ISO 9920:2007
(Main)Ergonomics of the thermal environment — Estimation of thermal insulation and water vapour resistance of a clothing ensemble
Ergonomics of the thermal environment — Estimation of thermal insulation and water vapour resistance of a clothing ensemble
ISO 9920:2007 specifies methods for estimating the thermal characteristics (resistance to dry heat loss and evaporative heat loss) in steady-state conditions for a clothing ensemble based on values for known garments, ensembles and textiles. It examines the influence of body movement and air penetration on the thermal insulation and water vapour resistance. It does not deal with other effects of clothing, such as adsorption of water, buffering or tactile comfort, take into account the influence of rain and snow on the thermal characteristics, consider special protective clothing (water-cooled suits, ventilated suits, heated clothing), or deal with the separate insulation on different parts of the body and discomfort due to the asymmetry of a clothing ensemble.
Ergonomie des ambiances thermiques — Détermination de l'isolement thermique et de la résistance à l'évaporation d'une tenue vestimentaire
L'ISO 9920:2007 spécifie des méthodes pour la détermination des caractéristiques thermiques d'une tenue vestimentaire, dans des conditions d'équilibre, à partir des valeurs de pièces vestimentaires, de tenues et de textiles connus. L'influence des mouvements du corps et de la pénétration de l'air sur l'isolement thermique et sur la résistance à l'évaporation est examinée. L'ISO 9920:2007 ne traite pas des autres effets des pièces vestimentaires, tels que l'adsorption d'eau, l'effet tampon, le confort au toucher, ne tient pas compte de l'influence de la pluie et de la neige sur les caractéristiques thermiques, n'est pas applicable aux tenues de protection spéciales (tenues refroidies par eau, tenues ventilées, vêtements chauffants), et ne traite pas d'isolements thermiques distincts sur différentes parties du corps, ni de l'inconfort dû à l'asymétrie d'une tenue vestimentaire.
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 9920
Second edition
2007-06-01
Ergonomics of the thermal
environment — Estimation of thermal
insulation and water vapour resistance of
a clothing ensemble
Ergonomie des ambiances thermiques — Détermination de l'isolement
thermique et de la résistance à l'évaporation d'une tenue vestimentaire
Reference number
©
ISO 2007
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ii © ISO 2007 – All rights reserved
Contents Page
Foreword. v
Introduction . vi
1 Scope . 1
2 Terms and definitions. 1
3 Application of this International Standard . 5
4 Estimation of thermal insulation of clothing ensemble based on tables and with values
measured on a standing thermal manikin.7
4.1 General. 7
4.2 Insulation values of complete ensembles. 8
4.3 Ensemble thermal insulation values based on individual garments . 8
4.4 Complete ensemble insulation corrected for small differences in composition . 8
4.5 Calculation of thermal insulation for clothing ensembles . 9
4.6 Calculation of thermal insulation for individual garments. 9
5 Estimation of clothing area factor. 10
6 Estimation of surface (or boundary) air layer insulation. 10
7 Estimation of water vapour resistance. 12
7.1 General. 12
7.2 Estimation of vapour resistance of clothing ensembles based on tables with values
measured on standing thermal manikin. 12
7.3 Estimation of vapour resistance of clothing ensemble based on its relation with dry heat
resistance . 12
8 Influence of body movement and air movement on the thermal insulation and vapour
resistance of a clothing ensemble . 13
8.1 General. 13
8.2 Correction of clothing insulation . 13
8.3 Correction of clothing vapour resistance .18
8.4 Activities other than walking . 20
8.5 Relative air velocity . 20
9 Other factors influencing clothing insulation. 22
9.1 General. 22
9.2 Posture. 22
9.3 Effect of seats . 22
9.4 Effect of pressure . 22
9.5 Wetting. 22
9.6 Washing . 22
Annex A (normative) Thermal insulation values for clothing ensembles . 23
Annex B (normative) Thermal insulation values for individual garments. 45
Annex C (normative) Vapour permeability index values for clothing ensembles. 72
Annex D (informative) Measurement of thermal insulation and water vapour resistance of clothing
ensembles on a thermal manikin . 87
Annex E (informative) Measurement of thermal insulation and water vapour resistance of a
clothing ensemble on human subjects . 93
Annex F (informative) Different expressions for the thermal insulation of clothing. 95
Annex G (informative) Estimation of the heat exchanges for reflective clothing. 97
Annex H (informative) Guidance on the determination of the covered body surface area. 99
Bibliography . 101
iv © ISO 2007 – 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 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 9920 was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 5, Ergonomics
of the physical environment.
This second edition cancels and replaces the first edition (ISO 9920:1995), which has been technically revised.
It includes major changes to the sections on clothing vapour resistance as well as those dealing with the
effects of air movement and body motion on clothing insulation and vapour resistance.
Introduction
This International Standard is one of a series of International Standards intended for use in the study of
thermal environments. It is a basic document for evaluation of the thermal characteristics of a clothing
ensemble (thermal insulation and water vapour resistance). It is necessary to know these values when
evaluating the thermal stress or degree of comfort provided by the physical environment according to
standardized methods. The thermal characteristics determined in this International Standard are values for
steady-state conditions. Properties like “buffering”, adsorption of water and similar are not dealt with.
The emphasis in this International Standard is on the estimation of the thermal characteristics. The heat and
vapour resistance may also be measured directly, and this is discussed in the annexes.
This International Standard does not deal with the local thermal insulation on different body parts, nor the
discomfort due to a non-uniform distribution of the clothing on the body.
Man’s thermal balance in neutral, cold and warm environments is influenced by the clothing worn. For
evaluating the thermal stress on human beings in the cold (IREQ, see ISO/TR 11079, insulation index),
neutral environments (PMV-PPD, see ISO 7730, indices) and the heat (predicted heat strain, see ISO 7933,
index), it is necessary to know the thermal characteristics of the clothing ensemble, i.e. the thermal insulation
and the water vapour resistance.
vi © ISO 2007 – All rights reserved
INTERNATIONAL STANDARD ISO 9920:2007(E)
Ergonomics of the thermal environment — Estimation of
thermal insulation and water vapour resistance of a clothing
ensemble
1 Scope
This International Standard specifies methods for estimating the thermal characteristics (resistance to dry heat
loss and evaporative heat loss) in steady-state conditions for a clothing ensemble based on values for known
garments, ensembles and textiles. It examines the influence of body movement and air penetration on the
thermal insulation and water vapour resistance.
This International Standard does not
⎯ deal with other effects of clothing, such as adsorption of water, buffering or tactile comfort,
⎯ take into account the influence of rain and snow on the thermal characteristics,
⎯ consider special protective clothing (water-cooled suits, ventilated suits, heated clothing), or
⎯ deal with the separate insulation on different parts of the body and discomfort due to the asymmetry of a
clothing ensemble.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
thermal insulation
I
2 −1
resistance to dry heat loss between two surfaces, expressed in square metres Kelvin per watt (m ⋅ K ⋅ W )
NOTE 1 In this International Standard it is considered as the equivalent uniform thermal resistance, or thermal
insulation, on a human body. This is the clothing heat resistance (thermal insulation) that, when uniformly covering the
whole body surface (including hands, face, etc.), would result in the same heat loss as the actual, possibly non-uniform,
clothing heat resistance. This heat resistance is the quotient of the temperature gradient between the surfaces (the driving
force) over the dry heat loss per unit of body surface area (the flux):
temperature gradient
I= (1)
heat loss per unit of body surfacearea
For the human body, this resistance can be divided into specific layers, as illustrated in Figure 1 (see also Annex F).
NOTE 2 Because of the special definition of thermal insulation in this International Standard, it is usually expressed
in clo, the unit of thermal insulation of clothing. Although it can be converted into SI units in similar fashion to the thermal
2 −1
insulation of, for example, textile samples [symbol: R ; 1 clo = 0,155 (m ⋅ K ⋅ W )], the meaning is not the same.
ct
2.1.1
total insulation
I
T
thermal insulation from the body surface to the environment (including all clothing, enclosed air layers and
boundary air layer) under reference conditions, static
See Figure 1.
NOTE Based on Equation (1), it is expressed as:
tt−
sk o
I = (2)
T
H
where
t is the mean skin surface temperature, in degrees Celsius;
sk
t is the operative temperature, in degrees Celsius (in most cases equal to the air temperature, t );
o a
H is the dry heat loss per square metre of skin, in watts per square metre.
2.1.2
basic insulation
intrinsic insulation
I
cl
thermal insulation from the skin surface to the outer clothing surface (including enclosed air layers) under
reference conditions, static
See Figure 1.
NOTE Based on Equation (1), it is expressed as:
tt−
sk cl
I = (3)
cl
H
where t is the mean outer clothing surface temperature, in degrees Celsius.
cl
2.1.3
air insulation
I
a
thermal insulation of the boundary (surface) air layer around the outer clothing or, when nude, around the skin
surface
See Figure 1.
NOTE 1 Based on Equation (1), it is expressed as
tt−
cl o
I = (4)
a
H
NOTE 2 The dry heat loss is composed of radiant and convective heat loss (see Annex G). These heat transfers
through the clothing layers are not considered separately in this International Standard; for the air layer, they can be
considered separately. The alternative representation is then:
I = (5)
a
hh+
cr
2 © ISO 2007 – All rights reserved
where
−2 −1
h is the convective heat transfer coefficient, in watts per square metre Kelvin (W ⋅ m ⋅ K );
c
−2 −1
h is the radiative heat transfer coefficient, in watts per square metre Kelvin (W ⋅ m ⋅ K ).
r
−1
NOTE 3 Such values are defined for standardized conditions (static body, wind still, i.e. speed < 0,2 m ⋅ s ). When air
movement is present, or when the body moves, this will affect the insulation (typically lowering it), in which case, it is
referred to as resultant or dynamic heat resistance.
Key
1 surface (or boundary) air layer
2 enclosed air layer
3 clothing
4 body
Figure 1 — Schematic representation of total, basic and air insulations
2.1.4
clothing area factor
f
cl
ratio of the outer surface area of the clothed body to the surface area of the nude body
NOTE 1 The outer surface area of a clothed person, A , is greater than the surface area of a nude body, A . Their
cl Du
ratio is therefore larger than 1:
A
cl
f = (6)
cl
A
Du
NOTE 2 Basic and air insulation do not simply add up to total insulation. This is explained by the difference in surface
area between the outer clothing surface and the skin surface. Owing to this higher surface area, the insulative effect for
the body of the air insulation is reduced the thicker the clothing (the larger the outer clothing surface area):
I
a
II=+ (7)
Tcl
f
cl
2.1.5
resultant total insulation
dynamic total insulation
I
T,r
actual thermal insulation from the body surface to the environment (including all clothing, enclosed air layers
and boundary air layers) under given environmental conditions and activities
NOTE It is the total insulation (I ) value in actual situations (as opposed to reference conditions), including the effects
T
of movements and wind. Values for Ι given in this International Standard and in most of the literature are obtained on a
T
thermal manikin which remains static in a low wind condition, and such values need to be corrected for wind and
movement effects.
2.1.6
resultant basic insulation
dynamic basic insulation
I
cl,r
actual thermal insulation from the body surface to the outer clothing surface (including enclosed air layers)
under given environmental conditions and activities
NOTE It is the basic (intrinsic) insulation (I ) value in actual situations (as opposed to reference conditions), including
cl
the effects of movements and wind.
2.1.7
effective insulation
I
clu
increase in insulation provided to a thermal manikin by a single garment compared to the nude manikin
insulation
NOTE For insulation of individual garments, the term effective thermal insulation is used (I ). The effective thermal
clu
insulation of individual garments making up the ensemble (see Table B.2) is determined on a manikin wearing only that
single garment as:
tt−
sk o
I =−II= −I (8)
clu T a a
H
where
2 −1
I is the total thermal insulation of the garment, in square metres Kelvin per watt (m ⋅ K ⋅ W ) or in clo;
T
t is the operative temperature, in degrees Celsius (equal to the air temperature, t , for most measuring conditions
o a
in climatic chambers).
2.2
water vapour resistance
evaporative resistance
R
e
resistance to water vapour transfer between two surfaces, expressed in square metres kilopascal per watt
NOTE 1 In this International Standard it is considered as the equivalent uniform vapour resistance. This is the
resistance that, when uniformly covering the whole body surface (including hands, face, etc.), would result in the same
heat loss through evaporation as the actual, possibly non-uniform, vapour resistance. This resistance is the quotient of the
vapour pressure gradient between the surfaces (the driving force) over the evaporative heat loss per unit of body surface
area:
vapour pressure gradient
R = (9)
e
evaporative heat loss per unit of body surface area
NOTE 2 Similarly to heat resistance, it is divided into specific layers.
4 © ISO 2007 – All rights reserved
2.2.1
total water vapour resistance
R
e,T
vapour resistance from the body surface to the environment (including all clothing, enclosed air layers and
boundary air layers) under reference conditions, static
2.2.2
basic water vapour resistance
R
e,cl
vapour resistance from the body surface to the outer clothing surface (including enclosed air layers) under
reference conditions, static
2.2.3
air water vapour resistance
R
e,a
vapour resistance of the boundary (surface) air layer around the outer clothing or, when nude, around the skin
surface
NOTE In analogy to heat resistance:
R
e,a
RR=+ (10)
e,T e,cl
f
cl
2.2.4
resultant total water vapour resistance
dynamic total water vapour resistance
R
e,T,r
vapour resistance from the body surface to the environment (including all clothing, enclosed air layers and
boundary air layers) under given environmental conditions and activities
NOTE 1 It is the total water vapour resistance (R ) value in actual situations (as opposed to reference conditions),
e,T
including the effects of movements and wind.
