ISO 5222-1:2025

International
Standard
ISO 5222-1
Second edition
Heat recovery ventilators and
2025-10
energy recovery ventilators —
Testing and calculating methods for
performance factor —
Part 1:
Sensible heating recovery seasonal
performance factors of heat
recovery ventilators (HRVs)
Ventilateurs récupérateurs de chaleur et ventilateurs
récupérateurs d'énergie — Méthodes d'essai et de calcul des
facteurs de performances —
Partie 1: Facteurs de performances saisonnières de la
récupération de chaleur sensible des ventilateurs récupérateurs
de chaleur (HRV)
Reference number
© ISO 2025
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 2
5 Tests . 3
5.1 General requirements .3
5.2 Test conditions .3
5.3 Test methods .3
5.3.1 General .3
5.3.2 Energy saving stage limit temperature .4
5.3.3 Sensible heating recovery performance test . .4
5.3.4 Determination of bypass outdoor temperature .4
5.3.5 Measurement of power input of heat recovery ventilator with bypass ventilation
function.4
5.3.6 Determination of the frosting temperature by test .5
6 Calculations . 6
6.1 Gross sensible heating recovery effectiveness (ε ) .6
sh
6.2 Calculation of seasonal performance factor of sensible heating recovery (F ) .6
sh
6.2.1 Reference outdoor air heating load and sensible heating recovery capacity .6
6.2.2 The characteristics of sensible heating recovery capacity against outdoor
temperature .7
6.2.3 Power input characteristics of sensible heating recovery against outdoor
temperature .7
6.2.4 Outdoor temperature bin distribution for heating .8
6.2.5 Calculation of seasonal sensible heating recovery capacity (E ) .8
sh
6.2.6 Calculation of seasonal sensible heating recovery power input (P ) .9
in,E
6.2.7 Calculation of seasonal performance factor for sensible heating recovery (F ) .9
sh
7 Test report . 9
Annex A (informative) The schematic diagram of heat recovery ventilators (HRVs) heating (H)
operation . 10
Annex B (informative) The default outdoor temperature bin distribution for heating .13
Annex C (normative) Method of determination of the temperature T . 14
F,0
Annex D (informative) Calculating method for seasonal performance factor when setting a
specific application heating load .15
Annex E (normative) Calculation of the bypass outdoor temperature . 17
Annex F (informative) Report template .18
Bibliography .21

iii
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
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with the International Electrotechnical Commission (IEC) on all matters of 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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
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Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 86, Refrigeration and air-conditioning,
Subcommittee SC 6, Testing and rating of air-conditioners and heat pumps.
This second edition cancels and replaces the first edition (ISO 5222-1:2023), which has been technically
revised. The main changes are as follows:
— terms and definitions have been revised to align with ISO 5222-2 and ISO 5222-3;
— symbols have been revised in accordance with the ISO/IEC Directives, Part 2;
— names of stages have been revised to align with ISO 5222-2 and ISO 5222-3;
— 6.2 sensible heating coefficient of energy and 3.3 coefficient of energy have been deleted;
— errors in 6.2.3 have been corrected;
— a note has been added to 6.2.5 for clarification;
— Figure A.1 has been revised to align with ISO 5222-2 and ISO 5222-3.
A list of all parts in the ISO 5222 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
International Standard ISO 5222-1:2025(en)
Heat recovery ventilators and energy recovery ventilators —
Testing and calculating methods for performance factor —
Part 1:
Sensible heating recovery seasonal performance factors of
heat recovery ventilators (HRVs)
1 Scope
This document specifies the testing and calculating methods for sensible heating recovery seasonal
performance factor of heat recovery ventilators (HRVs) covered by ISO 16494-1.
This document also specifies the test conditions and the corresponding test procedures for determining the
sensible heating recovery seasonal performance factor of HRVs. It is intended for use only for marking and
comparison purposes.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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 16494-1:2022/Amd 1:2023, Heat recovery ventilators and energy recovery ventilators — Method of test for
performance — Part 1: Development of metrics for evaluation of energy related performance
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 16494-1 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
heat recovery
transfer of sensible energy from exhaust air to supply air in heat recovery ventilators
while heating
3.2
bypass ventilation function
function for reducing power input of the fans while the heat energy recovered is less than the additional
energy input due to overcoming the resistance of recovery heat exchanger during its operation time
Note 1 to entry: The bypass ventilation function makes either the supply air or exhaust air or both airflows go through
the bypass passage with energy saving control.

