IEC 62999:2016

Electric room heating - Underfloor heating - Performance characteristics - Definitions, method of testing, sizing and formula symbols

IEC 62999:2016 applies to electrical underfloor heating of dwellings and all other buildings whose use corresponds to dwellings or is at least similar, having a maximum load bearing in use of 4 kN/m2. This Standard defines the main characteristics of electrical underfloor heating and establishes the method of testing of these characteristics as information for the user. This Standard does not deal with installation and safety requirements.

Chauffage électrique de locaux - Chauffage par le sol - Caractéristiques de performance - Définitions, méthode d'essai, calibrage et symboles de formule

L'IEC 62999:2016 s'applique aux systèmes de chauffage par le sol électrique pour locaux résidentiels et autres locaux, destinés à un usage résidentiel ou analogue, et dont la portance maximale en utilisation est de 4 kN/m2. La présente norme définit les principales caractéristiques des systèmes de chauffage par le sol électrique et fournit à l'utilisateur les méthodes d'essai correspondantes à titre informatif. La présente norme ne couvre pas les exigences en matière d'installation et de sécurité.

General Information

• Status: Published
• Publication Date: 30-Sep-2021
• ICS: 97.100.10 - Electric heaters
• Technical Committee: SC 59C - Electrical heating appliances for household and similar purposes
• Current Stage: PPUB - Publication issued
• Start Date: 23-Feb-2016
• Completion Date: 31-May-2016

Relations

• Amended By: IEC 62999:2016/AMD1:2021 - Amendment 1 - Electric room heating - Underfloor heating - Performance characteristics - Definitions, method of testing, sizing and formula symbols
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 62999 ®
Edition 1.0 2016-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electric room heating – Underfloor heating – Performance characteristics –
Definitions, method of testing, sizing and formula symbols

Chauffage électrique de locaux – Chauffage par le sol – Caractéristiques de
performance – Définitions, méthode d'essai, calibrage et symboles de formule

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IEC 62999 ®
Edition 1.0 2016-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electric room heating – Underfloor heating – Performance characteristics –

Definitions, method of testing, sizing and formula symbols

Chauffage électrique de locaux – Chauffage par le sol – Caractéristiques de

performance – Définitions, méthode d'essai, calibrage et symboles de formule

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 97.100.10 ISBN 978-2-8322-3213-2

– 2 – IEC 62999:2016 © IEC 2016
CONTENTS
FOREWORD .6
1 Scope .8
2 Normative references .8
3 Terms and definitions .8
4 Method of testing for the determination of characteristics of performance . 16
4.1 General . 16
4.2 Standard heating load per unit area . 16
4.3 Maximum power rating per unit area . 16
4.4 Maximum surface temperature . 17
4.5 Maximum floor surface temperature for underfloor storage heating . 18
4.6 Room air temperature . 19
4.7 Internal surface temperatures on the surrounding surfaces of the room . 20
4.8 Thermal pre-conditioning of the room to be tested . 20
4.9 Floor temperature in the case of continuous local hot spots . 21
4.10 Floor temperature of underfloor storage heating through failure of a
switching, controlling or regulation apparatus . 23
4.11 Floor temperature of controlled underfloor heating and underfloor direct
heating through failure of a switching, controlling or regulation apparatus . 23
4.12 Regulation of room temperature using peripheral areas for underfloor
storage heating . 23
4.13 Regulation of room temperature using controlled underfloor heating and

underfloor direct heating . 23
4.14 Regulation of room temperature using underfloor warming . 24
4.15 Relationship of coefficients of heat transfer . 24
4.16 Insulating layers . 24
4.17 Edging insulation strips . 25
4.18 Damp-proofing . 25
4.19 Electrical auxiliary heating . 26
4.20 Load distribution layer in electrical underfloor heating . 26
4.21 Bedding in or under heating screed or directly below floor covering . 26
4.22 Dry laying of electrical heating elements. 26
4.23 Heating element . 26
4.24 Heating cable and laminar heating element . 26
4.24.1 Heating cable for bedding in or under screeding or directly below floor
covering. 26
4.24.2 Heating cable for dry laying . 26
4.24.3 Laminar heating elements for installation below or in screeding . 27
4.25 Characteristics of heating cables . 27
4.26 Characteristics of laminar heating elements . 27
4.27 Cold tails . 27
4.28 Point of connection . 27
4.29 Bending radius of the heating cable . 27
4.30 Heating element labelling . 27
4.31 Pulsation factor . 27
4.32 Installation of heating elements for underfloor direct heating . 28
4.33 Adhesive and fixing material . 28
4.34 Permanent installation areas . 28