−1
NOTE 2 Values of R are defined for standardized conditions (static body, wind still, i.e. speed < 0,2 m ⋅ s ). When air
e,T
movement is present, or when the body moves, this will affect the vapour resistance (typically lowering it), in which case it
is referred to as the resultant or dynamic total water vapour resistance.
2.2.5
resultant basic water vapour resistance
dynamic basic water vapour resistance
R
e,cl,r
vapour resistance from the body surface to the outer clothing surface (including enclosed air layers) under
given environmental conditions and activities
NOTE 1 It is the basic water vapour resistance (R ) value in actual situations (as opposed to reference conditions),
e,cl
including the effects of movements and wind.
−1
NOTE 2 Values of R are defined for standardized conditions (static body, wind still, i.e. speed < 0,2 m ⋅ s ). When
e,cl
air movement is present, or when the body moves, this will affect the vapour resistance (typically lowering it), in which
case it is referred to as the resultant or dynamic basic water vapour resistance.
3 Application of this International Standard
Where possible, the insulation and vapour resistance values of a clothing ensemble should be measured
using equipment such as thermal (wetted or sweating) manikins, or by performing experiments involving
human subjects. Test procedures for the measurement of heat and vapour resistance are outlined in
Annexes D and E. However, given the cost and the need for specialized equipment, actual measurement will
most likely be beyond the reach of most users of this International Standard. In that case, the insulation and
vapour resistance shall be estimated using the methods specified in the following clauses and Annexes A, B
and C.
For guidance, the stepwise approach is schematically represented in the flowcharts of Figure 2, for the
determination of heat resistance, and Figure 3, for the determination of vapour resistance. The various options
are described.
Figure 2 — Determining clothing insulation
6 © ISO 2007 – All rights reserved
Figure 3 — Determining clothing vapour resistance
4 Estimation of thermal insulation of clothing ensemble based on tables and with
values measured on a standing thermal manikin
4.1 General
Tables in this International Standard provide data on the insulation of complete clothing ensembles, as well as
insulation values for individual garments that can be added to create complete ensembles. It is advisable to
use the tables of complete ensembles to match the actual ensemble, as this will provide a more accurate
value for clothing insulation than the summation of individual garments. Interpolation between the thermal
insulation of two ensembles may be used and, when an ensemble is found similar to the actual ensemble,
small corrections may also be made by adding or subtracting individual garment insulations to achieve the
best estimate of the insulation of the actual ensemble. Finally, corrections for movement and air velocity shall
be applied.
4.2 Insulation values of complete ensembles
In Annex A, I and I values are listed for a selection of clothing ensembles. All of the values were measured
T cl
−1
on a static, standing, thermal manikin in low air movement (< 0,2 m ⋅ s ). In Table A.1, a short description of
the clothing ensembles is given. Tables A.2 to A.10 present more extended lists that can be used for finding a
clothing ensemble that is comparable with the actual clothing ensemble; f values are also given. The total
cl
clothing mass, where this is given, is based on garments that fit a standard person (European male size 52)
and does not include shoes. A number following the listing in the tables of individual garments making up most
of the ensembles refers to Annex B, where a more detailed description of the individual garment is presented,
including figures.
Annex A can also be used to select clothing for a workplace when the required insulation is known.
4.3 Ensemble thermal insulation values based on individual garments
Instead of using the ensembles in Annex A, the insulation for an ensemble, I , expressed in clo, may also be
cl
estimated, based on a summation of the insulation of individual garments using the following empirical
[31], [36]
equation :
I=+0,161 0,835 I (11)
cl ∑ clu
expressed in clo.
[32], [37]
Or, with slightly reduced accuracy :
I = I (12)
cl ∑ clu
expressed in square metres Kelvin per watt, or clo, and where I is the effective thermal insulation of the
clu
individual garments making up the ensemble, in values of either square metres Kelvin per watt or clo.
Such values are listed in Annex B.
The design of the various garments in Annex B is indicated by a type number, referring to drawings showing a
person dressed in various garment designs (Figures B.1 to B.14).
In some cases, the fabrics used are also listed. The type of material, however, has a limited influence on the
thermal insulation. Instead, the insulation is mainly influenced by the thickness (indicated in Annex B) and the
body surface area covered (indicated on the drawings).
It should be noted that the summations presented in Equations (11) and (12) are based on data with rather
uniform insulation distributions over the body. Such summations should not be used for extreme situations
(e.g. three layers on lower body and only a thin layer on upper body). The accuracy of the summation was
acceptable when actually measured data for the respective garments were used. When the separate
garments’ insulations were obtained from the tables, the accuracy of the summation was limited. Hence, it is
preferable to work with values of full ensembles (see Annex A).
The application range for which these relationships [Equations (11) and (12)] were tested is between 0,2 clo
and 1,6 clo.
4.4 Complete ensemble insulation corrected for small differences in composition
The accuracy of the summation of individual garments (4.3) is much less than that of matching the actual
ensemble with an ensemble taken from Annex A (4.2). Hence, when an exact match of the actual ensemble
with those of the tables of Annex A is not possible, but similar ensembles can be found, it is best to take the
similar ensemble insulation value and correct this for the difference in ensemble composition. For example, if
the actual ensemble has a different type of sweater, the ensemble insulation may be corrected for the
difference in insulation between the actual sweater and that of the sweater in the ensemble description of
8 © ISO 2007 – All rights reserved
Annex A. For this purpose, the effective insulations of both clothing items are compared and the difference
used for adjustment of the ensemble value:
I =+II0,835×∆ (13)
cl,a cl,A clu
2 −1
with the result expressed in clo or in m⋅k⋅w , and where I is the basic insulation of the actual ensemble,
cl,a
I is the basic insulation of the ensemble according to Annex A, and ∆I is the correction for the difference
c l , A clu
in individual garments (negative for subtracting a garment or when replacing with a less insulative garment).
This can be the difference between two garments of the same type (replacing one sweater by another), or the
effective insulation of an extra garment, or a negative value in the case where the actual ensemble contains
one garment less. The I values are taken from Annex B.
clu
Corrections should be kept to a minimum, and interpolation between two relevant ensembles is preferred. In
adding and removing garments, it should be considered how the insulation is distributed. Adding a thin layer to
an already covered part of a cold weather ensemble will have minimal impact, compared with the large impact
of adding a thin layer to a nude part in such an ensemble.
4.5 Calculation of thermal insulation for clothing ensembles
As an alternative to the selection of an ensemble from the tables, it is also possible to determine the clothing
[32], [37]
insulation of an ensemble using the following empirically determined relationship :
Im=+0,919 0,255×− 0,008 74×A − 0,005 10×A (14)
cl COV,0 COV,1
where
I is the intrinsic clothing insulation, in clo;
cl
m is the clothing weight (without shoes), in kilograms;
A is the body surface area not covered by clothing, as a percentage of total body surface area;
COV,0
A is the body surface area covered by a single clothing layer, as a percentage of total body
COV,1
surface area.
In effect, Equation (14) assumes a certain multi-layer insulation for a given clothing weight and then subtracts
insulation for areas only covered with a single layer and for areas without clothing. The application range for
which this relation was tested is between 0,2 clo and 1,8 clo.
Guidance on how to calculate A is given in Annex H.
COV
4.6 Calculation of thermal insulation for individual garments
2 −1
The effective thermal insulation of an individual garment, I (m ⋅ K ⋅ W ), may also be estimated by
clu
IA=×0,00095 (15)
clu COV
or, if expressed in clo, using
IA=×0,0061 (16)
clu COV
where A is the body surface area covered by clothing (percentage of total skin area).
COV
The values for body surface area covered by clothing are shown for garments in the figures of Annex B.
[32]
Garment weight on its own is not a good predictor of garment insulation .
When the thickness of the fabric used, d , expressed in metres, is also known, a more exact estimation of
fab
2 −1
I (m ⋅ K ⋅ W ) may be made using
clu
IA=+0,00067 0,217×d×A (17)
clu COV fab COV
or, if expressed in clo, using
IA=+0,0043 1,4×d×A (18)
clu COV fab COV
where d is the thickness of the fabric, in metres, measured in accordance with ASTM D1777 using a 7,5 cm
fab
−2
diameter pressure foot and 69,1 N ⋅ m pressure.
NOTE As the formula was derived using the ASTM method, no ISO alternative can be given, as this could affect the
relation.
The application range for which this relation [Equation (15)] was tested is between 0,02 clo and 0,5 clo or 5 %
to 82 % A . For Equation (17), the range was 0,02 clo to 1,05 clo.
COV
5 Estimation of clothing area factor
The outer surface area of a clothed person, A , is greater than the surface area of a nude body, A . The ratio
cl Du
of these is the clothing area factor, f [Equation (6)].
cl
[32], [45], [47]
The value of f is listed in Annex A for all clothing ensembles. It can be measured by photographic
cl
or whole body scanning methods. Pictures from different directions or whole body scans of the nude
person/manikin are compared with similar pictures/scans of the clothed person/manikin.
In view of the fact that the surface area increase depends on the clothing ensemble thickness, usually related
[32], [46], [48]
to its insulation, I , the clothing area factor may also be estimated from the following equations:
cl
2 −1
⎯ If I is expressed in square metres Kelvin per watt (m ⋅ K ⋅ W ):
cl
f=+1, 00 1, 81× I (19)
cl cl
⎯ If I is expressed in clo:
cl
f=+1,00 0,28× I (20)
cl cl
It should be noted that the correlation between f and I observed was low, so the estimate has limited
cl cl
[1]
reliability, especially for non-western clothing . Determination of f based on the table examples in Annex A,
cl
or, ideally, by actually measuring it, is therefore preferable, although in general the actual impact of f on the
cl
overall result for the insulation values is small. The application range for which these relations were tested is
between 0,2 clo and 1,7 clo.
6 Estimation of surface (or boundary) air layer insulation
In some cases, it is necessary to know the insulation of the surface air layer I (also called “boundary air
a
layer”) — for example, if I is known, but I is needed, or vice versa. In that case, Equation (7) may be used
T cl
with I and f , and either I or I as input.
a cl T cl
The static value of I ranges in most studies on which the tables in Annex A were based around 0,7 clo
a
2 −1 −1 −1
(0,109 m ⋅ K ⋅ W ) when measured at air velocities around 0,1 m ⋅ s to 0,15 m ⋅ s . Thus, for static
conditions, this value may be used as an estimate. For some cold weather clothing measurements the
−1
reference wind speed is set at 0,4 m ⋅ s ; see Reference [6].
10 © ISO 2007 – All rights reserved
The insulation provided by the outer surface (boundary layer) thermal insulation (see Figure 1) is disturbed
[17]
when air movement increases or the person starts to move. The following correction equation shows by
−1
how much this reduction takes place, compared to the static, no-wind (v = 0,15 m ⋅ s ) I value taken
ar a
from Reference [11]:
⎡⎤
−×0,533 (vv− 0,15)+ 0,069× (− 0,15)− 0,462v+ 0,201v
ar ar w w
⎢⎥
⎣⎦
Ie=⋅I (21)
a,r a,static
where
I is the boundary layer thermal insulation, in clo;
a,r
−1 −1
v is the relative air velocity, in metres per second (minimum = 0,15 m ⋅ s ; maximum = 3,5 m ⋅ s );
ar
-1
v is the walking speed, in metres per second (maximum = 1,2 m ⋅ s );
w
I is the reference value for air insulation (= 0,7 clo).
a,static
Alternatively, I may be calculated as:
a
I = (22)
a
hh+
()
cr
where
h is the convective heat transfer coefficient, in watt per metre squared per degree Celsius
c
−2 −1
(W⋅m ⋅°C );
−2 −1
h is the radiative heat transfer coefficient, in watt per metre squared per degree Celsius (W⋅m ⋅°C ).
r
This does not include a correction for the effect of movement. The convective heat exchange coefficient, h ,
c
may be estimated as the greatest value from the following:
0,25
2,38 tt− (23)
sk a
3,5+ 5,2 v (24)
ar
0,6
8,7 v (25)
ar
The radiative heat exchange, h , may be estimated using:
r
A (tt+−273) (+ 273)
−8 r cl r
h=⋅5,67 10 ε× × (26)
r
At −t
DU cl r
The fraction of skin surface involved in heat exchange by radiation, A /A , is equal to 0,67 for a crouching
r DU
subject, 0,70 for a seated subject and 0,77 for a standing subject.
7 Estimation of water vapour resistance
7.1 General
The water vapour resistance, R , of a clothing ensemble may be measured in experiments with subjects or
e,T
with a wetted or sweating thermal manikin. If this is not possible, R may be estimated using existing data, or
e,T
using a relationship between vapour and heat resistance to derive it from the latter.
7.2 Estimation of vapour resistance of clothing ensembles based on tables with values
measured on standing thermal manikin
In Annex C, R and R values are listed for a selection of clothing ensembles. All of the values were
e,T e,cl
−1
measured on a static, standing thermal manikin in low air movement (< 0,2 m ⋅ s ). A short description of the
clothing ensembles is given and the f values are also listed.
cl
A number following the listing in the tables of individual garments making up most of the ensembles refers to
Table C.5, where a detailed description of the garment fabric is presented.
