or their
contribution is calculated.
5.2.4 Air-moving equipment
Connect the air-moving equipment to the building envelope using a window, door, or vent opening. Ensure
that the joints between the equipment and the building are sealed to eliminate any leakage.
If the building heating, ventilation and air conditioning system is used as the air-moving equipment, arrange
the fans and dampers to allow the system to pressurize or to depressurize the building in a manner such that
the total inward or outward air flow rate can be measured (see A.4).
NOTE In an airtight building, it is possible for the door, window or vent used to pass air during the test to produce the
most leakage. It is important to be careful in such a case with regards to the selection of the position of the air-moving
equipment and/or the interpretation of the test results.
5.2.5 Pressure measuring devices
The indoor/outdoor pressure difference is usually measured at the lowest floor level of the building envelope
under consideration.
NOTE In tall buildings, it is good practice to measure the pressure difference at the top floor level of the building
envelope under consideration as well.
Ensure that interior and exterior pressure drops are not influenced by the air moving equipment. The exterior
pressure tap should be protected from the effects of dynamic pressure, e.g. by fitting a T-pipe or connecting it
to a perforated box. Especially in windy conditions, it is good practice to place the exterior pressure tap some
distance away from the building, but not close to other obstacles.
The pressure tubes should not be aligned vertically. The tubing shall not be exposed to large temperature
differences (e.g. due to the sun).
5.3 Steps of the procedure
5.3.1 Preliminary check
Always check the complete building envelope at approximately the highest pressure difference used in the
test for large leaks and failings of temporarily sealed openings. If such leaks are detected, take detailed notes.
Any temporary sealings found missing or deficien
...

INTERNATIONAL ISO
STANDARD 9972
Second edition
2006-05-01
Thermal performance of buildings —
Determination of air permeability of
buildings — Fan pressurization method
Performance thermique des bâtiments — Détermination de la
perméabilité à l'air des bâtiments — Méthode de pressurisation par
ventilateur
Reference number
©
ISO 2006
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO 2006
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2006 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols. 1
4 Apparatus . 3
5 Measurement procedure . 4
6 Expression of results . 8
7 Test report . 12
8 Uncertainty . 13
Annex A (informative) Description of equipment used to pressurize buildings. 14
Annex B (informative) Dependence of air density on temperature, dew point and barometric
pressure. 16
Annex C (informative) Recommended procedure for estimating uncertainty in derived quantities. 17
Annex D (informative) Beaufort scale for wind force (extract) . 20

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 9972 was prepared by Technical Committee ISO/TC 163, Thermal performance and energy use in the
built environment, Subcommittee SC 1, Test and measurement methods.
This second edition cancels and replaces the first edition (ISO 9972:1996), which has been technically revised.
iv © ISO 2006 – All rights reserved

Introduction
The fan-pressurization method is intended to characterize the air permeability of the building envelope or parts
thereof. It can be used
a) to measure the air permeability of a building or part thereof for compliance with a design air-tightness
specification;
b) to compare the relative air permeability of several similar buildings or parts of buildings;
c) to identify the leakage sources;
d) to determine the air-leakage reduction resulting from individual retrofit measures applied incrementally to
an existing building or part of building.
The fan-pressurization method is suitable for the respective diagnostic purposes. Although the air infiltration
and exfiltration cannot be measured directly, the results of this method can also be used to estimate with
adequate precision by means of calculation both the mean infiltration through unintended leakages and the
mean air flow through intended air flow devices from outside, in relation to the pressure conditions to be
expected within the building.
This method does not measure the air-infiltration rate of a building. The results of the fan-pressurization test
can be used to estimate the air infiltration by means of calculation. Other methods are applicable when it is
desired to obtain a direct measurement of the air infiltration rate. It is better to use the fan-pressurization
method for diagnostic purposes and measure the actual infiltration rate with tracer gas methods. A single
tracer gas measurement gives limited information on the performance of ventilation and infiltration of buildings.
This method applies to measurements of air flow through the construction from outside to inside or vice versa.
It does not apply to air flow measurements from outside through the construction and from other places within
the construction back to outside.
The proper use of this International Standard requires a knowledge of the principles of air flow and pressure
measurements. Ideal conditions for the test described in this standard are small temperature differences and
low wind speeds. For tests conducted in the field, it needs to be recognized that field conditions can be less
than ideal. Nevertheless, strong winds and large indoor-outdoor temperature differences should be avoided.
INTERNATIONAL STANDARD ISO 9972:2006(E)