4.35 Pre-heating of screeding . 28
4.36 Floor coverings . 28
4.37 Control and regulation equipment . 28
4.38 Control and regulation equipment for underfloor storage heating . 28
4.39 Control and regulation equipment for controlled underfloor heating and

underfloor direct heating . 28
4.40 Floor temperature measurement . 29
4.41 Auxiliary supply period . 29
4.42 Period of room use . 29
4.43 Insulation and dielectric resistance of the heating element . 29
4.44 Instructions for construction workers . 29
4.44.1 Protective measures when pouring flooring screed . 29
4.44.2 Pouring the screed . 29
4.45 Data for owner and user of the building . 29
4.46 Report of testing . 30
Annex A (informative) Sizing procedure – Range of application and purpose . 31
A.1 General . 31
A.2 Basic principles – Basic parameters of the room to be heated . 31
A.2.1 General . 31
A.2.2 Standard heat load of an underfloor heated room . 31
A.2.3 Standard heating load per unit area . 31
A.2.4 Effective heat storage capacity of the room to be heated . 32
A.2.5 Peripheral conditions and limiting values . 32
A.3 Sizing an underfloor heating system . 33
A.3.1 Storage layer depth of an underfloor heating system . 33
A.3.2 Heat load coverage for the underfloor heated room . 33
Annex B (informative) Sizing procedure – Examples of sizing procedure of an
underfloor storage heating system – Example for a living area . 48
B.1 General . 48
 ∗
B.2 Standard heat load of an underfloor heated room Q . 48
N
∗

B.3 Standard heat load per unit area q . 48
N
B.4 Storage mass per unit external area of the room m/ΣA . 48
a
B.5 Thickness of storage layer δ . 49
B.6 Relation of coefficients of conductivity . 49
B.7 Maximum rating per unit area P′ . 50
F
P′
B.8 Limited rating per unit area . 50
FE
B.9 Heating floor area A . 50
F
B.10 Permissible rating P . 50
ZUL
B.11 Rating of the room P . 51
′
B.12 Rating per unit area P . 51
IN

B.13 Mean heating capacity Q . 51
F

B.14 Auxiliary heating capacity Q . 51
Z
B.15 Auxiliary heat rating . 52
Annex C (informative) Sizing procedure – Example of sizing procedure of an
underfloor direct heating system – Example for a living area . 53
C.1 General . 53

– 4 – IEC 62999:2016 © IEC 2016
 ∗
C.2 Design heating capacity Q of a room with underfloor direct heating . 53
H
∗

C.3 Design heating capacity per unit area q . 53
H
C.4 Depth of the heating screed . 54
C.5 Relation of coefficients of conductivity . 54
′
C.6 Maximum rating per unit area P . 55
F
C.7 Limited rating per unit area P′ . 55
FE
C.8 Heating floor area A . 55
F
C.9 Permissible rating P . 56
ZUL
C.10 Rating of the room P . 56
′
C.11 Rating per unit area P . 56
IN

C.12 Mean heating capacity Q . 56
F

C.13 Auxiliary heating capacity Q . 56
Z
C.14 Formula symbols and units . 56

Figure 1 – Layout diagram of an underfloor heating system . 14
Figure 2 – Construction A, cross-section A – B. 14
Figure 3 – Construction B, cross-section A – B. 15
Figure 4 – Construction C, cross-section A – B . 15
Figure 5 – Examples for the effect of floor excess temperature T . 18
E
Figure 6 – Basic circuit diagram of underfloor storage heating . 19
Figure 7 – Underfloor direct heating, controlled underfloor heating and warming –
Example of a circuit for individual room regulation (rooms have one heating circuit
each) . 21
Figure 8 – Construction of model . 22
Figure A.1 – Monogram for determining the storage layer depth . 32
Figure A.2 – Electric underfloor storage heating, sizing chart . 34
Figure A.3 – Electric underfloor direct and controlled heating, sizing chart . 35
Figure A.4 – Plan of basement . 43
Figure A.5 – Plan of ground floor . 44
Figure A.6 – Plan of upper floor . 45
Figure A.7 – Cross-section A – B . 46
Figure A.8 – Cross-section C – D . 47
Figure B.1 – Ceiling construction . 48
Figure C.1 – Ceiling construction . 53

