ISO 16956:2015

INTERNATIONAL ISO
STANDARD 16956
First edition
2015-02-01
Thermal performance in the built
environment — Determination of air
flow rate in building applications by
field measuring methods
Performance thermique des bâtiments — Détermination du taux de
renouvellement d’air dans les bâtiments par des méthodes de mesure
sur site
Reference number
©
ISO 2015
© ISO 2015
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ii © ISO 2015 – All rights reserved

Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 Types and selection of measurement method . 2
5.1 Types of measurement methods and their application . 2
5.2 Selection of measurement method . 2
6 Basic specifications measuring instruments and utilization methods .2
6.1 General . 2
6.2 Thermal anemometer . 2
6.3 Pitot tube and manometer . 3
6.4 Vane-type anemometer . 3
7 Field measuring methods of air flow rate of ventilation and air conditioning systems .3
7.1 Multipoint air velocity measurement method . 3
7.1.1 Measurement in a duct . 4
7.1.2 Measurement method at duct connection of air-conditioning system . 6
7.1.3 Selection of measuring instruments . 7
7.2 Tracer gas measurement method . 7
7.2.1 Formula . 7
7.2.2 Tracer gas . 8
7.2.3 Procedures for measuring air flow rate . 8
7.2.4 Tracer gas injection procedures . 9
7.2.5 Tracer gas sampling procedures .10
7.3 Flow hood method .10
7.3.1 General.10
7.3.2 Equipment composition .10
7.3.3 Measurement procedures .11
7.4 Pressure compensation measurement method .11
7.4.1 Equipment composition .12
7.4.2 Measurement procedures .13
7.4.3 Effective application range .13
7.5 Pressure difference measurement method .13
7.5.1 Measuring equipment .13
7.5.2 Selection of measuring instruments .14
7.5.3 Measuring procedures .14
8 Uncertainty .15
8.1 Uncertainty of each measurement .15
8.1.1 Multipoint air velocity measurement method .15
8.1.2 Tracer gas measurement method.15
8.1.3 Flow hood method .15
8.1.4 Pressure-loss compensation measurement method .15
8.1.5 Pressure difference measurement method .15
8.2 Analysis of uncertainty .15
9 Measurement report .16
9.1 Information related to measured object .16
9.2 Items related to measuring method .16
9.3 Measurement results .16
Annex A (normative) Position for cross-section measurement in a duct using multipoint
measurement method .17
Annex B (normative) Accuracy of air velocity measurement instrument .21
Annex C (informative) Types of tracer gas .22
Bibliography .23
iv © ISO 2015 – All rights reserved

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
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electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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to Trade (TBT), see the following URL: Foreword — Supplementary information.
The committee responsible for this document is ISO/TC 163, Thermal performance and energy use in the
built environment, Subcommittee SC 1, Test and measurement methods.
INTERNATIONAL STANDARD ISO 16956:2015(E)
Thermal performance in the built environment —
Determination of air flow rate in building applications by
field measuring methods
1 Scope
In the cooling and heating loads of a building, the air taken in from outside account for a large portion
of the entire load; in order to estimate this load, it is necessary to correctly grasp the air flow rate
of ventilation and air-conditioning systems. This International Standard stipulates the methods for
measuring the rate of air flow through the ducts in a steadily operating ventilation and air-conditioning
system and in the air control ports including air diffuser, suction opening, and exhaust opening.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 5168, Measurement of fluid flow — Procedures for the evaluation of uncertainties
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
orifice plate
thin plate having a hole, or holes, bored through it
Note 1 to entry: These are used for measuring the difference in static pressure of the flow before and after the disc
and obtaining the air flow rate in the duct by multiplying by a predetermined coefficient.
3.2
tracer gas
gas used to measure its concentration varying in the air
Note 1 to entry: This gas is mixed with a sufficiently small amount of air so as not to affect the flow, and the
amount of air is determined by measuring the gas concentration diluted in the air.
3.3
volumetric concentration
ratio of the volume of the specific gas to the unit volume of the mixture of air
Note 1 to entry: It is expressed in cubic meters per cubic meters or 10-6 ∙ vol.
3.4
mass flow
mass of air or tracer gas flowing in unit time
Note 1 to entry: It is expressed in mg per second or kg per hour.
3.5
volumetric flow
volume of air flowing in unit time
Note 1 to entry: It is expressed in cubic meters per hour.
4 Symbols and abbreviated terms
A
...