7.3 Estimation of vapour resistance of clothing ensemble based on its relation with dry
heat resistance
2 −1
The total water vapour resistance, R , in square metre kilopascals per watt (m ⋅ kPa ⋅ W ) may be
e,T
estimated on the basis of the thermal insulation of that ensemble, I or I , by means of the permeability index,
T cl
−1
i , and the Lewis relation (L = 16,5 K ⋅ kPa ):
m
⎛⎞
I 0,06 I
a
T
R== + I (27)
⎜⎟
e,T cl
iL i f
mm cl
⎝⎠
2 −1
with I , I and I expressed in m ⋅ K ⋅ W .
T a cl
Typical values for i are given in Annex C, Table C.1. These are not as such related to the clothing’s
m
insulation, but to the permeability of the fabric layers. Based on the data for I and i , it is now possible to
T m
estimate R .
e,T
For an air layer, i as defined and used in Equation (27), is around 0,5. For impermeable garments that cover
m
the whole body including hands, feet and head it is close to zero. For many types of one- or two-layer,
permeable clothing, the permeability index, i , may be set to 0,38 and the equation for vapour resistance
m
2 −1
(m ⋅ kPa ⋅ W ) simplified to:
⎛⎞
I
a
R=×0,16II= 0,16 + (28)
⎜⎟
e,T T cl
f
cl
⎝⎠
For the clothing and air layer alone, similar relations apply:
0,06
R = (29)
e,a
f × h
cl c
I
cl
R=×0,06 (30)
e,cl
i
m,cl
where i is the permeability index for the clothing layer alone.
m,cl
For many permeable one- or two-layer clothing ensembles, i may be set to 0,34, giving:
m,cl
2 −1
R =×0,18 I m ⋅ kPa ⋅ W (31)
e,cl cl
12 © ISO 2007 – All rights reserved
Clothing with specific protective properties against chemical, physical or biological agents such as oil, radiant
heat or bacteria, may have considerably lower values for i . Refer to the tabular values for heat protective
m
clothing given in Annex C.
CAUTION — For the application of ISO 7933 with such special garments, it is recommended that an
expert be consulted.
Typical values for the permeation efficiency ratio, or permeability index, i , are given in Tables C.1, C.2 and
m
C.3, in which the numbers of the clothing ensembles and garments refer to Annexes A and B.
8 Influence of body movement and air movement on the thermal insulation and
vapour resistance of a clothing ensemble
8.1 General
Most types of clothing ensembles have openings (e.g. collars, cuffs) which allow a certain air exchange with
the environment. When work is performed, this air exchange can increase, changing the insulation of the
clothing. This is called the “pumping effect”. In addition, clothing may be compressed by wind, reducing its
thickness, and wind may enter through the fabrics or openings, increasing the air exchange of the
microclimate air with the external environment. This would also change the resistance to heat and moisture
transfer provided by the clothing.
To estimate the effect of body motion (pumping effect) and wind on the clothing insulation, a movable thermal
manikin may be used in simulated wind conditions. The methods given in Annex D can be used. I is then
a,r
measured with a nude manikin engaged in the appropriate activity (seated, standing, walking, bicycling) and
air movement and I or I on the clothed manikin in the same conditions. From these measurements,
cl,r T,r
corrections of the I , I , and I values measured on the standing manikin can be estimated and used for other
a cl T
clothing ensembles. The pumping effect can also be measured on human subjects: see Annex E.
For vapour resistance, this same procedure can be followed with specialized “sweating manikins”, or with
human subjects.
The effect of body motion is only measured on a whole clothing ensemble and not on each single garment.
The influence of wind depends on the air permeability of the outer textile layer and on the types and number of
openings, though for many ensembles the effects have been shown to be similar. Based on such
measurements, correction equations have been obtained that allow the correction of the values presented in
the tables in Annexes A and C, which were derived from measurements on static manikins, without any wind
−1
present (v < 0,2 m⋅s ).
ar
8.2 Correction of clothing insulation
Owing to the type of data that are available, the correction equations used to correct static clothing insulation
for the effects of air and body movement are based on correction of the total static insulation value, I . The
T
following two equations are to be used for the correction of total clothing insulation to obtain the resultant total
[17], [18]
clothing insulation, I , i.e. the actual clothing insulation in the current conditions :
T,r
⎯ For a clothed person in normal or light clothing (0,6 clo < I < 1,4 clo or 1,2 clo < I < 2,0 clo):
cl T
⎡⎤
−×0,281 (vv− 0,15)+ 0,044× ( − 0,15)− 0,492v+ 0,176v
ar ar w w
⎢⎥
⎣⎦
I = corrII×=e ⋅I (32)
T,r T T T
⎯ For a nude person (I = 0 clo):
cl
⎡⎤
−×0,533 (vv− 0,15)+ 0,069× (− 0,15)− 0,462v+ 0,201v
ar ar w w
⎢⎥
⎣⎦
II=×= corrI I=e ⋅I (33)
T,r a,r a a,static a,static
where
corr I is the correction factor for total insulation;
T
corr I is the correction factor for air insulation;
a
−1 −1
v is the air velocity relative to the person, in metres per second, from 0,15 m⋅s to 3,5 m⋅s ;
ar
−1 −1
v is the walking speed, in metres per second, from 0 m⋅s to 1,2 m⋅s .
w
These corrections for clothed and nude subjects are graphically represented in Figures 4 and 5.
−1 −1
Valid up to 1,2 m⋅s walking speed (v ) and 3,5 m⋅s relative wind speed (v ) (from References [17]
w ar
and [18])
Key
−1
X relative wind speed, m⋅s
−1
Y walking speed, m⋅s
Figure 4 — Correction factor (I /I ) for dressed subjects
T,r T
14 © ISO 2007 – All rights reserved
−1 −1
Valid up to 1,2 m⋅s walking speed (v ) and 3,5 m⋅s relative wind speed (v ) (from Reference [4])
w ar
Key
−1
X relative wind speed, m⋅s
−1
Y walking speed, m⋅s
Figure 5 — Correction factor (I /I ) for nude subjects
a,r a
For very low clothing insulations, i.e. I between 0 clo and 0,6 clo, an equation for interpolation between
cl
[11]
Equations (32) (I dressed) and (33) (I nude = I ) was derived :
T T a
⎡⎤
(0,6−+II) I×I
T,r,nude cl T,r,dressed
⎣⎦cl
I = 0 < I < 0,6 clo (34)
cl
T,r
0,6
For specialized, insulating, cold weather clothing (I > 2 clo), which typically has low air permeability, and
T
[16], [41]
where high wind speeds occur more frequently, the formula for the correction factor to be used is :
−3 2 0,144
⎡⎤
−×0,0512 (vv− 0,4)+ 0,794×10 *(− 0,4)− 0,0639×v×p
ar ar w
{ }
⎢⎥
⎣⎦
I=⋅eI (35)
T,r T
r = 0,968 and SEE = 0,048
where
−1 −1
v is the air velocity relative to the person, in metres per second, from 0,4 m⋅s to 18 m⋅s ;
ar
−1 −1
v is the walking speed, in metres per second, from 0 m⋅s to 1,2 m⋅s ;
w
−2 −1
p is the air permeability of outer fabric, in litres per square metre per second, from 1 l⋅m ⋅ s to
−2 −1
1 000 l⋅m ⋅ s [low (e.g. coating or laminate) = 1; medium = 50; high (open weave)
−2 −1
= 1 000 l⋅m ⋅ s ].
SEE is the standard error of the estimate.
[17], [42]
For the lower area of the wind range, better results were obtained in a separate analysis :
2 0,2648
⎡⎤
−×0,0881 (vv− 0,4)+ 0,0779× (− 0,4)− 0,0317× (w)×p
ar ar
{ }
⎢⎥
⎣⎦
I=⋅eI (36)
T,r T
2 −1 −1 −1 −1
with r = 0,931 and SEE = 0,023; 0 m⋅s < walking speed < 1,2 m⋅s and 0,4 m⋅s < wind speed < 1 m⋅s
−2 −1 −2 −1
and 1 l⋅m ⋅ s < p < 1 000 l⋅m ⋅ s .
Here, it is assumed that the head and hands are covered with a hood or hat and gloves, i.e. the body is totally
covered. This relation is presented in Figure 6 for three wind speed ranges and the three permeability levels.
−1 [6], [17], [42]
Note that the reference wind speed in these data was 0,4 m⋅s .
16 © ISO 2007 – All rights reserved
...
INTERNATIONAL ISO
STANDARD 9920
Second edition
2007-06-01
Corrected version
2008-11-01
Ergonomics of the thermal
environment — Estimation of thermal
insulation and water vapour resistance of
a clothing ensemble
Ergonomie des ambiances thermiques — Détermination de l'isolement
thermique et de la résistance à l'évaporation d'une tenue vestimentaire
Reference number
©
ISO 2007
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Published in Switzerland
ii © ISO 2007 – All rights reserved
Contents Page
Foreword. v
Introduction . vi
1 Scope . 1
2 Terms and definitions. 1
3 Application of this International Standard . 5
4 Estimation of thermal insulation of clothing ensemble based on tables and with values
measured on a standing thermal manikin.7
4.1 General. 7
4.2 Insulation values of complete ensembles. 8
4.3 Ensemble thermal insulation values based on individual garments . 8
4.4 Complete ensemble insulation corrected for small differences in composition . 8
4.5 Calculation of thermal insulation for clothing ensembles . 9
4.6 Calculation of thermal insulation for individual garments. 9
5 Estimation of clothing area factor. 10
6 Estimation of surface (or boundary) air layer insulation. 10
7 Estimation of water vapour resistance. 12
7.1 General. 12
7.2 Estimation of vapour resistance of clothing ensembles based on tables with values
measured on standing thermal manikin. 12
7.3 Estimation of vapour resistance of clothing ensemble based on its relation with dry heat
resistance . 12
8 Influence of body movement and air movement on the thermal insulation and vapour
resistance of a clothing ensemble . 13
8.1 General. 13
8.2 Correction of clothing insulation . 13
8.3 Correction of clothing vapour resistance .18
8.4 Activities other than walking . 20
8.5 Relative air velocity . 20
9 Other factors influencing clothing insulation. 22
9.1 General. 22
9.2 Posture. 22
9.3 Effect of seats . 22
9.4 Effect of pressure . 22
9.5 Wetting. 22
9.6 Washing . 22
Annex A (normative) Thermal insulation values for clothing ensembles . 23
Annex B (normative) Thermal insulation values for individual garments. 46
Annex C (normative) Vapour permeability index values for clothing ensembles. 73
Annex D (informative) Measurement of thermal insulation and water vapour resistance of clothing
ensembles on a thermal manikin . 88
Annex E (informative) Measurement of thermal insulation and water vapour resistance of a
clothing ensemble on human subjects . 94
Annex F (informative) Different expressions for the thermal insulation of clothing. 96
Annex G (informative) Estimation of the heat exchanges for reflective clothing. 98
Annex H (informative) Guidance on the determination of the covered body surface area. 100
Bibliography . 102
iv © ISO 2007 – 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 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 9920 was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 5, Ergonomics
of the physical environment.
This second edition cancels and replaces the first edition (ISO 9920:1995), which has been technically revised.
It includes major changes to the sections on clothing vapour resistance as well as those dealing with the
effects of air movement and body motion on clothing insulation and vapour resistance.
This corrected version of ISO 9920:2007 incorporates the following corrections.
⎯ A value and a symbol missing from Equation (38) have been reinstated.
⎯ In Equation (15), the multiplication symbol has been substituted for an (incorrect) asterisk.
⎯ In Figure A.1, traditional Korean garments erroneously captioned “China” and “Sokchina” have been
corrected to read Chima and Sokchima.
⎯ In Equation (F.8), the subscript of the second representation of “I ” has been changed to I .
cl cli
⎯ In the description of symbol H given with Equation (F.1), the minus sign missing from the superscript
−2
attached to the unit W⋅m has been inserted.
⎯ “Mean skin temperature”, given as the description for t with Equation (G.6), has been corrected to
cl
“mean outer clothing surface temperature”.
⎯ In a number of instances, “weight” has been changed to the accepted ISO term, mass.
⎯ Values in Table A.2, No. 134 for I and I have been corrected.
cl T
⎯ Introductory text similar to that present in the first edition has been reinstated in Annex A, and a new
introductory text has been added to Annex C.
⎯ Some minor editorial corrections and additions have been made.
Introduction
This International Standard is one of a series of International Standards intended for use in the study of
thermal environments. It is a basic document for evaluation of the thermal characteristics of a clothing
ensemble (thermal insulation and water vapour resistance). It is necessary to know these values when
evaluating the thermal stress or degree of comfort provided by the physical environment according to
standardized methods. The thermal characteristics determined in this International Standard are values for
steady-state conditions. Properties like “buffering”, adsorption of water and similar are not dealt with.
The emphasis in this International Standard is on the estimation of the thermal characteristics. The heat and
vapour resistance may also be measured directly, and this is discussed in the annexes.
This International Standard does not deal with the local thermal insulation on different body parts, nor the
discomfort due to a non-uniform distribution of the clothing on the body.