Table 1 – Minimum coefficient of heat transfer and minimum resistance to thermal
conductivity of construction elements . 25
′
Table A.1 – ϑ – ϑ = 0K . 36
1 1
′
Table A.2 – ϑ – ϑ = 5K . 36
1 1
′
Table A.3 – ϑ – ϑ = 10K . 37
1 1
′
Table A.4 – ϑ – ϑ = 15K . 37
1 1
′
Table A.5 – ϑ – ϑ = 20K . 38
1 1
′
Table A.6 – ϑ – ϑ = 30K . 38
1 1
′
Table A.7 – ϑ – ϑ = 35K . 39
1 1
′
Table A.8 – ϑ – ϑ = 38K . 39
1 1
Table B.1 – Determination of heat conductivity coefficient U . 49
o
Table B.2 – Determination of heat conductivity coefficient U . 50
u
Table C.1 – Determination of heat conductivity coefficient U . 54
o
Table C.2 – Determination of heat conductivity coefficient U . 55
u
– 6 – IEC 62999:2016 © IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRIC ROOM HEATING – UNDERFLOOR HEATING –
PERFORMANCE CHARACTERISTICS – DEFINITIONS, METHOD
OF TESTING, SIZING AND FORMULA SYMBOLS

FOREWORD
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International Standard IEC 62999 has been prepared by subcommittee 59C: Heating
appliances, of IEC technical committee 59: Performance of household and similar electrical
appliances.
The text of this standard is based on the following documents:
CDV Report on voting
59C/193/CDV 59C/197/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 8 – IEC 62999:2016 © IEC 2016
ELECTRIC ROOM HEATING – UNDERFLOOR HEATING –
PERFORMANCE CHARACTERISTICS – DEFINITIONS, METHOD
OF TESTING, SIZING AND FORMULA SYMBOLS

1 Scope
This International Standard applies to electrical underfloor heating of dwellings and all other
buildings whose use corresponds to dwellings or is at least similar, having a maximum load
bearing in use of 4 kN/m .
This Standard defines the main characteristics of electrical underfloor heating and
establishes the method of testing of these characteristics as information for the user.
This Standard does not deal with:
– installation and safety requirements.
2 Normative references
IEC 60335-2-96, Household and similar electrical appliances – Safety – Part 2-96: Particular
requirements for flexible sheet heating elements for room heating
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
electrical underfloor heating system
electrical underfloor heating, switching, control and regulation appliances and electrical
installation
3.1.1
underfloor heating
in situ flooring constructed as an electrical underfloor heating system
Note 1 to entry: It is generally laid on a dry, level, load-bearing substructure.
3.1.2
underfloor direct heating
underfloor direct heating, by which the heat generated from electrical energy is transferred
with the least possible time lag to the room to be heated mainly via the surface of the floor
Note 1 to entry: There is no restriction on the amount of time electrical energy can be converted into heat.
3.1.3
underfloor warming
underfloor warming increases comfort by means of pleasant warmth on the feet
Note 1 to entry: It is not necessary to calculate the heat load of the room, and the insulating layers as the
underfloor warming are not considered when calculating the heat load of the room.

