SIST EN ISO 7730:2026

SLOVENSKI STANDARD
01-februar-2026
Nadomešča:
SIST EN ISO 7730:2006
Ergonomija toplotnega okolja - Analitično ugotavljanje in razlaga toplotnega
ugodja z izračunom PMV in PPD vrednosti ter merili za lokalno toplotno ugodje
(ISO 7730:2025)
Ergonomics of the thermal environment - Analytical determination and interpretation of
thermal comfort using calculation of the PMV and PPD indices and local thermal comfort
criteria (ISO 7730:2025)
Ergonomie der thermischen Umgebung - Analytische Bestimmung und Interpretation der
thermischen Behaglichkeit durch Berechnung des PMV- und des PPD-Indexes und
Kriterien der lokalen thermischen Behaglichkeit (ISO 7730:2025)
Ergonomie des ambiances thermiques - Détermination analytique et interprétation du
confort thermique par le calcul des indices PMV et PPD et par des critères de confort
thermique local (ISO 7730:2025)
Ta slovenski standard je istoveten z: EN ISO 7730:2025
ICS:
13.180 Ergonomija Ergonomics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 7730
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2025
EUROPÄISCHE NORM
ICS 13.180 Supersedes EN ISO 7730:2005
English Version
Ergonomics of the thermal environment - Analytical
determination and interpretation of thermal comfort using
calculation of the PMV and PPD indices and local thermal
comfort criteria (ISO 7730:2025)
Ergonomie des ambiances thermiques - Détermination Ergonomie der thermischen Umgebung - Analytische
analytique et interprétation du confort thermique par Bestimmung und Interpretation der thermischen
le calcul des indices PMV et PPD et par des critères de Behaglichkeit durch Berechnung des PMV- und des
confort thermique local (ISO 7730:2025) PPD-Indexes und Kriterien der lokalen thermischen
Behaglichkeit (ISO 7730:2025)
This European Standard was approved by CEN on 24 August 2025.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 7730:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 7730:2025) has been prepared by Technical Committee ISO/TC 159
"Ergonomics " in collaboration with Technical Committee CEN/TC 122 “Ergonomics” the secretariat of
which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by March 2026, and conflicting national standards shall
be withdrawn at the latest by March 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 7730:2005.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 7730:2025 has been approved by CEN as EN ISO 7730:2025 without any modification.

International
Standard
ISO 7730
Fourth edition
Ergonomics of the thermal
2025-09
environment — Analytical
determination and interpretation of
thermal comfort using calculation
of the PMV and PPD indices and
local thermal comfort criteria
Ergonomie des ambiances thermiques — Détermination
analytique et interprétation du confort thermique par le calcul des
indices PMV et PPD et par des critères de confort thermique local
Reference number
ISO 7730:2025(en) © ISO 2025
ISO 7730:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 7730:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Whole body thermal comfort predicted mean vote (PMV) . 2
4.1 Determination .2
4.2 Applications.4
5 Predicted percentage dissatisfied (PPD) . . 4
6 Local thermal comfort . 5
6.1 General .5
6.2 Draught .6
6.3 Vertical air temperature difference .6
6.4 Warm and cool floors .7
6.5 Radiant temperature asymmetry .8
7 Thermal environments for comfort . 9
8 Non-steady-state thermal environments . 10
8.1 General .10
8.2 Temperature cycles .10
8.3 Temperature drifts or ramps . .10
8.4 Transients .10
Annex A (informative) Examples of thermal comfort requirements for different categoriesof
environment and types of space .11
Annex B (informative) Metabolic rates of different activities .16
Annex C (informative) Estimation of thermal insulation of clothing ensembles . 17
Annex D (normative) Computer program for calculating PMV and PPD .21
Annex E (informative) Graphics for determination of predicted mean vote (PMV) .25
Annex F (informative) Humidity .29
Annex G (informative) Air velocity .30
Bibliography .32