3.3
gross effectiveness
measured effectiveness, not adjusted for leakage, motor heat gain or heat transfer
through the unit casing
Note 1 to entry: The sensible heating gross effectiveness of heat recovery ventilators, at equal airflow, is described in
ISO 16494-1:2022, 9.5.
3.4
bypass outdoor temperature
T
b
outdoor temperature in heating conditions, at which the power reduction to heat recovery ventilators
(HRVs) by operating in bypass mode is equal to the saving of power input to the heating system due to the
heat recovered by HRVs
3.5
seasonal performance factor of sensible heating recovery
F
sh
ratio of seasonal amount of sensible heat recovered together with power value of moving air to the whole
power input of heat recovery ventilators, under the rating conditions and seasonal outdoor temperature
bins selected from this standard
3.6
building heating balance temperature
T
BHB
outdoor air temperature at which building internal heat gain, solar radiation, and so on, equals to heat loss
through the building envelope
4 Symbols and abbreviated terms
Symbol Description Unit
c specific heat of leaving supply air (SA) kJ/(kg· °C)
p
E capacity of seasonal sensible heating recovery Wh
sh
F seasonal performance factor of sensible heating recovery Wh/Wh
sh
reference outdoor air sensible heating load at outdoor air bin temperature
L W
sh,t,j
t
j
n number of temperature bins –
n bin hours which the outdoor air bin temperature occurs h
j
P differential between fan power without bypass and fan power with bypass kW
diff
power input to HRVs at outdoor air bin temperature t for bin temperature
j
P W
in,by,t,j
in H,Stage 1, for HRVs with bypass
P power input of seasonal sensible heating recovery Wh
in,E
P power input to a supplementary preheater at full capacity W
in,h,t,j
power input to HRVs to operate the fans at outdoor air bin temperature t
j
P W
in,no,t,j
for all stages, for HRVs without bypass
P power input to ventilator at outdoor air bin temperature t W
in,t,j j
P ventilation power input of HRVs at outdoor air bin temperature W
in,v,t,j
P power value of moving air at outdoor air bin temperature t J/s or W
vma,t,j j
Q heating load from heat inflow of building kW
cn
Q heating load from internal gain kW
ig
Q net supply mass flow rate kg/s
m2, net
Q reduced heating load due to heat recovery kW
s
Q total heating load of building kW
t
Q ventilation air heating load without recovery kW
v
Symbol Description Unit
Q ventilation air heating load with recovery kW
vwr
T outdoor air temperature when HRVs operates under air bypass function °C
b
T building heat balance temperature; at this temperature, Q will equal zero °C
BHB t
T outdoor air bin temperature at which the frost occurs °C
F
temperature at which the test to determine the frost temperature can be
T °C
F,0
started to reduce duration time of the test
temperature defined in ISO 16494-1:2022, Table 2 as T5/T6/T7; indicates
T °C
0,h
the indoor design temperature of the building
ε gross sensible heating recovery effectiveness of HRVs %
sh
ϕ sensible heat recovery capacity of HRVs at outdoor air bin temperature t W
sh,t,j j
5 Tests
5.1 General requirements
The test conditions used and the accuracy and uncertainties of the instruments used shall conform with
ISO 16494-1 and this document.
5.2 Test conditions
For the purpose of ε , E and F , there are three standard test conditions T5/T6/T7 in accordance with
sh sh sh
ISO 16494-1:2022, Table 2. HRVs shall be tested at one of the three test conditions. It is recommended to
select test conditions that most closely represent the outdoor temperature bin distribution in the region as
described in Annex B and Annex D.
Outdoor temperature bin distribution and bin hours differ from region to region. If bin hours are set to
a certain value for a certain region, the integrated value of heating load and energy consumption can be
determined.
Table 1 shows the requirement of default values and the reference outdoor temperature bin distribution
for test and calculation. In case of setting other outdoor temperature bin distribution, refer to the setting
method described in Annex D.
Table 1 — Conditions of performance test (heating)
Outdoor air temperature Indoor air temperature Application
(°C) (°C) temperature bin type
for calculation
Dry bulb Wet bulb Dry bulb Wet bulb
T5 2 1 21 14
T6 5 3 20 15 In Annex B or D
T7 7 6 20 12
NOTE The allowable variation of readings is given in ISO 16494-1:2022, Table F.2.
5.3 Test methods
5.3.1 General
For higher seasonal energy performance, HRVs can be designed with an airflow bypass function that
integrates fan speed control or airflow control devices, which can change the fan power input according to
different outdoor temperature conditions while maintaining the aerodynamic performance.