3.1.4
controlled underfloor heating
underfloor direct heating, by which the conversion of electricity into heat may be interrupted
according to the provisions laid out in Note 1
Note 1 to entry: The conversion of electricity into heat may be interrupted – for no longer than 2 h continuously –
no longer than 8 h total in a 24 h period. The period of use will be equivalent to at least the previous period of
interruption.
3.1.5
underfloor storage heating
underfloor heating, by which the electrical energy is converted into heat and transferred with
an intended time lag to the room to be heated mainly via the surface of the floor
Note 1 to entry: The charging takes place during the charging time period t and, as a rule, during an additional
F
charging time t of minimum 2 h.
ZF
3.1.6
underfloor storage heating system
underfloor heating, auxiliary heating, switching, control and regulation appliances and
electrical installation
3.1.7
electrical auxiliary heating
necessary heating equipment with a rating Q in the room being heated, additional to, and
Z
different from, the underfloor heating (e.g. periphery heating, convector panels, etc.)
3.1.8
heating circuit
independently switched, regulated or controlled section of an underfloor heating system
3.2
duration of design charge
duration of the charge for which the storage heating system is designed and which is
determined as the basis for testing
Note 1 to entry: It constitutes the largest continuous charging time within a period of 24 h.
3.3
auxiliary charge
sum of the auxiliary charging times occurring between two design charge times
3.4
designed rating of a heating element
manufacturer’s stated power rating for the heating element in W at the design voltage
3.5
capacity of a room
capacity in W of underfloor heating in a room is the sum of the measured power ratings of the
installed heating elements of an underfloor heating system in that room
3.6
design temperature
ϑ
N
highest permissible heating cable nominal temperature in °C, taking into consideration the
specific operating properties, such as heat resistance of heat and sound insulation materials
Note 1 to entry: The design limiting temperature is the highest permissible temperature which is allowed by the
manufacturer of the surface heating element.

– 10 – IEC 62999:2016 © IEC 2016
3.7
maximum surface temtperature
temperature which, for physiological purposes, cannot be exceeded on the uncovered upper
surface of the flooring
Note 1 to entry: This temperature may be exceeded in peripheral areas.
3.8
standard internal temperature
value of the room temperature necessary for the calculation, ϑ in °C; it is the resulting
i
temperature, defined as the mean of the dry air temperature and the mean radiant
temperature
3.9
standard heat load of an underfloor heated room
 ∗
Q
N
standard heat load of an underfloor heated room, it is used only to size the underfloor

heating
 ∗
Note 1 to entry: Its value (as with that of the standard heat load of an underfloor heated room Q ) in W, is
N
calculated, taking into account the partially limited heating of the rooms in the dwelling. Areas of the room which
are equipped with surface heating elements (flooring, ceiling) remain unconsidered. To differentiate between the

standard heat load Q in W this value will be denoted as the standard heat load of an underfloor heated room,
N
 ∗
Q in W.
N
3.10
standard heat load per unit surface area

∗

q
N

standard heat load Q related to the area of the flooring surface A of the room to be heated,
N
in W/m

Q
∗ N

q =
N
A
3.11
design heating capacity of a room with an underfloor direct heating system

 ∗
Q
H
 ∗
design heating capacity of a room with underfloor direct heating Q in W
N
3.12
design heating capacity per unit area of a room with an underfloor direct heating
∗

system q
H
 ∗
design heating capacity of a room with underfloor direct heating Q in relation to its floor area
H
2 2
A in m , in W/m
 ∗
Q
∗
H

q =
H
A
3.13
maximum capacity per unit area
P
F
largest possible capacity in W/m which can be installed, taking into account the maximum
surface temperature, the construction of the underfloor heating system and the energy supply
charging time
3.14
capacity per unit area
capacity P in W in relation to the floor area to be heated A
F
P
P =
IN
A
F
3.15
mean heating capacity
average heating capacity in W of the heating floor area for a given time, taking into account
the floor upper surface temperature, the standard room temperature and the mean
temperature on the inside surfaces of walls and ceilings
3.16
mean heat flow density

q
F
heat flow per surface area in W/m from the floor to the heated room
3.17
localised hot spots
occur when the floor area is covered with a highly insulating material (such as cushions or
mattresses) or by defective switching, regulation or control apparatus. This results in an
undue thermal strain on the underfloor heating
3.18
effective heat storage capacity for underfloor storage heating
partial amount of the heat storage capacity of a building (room) in W/m K, having an
influence on the heat load
3.19
storage mass of a heated room in relation to external surface
m/∑A in kg/m is the quotient of the storage mass of the room m in kg and the sum of the
a
external surfaces of the room ∑A in m
a
3.20
permanent fixture area
non-heating area of the floor surface which is designated for full-surface mounting or the
installation of furnishings
Note 1 to entry: The floor areas in WC, shower or bathroom, on which bathroom fittings such as WC, shower or
bathtub are to be installed, count as permanent fixture areas.
3.21
peripheral zone area
A
R
floor area with a maximum width of 1 m which heats at a higher temperature, generally in
front of glazed external walls or external doors
Note 1 to entry: This is not deemed to be an area of permanent dwelling; in m .