iii
ISO 7730:2025(en)
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.
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)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
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 159, Ergonomics, Subcommittee SC 5,
Ergonomics of the physical environment, in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 122, Ergonomics, in accordance with the Agreement on technical
cooperation between ISO and CEN (Vienna Agreement).
This fourth edition cancels and replaces the third edition (ISO 7730:2005), which has been technically
revised.
The main changes are as follows:
— deletion of sections of the text (long-term evaluations, adaptation and diversity);
— correction of the calculation program;
— deletion of tables for predicting predicted mean vote (PMV).
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
ISO 7730:2025(en)
Introduction
This document, covering the evaluation of moderate thermal environments, is one of a number of ISO
documents (alongside ISO 7243, ISO 7933 and ISO 11079, all dealing with extreme environmental conditions)
specifying methods for the measurement and evaluation of the moderate and extreme thermal environments
to which human beings are exposed.
A human being's thermal sensation is mainly related to the thermal balance of his or her body as a whole.
This balance is influenced by physical activity and clothing, as well as the environmental parameters such
as air temperature, mean radiant temperature, air velocity and air humidity. When these factors have been
estimated or measured, the index for thermal comfort predicted mean vote (PMV) can be calculated. See
Clause 4.
The predicted percentage dissatisfied (PPD) index provides information on thermal discomfort or
thermal dissatisfaction expressed as the percentage of people likely to feel too warm or too cool in a given
environment. The PPD can be obtained from the PMV. See Clause 5.
Thermal discomfort can also be caused by unwanted local cooling or heating of the body. The most common
local discomfort factors are radiant temperature asymmetry (cold or warm surfaces), draught (defined as
a local cooling of the body caused by air movement), vertical air temperature difference and cold or warm
floors. Clause 6 specifies how to predict the percentage dissatisfied owing to local discomfort parameters.
Dissatisfaction can be caused by hot or cold discomfort for the body as a whole. Comfort limits can, in this
case, be expressed by the PMV and PPD indices. But thermal dissatisfaction can also be caused by local
thermal discomfort parameters. Clause 7 deals with acceptable thermal environments for comfort.
Clauses 6 and 7 are based mainly on steady-state conditions. Means of evaluating non-steady-state
conditions, such as transients (temperature steps), cycling temperatures or temperature ramps, are
presented in Clause 8. Thermal environments in buildings or workplaces change over time and it is not
always possible to keep conditions within recommended limits.
This document is intended to be used together with ISO/TR 23663. It is also intended to be used along with
ISO 28803 when considering persons with special requirements, such as those with physical disabilities.
Ethnic, national or geographical differences are also important, especially when considering non-conditioned
spaces. Guidance is given in Clause 8 and 10 in ISO/TR 23663.

v
International Standard ISO 7730:2025(en)
Ergonomics of the thermal environment — Analytical
determination and interpretation of thermal comfort using
calculation of the PMV and PPD indices and local thermal
comfort criteria
1 Scope
This document specifies a method to evaluate the general thermal comfort of people in a space and the degree
of discomfort (thermal dissatisfaction) of people exposed to moderate thermal environments. It defines
the analytical determination and interpretation of thermal comfort using calculation of predicted mean
vote (PMV) and predicted percentage of dissatisfied (PPD) and local thermal comfort criteria, giving the
environmental conditions considered acceptable for general thermal comfort as well as those representing
local discomfort.
It is applicable to healthy men and women exposed to indoor environments where thermal comfort is
desirable, but where moderate deviations from thermal comfort occur, in the design of new environments or
the assessment of existing ones.
Although developed specifically for the work environment, this document is applicable to other kinds of
environment as well.
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 9920, Ergonomics of the thermal environment — Estimation of thermal insulation and water vapour
resistance of a clothing ensemble
ISO 13731, Ergonomics of the thermal environment — Vocabulary and symbols
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13731 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
temperature cycle
variable temperature with a given amplitude and frequency
3.2
temperature drift
passive monotonic, steady, non-cyclic change in the operative temperature of an enclosed space