Thermal performance of buildings — Determination of air
permeability of buildings — Fan pressurization method
1 Scope
This International Standard is intended for the measurement of the air permeability of buildings or parts of
buildings in the field. It specifies the use of mechanical pressurization or depressurization of a building or part
of a building. It describes the measurement of the resulting air flow rates over a range of indoor-outdoor static
pressure differences.
This International Standard is intended for the measurement of the air leakage of building envelopes of
single-zone buildings. For the purpose of this International Standard, many multi-zone buildings can be
treated as single-zone buildings by opening interior doors or by inducing equal pressures in adjacent zones.
It does not address evaluation of air permeability through individual components.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 6781, Thermal Insulation — Qualitative detection of thermal irregularities in building envelopes — Infrared
method
ISO 7345, Thermal Insulation — Physical quantities and definitions
ISO 13790:2004, Thermal performance of buildings — Calculation of energy use for space heating and
cooling
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7345 and the following apply.
3.1.1
air leakage rate
air flow rate across the building envelope
NOTE This movement includes flow through joints, cracks and porous surfaces, or a combination thereof, induced by
the air-moving equipment used in this standard (see Clause 4).
3.1.2
internal volume
deliberately heated, cooled or mechanically ventilated space within a building or part of a building subject to
the measurement, generally not including the attic space, basement space and attached structures
3.1.3
building envelope
boundary or barrier separating the internal volume subject to the test from the outside environment or another
part of the building
3.1.4
air change rate at reference pressure
air leakage rate per internal volume at the reference pressure difference across the building envelope
NOTE The reference pressure is usually 50 Pa.
3.1.5
air permeability
air leakage rate per envelope area at the reference pressure difference across the building envelope
NOTE The reference pressure is usually 50 Pa.
3.1.6
specific leakage rate
air leakage rate per net floor area at the reference pressure difference across the building envelope
NOTE A pressure difference of 50 Pa is the most common.
3.1.7
leakage area
area corresponding to air leakage rate at the reference pressure difference across the building envelope
NOTE A pressure difference of 10 Pa is the most common.
3.1.8
specific leakage area
leakage area per net floor area or envelope area at the test reference pressure difference across the building
envelope
3.2 Symbols
Symbol Quantity Unit
2 2
a specific leakage area at 10 Pa m /m
A envelope area m
E
A floor area m
F
A leakage area m
L
3 n
C air flow coefficient m /(h⋅Pa )
env
3 n
C air leakage coefficient m /(h⋅Pa )
L
–1
n air change rate at 50 Pa h
p pressure Pa
p uncorrected barometric pressure Pa
bar
p partial vapour pressure of water Pa
v
p saturation vapour pressure of water Pa
vs
Q tracer gas injection rate m /h
q air permeability at 50 Pa m /h
q air permeability
a50
2 © ISO 2006 – All rights reserved