– 12 – IEC 62999:2016 © IEC 2016
3.22
dwelling area
A
V
area of permanent residing within the heating floor area
Note 1 to entry: It is the product of the heating floor area minus the border area, in m .
3.23
components of electric underfloor heating
• insulating layer (for heat- and soundproofing);
• damp proofing;
• heating element;
• heat and load distribution layer;
• floor covering
3.24
insulating layer
heat insulation below the flooring, which can also serve as sound proofing
3.25
damp proofing
layer of material that serves to prevent the insulating layer becoming damp from the water
used to mix the flooring screed and also to prevent mortar pollution
Note 1 to entry: At the same time it prevents the heating cables from sinking into open joints in the insulation.
3.26
heating element
combination of a heating cable or laminar heating element and, if applicable, its cold tails
which connect it to the terminals of the electrical installation
3.26.1
heating conductor
electrically conducting component of the heating cable in which electrical energy is directly
converted into heat
3.26.2
heating cable
insulated heating conductor
3.26.3
laminar heating conductor
electrically conducting planar component of a laminar heating element allowing the direct
conversion of electrical energy into heat
3.26.4
laminar heating element
insulated laminar heating conductor. Contact strips provide power supply
3.26.5
heating loop
heating element comprising a heating cable and its connected cold tails, whose geometric
fixing takes place during the installation of the system

3.26.6
heating mat
combination of one or more heating elements, geometrically fixed by the manufacturer using
suitable equipment
3.26.7
cold tail
insulated conductor providing the connection between the heating cable and the terminals of
the electrical installation, at the same time preventing an undue warming of the terminals on
the supply side
3.26.8
point of connection
connection (e.g. coupling sleeve) between a heating cable or laminar heating element and its
cold tail
3.27
load distribution layer in electric underfloor heating
for example heating screed
3.28
storage layer
comprises the heating screed, floor covering and all other construction elements above the
heating layer which have heat conductivity values of λ ≥ 1,0 W/(m ⋅ K)
3.29
floor covering
upper layer of the underfloor heating able to be walked upon
3.30
laying methods (see Figure 1)
3.30.1
bedding in heating screed
the heating element is bedded directly in the freshly laid heating screed as shown in Figure 2
construction A
3.30.2
bedding below heating screed
the heating element is bedded directly below, or only partially in the fresh heating screed as
shown in Figure 3, construction B. The heating screed can have a separating layer

– 14 – IEC 62999:2016 © IEC 2016
d
A
d
2d
B
Heating cable
Connection
Cold cable
IEC
Key
d depth of heating screed
Figure 1 – Layout diagram of an underfloor heating system
Floor
Screed
Heating cable
Conductor
Cover
Insulation
Base ground
IEC
Figure 2 – Construction A, cross-section A – B
3.30.3
dry laying of electrical heating elements
the heating element is laid in pre-fabricated, grooved slabs, tubes or canals below, or in the
heating screed. The heating element does not come into contact with the heating screed
3.30.4
bedding directly below the floor covering
the heating element is laid on the existing sub-structure (e.g. screeding) as shown in Figure
4, construction C. It is normally fixed to the sub-structure with grouting
Note 1 to entry: It is normally fixed to the sub-structure with grouting.
3.31
pulsation factor
∆ϑ
F
maximum temperature difference in Kelvin which can occur on the upper surface of a flooring
within the dwelling area
Floor
Screed
Separating layer
Screed
Heating cable
Cover
Insulation
Base ground
IEC
Figure 3 – Construction B, cross-section A – B
Floor
Tile glue
Heating cable
Mortar
Screed
Cover
Insulation
Base ground
IEC
Figure 4 – Construction C, cross-section A – B
3.32
control and regulation equipment