ISO 7730:2025(en)
3.3
temperature ramp
actively controlled monotonic, steady, non-cyclic change in the operative temperature of an enclosed space
3.4
operative temperature
uniform temperature of an imaginary black enclosure in which an occupant exchanges the same amount of
heat by radiation and convection as in the actual non-uniform environment
3.5
transient
sudden change in the thermal conditions due to step change in temperature, humidity, activity or clothing
3.6
draught
unwanted local cooling of the body caused by air movement
4 Whole body thermal comfort predicted mean vote (PMV)
4.1 Determination
The PMV is an index that predicts the mean value of the votes of a large group of persons on the seven-point
thermal sensation scale (see Table 1), based on the heat balance of the human body. Thermal balance is
obtained when the internal heat production in the body is equal to the loss of heat to the environment. In
a moderate environment, the human thermoregulatory system will automatically attempt to modify skin
temperature and sweat secretion to maintain heat balance.
Table 1 — Seven-point thermal sensation scale
+ 3 Hot
+ 2 Warm
+ 1 Slightly warm
0 Neutral
− 1 Slightly cool
−2 Cool
− 3 Cold
Calculate the PMV using Formulae (1) to (4):
PM=−[,0 303··exp(,0 036 ),+∗0 028]
PMV
−3
 
MW− −⋅3,05 105⋅−733 69,,90⋅−MW −pM−⋅42 −W −58,15
() []() []()
a
 
 
−5
−1,771⋅⋅05Mp⋅−()867 −⋅0,00143Mt⋅−()4 (1)
 
aa
 
−8 44
 
−⋅39, 610 ⋅⋅ft(()+273 −+()tf273 −⋅ht⋅−()t 
cl cl rclc cl a
   
4 44
−8
 
tM=−35,70,028⋅−()WI−⋅ 39, 61⋅⋅0 ft⋅+()273 −+()t 273 +⋅fh ⋅−()tt (2)
{}
cl cl cl cl r cl ccla
 
02,,50 25

23,,81⋅−tt for 2,38⋅−tt >⋅21 v
 cl acla ar
h = (3)

c
02, 5

12,1⋅ v for 22,38⋅−tt <⋅12,1 v

ar cl aar
ISO 7730:2025(en)

10,,01+⋅290llformu0,078 K/W
 cl cl
f = (4)

cl

10,,50+>645llfor 00, 778mK⋅ /W

cl cl
where
P is the PMV;
PMV
M is the metabolic rate, in watts per square metre (W/m );
W is the effective mechanical power, in watts per square metre (W/m );
I is the clothing insulation, in square metres kelvin per watt (m ⋅ K/W);
cl
f is the clothing surface area factor;
cl
t is the air temperature, in degrees Celsius (°C);
a
t is the mean radiant temperature, in degrees Celsius (°C);
r
v is the relative air velocity, in metres per second (m/s);
ar
p is the water vapour partial pressure, in pascals (Pa);
a
h is the convective heat transfer coefficient, in watts per square metre kelvin [W/(m ⋅ K)];
c
t is the clothing surface temperature, in degrees Celsius (°C).
cl
2 2
NOTE 1 1 metabolic unit = 1 met = 58,2 W/m ; 1 clothing unit = 1 clo = 0,155 m ⋅ °C/W.
PMV can be calculated for different combinations of metabolic rate, clothing insulation, air temperature,
mean radiant temperature, air velocity and air humidity. Formulae (2) and (3) for t and h can be solved by
cl c
iteration.
The PMV index is derived for steady-state conditions but can be applied with good approximation during
minor fluctuations of one or more of the variables, provided that time-weighted averages of the variables
during the previous 1 h period are applied.
The index should be used only for values of PMV between −2 and +2, and when the six main parameters are
within the following intervals:
2 2
M 46 W/m to 232 W/m (0,8 met to 4 met);
2 2
I 0 m ⋅ K/W to 0,310 m ⋅ K/W (0 clo to 2 clo);
cl
t 10 °C to 30 °C;
a
t 10 °C to 40 °C;
r
v 0 m/s to 1 m/s;
ar
p 0 Pa to 2 700 Pa.
a
NOTE 2 In respect of v , during light, mainly sedentary, activity, a mean velocity within this range can be felt as a
ar
draught.
The metabolic rate to be used in Formulae (1) and (2) can be estimated using values shown in Annex B or
in ISO 8996. In the latter case, the value in watts estimated according to ISO 8996 should be divided by the
commonly accepted mean value of the body surface area, ADu = 1,8 m . For varying metabolic rates, a time-
weighted average should be estimated during the previous 1 h period. Estimate the thermal resistance of
clothing and chair using ISO 9920 or Annex C, taking into account the season of year.