5.3.2 Energy saving stage limit temperature
To assess the energy saving ability of HRVs, the operation stages under the application temperature bin are
shown in Annex A using a schematic diagram.
5.3.3 Sensible heating recovery performance test
5.3.3.1 Standard condition performance tests
The sensible heating recovery performance tests shall be conducted in accordance with ISO 16494-1. The
sensible heating recovery performance, efficiency as well as airflow and static pressure shall be measured
in accordance with the selected standard heating performance tests conditions in Table 1.
5.3.3.2 Determination of performance at application climate
The sensible heating recovery performance under certain climate temperature bins shall also be determined
by calculation using the temperature bins; see Annex B and Annex D.
5.3.4 Determination of bypass outdoor temperature
The manufacturer shall specify the value of bypass outdoor temperature. The laboratory shall verify
that the unit under test is functioning and what the test action temperature is. If it is not specified by
the manufacturer, the laboratory shall calculate the outdoor bypass temperature and set it as the T in
b
accordance with Annex E.
5.3.5 Measurement of power input of heat recovery ventilator with bypass ventilation function
5.3.5.1 The manufacturer can provide information on how to set the bypass function if requested by the
testing laboratories.
NOTE 1 Due to the additional air resistance of the heat recovery exchanger, when the heat energy recovered is less
than the additional energy input due to overcoming the resistance of recovery heat exchanger during its operation
time, the equipment can provide the bypass ventilation function to reduce the additional energy consumption, when
only ventilation is necessary.
NOTE 2 When the bypass ventilation function acts, there can be several means to reduce the additional energy
consumption (e.g. with fan speed control or valve control in the fan’s inlet or outlet, to keep the same airflow rate and
pressure as rating performance condition).
5.3.5.2 The tests shall be conducted at the required control set which allows steady state operation of the
equipment at the given test conditions.
5.3.5.3 The test of unit with bypass ventilation function and fan speed control shall be as follows:
a) Set up the bypass ventilation function according to the manufacturer's instructions.
b) Adjust the test auxiliary device to keep the average pressure value at air outlet and inlet of unit in
ISO 16494-1:2022/Amd 1:2023, Figure A.1 within the 5 % of tested unit’s nominal value, the airflow rate
larger or equal to its nominal value.
c) In accordance with ISO 16494-1, measure and record the data of airflow rate, the pressure and power input.
d) Determine and record the outdoor temperature at which the bypass ventilation function acts, either by
manufacturer's statement or by measure. The power input value measured when the bypass ventilation
functions are activated is recorded as the bypass ventilation function power input, used for the
calculation of F corresponding to each outdoor bin temperature in the ventilation period.
sh
5.3.5.4 The test of unit with bypass ventilation function and airflow control devices but without fan speed
control shall be as follows:
a) Set up the bypass ventilation function according to the manufacturer's instructions.
b) Adjust the test auxiliary device to keep the average pressure value within the 5 % of the tested unit’s
nominal value, the airflow rate larger or equal to its nominal value.
c) Determine and record the outdoor temperature at which the bypass ventilation function acts, either by
the manufacturer's statement or by measurement. The power input value measured when the bypass
ventilation function is on shall be recorded as the bypass ventilation function power input, used for the
calculation of F corresponding to each outdoor bin temperature in the ventilation period.
sh
5.3.5.5 The test of equipment with bypass ventilation function and without fan speed control and without
automatic airflow control devices shall be as follows:
a) Set up the bypass ventilation function according to manufacturer’s instruction.
b) According to ISO 16494-1, do not adjust any of the test auxiliary devices during the test and record the
data of airflow rate, the pressure and power input.
c) Determine and record the outdoor temperature that the bypass ventilation function acts, either by the
manufacturer's statement or by test.
d) The power input value measured when bypass ventilation functions are on is recorded as the bypass
ventilation function power input, used for the calculation of F corresponding to each outdoor bin
sh
temperature in ventilation period.
5.3.5.6 The test of equipment with no bypass ventilation function shall be as follows:
For equipment with no bypass ventilation function, the power input is the same value as the values outlined
in 5.3.3.1 at all stages, which shall be used for calculating F corresponding to each outdoor temperature in
sh
the ventilation period.
5.3.6 Determination of the frosting temperature by test
5.3.6.1 The frost temperature test shall be conducted in accordance with Annex C. The manufacturer can
provide information on how to operate the equipment if requested by the testing laboratories.
5.3.6.2 The test conditions shall be as follows:
a) The airflow rate and static pressure shall be as specified in 5.3.3.1.
b) The entering exhaust air (RA) temperature shall be kept at conditions T5/T6/T7 specified in Table 1.
The entering supply air (OA) temperature shall be gradually reduced from 0 °C, or, to save time, from the
T , which is described in Annex C, plus 2 K.
F,0
5.3.6.3 Confirmation of frost outdoor air temperature shall be as follows:
a) Turn off the supplement heat function for anti-frost.
b) Conduct the tests of gross sensible heating recovery effectiveness of HRVs by changing outdoor
temperature from the T plus 2 K to lower temperature. While adjusting the outdoor air temperature,
F,0
keep the reducing rate of temperature not less than 0,5 K per hour and not greater than 1,0 K per hour.
c) Record the inlet and outlet air parameters so that gross sensible heating effectiveness can be calculated
every 0,5 h.
d) Calculate the gross sensible heat effectiveness in accordance with ISO 16494-1:2022, 9.5.

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