3.32.1
weather sensor
component which measures prevailing weather conditions (e.g. outside temperatures) and
transmits these values as reference input to other components of the charge control
3.32.2
floor temperature sensor
component which measures the temperature of a fixed point in the heating floor surface and
transmits this value as a reference input to other components of the charge control/regulator
3.32.3
floor temperature limiter
operating temperature limiter as defined in IEC 60730-1
Note 1 to entry: It is a self-resetting component with which the temperature at a fixed point in the heating floor
surface is kept below a set value by automatically controlling the heating system.
3.32.4
floor temperature regulator
component which maintains the temperature of the floor temperature sensor within settable
limits by automatically controlling the heating system
3.32.5
room temperature regulator
component which maintains the temperature of the room air within settable limits by
automatically controlling the heating system

– 16 – IEC 62999:2016 © IEC 2016
3.32.6
supply period
t
F
largest possible continuous period of time, in which during a time-period of 24 h electrical
energy can be obtained for the underfloor heating at its point of installation
Note 1 to entry: In practical operation the supply period can either be continuous or, for reasons of load control in
supply networks, divided into individual sectors.
3.32.7
auxiliary supply period
t
ZF
sum of the additional periods, between two supply periods, in which electrical energy is
supplied for underfloor heating, in hours
3.32.8
period of room use
t
B
period for which the underfloor heating system is designed, in hours
4 Method of testing for the determination of characteristics of performance
4.1 General
Electrical underfloor heating systems are deemed to be a fixed component of the building to
be heated. The testing of underfloor heating systems and their conformity to sizing standards
shall be confirmed by calculation and if necessary by measurement. A confirmation by
measurement of the installed system should only be carried out in justifiable cases.
4.2 Standard heating load per unit area
In consideration of functionality, efficiency and maintenance of hygienic conditions, the
standard heating load per unit area of dwellings and buildings with similar use heated by
underfloor heating should not exceed 70 W/m . The standard heating load per unit area of an
∗
 2
individual room q in W/m may in exceptional circumstances exceed this value when
N
justified by the heat load calculation according to Annex A.
4.3 Maximum power rating per unit area
The maximum power rating per unit area shall be selected so that even at localised hot spots
no damage can occur on the underside of the load distribution layer. An additional localised
hot spot above the intended floor covering is assumed to exist due to covering by an
additional insulating layer with a resistance to heat conductivity of:
m ×K
R = 2
λ
W
(Corresponds to e.g. 0,08 m of a material with λ = 0,04 W/(m K).)
Limiting values of the maximum power rating based on surface are to be found in Annex A of
this Standard, Tables A.1 to A.8.
The rating of the room shall be determined. The rating per unit area P′ in W/m is:
IN
P
P′ =
IN
AF
4.4 Maximum surface temperature
The temporal average temperature difference between floor surface and room air
temperature during usage time in dwelling areas is
– not more than 6,5 K for underfloor storage heating,
– not more than 9,0 K for underfloor direct heating and controlled underfloor heating.
The value of the average heat flow density is based on this temperature difference.
The mean surface temperature shall be measured in the actual condition of the room
(condition of use). It shall be determined whether the actual and designed conditions of the
floor covering are correspondent. The surface temperature shall be measured and recorded
at a minimum of 5 random points in dwelling areas, in peripheral areas at a minimum of 3
random points, which are at least 0,4 m from lateral confinements of the heating area.
Measurements shall not be carried out at points whose temperature can be influenced by
outside sources, e.g. sun’s rays.
The measurement of temperature s
...

IEC 62999 ®
Edition 1.1 2021-10
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electric room heating – Underfloor heating – Performance characteristics –
Definitions, method of testing, sizing and formula symbols

Chauffage électrique de locaux – Chauffage par le sol – Caractéristiques de
performance – Définitions, méthode d'essai, calibrage et symboles de formule

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IEC 62999 ®
Edition 1.1 2021-10
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electric room heating – Underfloor heating – Performance characteristics –
Definitions, method of testing, sizing and formula symbols
Chauffage électrique de locaux – Chauffage par le sol – Caractéristiques de
performance – Définitions, méthode d'essai, calibrage et symboles de formule
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 97.100.10 ISBN 978-2-8322-5465-3