ISO 7730:2025(en)
Determine the PMV in one of the following ways:
a) From Formula (1) using a digital computer. A BASIC program is given in Annex D for this purpose. For
verification of other computer programs, Annex D provides example output.
b) From Annex E, where graphics of PMV values are given for different combinations of activity, clothing,
operative temperature and relative velocity.
c) By measurement, using an integrating sensor (equivalent and operative temperatures).
The influence of humidity on thermal sensation is small at moderate temperatures close to comfort and can
usually be disregarded when determining the PMV value (see Annex F).
4.2 Applications
The PMV can be used to check whether a given thermal environment conforms to comfort criteria (see
Clause 7 and Annex A) and to establish requirements for different categories of acceptability.
By setting PMV = 0, an equation is established which predicts combinations of activity, clothing and
environmental parameters which on average will provide a thermally neutral sensation.
5 Predicted percentage dissatisfied (PPD)
The PMV index is defined in relation to the mean value of the thermal votes of a large group of people
exposed to the same environment. But individual votes are scattered around this mean value and it is useful
to be able to predict the number of people likely to feel uncomfortably warm or cool.
The PPD is an index that establishes a quantitative index related to the percentage of thermally dissatisfied
people who feel too cool or too warm. For the purposes of this document, thermally dissatisfied people are
those who will vote 'hot', 'warm', 'cool' or 'cold' on the seven-point thermal sensation scale given in Table 1.
With the PMV value determined, calculate the PPD using Formula (5), see Figure 1:
PP=−100 95⋅−exp(,0 03353⋅−0,)2179⋅ P (5)
PPD PMVPMV
ISO 7730:2025(en)
Key
PMV is the PMV;
PPD is the PPD, %
Figure 1 — PPD as a function of PMV
The PPD is related to the number of thermally dissatisfied persons among a large group of people. The rest
of the group will feel thermally neutral, slightly warm or slightly cool. The relation between PMV and PPD
distribution is given in Table 2.
Table 2 — Distribution of individual thermal sensation votes for different values of mean vote
a
PMV PPD Persons predicted to vote
%
0 −1, 0 or +1 −2, −1, 0, +1 or +2
+2 75 5 25 70
+1 25 30 75 95
+0,5 10 55 90 98
0 5 60 95 100
−0,5 10 55 90 98
−1 25 30 75 95
−2 75 5 25 70
a
Based on experiments involving 1 300 subjects.
6 Local thermal comfort
6.1 General
The PMV and PPD are indices related to warm and cold discomfort for the body as a whole. But thermal
dissatisfaction can also be caused by unwanted cold or warm sensation of a particular part of the body.
This is known as local discomfort. The most common cause of local discomfort is draught (6.2). But local
discomfort can also be caused by an abnormally high vertical temperature difference between the head and

ISO 7730:2025(en)
ankles (6.3), by too warm or too cool a floor (6.4) or by a radiant temperature asymmetry (6.5). Annex A
provides examples of local and overall thermal comfort requirements for different categories of environment
and types of space.
It is mainly people at light sedentary activity who are sensitive to local discomfort. These will have a thermal
sensation for the whole body close to neutral. At higher levels of activity, people are less thermally sensitive
and, consequently, the risk of local discomfort is lower.
6.2 Draught
The discomfort due to draught can be expressed as the percentage of people predicted to be bothered by
draught. Calculate the draught rate (DR) using Formula (6) (model of draught):
06, 2
Pt=−34 vv−00,,50 37⋅⋅T +31, 4 (6)
()()a,la(),l
DR a,l u
where
P is the DR;
DR
t is the local air temperature, in degrees Celsius, 20 °C to 26 °C;
a,l
v is the local mean air velocity, in metres per second, < 0,5 m/s;
a,l
T is the local turbulence intensity, in percent, 10 % to 60 % (if unknown, 40 % may be used).
u
For < 0,05 m/s, use = 0,05 m/s.
For P > 100 %, use P = 100 %.
DR DR
The model applies to people at light, mainly sedentary activity with a thermal sensation for the whole
body close to neutral and for prediction of draught at the neck. At the level of arms and feet, the model
can overestimate the predicted draught rate. The sensation of draught is lower at activities higher than
sedentary (> 1,2 met) and for people feeling warmer than neutral. Additional information on the effect of air
velocity can be found in Annex G.
6.3 Vertical air temperature difference
A high vertical air temperature difference between head and ankles can cause discomfort. Figure 2 shows
the percentage dissatisfied (PD) as a function of the vertical air temperature difference between head
and ankles. The figure applies when the temperature increases upwards. People are less sensitive under
decreasing temperatures. Determine the PD using Formula (7):
P = (7)
PD
15+−exp(,76 0,)856⋅Δt
a,v
Formula (7), derived from the original data using logistic regression analysis, should only be used at
Δt < 8 °C.
a,v
ISO 7730:2025(en)
Key
PD percentage dissatisfied, %
Δt vertical air temperature difference between head and feet, °C
a,v
Figure 2 — Local discomfort caused by vertical air temperature difference
6.4 Warm and cool floors
If the floor is too warm or too cool, the occupants of the space can feel uncomfortable owing to thermal
sensation of their feet. For people wearing light indoor shoes, it is the temperature of the floor rather than
the material of the floor covering which is important for comfort. Figure 3 shows the percentage dissatisfied
as a function of the floor temperature, based on studies with either standing or sedentary people, or both.