Man’s thermal balance in neutral, cold and warm environments is influenced by the clothing worn. For
evaluating the thermal stress on human beings in the cold (IREQ, see ISO/TR 11079, insulation index),
neutral environments (PMV-PPD, see ISO 7730, indices) and the heat (predicted heat strain, see ISO 7933,
index), it is necessary to know the thermal characteristics of the clothing ensemble, i.e. the thermal insulation
and the water vapour resistance.
vi © ISO 2007 – All rights reserved
INTERNATIONAL STANDARD ISO 9920:2007(E)
Ergonomics of the thermal environment — Estimation of
thermal insulation and water vapour resistance of a clothing
ensemble
1 Scope
This International Standard specifies methods for estimating the thermal characteristics (resistance to dry heat
loss and evaporative heat loss) in steady-state conditions for a clothing ensemble based on values for known
garments, ensembles and textiles. It examines the influence of body movement and air penetration on the
thermal insulation and water vapour resistance.
This International Standard does not
⎯ deal with other effects of clothing, such as adsorption of water, buffering or tactile comfort,
⎯ take into account the influence of rain and snow on the thermal characteristics,
⎯ consider special protective clothing (water-cooled suits, ventilated suits, heated clothing), or
⎯ deal with the separate insulation on different parts of the body and discomfort due to the asymmetry of a
clothing ensemble.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
thermal insulation
I
2 −1
resistance to dry heat loss between two surfaces, expressed in square metres Kelvin per watt (m ⋅ K ⋅ W )
NOTE 1 In this International Standard it is considered as the equivalent uniform thermal resistance, or thermal
insulation, on a human body. This is the clothing heat resistance (thermal insulation) that, when uniformly covering the
whole body surface (including hands, face, etc.), would result in the same heat loss as the actual, possibly non-uniform,
clothing heat resistance. This heat resistance is the quotient of the temperature gradient between the surfaces (the driving
force) over the dry heat loss per unit of body surface area (the flux):
temperature gradient
I= (1)
heat loss per unit of body surfacearea
For the human body, this resistance can be divided into specific layers, as illustrated in Figure 1 (see also Annex F).
NOTE 2 Because of the special definition of thermal insulation in this International Standard, it is usually expressed
in clo, the unit of thermal insulation of clothing. Although it can be converted into SI units in similar fashion to the thermal
2 −1
insulation of, for example, textile samples [symbol: R ; 1 clo = 0,155 (m ⋅ K ⋅ W )], the meaning is not the same.
ct
2.1.1
total insulation
I
T
thermal insulation from the body surface to the environment (including all clothing, enclosed air layers and
boundary air layer) under reference conditions, static
See Figure 1.
NOTE Based on Equation (1), it is expressed as:
tt−
sk o
I = (2)
T
H
where
t is the mean skin surface temperature, in degrees Celsius;
sk
t is the operative temperature, in degrees Celsius (in most cases equal to the air temperature, t );
o a
H is the dry heat loss per square metre of skin, in watts per square metre.
2.1.2
basic insulation
intrinsic insulation
I
cl
thermal insulation from the skin surface to the outer clothing surface (including enclosed air layers) under
reference conditions, static
See Figure 1.
NOTE Based on Equation (1), it is expressed as:
tt−
sk cl
I = (3)
cl
H
where t is the mean outer clothing surface temperature, in degrees Celsius.
cl
2.1.3
air insulation
I
a
thermal insulation of the boundary (surface) air layer around the outer clothing or, when nude, around the skin
surface
See Figure 1.
NOTE 1 Based on Equation (1), it is expressed as
tt−
cl o
I = (4)
a
H
NOTE 2 The dry heat loss is composed of radiant and convective heat loss (see Annex G). These heat transfers
through the clothing layers are not considered separately in this International Standard; for the air layer, they can be
considered separately. The alternative representation is then:
I = (5)
a
hh+
cr
2 © ISO 2007 – All rights reserved
where
−2 −1
h is the convective heat transfer coefficient, in watts per square metre Kelvin (W ⋅ m ⋅ K );
c
−2 −1
h is the radiative heat transfer coefficient, in watts per square metre Kelvin (W ⋅ m ⋅ K ).
r
−1
NOTE 3 Such values are defined for standardized conditions (static body, wind still, i.e. speed < 0,2 m ⋅ s ). When air
movement is present, or when the body moves, this will affect the insulation (typically lowering it), in which case, it is
referred to as resultant or dynamic heat resistance.
Key
1 surface (or boundary) air layer
2 enclosed air layer
3 clothing
4 body
Figure 1 — Schematic representation of total, basic and air insulations
2.1.4
clothing area factor
f
cl
ratio of the outer surface area of the clothed body to the surface area of the nude body
NOTE 1 The outer surface area of a clothed person, A , is greater than the surface area of a nude body, A . Their
cl Du
ratio is therefore larger than 1:
A
cl
f = (6)
cl
A
Du
NOTE 2 Basic and air insulation do not simply add up to total insulation. This is explained by the difference in surface
area between the outer clothing surface and the skin surface. Owing to this higher surface area, the insulative effect for
the body of the air insulation is reduced the thicker the clothing (the larger the outer clothing surface area):
I
a
II=+ (7)
Tcl
f
cl
2.1.5
resultant total insulation
dynamic total insulation
I
T,r
actual thermal insulation from the body surface to the environment (including all clothing, enclosed air layers
and boundary air layers) under given environmental conditions and activities
NOTE It is the total insulation (I ) value in actual situations (as opposed to reference conditions), including the effects
T
of movements and wind. Values for Ι given in this International Standard and in most of the literature are obtained on a
T
thermal manikin which remains static in a low wind condition, and such values need to be corrected for wind and
movement effects.
2.1.6
resultant basic insulation
dynamic basic insulation
I
cl,r
actual thermal insulation from the body surface to the outer clothing surface (including enclosed air layers)
under given environmental conditions and activities
NOTE It is the basic (intrinsic) insulation (I ) value in actual situations (as opposed to reference conditions), including
cl
the effects of movements and wind.
2.1.7
effective insulation
I
clu
increase in insulation provided to a thermal manikin by a single garment compared to the nude manikin
insulation
NOTE For insulation of individual garments, the term effective thermal insulation is used (I ). The effective thermal
clu
insulation of individual garments making up the ensemble (see Table B.2) is determined on a manikin wearing only that
single garment as:
tt−
sk o
I =−II= −I (8)
clu T a a
H
where
2 −1
I is the total thermal insulation of the garment, in square metres Kelvin per watt (m ⋅ K ⋅ W ) or in clo;
T
t is the operative temperature, in degrees Celsius (equal to the air temperature, t , for most measuring conditions
o a
in climatic chambers).
2.2
water vapour resistance
evaporative resistance
R
e
resistance to water vapour transfer between two surfaces, expressed in square metres kilopascal per watt
NOTE 1 In this International Standard it is considered as the equivalent uniform vapour resistance. This is the
resistance that, when uniformly covering the whole body surface (including hands, face, etc.), would result in the same
heat loss through evaporation as the actual, possibly non-uniform, vapour resistance. This resistance is the quotient of the
vapour pressure gradient between the surfaces (the driving force) over the evaporative heat loss per unit of body surface
area:
vapour pressure gradient
R = (9)
e
evaporative heat loss per unit of body surface area
NOTE 2 Similarly to heat resistance, it is divided into specific layers.
4 © ISO 2007 – All rights reserved
2.2.1
total water vapour resistance
R
e,T
vapour resistance from the body surface to the environment (including all clothing, enclosed air layers and
boundary air layers) under reference conditions, static
2.2.2
basic water vapour resistance
R
e,cl
vapour resistance from the body surface to the outer clothing surface (including enclosed air layers) under
reference conditions, static
2.2.3
air water vapour resistance
R
e,a
vapour resistance of the boundary (surface) air layer around the outer clothing or, when nude, around the skin
surface
NOTE In analogy to heat resistance:
R
e,a
RR=+ (10)
e,T e,cl
f
cl
2.2.4
resultant total water vapour resistance
dynamic total water vapour resistance
R
e,T,r
vapour resistance from the body surface to the environment (including all clothing, enclosed air layers and
boundary air layers) under given environmental conditions and activities
NOTE 1 It is the total water vapour resistance (R ) value in actual situations (as opposed to reference conditions),
e,T
including the effects of movements and wind.
−1
NOTE 2 Values of R are defined for standardized conditions (static body, wind still, i.e. speed < 0,2 m ⋅ s ). When air
e,T
movement is present, or when the body moves, this will affect the vapour resistance (typically lowering it), in which case it
is referred to as the resultant or dynamic total water vapour resistance.
2.2.5
resultant basic water vapour resistance
dynamic basic water vapour resistance
R
e,cl,r
vapour resistance from the body surface to the outer clothing surface (including enclosed air layers) under
given environmental conditions and activities
NOTE 1 It is the basic water vapour resistance (R ) value in actual situations (as opposed to reference conditions),
e,cl
including the effects of movements and wind.
−1
NOTE 2 Values of R are defined for standardized conditions (static body, wind still, i.e. speed < 0,2 m ⋅ s ). When
e,cl
air movement is present, or when the body moves, this will affect the vapour resistance (typically lowering it), in which
case it is referred to as the resultant or dynamic basic water vapour resistance.
3 Application of this International Standard
Where possible, the insulation and vapour resistance values of a clothing ensemble should be measured
using equipment such as thermal (wetted or sweating) manikins, or by performing experiments involving
human subjects. Test procedures for the measurement of heat and vapour resistance are outlined in
Annexes D and E. However, given the cost and the need for specialized equipment, actual measurement will
most likely be beyond the reach of most users of this International Standard. In that case, the insulation and
vapour resistance shall be estimated using the methods specified in the following clauses and Annexes A, B
and C.
For guidance, the stepwise approach is schematically represented in the flowcharts of Figure 2, for the
determination of heat resistance, and Figure 3, for the determination of vapour resistance. The various options
are described.
Figure 2 — Determining clothing insulation
6 © ISO 2007 – All rights reserved
Figure 3 — Determining clothing vapour resistance
4 Estimation of thermal insulation of clothing ensemble based on tables and with
values measured on a standing thermal manikin
4.1 General
Tables in this International Standard provide data on the insulation of complete clothing ensembles, as well as
insulation values for individual garments that can be added to create complete ensembles. It is advisable to
use the tables of complete ensembles to match the actual ensemble, as this will provide a more accurate
value for clothing insulation than the summation of individual garments. Interpolation between the thermal
insulation of two ensembles may be used and, when an ensemble is found similar to the actual ensemble,
small corrections may also be made by adding or subtracting individual garment insulations to achieve the
best estimate of the insulation of the actual ensemble. Finally, corrections for movement and air velocity shall
be applied.
4.2 Insulation values of complete ensembles
In Annex A, I and I values are listed for a selection of clothing ensembles. All of the values were measured
T cl
−1
on a static, standing, thermal manikin in low air movement (< 0,2 m ⋅ s ). In Table A.1, a short description of
the clothing ensembles is given. Tables A.2 to A.10 present more extended lists that can be used for finding a
clothing ensemble that is comparable with the actual clothing ensemble; f values are also given. The total
cl
clothing mass, where this is given, is based on garments that fit a standard person (European male size 52)
and does not include shoes. A number following the listing in the tables of individual garments making up most
of the ensembles refers to Annex B, where a more detailed description of the individual garment is presented,
including figures.
Annex A can also be used to select clothing for a workplace when the required insulation is known.
4.3 Ensemble thermal insulation values based on individual garments
Instead of using the ensembles in Annex A, the insulation for an ensemble, I , expressed in clo, may also be
cl
estimated, based on a summation of the insulation of individual garments using the following empirical
[31], [36]
equation :
I=+0,161 0,835 I (11)
cl ∑ clu
expressed in clo.
[32], [37]
Or, with slightly reduced accuracy :
I = I (12)
cl ∑ clu
expressed in square metres Kelvin per watt, or clo, and where I is the effective thermal insulation of the
clu
individual garments making up the ensemble, in values of either square metres Kelvin per watt or clo.
Such values are listed in Annex B.
The design of the various garments in Annex B is indicated by a type number, referring to drawings showing a
person dressed in various garment designs (Figures B.1 to B.14).
In some cases, the fabrics used are also listed. The type of material, however, has a limited influence on the
thermal insulation. Instead, the insulation is mainly influenced by the thickness (indicated in Annex B) and the
body surface area covered (indicated on the drawings).
It should be noted that the summations presented in Equations (11) and (12) are based on data with rather
uniform insulation distributions over the body. Such summations should not be used for extreme situations
(e.g. three layers on lower body and only a thin layer on upper body). The accuracy of the summation was
acceptable when actually measured data for the respective garments were used. When the separate
garments’ insulations were obtained from the tables, the accuracy of the summation was limited. Hence, it is
preferable to work with values of full ensembles (see Annex A).
The application range for which these relationships [Equations (11) and (12)] were tested is between 0,2 clo
and 1,6 clo.
4.4 Complete ensemble insulation corrected for small differences in composition
The accuracy of the summation of individual garments (4.3) is much less than that of matching the actual
ensemble with an ensemble taken from Annex A (4.2). Hence, when an exact match of the actual ensemble
with those of the tables of Annex A is not possible, but similar ensembles can be found, it is best to take the
similar ensemble insulation value and correct this for the difference in ensemble composition. For example, if
the actual ensemble has a different type of sweater, the ensemble insulation may be corrected for the
difference in insulation between the actual sweater and that of the sweater in the ensemble description of
8 © ISO 2007 – All rights reserved
Annex A. For this purpose, the effective insulations of both clothing items are compared and the difference
used for adjustment of the ensemble value:
I =+II0,835×∆ (13)
cl,a cl,A clu
2 −1
with the result expressed in clo or in m⋅K⋅W , and where I is the basic insulation of the actual ensemble,
cl,a
I is the basic insulation of the ensemble according to Annex A, and ∆I is the correction for the difference
cl,A clu
in individual garments (negative for subtracting a garment or when replacing with a less insulative garment).