IEC 62999 ®
Edition 1.1 2021-10
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
Electric room heating – Underfloor heating – Performance characteristics –
Definitions, method of testing, sizing and formula symbols

Chauffage électrique de locaux – Chauffage par le sol – Caractéristiques de
performance – Définitions, méthode d'essai, calibrage et symboles de formule

– 2 – IEC 62999:2016+AMD1:2021 CSV
© IEC 2021
CONTENTS
FOREWORD . 6
1 Scope . 8
2 Normative references. 8
3 Terms and definitions . 8
4 Method of testing for the determination of characteristics of performance . 15
4.1 General . 15
4.2 Standard heating load per unit area . 16
4.3 Maximum power rating per unit area . 16
4.4 Maximum surface temperature . 16
4.5 Maximum floor surface temperature for underfloor storage heating . 17
4.6 Room air temperature. 19
4.7 Internal surface temperatures on the surrounding surfaces of the room . 20
4.8 Thermal pre-conditioning of the room to be tested . 20
4.9 Floor temperature in the case of continuous local hot spots . 21
4.10 Floor temperature of underfloor storage heating through failure of a
switching, controlling or regulation apparatus . 23
4.11 Floor temperature of controlled underfloor heating and underfloor direct
heating through failure of a switching, controlling or regulation apparatus . 23
4.12 Regulation of room temperature using peripheral areas for underfloor
storage heating . 23
4.13 Regulation of room temperature using controlled underfloor heating and
underfloor direct heating . 23
4.14 Regulation of room temperature using underfloor warming . 24
4.15 Relationship of coefficients of heat transfer . 24
4.16 Insulating layers . 24
4.17 Edging insulation strips . 25
4.18 Damp-proofing . 25
4.19 Electrical auxiliary heating . 26
4.20 Load distribution layer in electrical underfloor heating . 26
4.21 Bedding in or under heating screed or directly below floor covering . 26
4.22 Dry laying of electrical heating elements . 26
4.23 Heating element . 26
4.24 Heating cable and laminar heating element . 26
4.24.1 Heating cable for bedding in or under screeding or directly below floor
covering . 26
4.24.2 Heating cable for dry laying . 26
4.24.3 Laminar heating elements for installation below or in screeding . 26
4.25 Characteristics of heating cables . 27
4.26 Characteristics of laminar heating elements . 27
4.27 Cold tails . 27
4.28 Point of connection . 27
4.29 Bending radius of the heating cable . 27
4.30 Heating element labelling . 27
4.31 Pulsation factor . 27
4.32 Installation of heating elements for underfloor direct heating . 27
4.33 Adhesive and fixing material . 28
4.34 Permanent installation areas . 28

© IEC 2021
4.35 Pre-heating of screeding . 28
4.36 Floor coverings . 28
4.37 Control and regulation equipment . 28
4.38 Control and regulation equipment for underfloor storage heating . 28
4.39 Control and regulation equipment for controlled underfloor heating and
underfloor direct heating . 28
4.40 Floor temperature measurement . 28
4.41 Auxiliary supply period . 29
4.42 Period of room use . 29
4.43 Insulation and dielectric resistance of the heating element . 29
4.44 Instructions for construction workers . 29
4.44.1 Protective measures when pouring flooring screed . 29
4.44.2 Pouring the screed . 29
4.45 Data for owner and user of the building . 29
4.46 Report of testing . 30
Annex A (informative) Sizing procedure – Range of application and purpose . 31
A.1 General . 31
A.2 Basic principles – Basic parameters of the room to be heated . 31
A.2.1 General . 31
A.2.2 Standard heat load of an underfloor heated room . 31
A.2.3 Standard heating load per unit area . 31
A.2.4 Effective heat storage capacity of the room to be heated . 32
A.2.5 Peripheral conditions and limiting values . 32
A.3 Sizing an underfloor heating system . 33
A.3.1 Storage layer depth of an underfloor heating system . 33
A.3.2 Heat load coverage for the underfloor heated room . 33
Annex B (informative) Sizing procedure – Examples of sizing procedure of an

underfloor storage heating system – Example for a living area . 48
B.1 General . 48
 ∗
B.2 Standard heat load of an underfloor heated room Q . 48
N
∗