ISO 7730:2025(en)
Key
PD percentage dissatisfied, %
t floor temperature, °C
f
Figure 3 — Local thermal discomfort caused by warm or cold floors
For people sitting or lying on the floor, similar values may be used. Determine the PD using Formula (8),
derived from the original data using non-linear regression analysis:
Pt=−100 94⋅−exp( 1,,387+⋅0 118 −⋅0,)0025 t (8)
PD ff
For longer occupancy, the results are not valid for electrically heated floors.
NOTE By electrical heating, a certain heat input is provided independent of the surface temperature. A water-
based heating system will not produce temperatures higher than the water temperature.
For spaces that people occupy with bare feet, see ISO/TS 13732-2.
6.5 Radiant temperature asymmetry
Radiant temperature asymmetry (Δt ) can also cause discomfort. People are most sensitive to radiant
pr
asymmetry caused by warm ceilings or cool walls (windows). Figure 4 shows the percentage dissatisfied
as a function of the radiant temperature asymmetry caused by a warm ceiling, cool wall, cool ceiling or
warm wall. For horizontal radiant asymmetry, Figure 4 applies from side-to-side (left–right or right–left)
asymmetry, the curves providing a conservative estimate of the discomfort: no other positions of the body
in relation to the surfaces (e.g. front–back) cause higher asymmetry discomfort. Determine the PD using
Formula (9) as applicable.
P = 100/(1+exp(K −K *Δt ))−K (9)
PD 1 2 pr 3
ISO 7730:2025(en)
Table 3 — Constants used in Formula (9) for different types of radiant asymmetry
Asymmetry Δt limit K K K
pr 1 2 3
1: warm ceiling < 23 K 2,94 0,166 5,5
2: cool wall < 15 K 5,89 0,297 1
3: cool ceiling < 15 K 5,19 0,173 1
4: warm wall < 35 K 3,41 0,044 3,5
The numbers refer to the corresponding curves in Figure 4.
Formula (9) was derived from the original data using logistic regression analysis and should not be used
beyond the ranges shown in Table 3. Those for 1) (warm ceiling) and for 4) (warm wall) have been adjusted
to account for discomfort not caused by radiant asymmetry. See Figure 4.
Key
PD percentage dissatisfied, %
Δt radiant temperature asymmetry, °C
pr
1 warm ceiling
2 cool wall
3 cool ceiling
4 warm wall
Figure 4 — Local thermal discomfort caused by radiant temperature asymmetry
7 Thermal environments for comfort
Thermal comfort is that condition of mind which expresses satisfaction with the thermal environment.
Dissatisfaction can be caused by warm or cool discomfort of the body as a whole, as expressed by the PMV
and PPD, or by a warm or cold sensation of one particular part of the body (local comfort).
Due to individual differences, it is impossible to specify a thermal environment that will satisfy everybody.
There will always be a percentage of dissatisfied occupants.
Often it will be the same persons who are sensitive to different types of local discomfort. For instance, a
person sensitive to draught can also be sensitive to local cooling caused by radiant asymmetry or by a cold