Symbol Quantity Unit
q air flow rate through the building envelope m /h
env
q air flow rate through the building envelope m /s
env,s
q air leakage rate at 50 Pa m /h
L50
q measured air flow rate m /h
m
3 2
q air permeability at 50 Pa m /(h⋅m )
p50
q air leakage rate at a specified reference pressure m /h
pr
difference
q readings of air flow rate m /h
r
V internal volume m
3 2
w specific leakage rate at 50 Pa m /(h⋅m )
∆p induced pressure difference Pa
∆p zero flow pressure difference (average) Pa
∆p ; ∆p zero-flow pressure difference before and after the Pa
0,1 0,2
test (air moving equipment closed)
∆p measured pressure difference Pa
m
∆p reference pressure Pa
r
Φ relative humidity –
Τ absolute temperature K
Τ external air absolute temperature K
e
Τ internal air absolute temperature K
int
ρ air density kg/m
ρ external air density kg/m
e
ρ internal air density kg/m
int
4 Apparatus
4.1 General
The following description of apparatus is general in nature. Any arrangement of equipment using the same
principles and capable of performing the test procedure within the allowable tolerances is permitted. Examples
of equipment configurations commonly used are indicated in Annex A.
Periodic calibration of the measurement system, used in this test method, according to manufacturer
specifications or to standardized quality insurance systems is required.
4.2 Equipment
4.2.1 Air-moving equipment
This includes any device that is capable of inducing a specific range of positive and negative pressure
differences across the building envelope or part thereof. The system shall provide a constant air flow at each
pressure difference for the period required to obtain readings of air flow rate.
4.2.2 Pressure-measuring device
This includes any instrument capable of measuring pressure differences with an accuracy of ± 2 Pa in the
range of 0 Pa to 100 Pa.
4.2.3 Air flow rate measuring system
This includes any device capable of measuring air flow rate within ± 7 % of the reading.
Care shall be taken if the principle underlying the measurement of volumetric flow rate is an orifice. The
reading of the air flow rate shall be corrected according to air density (see manufacturers' specifications).
4.2.4 Temperature-measuring device
This includes any instrument capable of measuring temperature to an accuracy of ± 1 K.
5 Measurement procedure
5.1 Measurement conditions
5.1.1 General
There are two methods for this measurement procedure: depressurization or pressurization of a building or
part of a building. Regardless of which method is used, the air leakage of building envelope can be measured.
The accuracy of this measurement procedure is largely dependent on the instrumentation and apparatus used
and on the ambient conditions under which the data are taken.
NOTE In general, the measurement result of the depressurization method is larger than that for the pressurization
method. However, when air-tightness in the building is high, the test results of both methods are almost equal.
5.1.2 Measured extent
The extent of the building or part of the building measured is defined as follows.
a) Normally, the part of the building measured includes all deliberately conditioned rooms.
b) In special cases, the extent of the part of the building actually to be tested can be defined in agreement
with the client.
c) If the aim of the measurement is compliance with the air-tightness specification of a building code or
standard and the measured extent is not defined in this code or by a standard, the measured extent is
defined as in a).
Individual parts of a building can be measured separately; e.g. in apartment buildings, each apartment can be
measured individually. However, interpretation of results shall consider that air leakage measured in this way
can include flow through leaks to adjacent parts of the building.
NOTE 1 It is possible that an apartment building meets air-tightness requirements, but that one or more individual
apartments do not.
NOTE 2 Good practice requires measuring pressures induced in adjoining spaces, such as the attic and basement or
adjacent apartments, since air flow into or out of these spaces can be induced by the test method.
5.1.3 Time of measurement
The measurement can take place only after the completion of the envelope of the building or part of the
building to be tested.
NOTE A preliminary air permeability measurement of the air barrier of the building under construction can allow
leakages to be repaired more easily than after the building has been completed.
4 © ISO 2006 – All rights reserved