This can be the difference between two garments of the same type (replacing one sweater by another), or the
effective insulation of an extra garment, or a negative value in the case where the actual ensemble contains
one garment less. The I values are taken from Annex B.
clu
Corrections should be kept to a minimum, and interpolation between two relevant ensembles is preferred. In
adding and removing garments, it should be considered how the insulation is distributed. Adding a thin layer to
an already covered part of a cold weather ensemble will have minimal impact, compared with the large impact
of adding a thin layer to a nude part in such an ensemble.
4.5 Calculation of thermal insulation for clothing ensembles
As an alternative to the selection of an ensemble from the tables, it is also possible to determine the clothing
[32], [37]
insulation of an ensemble using the following empirically determined relationship :
Im=+0,919 0,255×− 0,008 74×A − 0,005 10×A (14)
cl COV,0 COV,1
where
I is the intrinsic clothing insulation, in clo;
cl
m is the clothing mass (without shoes), in kilograms;
A is the body surface area not covered by clothing, as a percentage of total body surface area;
COV,0
A is the body surface area covered by a single clothing layer, as a percentage of total body
COV,1
surface area.
In effect, Equation (14) assumes a certain multi-layer insulation for a given clothing mass and then subtracts
insulation for areas only covered with a single layer and for areas without clothing. The application range for
which this relation was tested is between 0,2 clo and 1,8 clo.
Guidance on how to calculate A is given in Annex H.
COV
4.6 Calculation of thermal insulation for individual garments
2 −1
The effective thermal insulation of an individual garment, I (m ⋅ K ⋅ W ), may also be estimated by
clu
IA=×0,00095 (15)
clu COV
or, if expressed in clo, using
IA=×0,0061 (16)
clu COV
where A is the body surface area covered by clothing (percentage of total skin area).
COV
The values for body surface area covered by clothing are shown for garments in the figures of Annex B.
[32]
Garment mass on its own is not a good predictor of garment insulation .
When the thickness of the fabric used, d , expressed in metres, is also known, a more exact estimation of
fab
2 −1
I (m ⋅ K ⋅ W ) may be made using
clu
IA=+0,00067 0,217×d×A (17)
clu COV fab COV
or, if expressed in clo, using
IA=+0,0043 1,4×d×A (18)
clu COV fab COV
where d is the thickness of the fabric, in metres, measured in accordance with ASTM D1777 using a 7,5 cm
fab
−2
diameter pressure foot and 69,1 N ⋅ m pressure.
NOTE As the formula was derived using the ASTM method, no ISO alternative can be given, as this could affect the
relation.
The application range for which this relation [Equation (15)] was tested is between 0,02 clo and 0,5 clo or 5 %
to 82 % A . For Equation (17), the range was 0,02 clo to 1,05 clo.
COV
5 Estimation of clothing area factor
The outer surface area of a clothed person, A , is greater than the surface area of a nude body, A . The ratio
cl Du
of these is the clothing area factor, f [Equation (6)].
cl
[32], [45], [47]
The value of f is listed in Annex A for all clothing ensembles. It can be measured by photographic
cl
or whole body scanning methods. Pictures from different directions or whole body scans of the nude
person/manikin are compared with similar pictures/scans of the clothed person/manikin.
In view of the fact that the surface area increase depends on the clothing ensemble thickness, usually related
[32], [46], [48]
to its insulation, I , the clothing area factor may also be estimated from the following equations:
cl
2 −1
⎯ If I is expressed in square metres Kelvin per watt (m ⋅ K ⋅ W ):
cl
f=+1, 00 1, 81× I (19)
cl cl
⎯ If I is expressed in clo:
cl
f=+1,00 0,28× I (20)
cl cl
It should be noted that the correlation between f and I observed was low, so the estimate has limited
cl cl
[1]
reliability, especially for non-western clothing . Determination of f based on the table examples in Annex A,
cl
or, ideally, by actually measuring it, is therefore preferable, although in general the actual impact of f on the
cl
overall result for the insulation values is small. The application range for which these relations were tested is
between 0,2 clo and 1,7 clo.
6 Estimation of surface (or boundary) air layer insulation
In some cases, it is necessary to know the insulation of the surface air layer I (also called “boundary air
a
layer”) — for example, if I is known, but I is needed, or vice versa. In that case, Equation (7) may be used
T cl
with I and f , and either I or I as input.
a cl T cl
The static value of I ranges in most studies on which the tables in Annex A were based around 0,7 clo
a
2 −1 −1 −1
(0,109 m ⋅ K ⋅ W ) when measured at air velocities around 0,1 m ⋅ s to 0,15 m ⋅ s . Thus, for static
conditions, this value may be used as an estimate. For some cold weather clothing measurements the
−1
reference wind speed is set at 0,4 m ⋅ s ; see Reference [6].
10 © ISO 2007 – All rights reserved
The insulation provided by the outer surface (boundary layer) thermal insulation (see Figure 1) is disturbed
[17]
when air movement increases or the person starts to move. The following correction equation shows by
−1
how much this reduction takes place, compared to the static, no-wind (v = 0,15 m ⋅ s ) I value taken
ar a
from Reference [11]:
⎡⎤
−×0,533 (vv− 0,15)+ 0,069× (− 0,15)− 0,462v+ 0,201v
ar ar w w
⎢⎥
⎣⎦
Ie=⋅I (21)
a,r a,static
where
I is the boundary layer thermal insulation, in clo;
a,r
−1 −1
v is the relative air velocity, in metres per second (minimum = 0,15 m ⋅ s ; maximum = 3,5 m ⋅ s );
ar
-1
v is the walking speed, in metres per second (maximum = 1,2 m ⋅ s );
w
I is the reference value for air insulation (= 0,7 clo).
a,static
Alternatively, I may be calculated as:
a
I = (22)
a
hh+
()
cr
where
h is the convective heat transfer coefficient, in watt per metre squared per degree Celsius
c
−2 −1
(W⋅m ⋅°C );
−2 −1
h is the radiative heat transfer coefficient, in watt per metre squared per degree Celsius (W⋅m ⋅°C ).
r
This does not include a correction for the effect of movement. The convective heat exchange coefficient, h ,
c
may be estimated as the greatest value from the following:
0,25
2,38 tt− (23)
sk a
3,5+ 5,2 v (24)
ar
0,6
8,7 v (25)
ar
The radiative heat exchange, h , may be estimated using:
r
A (tt+−273) (+ 273)
−8 r cl r
h=⋅5,67 10 ε× × (26)
r
At −t
DU cl r
The fraction of skin surface involved in heat exchange by radiation, A /A , is equal to 0,67 for a crouching
r DU
subject, 0,70 for a seated subject and 0,77 for a standing subject.
7 Estimation of water vapour resistance
7.1 General
The water vapour resistance, R , of a clothing ensemble may be measured in experiments with subjects or
e,T
with a wetted or sweating thermal manikin. If this is not possible, R may be estimated using existing data, or
e,T
using a relationship between vapour and heat resistance to derive it from the latter.
7.2 Estimation of vapour resistance of clothing ensembles based on tables with values
measured on standing thermal manikin
In Annex C, R and R values are listed for a selection of clothing ensembles. All of the values were
e,T e,cl
−1
measured on a static, standing thermal manikin in low air movement (< 0,2 m ⋅ s ). A short description of the
clothing ensembles is given and the f values are also listed.
cl
A number following the listing in the tables of individual garments making up most of the ensembles refers to
Table C.5, where a detailed description of the garment fabric is presented.
7.3 Estimation of vapour resistance of clothing ensemble based on its relation with dry
heat resistance
2 −1
The total water vapour resistance, R , in square metre kilopascals per watt (m ⋅ kPa ⋅ W ) may be
e,T
estimated on the basis of the thermal insulation of that ensemble, I or I , by means of the permeability index,
T cl
−1
i , and the Lewis relation (L = 16,5 K ⋅ kPa ):
m
⎛⎞
I 0,06 I
a
T
R== + I (27)
⎜⎟
e,T cl
iL i f
mm cl
⎝⎠
2 −1
with I , I and I expressed in m ⋅ K ⋅ W .
T a cl
Typical values for i are given in Annex C, Table C.1. These are not as such related to the clothing’s
m
insulation, but to the permeability of the fabric layers. Based on the data for I and i , it is now possible to
T m
estimate R .
e,T
For an air layer, i as defined and used in Equation (27), is around 0,5. For impermeable garments that cover
m
the whole body including hands, feet and head it is close to zero. For many types of one- or two-layer,
permeable clothing, the permeability index, i , may be set to 0,38 and the equation for vapour resistance
m
2 −1
(m ⋅ kPa ⋅ W ) simplified to:
⎛⎞
I
a
R=×0,16II= 0,16 + (28)
⎜⎟
e,T T cl
f
cl
⎝⎠
For the clothing and air layer alone, similar relations apply:
0,06
R = (29)
e,a
f × h
cl c
I
cl
R=×0,06 (30)
e,cl
i
m,cl
where i is the permeability index for the clothing layer alone.
m,cl
For many permeable one- or two-layer clothing ensembles, i may be set to 0,34, giving:
m,cl
2 −1
R =×0,18 I m ⋅ kPa ⋅ W (31)
e,cl cl
12 © ISO 2007 – All rights reserved
Clothing with specific protective properties against chemical, physical or biological agents such as oil, radiant
heat or bacteria, may have considerably lower values for i . Refer to the tabular values for heat protective
m
clothing given in Annex C.
CAUTION — For the application of ISO 7933 with such special garments, it is recommended that an
expert be consulted.
Typical values for the permeation efficiency ratio, or permeability index, i , are given in Tables C.1, C.2 and
m
C.3, in which the numbers of the clothing ensembles and garments refer to Annexes A and B.
8 Influence of body movement and air movement on the thermal insulation and
vapour resistance of a clothing ensemble
8.1 General
Most types of clothing ensembles have openings (e.g. collars, cuffs) which allow a certain air exchange with
the environment. When work is performed, this air exchange can increase, changing the insulation of the
clothing. This is called the “pumping effect”. In addition, clothing may be compressed by wind, reducing its
thickness, and wind may enter through the fabrics or openings, increasing the air exchange of the
microclimate air with the external environment. This would also change the resistance to heat and moisture
transfer provided by the clothing.
To estimate the effect of body motion (pumping effect) and wind on the clothing insulation, a movable thermal
manikin may be used in simulated wind conditions. The methods given in Annex D can be used. I is then
a,r
measured with a nude manikin engaged in the appropriate activity (seated, standing, walking, bicycling) and
air movement and I or I on the clothed manikin in the same conditions. From these measurements,
cl,r T,r
corrections of the I , I , and I values measured on the standing manikin can be estimated and used for other
a cl T
clothing ensembles. The pumping effect can also be measured on human subjects: see Annex E.
For vapour resistance, this same procedure can be followed with specialized “sweating manikins”, or with
human subjects.
The effect of body motion is only measured on a whole clothing ensemble and not on each single garment.
The influence of wind depends on the air permeability of the outer textile layer and on the types and number of
openings, though for many ensembles the effects have been shown to be similar. Based on such
measurements, correction equations have been obtained that allow the correction of the values presented in
the tables in Annexes A and C, which were derived from measurements on static manikins, without any wind
−1
present (v < 0,2 m⋅s ).
ar
8.2 Correction of clothing insulation
Owing to the type of data that are available, the correction equations used to correct static clothing insulation
for the effects of air and body movement are based on correction of the total static insulation value, I . The
T
following two equations are to be used for the correction of total clothing insulation to obtain the resultant total
[17], [18]
clothing insulation, I , i.e. the actual clothing insulation in the current conditions :
T,r
⎯ For a clothed person in normal or light clothing (0,6 clo < I < 1,4 clo or 1,2 clo < I < 2,0 clo):
cl T
⎡⎤
−×0,281 (vv− 0,15)+ 0,044× ( − 0,15)− 0,492v+ 0,176v
ar ar w w
⎢⎥
⎣⎦
I = corrII×=e ⋅I (32)
T,r T T T
⎯ For a nude person (I = 0 clo):
cl
⎡⎤
−×0,533 (vv− 0,15)+ 0,069× (− 0,15)− 0,462v+ 0,201v
ar ar w w
⎢⎥
⎣⎦
II=×= corrI I=e ⋅I (33)
T,r a,r a a,static a,static
where
corr I is the correction factor for total insulation;
T
corr I is the correction factor for air insulation;
a
−1 −1
v is the air velocity relative to the person, in metres per second, from 0,15 m⋅s to 3,5 m⋅s ;
ar
−1 −1
v is the walking speed, in metres per second, from 0 m⋅s to 1,2 m⋅s .
w
These corrections for clothed and nude subjects are graphically represented in Figures 4 and 5.