ISO 7730:2025(en)
floor. Such a cold-sensitive person can also more easily experience cool discomfort for the body as a whole.
Therefore, the PPD, DR or PD caused by other types of local discomfort should not be added.
Due to local or national priorities, technical developments and climatic regions, a higher thermal quality
(fewer dissatisfied) or lower quality (more dissatisfied) in some cases may be accepted. In such cases,
the PMV and PPD, the model of draught, the relation between local thermal discomfort parameters (see
Clause 6) and the expected percentage of dissatisfied people may be used to determine different ranges of
environmental parameters for the evaluation and design of the thermal environment.
Examples of different categories of requirements are given in Annex A.
8 Non-steady-state thermal environments
8.1 General
The basis for the methods given in Clauses 4 to 6 is steady-state conditions. The thermal environment is,
however, often in a non-steady-state and the question arises as to whether the methods then apply. Three
types of non-steady-state conditions can occur: temperature cycles, temperature drifts or ramps and
transients.
8.2 Temperature cycles
Temperature cycles can occur due to the control of the temperature in a space. If the peak-to-peak variation
is less than 1 K, there will be no influence on the comfort and the recommendations for steady-state may be
used. Higher peak variations can decrease comfort.
8.3 Temperature drifts or ramps
If the rate of temperature change for drifts or ramps is lower than 4,0 K/h, the methods for steady-state
variation apply.
8.4 Transients
In general, the following statements regarding transients can be made:
— A step-change of operative temperature is felt instantaneously.
— After an up-step in operative temperature, the new steady-state thermal sensation is experienced
immediately, i.e. the PMV-PPD indices can be used.
— Following a down-step in operative temperature, the thermal sensation drops at first to a level beneath
the PMV index, then increases and reaches under steady-state conditions the steady-state level after
approximately 30 min, i.e. the PMV-PPD index show values that are too high for the first 30 min. The time
to reach a new steady-state condition depends on the initial conditions.

ISO 7730:2025(en)
Annex A
(informative)
Examples of thermal comfort requirements for different categoriesof
environment and types of space
A.1 Categories of thermal environment
The desired thermal environment for a space may be selected from among the four categories, I, II, III and IV,
according to Table A.1. For local discomfort, only three categories apply. All the criteria should be satisfied
simultaneously for each category.
Table A.1 — Categories of thermal environment
Thermal state of the body as a whole Local discomfort
PPD PMV DR PD
% % %
Category
vertical air caused by radiant asym-
temperature warm or cool metry
difference floor
I < 6 − 0,2 < PMV < + 0,2 < 10 < 3 < 10 < 5
II < 10 − 0,5 < PMV < + 0,5 < 20 < 5 < 10 < 5
III < 15 − 0,7 < PMV < + 0,7 < 30 < 10 < 15 < 10
IV < 25 − 1,0 < PMV < + 1,0
Each category prescribes a maximum percentage dissatisfied for the body as a whole (PPD) and a PD for each
of the four types of local discomfort. Some requirements are difficult to meet in practice while others are
quite easily met. The different percentages express a balance struck between the aim of a few dissatisfied
persons and what is practically obtainable using existing technology.
Owing to the accuracy of instrumentation for measuring the input parameters according to ISO 7726, it
can be difficult to verify that the PMV conforms to the class A category (−0,2 < PMV < +0,2). Instead, the
verification may be based on the corresponding operative temperature range, as specified in A.2 and
Table A.5.
The four categories presented in Table A.1 apply to spaces where persons are exposed to the same
thermal environment. It is an advantage if some kind of individual control of the thermal environment
can be established for each person in a space. Individual control of the local air temperature, mean radiant
temperature or air velocity can contribute to balancing the rather large differences between individual
requirements and consequently can lead to fewer dissatisfied persons.
Modification of clothing can also contribute to balance individual differences. The effect on the optimum
operative temperature of adding or removing different garments is described in Table C.2.
A.2 Operative temperature range
For a given space there exists an optimum operative temperature corresponding to PMV = 0, depending on
the activity and the clothing of the occupants. Figure A.1 shows the optimum operative temperature and
the permissible temperature range as a function of clothing and activity for three of the four categories. The
optimum operative temperature is the same for the three categories, while the permissible range around
the optimum operative temperature varies.