5.1.4 Meteorological conditions
If the product of the indoor/outdoor air temperature difference, expressed in Kelvin, multiplied by the height,
expressed in metres, of the building or measured part of the building gives a result greater than 250 m⋅K, it is
unlikely that a satisfactory zero-flow pressure difference can be obtained (see 5.3.3).
If the wind speed near the ground exceeds 3 m/s or the meteorological wind speed exceeds 6 m/s or reaches
3 on the Beaufort scale, it is unlikely that a satisfactory zero-flow pressure difference can be obtained (see
5.3.3).
5.2 Preparation
5.2.1 General
This International Standard describes three types of test methods depending on the purpose. The preparation
of the building depends on the test method selected:
⎯ Method A (test of a building in use):
The condition of the building envelope should represent its condition during the season in which heating
or cooling systems are used.
⎯ Method B (test of the building envelope):
Any intentional opening in the building envelope shall be closed or sealed as specified in 5.2.2 and 5.2.3.
⎯ Method C (test of the building in use):
Automatically regulating, externally mounted air transfer devices are sealed, other openings are handled
in the same way as for method A.
5.2.2 Building components
Close all intentional exterior openings of the building or part of the building to be tested (windows, doors,
fireguard).
For the purpose of methods A and C (building in use), do not take any further measures to improve the
air-tightness of the building components (however, see also 5.2.3). For the purpose of method C, all
automatically regulating externally mounted air transfer devices are sealed. This is valid for natural supply and
exhaust systems, as well as for natural supply and mechanical exhaust systems.
For the purpose of method B (building envelope), all adjustable openings shall be closed and remaining
intentional openings shall be sealed.
The entire building or part of the building to be tested shall be configured to respond to pressurization as a
single zone.
All interconnecting doors (except for cupboards and closets, which should be closed) in the part of the building
to be tested shall be opened so that a uniform pressure is maintained within a range of less than 10 % of the
measured inside/outside pressure difference.
NOTE When testing large or complex buildings, this condition becomes increasingly important and can be verified by
selected differential pressure measurements between different rooms at the highest pressure contemplated.
Make general observations of the condition of the building. Take notes on the windows, doors, opaque walls,
roof and floor, position of adjustable openings and any sealings applied to intentional openings.
5.2.3 Heating, ventilation and air conditioning systems
Heating systems with indoor air intake shall be turned off. Open fireplaces shall be cleared of ashes.
Mechanical ventilation and air conditioning systems shall be turned off.
Air terminal devices of mechanical ventilation or air conditioning systems shall be sealed. Other ventilation
openings (for example, openings for natural ventilation) shall be closed for purposes of method A and sealed
for method B.
Take measures to avoid exhaust hazards from heating systems. Take into account heating sources in
adjacent apartments.
If there is an intention to estimate the infiltration/exfiltration air change rate in accordance with
ISO 13790:2004, natural system openings are kept open for the purpose of the pressurization test or their
contribution is calculated.
5.2.4 Air-moving equipment
Connect the air-moving equipment to the building envelope using a window, door, or vent opening. Ensure
that the joints between the equipment and the building are sealed to eliminate any leakage.
If the building heating, ventilation and air conditioning system is used as the air-moving equipment, arrange
the fans and dampers to allow the system to pressurize or to depressurize the building in a manner such that
the total inward or outward air flow rate can be measured (see A.4).
NOTE In an airtight building, it is possible for the door, window or vent used to pass air during the test to produce the
most leakage. It is important to be careful in such a case with regards to the selection of the position of the air-moving
equipment and/or the interpretation of the test results.
5.2.5 Pressure measuring devices
The indoor/outdoor pressure difference is usually measured at the lowest floor level of the building envelope
under consideration.
NOTE In tall buildings, it is good practice to measure the pressure difference at the top floor level of the building
envelope under consideration as well.
Ensure that interior and exterior pressure drops are not influenced by the air moving equipment. The exterior
pressure tap should be protected from the effects of dynamic pressure, e.g. by fitting a T-pipe or connecting it
to a perforated box. Especially in windy conditions, it is good practice to place the exterior pressure tap some
distance away from the building, but not close to other obstacles.
The pressure tubes should not be aligned vertically. The tubing shall not be exposed to large temperature
differences (e.g. due to the sun).
5.3 Steps of the procedure
5.3.1 Preliminary check
Always check the complete building envelope at approximately the highest pressure difference used in the
test for large leaks and failings of temporarily sealed openings. If such leaks are detected, take detailed notes.
Any temporary sealings found missing or deficient, e.g. of heating, ventilation and air conditioning components,
shall be fixed at this time.
Check that water traps in plumbing systems are correctly filled or sealed.
6 © ISO 2006 – All rights reserved

5.3.2 Temperature and wind conditions
To correct the air flow rate measurement for air density (see Annex B), read the temperature inside and
outside the building before, during or after the test.
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