−1 −1
Valid up to 1,2 m⋅s walking speed (v ) and 3,5 m⋅s relative wind speed (v ) (from References [17]
w ar
and [18])
Key
−1
X relative wind speed, m⋅s
−1
Y walking speed, m⋅s
Figure 4 — Correction factor (I /I ) for dressed subjects
T,r T
14 © ISO 2007 – All rights reserved
−1 −1
Valid up to 1,2 m⋅s walking speed (v ) and 3,5 m⋅s relative wind speed (v ) (from Reference [4])
w ar
Key
−1
X relative wind speed, m⋅s
−1
Y walking speed, m⋅s
Figure 5 — Correction factor (I /I ) for nude subjects
a,r a
For very low clothing insulations, i.e. I between 0 clo and 0,6 clo, an equation for interpolation between
cl
[11]
Equations (32) (I dressed) and (33) (I nude = I ) was derived :
T T a
⎡⎤
(0,6−+II) I×I
cl T,r,nude cl T,r,dressed
⎣⎦
I = 0 < I < 0,6 clo (34)
cl
T,r
0,6
For specialized, insulating, cold weather clothing (I > 2 clo), which typically has low air permeability, and
T
[16], [41]
where high wind speeds occur more frequently, the formula for the correction factor to be used is :
−3 2 0,144
⎡⎤
−×0,0512 (vv− 0,4)+ 0,794× 10× (− 0,4)− 0,0639×v×p
ar ar w
{ }
⎢⎥
⎣⎦
I=⋅eI (35)
T,r T
r = 0,968 and SEE = 0,048
where
−1 −1
v is the air velocity relative to the person, in metres per second, from 0,4 m⋅s to 18 m⋅s ;
ar
−1 −1
v is the walki
...
NORME ISO
INTERNATIONALE 9920
Deuxième édition
2007-06-01
Ergonomie des ambiances thermiques —
Détermination de l'isolement thermique et
de la résistance à l'évaporation d'une
tenue vestimentaire
Ergonomics of the thermal environment — Estimation of thermal
insulation and water vapour resistance of a clothing ensemble
Numéro de référence
©
ISO 2007
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ii © ISO 2007 – Tous droits réservés
Sommaire Page
Avant-propos. v
Introduction . vi
1 Domaine d'application. 1
2 Termes et définitions. 1
3 Application de logigrammes décrivant la manière d'utiliser la présente Norme
internationale . 6
4 Estimation de l'isolement thermique d'une tenue vestimentaire à partir de tableaux de
valeurs mesurées sur un mannequin thermique debout. 7
4.1 Généralités . 7
4.2 Valeurs d'isolement thermique des tenues complètes. 8
4.3 Valeurs d'isolement thermique des tenues complètes basées sur les pièces
vestimentaires. 8
4.4 Correction de l'isolement thermique de tenues vestimentaires complètes pour de faibles
différences de composition . 9
4.5 Calcul de l'isolement thermique des tenues vestimentaires . 9
4.6 Calcul de l'isolement thermique des pièces vestimentaires. 10
5 Estimation du facteur de surface du vêtement. 10
6 Estimation de l'isolement thermique de la couche d'air (ou limite) superficielle . 11
7 Estimation de la résistance à l'évaporation .12
7.1 Généralités . 12
7.2 Estimation de la résistance au transfert de vapeur d'une tenue vestimentaire à partir de
tableaux de valeurs mesurées sur un mannequin thermique debout. 12
7.3 Estimation de la résistance au transfert de vapeur d'une tenue vestimentaire sur la base
de sa relation avec la résistance au transfert de chaleur sèche . 12
8 Influence du mouvement du corps et de l'air sur l'isolement thermique et sur la résistance
au transfert de vapeur d'une tenue vestimentaire. 13
8.1 Généralités . 13
8.2 Correction de l'isolement thermique du vêtement. 14
8.3 Correction de la résistance au transfert de vapeur d'un vêtement . 19
8.4 Activités autres que la marche. 21
8.5 Vitesse relative de l'air . 21
9 Autres facteurs d'influence de l'isolement thermique du vêtement. 23
9.1 Généralités . 23
9.2 Posture. 23
9.3 Effet du siège . 23
9.4 Effet de la pression. 23
9.5 Vêtement mouillé . 23
9.6 Lavage. 23
Annexe A (normative) Valeurs de l'isolement thermique des tenues vestimentaires . 24
Annexe B (normative) Valeurs de l'isolement thermique des pièces vestimentaires. 51
Annexe C (normative) Valeurs de l'indice de perméabilité à la vapeur des tenues vestimentaires. 79
Annexe D (informative) Mesurage de l'isolement thermique et de la résistance au transfert de
vapeur des vêtements sur un mannequin thermique . 95
Annexe E (informative) Mesurage de l'isolement thermique et de la résistance au transfert de
vapeur d'une tenue vestimentaire sur des sujets humains . 102
Annexe F (informative) Différentes expressions de l'isolement thermique d'un vêtement. 104
Annexe G (informative) Détermination des échanges de chaleur pour des vêtements
réfléchissants . 106
Annexe H (informative) Lignes directrices pour déterminer la surface du corps recouverte . 108
Bibliographie . 110
iv © ISO 2007 – Tous droits réservés
Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes nationaux de
normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est en général confiée
aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude a le droit de faire partie du
comité technique créé à cet effet. Les organisations internationales, gouvernementales et non
gouvernementales, en liaison avec l'ISO participent également aux travaux. L'ISO collabore étroitement avec
la Commission électrotechnique internationale (CEI) en ce qui concerne la normalisation électrotechnique.
Les Normes internationales sont rédigées conformément aux règles données dans les Directives ISO/CEI,
Partie 2.
La tâche principale des comités techniques est d'élaborer les Normes internationales. Les projets de Normes
internationales adoptés par les comités techniques sont soumis aux comités membres pour vote. Leur
publication comme Normes internationales requiert l'approbation de 75 % au moins des comités membres
votants.
L'attention est appelée sur le fait que certains des éléments du présent document peuvent faire l'objet de
droits de propriété intellectuelle ou de droits analogues. L'ISO ne saurait être tenue pour responsable de ne
pas avoir identifié de tels droits de propriété et averti de leur existence.
L'ISO 9920 a été élaborée par le comité technique ISO/TC 159, Ergonomie, sous-comité SC 4, Ergonomie de
l'environnement physique.
Cette deuxième édition annule et remplace la première édition (ISO 9920:1995), qui a fait l'objet d'une
révision technique. Les principales modifications apportées concernent les sections relatives à la résistance à
l'évaporation des vêtements et aux effets des mouvements de l'air et du corps sur l'isolement thermique et la
résistance à l'évaporation des vêtements.
La présente version française de l'ISO 9920 correspond à la version anglaise publiée le 2007-06-01 et
corrigée le 2008-11-01.
Introduction
La présente Norme internationale fait partie d'une série de Normes internationales consacrées à l'étude des
ambiances thermiques. Elle constitue un document de référence pour l'évaluation des caractéristiques
thermiques d'une tenue vestimentaire (isolement thermique et résistance à l'évaporation). Il est nécessaire de
connaître ces valeurs lors de l'évaluation de la contrainte thermique ou du niveau de confort apportés par
l'environnement physique selon les méthodes normalisées. Les caractéristiques thermiques déterminées au
moyen de la présente Norme internationale sont des valeurs correspondant à des conditions d'équilibre. Les
phénomènes tels que l'effet tampon, l'adsorption d'eau, etc. n'y sont pas traités.
La présente Norme internationale est centrée sur l'estimation des caractéristiques thermiques. La résistance
aux transferts de chaleur et de vapeur peut également faire l'objet d'une mesure directe, exposée dans les
annexes.
La présente Norme internationale ne traite pas de l'isolement thermique local sur différentes parties du corps,
ni de l'inconfort dû à une répartition non uniforme du vêtement sur le corps.
Le bilan thermique de l'homme dans des ambiances neutre, froide ou chaude est influencé par les vêtements
qu'il porte. Pour évaluer la contrainte thermique exercée sur l'homme dans une ambiance froide [indice de
l'isolement requis des vêtements – IREQ (voir l'ISO/TR 11079)], neutre [indices PMV-PPD (voir l'ISO 7730)] et
chaude [indice d'astreinte thermique prévisible – PHS (voir l'ISO 7933)], il est nécessaire de connaître les
caractéristiques thermiques de la tenue vestimentaire, à savoir l'isolement thermique et la résistance à
l'évaporation.
vi © ISO 2007 – Tous droits réservés
NORME INTERNATIONALE ISO 9920:2007(F)
Ergonomie des ambiances thermiques — Détermination de
l'isolement thermique et de la résistance à l'évaporation d'une
tenue vestimentaire
1 Domaine d'application
La présente Norme internationale spécifie des méthodes pour la détermination des caractéristiques
thermiques (résistance aux pertes de chaleur sèche et aux pertes de chaleur par évaporation) d'une tenue
vestimentaire, dans des conditions d'équilibre, à partir des valeurs de pièces vestimentaires, de tenues et de
textiles connus. L'influence des mouvements du corps et de la pénétration de l'air sur l'isolement thermique et
sur la résistance à l'évaporation est examinée.
La présente Norme internationale:
⎯ ne traite pas des autres effets des pièces vestimentaires, tels que l'adsorption d'eau, l'effet tampon, le
confort au toucher;
⎯ ne tient pas compte de l'influence de la pluie et de la neige sur les caractéristiques thermiques;
⎯ n'est pas applicable aux tenues de protection spéciales (tenues refroidies par eau, tenues ventilées,
vêtements chauffants);
⎯ ne traite pas d'isolements thermiques distincts sur différentes parties du corps, ni de l'inconfort dû à
l'asymétrie d'une tenue vestimentaire.
2 Termes et définitions
Pour les besoins du présent document, les termes et définitions suivants s'appliquent.
2.1
isolement thermique
I
résistance au transfert de chaleur sèche entre deux surfaces, exprimée en mètres carrés kelvin par watt
2 −1
(m⋅K⋅W )
NOTE 1 Pour les besoins de la présente Norme internationale, elle est définie comme la résistance thermique
uniforme équivalente, ou isolement thermique, sur le corps humain. Il s'agit de la résistance thermique d'un vêtement
(isolement thermique) qui, recouvrant de manière uniforme toute la surface du corps (y compris les mains, le visage, etc.),
entraînerait les mêmes pertes de chaleur que la tenue réelle, éventuellement non uniforme. Cette résistance est égale au
quotient du gradient de température entre les surfaces (force motrice) par la perte de chaleur sèche par unité de surface
cutanée (l'écoulement):
gradient de température
I= (1)
perte de chaleur par unité de surface corporelle
Pour le corps humain, cette résistance peut être divisée en couches spécifiques, comme illustré à la Figure 1 (voir
également Annexe F).
NOTE 2 Du fait de la définition particulière de l'isolement thermique dans la présente Norme internationale, ce dernier
est généralement exprimé en «clo», l'unité de l'isolement thermique d'un vêtement. Bien que cette unité puisse être
convertie en unités SI semblables à celles de l'isolement thermique, par exemple d'échantillons textiles (symbole: R ;
ct
2 −1
1 clo = 0,155 m ·°K·W ), la signification est différente.
2.1.1
isolement thermique total
I
T
isolement thermique existant entre la surface corporelle et l'ambiance (comprenant l'ensemble des vêtements,
les couches d'air emprisonnées et la couche limite d'air), dans des conditions de référence statiques
Voir Figure 1.
NOTE Sur la base de l'Équation (1), il est exprimé comme suit:
tt−
sk o
I = (2)
T
H
où
t est la température surfacique cutanée moyenne, en degrés Celsius;
sk
t est la température opérative, en degrés Celsius (dans la plupart des cas, égale à la température de l'air t );
o a
H est la perte de chaleur sèche par mètre carré de surface cutanée, en watts par mètre carré.
2.1.2
isolement thermique de base
isolement thermique intrinsèque
I
cl
isolement thermique existant entre la surface corporelle et la surface extérieure du vêtement (y compris les
couches d'air emprisonnées), dans des conditions de référence statiques
Voir Figure 1.
NOTE Sur la base de l'Équation (1), il est exprimé comme suit:
tt−
sk cl
I = (3)
cl
H
où t est la température moyenne de la surface extérieure du vêtement, en degrés Celsius.
cl
2.1.3
isolement thermique dû à l'air
I
a
isolement thermique de la couche limite d'air à la périphérie de la surface extérieure du vêtement ou, lorsque
le corps est nu, de la peau
Voir Figure 1.
NOTE 1 Sur la base de l'Équation (1), il est exprimé comme suit:
tt−
cl o
I = (4)
a
H
NOTE 2 La perte de chaleur sèche comprend la perte de chaleur par rayonnement et la perte de chaleur par
convection (voir l'Annexe G). Dans le cadre de la présente Norme internationale, ces modes de transfert de chaleur à
travers les couches vestimentaires ne sont pas distingués. Ils peuvent cependant l'être au niveau de la couche d'air. La
représentation alternative de I est alors:
a
I = (5)
a
hh+
cr
2 © ISO 2007 – Tous droits réservés
où
−2 −1
h est le coefficient de transfert de chaleur par convection, en watts par mètre carré par kelvin (W·m ·K );
c
−2 −1
h est le coefficient de transfert de chaleur par rayonnement, en watts par mètre carré par kelvin (W·m ·K );
r
NOTE 3 Ces valeurs sont définies pour des conditions normalisées (corps statique, vent calme, c'est-à-dire avec une
−1
vitesse d'air < 0,2 m·s ). Tout mouvement de l'air ou du corps affecte la résistance thermique (il la réduit généralement).
On parlera, dans ce cas, de résistance thermique résultante ou dynamique.