ISO 7730:2025(en)
The operative temperature at all locations within the occupied zone of a space should, at all times, be within
the permissible range. This means that the permissible range should cover both spatial and temporal
variations, including fluctuations caused by the control system.
Figure A.1 applies for a relative humidity of 50 %; however, in moderate environments the air humidity has
only a modest impact on the thermal sensation. Typically, a 10 % higher relative humidity and a 0,3 °C higher
operative temperature are perceived as being warmer in equal measure.
The PDs in Table A.1 are not additive. In practice, a higher or lower number of dissatisfied persons can be
found when using subjective questionnaires in field investigations (see ISO 10551).
The air velocity in the space is assumed to be < 0,1 m/s. The relative air velocity, v , caused by body
ar
movement is estimated to be zero for a metabolic rate, M, less than 1 met and v = 0,3 (M − 1) for M > 1 met.
ar
The diagrams are determined for a relative humidity = 50 %, but the humidity only has a slight influence on
the optimum and permissible temperature ranges.
A.3 Local thermal comfort
Figure A.2 give ranges for local thermal comfort due to draught for the three categories presented in
Table A.1.
The maximum allowable mean air velocity is a function of local air temperature and turbulence intensity. The
turbulence intensity can vary between 30 % and 60 % in spaces with mixed-flow air distribution. In spaces
with displacement ventilation or without mechanical ventilation, the turbulence intensity can be lower.
a) Category I: PPD < 6 %
ISO 7730:2025(en)
b) Category II: PPD < 10 %
c) Category III: PPD < 15 %
Key
X basic clothing insulation, in clothing units, (clo)
X' basic clothing insulation, in clothing units, m ⋅°C/W
Y metabolic rate, in metabolic units, (met)
Y' metabolic rate, in metabolic units, W/m
PPD predicted percentage dissatisfied, %
NOTE The diagrams also show the range around the optimum temperature for the three categories.
Figure A.1 — Optimal operative temperature and the permissible temperature range

ISO 7730:2025(en)
a) Category I: DR = 10 % b) Category II: DR = 20 % c) Category III: DR = 30 %
Key
t local air temperature, °C
a,l
local mean air velocity, m/s
v
a,l
Tu turbulence intensity, %
Figure A.2 — Maximum allowable mean air velocity as function of local air temperature and
turbulence intensity
Tables A.2, A.3 and A.4 give values for-local thermal comfort related to vertical air temperature difference,
warm or cold floor and radiant temperature asymmetry, respectively.
Table A.2 — Vertical air temperature difference between head and ankles
a
Category Vertical air temperature difference
°C
I < 2
II < 3
III < 4
a
1,1 m and 0,1 m above floor.
Table A.3 — Range of floor temperature
Category Floor surface temperature range
°C
I 19 to 29
II 19 to 29
III 17 to 31
ISO 7730:2025(en)
Table A.4 — Radiant temperature asymmetry
Category Radiant temperature asymmetry
°C
Warm ceiling Cool wall Cool ceiling Warm wall
I < 5 < 10 < 14 < 23
II < 5 < 10 < 14 < 23
III < 7 < 13 < 18 < 35
A.4 Design criteria for different types of space — Examples
The design criteria specified in Table A.5 are derived under certain assumptions. For the thermal
environment, the criteria for the operative temperature are based on typical levels of activity, for clothing of
0,5 clo during summer (“cooling season”) and 1,0 clo during winter (“heating season”). The criteria for the
mean air velocity apply for a turbulence intensity of approximately 40 % (mixing ventilation). The design
criteria are valid for the occupancy conditions as given but can also be applicable to other types of spaces
used in similar ways.
Table A.5 — Example design criteria for spaces in various types of building
a
Type of building or Activity Category Operative temperature Maximum mean air velocity
space met °C m/s
W/m
Summer Winter Summer Winter
(cooling season) (heating season) (cooling season) (heating season)
Single office
I 24,5 ± 1,0 22,0
...