Légende
1 couche d'air de surface
2 couche d'air emprisonnée
3 vêtement
4 corps
Figure 1 — Représentation schématique de l'isolement thermique total,
de l'isolement thermique de base et de l'isolement thermique dû à l'air
2.1.4
facteur de surface du vêtement
f
cl
rapport de la surface extérieure du corps vêtu à la surface du corps nu
NOTE 1 La surface extérieure du corps vêtu, A , est supérieure à la surface du corps nu, A . Leur rapport est par
cl Du
conséquent plus grand que 1.
A
cl
f = (6)
cl
A
Du
NOTE 2 L'isolement de base et l'isolement dû à l'air ne viennent pas s'ajouter simplement pour donner l'isolement total.
Cela est dû à la différence de surface (aire) entre la surface extérieure du vêtement et celle de la peau, la première étant
plus grande que la seconde. Cette plus grande surface entraîne une réduction de l'effet isolant pour le corps de
l'isolement thermique de l'air (plus le vêtement est épais, plus la surface extérieure du vêtement est grande):
I
a
II=+ (7)
Tcl
f
cl
2.1.5
isolement thermique total résultant
isolement thermique total dynamique
I
T,r
isolement thermique existant entre la surface corporelle et l'ambiance (comprenant l'ensemble des vêtements,
les couches d'air emprisonnées et la couche limite d'air), pour des conditions d'ambiance et d'activité données
NOTE C'est la valeur d'isolement thermique total en situations réelles (contrairement aux conditions de référence)
comprenant les effets des mouvements et du vent. Les valeurs de Ι énumérées dans la présente Norme internationale et
T
dans la plupart de la documentation technique correspondante sont obtenues sur un mannequin thermique statique dans
des conditions de vent faible. Ces valeurs doivent être corrigées pour les effets du vent et des mouvements.
2.1.6
isolement thermique de base résultant
isolement thermique de base dynamique
I
cl,r
isolement thermique existant entre la surface corporelle et la surface extérieure du vêtement (comprenant les
couches d'air emprisonnées), pour des conditions d'ambiance et d'activité données
NOTE Il s'agit de la valeur d'isolement de base (intrinsèque) (I ) en situations réelles (contrairement aux conditions
cl
de référence) comprenant les effets des mouvements et du vent.
2.1.7
isolement thermique effectif
Ι
clu
augmentation de l'isolement thermique mesurée sur un mannequin thermique portant une pièce vestimentaire
comparée à la valeur d'isolement thermique sur mannequin nu
NOTE Le terme isolement thermique effectif (Ι ) est utilisé pour l'isolement thermique des pièces vestimentaires
clu
individuelles. L'isolement thermique effectif des pièces vestimentaires individuelles composant la tenue (voir Tableau B.2)
est déterminé sur un mannequin thermique portant uniquement la pièce vestimentaire considérée, de la manière suivante:
tt−
sk o
I =−II= −I (8)
clu T a a
H
où
2 −1
Ι est l'isolement thermique total de la pièce vestimentaire, en mètres carrés kelvin par watt (m ⋅K ⋅ W ) ou en
T
clo;
t est la température opérative, en degrés Celsius (pour la plupart des conditions de mesure dans des chambres
o
climatiques, elle est égale à la température de l'air t ).
a
2.2
résistance à l'évaporation
résistance évaporatoire
R
e
résistance au transfert de vapeur d'eau entre deux surfaces, exprimée en mètres carrés kilopascals par watt
NOTE 1 Pour les besoins de la présente Norme internationale, elle est définie comme la résistance uniforme
équivalente au transfert de vapeur. Il s'agit de la résistance évaporatoire d'un vêtement qui, recouvrant de manière
uniforme toute la surface du corps (y compris les mains, le visage, etc.), entraînerait les mêmes pertes de chaleur par
évaporation que la tenue réelle, éventuellement non uniforme. Cette résistance est égale au quotient du gradient de
pression de vapeur entre les surfaces (force motrice) par la perte de chaleur par évaporation par unité de surface cutanée
gradient de pression de vapeur
R = (9)
e
perte de chaleur par évaporation par unité de surface corporelle
NOTE 2 De la même manière que la résistance à la chaleur sèche, elle est divisée en couches spécifiques:
4 © ISO 2007 – Tous droits réservés
2.2.1
résistance totale à l'évaporation
R
e,T
résistance au transfert de vapeur existant entre la surface corporelle et l'ambiance (comprenant l'ensemble
des vêtements, les couches d'air emprisonnées et la couche limite d'air), dans des conditions de référence
statiques
2.2.2
résistance de base à l'évaporation
résistance intrinsèque à l'évaporation
R
e,cl
résistance au transfert de vapeur entre la surface corporelle et la surface extérieure du vêtement (y compris
les couches d'air emprisonnées), dans des conditions de référence statiques
2.2.3
résistance à l'évaporation due à l'air
R
e,a
résistance au transfert de vapeur due à la couche limite d'air à la périphérie de la surface extérieure du
vêtement ou, lorsque le corps est nu, de la peau
NOTE Par analogie à la résistance thermique:
R
e,a
RR=+ (10)
e,T e,cl
f
cl
2.2.4
résistance totale à l'évaporation résultante
résistance totale à l'évaporation dynamique
R
e,T,r
résistance au transfert de vapeur existant entre la surface corporelle et l'ambiance (comprenant l'ensemble
des vêtements, les couches d'air emprisonnées et la couche limite d'air), pour des conditions d'ambiance et
d'activité données
NOTE 1 Il s'agit de la valeur de la résistance totale à l'évaporation en situations réelles (R ) (contrairement aux
e,T
conditions de référence) comprenant les effets des mouvements et du vent.
NOTE 2 Les valeurs de R sont définies pour des conditions normalisées (corps statique, vent calme, c'est-à-dire
e,T
−1
avec une vitesse d'air < 0,2 m·s ). Tout mouvement de l'air ou du corps affecte la résistance à l'évaporation (il la réduit
généralement). On parlera, dans ce cas, de résistance totale à l'évaporation résultante ou dynamique.
2.2.5
résistance de base à l'évaporation résultante
résistance de base à l'évaporation dynamique
R
e,cl,r
résistance au transfert de vapeur existant entre la surface corporelle et la surface extérieure du vêtement (y
compris les couches d'air emprisonnées) pour des conditions d'ambiance et d'activité données
NOTE 1 Il s'agit de la valeur de la résistance de base à l'évaporation (R ) en situations réelles (contrairement aux
e,cl
conditions de référence) comprenant les effets des mouvements et du vent.
NOTE 2 Les valeurs de R sont définies pour des conditions normalisées (corps statique, vent calme, c'est-à-dire
e,cl
−1
avec une vitesse d'air < 0,2 m·s ). Tout mouvement de l'air ou du corps affecte la résistance à l'évaporation (il la réduit
généralement). On parlera, dans ce cas, de résistance de base à l'évaporation résultante ou dynamique.
3 Application de logigrammes décrivant la manière d'utiliser la présente Norme
internationale
Dans la mesure du possible, il convient de mesurer les valeurs d'isolement et de résistance à l'évaporation en
utilisant des équipements tels que des mannequins thermiques (mouillés ou transpirants) ou en effectuant des
expérimentations avec des sujets humains. Les méthodes d'essai pour la mesure des résistances thermique
et à l'évaporation des vêtements sont décrites dans les Annexes D et E. Cependant, en raison du coût et des
équipements spécialisés à utiliser, cette méthode réelle de mesure n'est pas à la portée de la plupart des
utilisateurs de la présente Norme internationale. Dans ce cas, l'isolement thermique et la résistance au
transfert de vapeur doivent être mesurés en utilisant les méthodes décrites dans les articles qui suivent et les
Annexes A, B et C.
Afin d'illustrer la démarche progressive, deux organigrammes sont respectivement fournis à la Figure 2, pour
la détermination de la résistance thermique et à la Figure 3 pour la détermination de la résistance au transfert
de vapeur. Les diverses options correspondantes sont décrites.
Figure 2 — Logigramme pour la détermination de l'isolement thermique du vêtement
6 © ISO 2007 – Tous droits réservés
Figure 3 — Logigramme pour la détermination de la résistance du vêtement au transfert de vapeur
4 Estimation de l'isolement thermique d'une tenue vestimentaire à partir
de tableaux de valeurs mesurées sur un mannequin thermique debout
4.1 Généralités
Le présent article fournit des tableaux de données concernant l'isolement de tenues vestimentaires complètes,
ainsi que des tableaux de valeurs d'isolement thermique pour des pièces vestimentaires pouvant être
ajoutées afin de reconstituer des tenues complètes. Il est recommandé d'utiliser les tableaux relatifs aux
tenues complètes pour identifier la tenue réelle, cette méthode fournissant une valeur de l'isolement
thermique du vêtement plus précise que l'addition de pièces vestimentaires. Une interpolation entre les
valeurs d'isolement thermique de deux tenues est possible, et lorsqu'une tenue se révèle proche de la tenue
réelle, de légères corrections peuvent également être apportées en ajoutant ou en retirant les isolements
thermiques de pièces vestimentaires afin d'obtenir une meilleure estimation de l'isolement de la tenue réelle.
En dernier lieu, des corrections pour la vitesse de l'air et des mouvements doivent être appliquées.
4.2 Valeurs d'isolement thermique des tenues complètes
L'Annexe A donne les valeurs de I et I pour un ensemble de tenues vestimentaires. Toutes ces valeurs ont
T cl
été mesurées sur un mannequin thermique statique, en position debout, avec de faibles mouvements d'air
−1
(< 0,2 m·s ). Le Tableau A.1 donne une brève description des tenues vestimentaires. Les Tableaux A.2
à A.10 contiennent une liste plus détaillée pouvant servir à identifier une tenue vestimentaire comparable à la
tenue vestimentaire réelle. Ces tableaux donnent également les différentes valeurs de f . La masse totale de
cl
la tenue, lorsqu'elle est indiquée, est basée sur des pièces vestimentaires convenant à un sujet standard
(taille européenne 52 pour homme), chaussures non comprises. Les pièces vestimentaires constituant la
plupart des tenues sont identifiées par un numéro, qui renvoie à l'Annexe B dans laquelle figure une
description plus détaillée de ces différentes pièces, y compris des dessins.
L'Annexe A peut également être utilisée pour choisir un vêtement pour un poste de travail donné, lorsque
l'isolement thermique requis est connu.
4.3 Valeurs d'isolement thermique des tenues complètes basées
sur les pièces vestimentaires
Au lieu d'utiliser les tenues décrites dans l'Annexe A, l'isolement thermique d'une tenue, I (en clo), peut
cl
également être estimé en agrégeant les isolements thermiques des pièces vestimentaires, à l'aide de
[31], [36]
l'équation empirique suivante :
I=+0,161 0,835 I (11)
cl ∑ clu
exprimé en clo.
[32], [37]
Ou bien, avec une précision sensiblement réduite :
I = I (12)
cl clu
∑
exprimé en mètres carrés kelvin par watt ou en clo, et où I est l'isolement thermique effectif des pièces
clu
vestimentaires composant la tenue, en mètres carrés kelvin par watt ou en clo.
Ces valeurs sont données dans l'Annexe B.
La forme des différentes pièces vestimentaires décrites dans l'Annexe B est précisée par un numéro de type,
qui renvoie aux dessins numérotés montrant un sujet vêtu de pièces vestimentaires variées (Figures B.1
à B.14).
Dans certains cas, les tissus employés sont également indiqués. Le type de tissu n'a toutefois qu'une
influence restreinte sur l'isolement thermique. En revanche, l'isolement dépend beaucoup de l'épaisseur du
tissu (indiquée dans l'Annexe B) et de la surface du corps recouverte (indiquée sur les dessins).
Il convient de noter que les sommations présentées dans les Équations (11) et (12) sont basées sur des
données relatives à des distributions plutôt uniformes de l'isolement thermique sur la surface du corps. Il
convient de ne pas utiliser ces équations pour des situations extrêmes (par exemple trois couches sur la
partie inférieure du corps et une couche mince unique sur la partie supérieure du corps). La précision de la
sommation est acceptable lorsque sont utilisées des données réellement mesurées sur les pièces
vestimentaires considérées. L'utilisation des tableaux pour déterminer les isolements thermiques des pièces
vestimentaires individuelles tend à limiter la précision de la sommation. Il est par conséquent préférable
d'utiliser les valeurs relatives aux tenues vestimentaires complètes (Annexe A).
Le domaine d'application pour lequel ces relations ont fait l'objet d'une vérification expérimentale
[Équations (11) et (12)] est compris entre 0,2 clo et 1,6 clo.
8 © ISO 2007 – Tous droits réservés
4.4 Correction de l'isolement thermique de tenues vestimentaires complètes
pour de faibles différences de composition
La précision de la sommation de pièces vestimentaires (4.3) est bien inférieure à la précision obtenue par
identification de la tenue réelle à une tenue décrite dans l'Annexe A (4.2). Ainsi, lorsqu'une concordance
parfaite de la tenue réelle avec les tenues décrites dans l'Annexe A n'est pas possible, mais que des tenues
similaires existent, il est préférable d'utiliser la valeur d'isolement thermique de la tenue similaire et de la
corriger pour la différence de composition des tenues. Par exemple, si la tenue réelle comprend un type de
tricot différent, l'isolement thermique de la tenue décrite dans l'Annexe A peut être corrigé pour la différence
d'isolement thermique entre le tricot réel et le tricot prédéfini. À cet effet, les isolements thermiques effectifs
des deux pièces vestimentaires sont comparés et la différence constatée est utilisée pour l'ajustement de la
valeur relative à la tenue.
I =+II0,835×∆ (13)
cl,a cl,A clu
2 −1
le résultat étant exprimé en clo ou en m⋅K⋅W , et où I est l'isolement thermique de base de la tenue réelle,
cl,a
I est l'isolement thermique de base de la tenue de l'Annexe A et ∆I représente la correction de la
cl,A clu
différence constatée sur certaines pièces vestimentaires (négative pour le retrait d'une pièce vestimentaire, ou
pour le remplacement par une pièce vestimentaire moins isolante).
Cette valeur peut correspondre à la différence entre deux pièces vestimentaires du même type (substitution
d'un tricot par un autre), à l'isolement thermique effectif d'une pièce vestimentaire supplémentaire ou à une
valeur négative dans le cas où la tenue réelle comprend une pièce vestimentaire de moins. Les valeurs I
clu
sont données dans l'Annexe B.
Il convient que les corrections restent minimales, une interpolation entre deux tenues appropriées étant
préférable. Il convient que l'ajout et le retrait de pièces vestimentaires tiennent compte de la répartition
effective de l'isolement thermique sur le corps. Pour un sujet vêtu d'une tenue d'hiver, l'ajout d'une couche
mince sur une partie déjà couverte aura un impact minimal, en comparaison avec l'impact significatif de l'ajout
de cette même couche sur une partie du corps non couverte.
4.5 Calcul de l'isolement thermique des tenues vestimentaires
En alternative à la sélection d'une tenue parmi celles décrites dans les tableaux, il est également possible de
[32], [37]
déterminer l'isolement thermique d'une tenue vestimentaire en utilisant la relation empirique suivante :
Im=+0,919 0,255×− 0,008 74×A − 0,005 10×A (14)
cl COV,0 COV,1
où
I est l'isolement thermique intrinsèque du vêtement, en clo;
cl
m est la masse du vêtement (sans les chaussures), en kilogrammes;
A est la surface du corps non recouverte par un vêtement, en pourcentage de la surface totale du
COV,0
corps;
A est la surface du corps recouverte d'une seule couche vestimentaire, en pourcentage de la
COV,1
surface totale du corps.
Concrètement, l'Équation (14) associe un certain isolement thermique multicouche au vêtement en fonction
de sa masse, valeur à laquelle sont soustraits l'isolement thermique relatif aux surfaces recouvertes d'une
seule couche et celui relatif aux surfaces nues. Le domaine d'application pour lequel cette relation a fait l'objet
d'une vérification expérimentale est compris entre 0,2 clo et 1,8 clo.
L'Annexe H fournit des recommandations concernant la méthode de calcul de la valeur A .
COV
4.6 Calcul de l'isolement thermique des pièces vestimentaires
2 −1
L'isolement thermique effectif d'une pièce vestimentaire, I (m ·K·W ), peut également être déterminé à
clu
l'aide de l'équation suivante:
IA=×0,000 95 (15)
clu COV
ou, s'il est exprimé en clo, à l'aide de l'équation suivante:
IA=×0,006 1 (16)
clu COV
où A est la surface du corps recouverte par la pièce vestimentaire (en pourcentage de la surface totale du
COV
corps).
Les valeurs de la surface du corps recouverte par les pièces vestimentaires sont indiquées sur les figures de
l'Annexe B. La masse de la pièce vestimentaire ne constitue pas un bon indicateur de son isolement
[32]
thermique .
2 −1
Lorsque l'épaisseur du tissu utilisé, d , exprimée en mètres, est également connue, I (en m ·K·W ) peut
fab clu
être estimé de manière plus précise à l'aide de l'équation suivante:
IA=×0,000 67 + 0,217×d×A (17)
clu COV fab COV
ou, s'il est exprimé en clo, à l'aide de l'équation suivante:
IA=×0,004 3 +1,4×d×A (18)
clu COV fab COV
où d est l'épaisseur du tissu (en mètres), mesurée conformément à l'ASTM D 1777 à l'aide d'un pied
fab
−2
presseur de 7,5 cm de diamètre et d'une pression de 69,1 N × m .
NOTE Dans la mesure où l'équation est issue de l'application de la méthode ASTM, aucune alternative ISO ne peut
être donnée au risque d'affecter la relation.
Le domaine d'application pour lequel cette relation [Équation (15)] a fait l'objet d'une vérification expérimentale
est compris entre 0,02 clo et 0,5 clo ou entre 5 % et 82 % A . Pour l'Équation (17), le domaine d'application
COV
est compris entre 0,02 clo et 1,05 clo.
5 Estimation du facteur de surface du vêtement
La surface extérieure d'un sujet habillé, A , est supérieure à la surface d'un corps nu, A . Le rapport entre
cl Du
ces deux surfaces est appelé facteur de surface du vêtement, f [Équation (6)].
cl
La valeur de f est indiquée dans l'Annexe A pour toutes les tenues vestimentaires. Elle peut être mesurée à
cl
[32], [45], [47]
l'aide de méthodes photographiques ou de balayage de l'ensemble du corps. Des clichés pris
sous des angles différents ou des balayages de l'ensemble du corps du sujet/mannequin nu sont comparés à
des clichés/balayages similaires du sujet/mannequin vêtu.
Compte tenu que l'accroissement de surface est fonction de l'épaisseur du vêtement, généralement liée à son
[32], [46], [48]
isolement intrinsèque, I , le facteur de surface du vêtement peut également être estimé à partir
cl
des équations suivantes:
2 −1
⎯ Si I est exprimé en m ·K·W :
cl
f=+1, 00 1, 81× I (19)
cl cl
⎯ Si I est exprimé en clo:
cl
f=+1,00 0,28× I (20)
cl cl
10 © ISO 2007 – Tous droits réservés
Il convient de noter que la faible corrélation existant entre f et I entraîne une fiabilité restreinte de ce type
cl cl
[1]
d'estimation, notamment pour les vêtements non occidentaux . Il est par conséquent préférable de
déterminer la valeur f sur la base des exemples donnés dans les tableaux de l'Annexe A, ou idéalement en
cl
la déterminant réellement, bien que l'impact réel de la valeur f sur le résultat global pour les valeurs
cl
d'isolement thermique soit généralement faible. Le domaine d'application pour lequel ces relations ont fait
l'objet d'une vérification expérimentale est compris entre 0,2 clo et 1,7 clo.
6 Estimation de l'isolement thermique de la couche d'air (ou limite) superficielle
Dans certains cas, il peut être nécessaire de connaître l'isolement thermique de la couche d'air superficielle,
I (également désignée «couche limite d'air»), par exemple, si la valeur I est connue et la valeur I est
a T cl
exigée, ou inversement. Dans ce cas, l'Équation (7) peut être utilisée avec I et f ainsi que I ou I comme
a cl T cl
valeurs d'entrée.
2 −1
La valeur statique de I avoisine 0,7 clo (0,109 m ·K·W ) dans la plupart des études sur lesquelles sont
a
fondés les tableaux présentés dans l'Annexe A, lorsqu'elle est mesurée à des vitesses d'écoulement d'air de
−1 −1
l'ordre de 0,1 m·s à 0,15 m·s . Ainsi, pour des conditions statiques, cette valeur peut être utilisée en
première estimation. Pour certains mesurages effectués sur des vêtements d'hiver, la vitesse de référence du
−1
vent est fixée à 0,4 m·s (voir Référence [6]).
L'isolement thermique procuré par la couche d'air (couche limite) à la surface du vêtement (voir Figure 1) est
perturbé lorsque les mouvements d'air augmentent ou lorsque le sujet commence à bouger. Une équation
[17] −1
corrective précisant le niveau de réduction effectif sur la valeur statique par vent nul (v = 0,15 m·s ) de
ar
[11]
I est donnée par la formule suivante:
a
⎡⎤
−×0,533vv−0,15+0,069× −0,15−0,462v+0,201v
() ( )
ar ar w w
⎢⎥
⎣⎦
Ie=×I (21)
a,r a,static
où
I est l'isolement thermique de la couche limite, en clo;
a,r
v est la vitesse relative du vent par rapport au sujet, en mètres par seconde
ar
−1 −1
(minimum = 0,15 m·s ; maximum = 3,5 m·s );
−1
v est la vitesse de marche, en mètres par seconde (maximum = 1,2 m·s );
w
I est la valeur de référence pour l'isolement thermique de la couche d'air (0,7 clo).
a,static
La valeur I peut également être calculée conformément à:
a
I = (22)
a
hh+
()
cr
où
h est le coefficient de transfert de chaleur par convection, en watts par mètre carré par degré
c
2 −1
Celsius (W·m⋅°C );
h est le coefficient de transfert de chaleur par rayonnement, en watts par mètre carré par degré
r
2 −1
Celsius (W·m⋅°C ).
Cela ne comprend pas une correction pour l'effet du mouvement. Le coefficient de transfert de chaleur par
convection, h , peut être évalué comme la plus grande valeur de:
c
0,25
2,38tt− (23)
sk a
3,5+ 5,2v (24)
ar
0,6
8,7v (25)
ar
Le coefficient de transfert de chaleur par rayonnement, h , peut être évalué à l'aide de:
r
A (tt+−273) (+ 273)
−8
r cl r
h=⋅5,67 10 ε× × (26)
r
At −t
DU cl r
La proportion de la surface cutanée concernée par le transfert de chaleur par rayonnement, A /A , est égale
r DU
à 0,67 pour un sujet recroquevillé, à 0,70 pour un sujet assis et à 0,77 pour un sujet debout.
7 Estimation de la résistance à l'évaporation
7.1 Généralités
La résistance à l'évaporation, R , d'une tenue vestimentaire peut être mesurée par des expérimentations
e,T
effectuées sur des sujets ou sur un mannequin thermique mouillé ou en exsudation. Lorsque cela n'est pas
possible, la valeur R peut être estimée sur la base des données existantes, ou sur la base d'une relation
e,T
existant entre la résistance au transfert de vapeur et la résistance au transfert de chaleur et permettant de la
déduire de cette dernière.
7.2 Estimation de la résistance au transfert de vapeur d'une tenue vestimentaire à partir de
tableaux de valeurs mesurées sur un mannequin thermique debout
L'Annexe C donne les valeurs de R et R pour un ensemble de tenues vestimentaires. Toutes ces valeurs
e,T e,cl
ont été mesurées sur un mannequin thermique statique en position debout avec de faibles mouvements d'air
−1
(< 0,2 m·s ). Une brève description des tenues vestimentaires est donnée, ainsi que les valeurs de f .
cl
Les pièces vestimentaires constituant la plupart des tenues sont identifiées par un numéro, qui renvoie au
Tableau C.5 pour une description détaillée du tissu de la pièce vestimentaire.
7.3 Estimation de la résistance au transfert de vapeur d'une tenue vestimentaire sur la base
de sa relation avec la résistance au transfert de chaleur sèche
2 −1
La résistance totale à l'évaporation, R , en mètres carrés kilopascals par watt (m ·kPa·W ) peut être
e,T
estimée sur la base de l'isolement thermique de la tenue concernée, I ou I , au moyen de l'indice de
T cl
−1
perméabilité, i , et de la relation de Lewis (L = 16,5 K·kPa ).
m
⎛⎞
I I
0,06
T a
R== + I (27)
⎜⎟
e,T cl
iL i f
mm⎝⎠cl
2 −1
avec I , I et I en m ·K·W .
T a cl
Les valeurs courantes de i sont données à l'Annexe C, Tableau C.1. Ces valeurs ne sont pas tant liées à
m
l'isolement thermique du vêtement, mais plutôt à la perméabilité des couches de tissu. Il est alors possible,
connaissant les valeurs de I et i , d'estimer la valeur de R .
T m e,T
Pour une couche d'air, la valeur i telle que définie et utilisée dans l'Équation (27), est approximativement
m
égale à 0,5. Pour les pièces vestimentaires imperméables qui recouvrent l'ensemble du corps, y compris les
mains, les pieds et la tête, cette valeur est proche de zéro. Pour de nombreux types de vêtements
perméables à une ou deux couches, l'indice de perméabilité, i , peut être fixé à 0,38 et l'équation pour le
m
2 −1
calcul de la résistance au transfert de vapeur (en m ·kPa·W ) peut être simplifiée comme suit:
12 © ISO 2007 – Tous droits réservés
⎛⎞
I
a
R=×0,16II= 0,16 + (28)
⎜⎟
e,T T cl
f
⎝⎠cl
Pour le vêtement et la couche d'air considérés isolément, des relations similaires s'appliquent:
0,06
R = (29)
e,a
f × h
cl c
I
cl
R=×0,06 (30)
e,cl
i
m,cl
où I est l'indice de perméabilité de la couche vestimentaire seule.
m,cl
Pour de nombreuses tenues vestimentaires perméables à une ou deux couches, I peut être fixé à 0,34, ce
m,cl
qui donne:
2 −1
R =×0,18 I (en m ·kPa·W) (31)
e,cl cl
Les vêtements ayant des propriétés de protection spécifiques contre les agents chimiques, physiques ou
biologiques (par exemple huile, chaleur radiante, bactéries) peuvent avoir des valeurs de i beaucoup plus
m
basses. Voir les valeurs données dans les tableaux de l'Annexe C relatifs aux vêtements de protection contre
la chaleur.
ATTENT
...
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