B.3 Standard heat load per unit area q . 48
N
B.4 Storage mass per unit external area of the room m/ΣA . 48
a
B.5 Thickness of storage layer δ . 49
B.6 Relation of coefficients of conductivity . 49
B.7 Maximum rating per unit area P′ . 50
F
′
B.8 Limited rating per unit area P . 50
FE
B.9 Heating floor area A . 50
F
B.10 Permissible rating P . 50
ZUL
B.11 Rating of the room P . 51
′
B.12 Rating per unit area P . 51
IN

B.13 Mean heating capacity Q . 51
F

B.14 Auxiliary heating capacity Q . 51
Z
B.15 Auxiliary heat rating . 52
Annex C (informative) Sizing procedure – Example of sizing procedure of an
underfloor direct heating system – Example for a living area . 53
C.1 General . 53

– 4 – IEC 62999:2016+AMD1:2021 CSV
© IEC 2021
 ∗
C.2 Design heating capacity Q of a room with underfloor direct heating . 53
H
∗

C.3 Design heating capacity per unit area q . 53
H
C.4 Depth of the heating screed . 54
C.5 Relation of coefficients of conductivity . 54
′
C.6 Maximum rating per unit area P . 55
F
C.7 Limited rating per unit area P′ . 55
FE
C.8 Heating floor area A . 55
F
C.9 Permissible rating P . 56
ZUL
C.10 Rating of the room P . 56
P′
C.11 Rating per unit area . 56
IN

C.12 Mean heating capacity Q . 56
F

C.13 Auxiliary heating capacity Q . 56
Z
C.14 Formula symbols and units . 56
Annex D (informative) Complete performance test according to Commission
Regulation (EU) 2015/1188 . 59
D.1 Test conditions . 59
D.2 Definitions . 59
D.3 Requirements to comply with functions according to Commission Regulation
(EU) 2015/1188 . 63
D.3.1 General . 63
D.3.2 Product equipped with single stage heat output, no room temperature
control . 63
D.3.3 Product equipped with two or more manual stages, no room
temperature control . 63
D.3.4 Product equipped with mechanical room temperature control . 63
D.3.5 Product equipped with electronic room temperature control . 63
D.3.6 Product equipped with electronic room temperature control plus day
timer . 63
D.3.7 Product equipped with electronic room temperature control plus week
timer . 64
D.3.8 Product equipped with room temperature control, with presence
detection . 64
D.3.9 Product equipped with room temperature control, with open window
detection . 64
D.3.10 Product equipped with distance control option . 65
D.3.11 Product equipped with adaptive start control . 65
D.3.12 Product equipped with working time limitation . 65
D.3.13 Product equipped with black bulb sensor . 66
D.4 Information provided at point of sale . 66
Annex E (informative) Climatic test room . 67
E.1 Climatic test room A . 67
E.2 Climatic test room B . 68
Bibliography . 69

Figure 1 – Layout diagram of an underfloor heating system . 13
Figure 2 – Construction A, cross-section A – B . 14
Figure 3 – Construction B, cross-section A – B . 14

© IEC 2021
Figure 4 – Construction C, cross-section A – B . 14
Figure 5 – Examples for the effect of floor excess temperature T . 17
E
Figure 6 – Basic circuit diagram of underfloor storage heating . 19
Figure 7 – Underfloor direct heating, controlled underfloor heating and warming –
Example of a circuit for individual room regulation (rooms have one heating circuit
each) . 21
Figure 8 – Construction of model . 22
Figure A.1 – Monogram for determining the storage layer depth . 32
Figure A.2 – Electric underfloor storage heating, sizing chart . 34
Figure A.3 – Electric underfloor direct and controlled heating, sizing chart . 35
Figure A.4 – Plan of basement . 43
Figure A.5 – Plan of ground floor . 44
Figure A.6 – Plan of upper floor . 45
Figure A.7 – Cross-section A – B . 46
Figure A.8 – Cross-section C – D . 47
Figure B.1 – Ceiling construction . 48
Figure C.1 – Ceiling construction . 53
Figure E.1 – Example of a climatic test room . 68

Table 1 – Minimum coefficient of heat transfer and minimum resistance to thermal
conductivity of construction elements . 25
Table A.1 – ϑ – ϑ′ = 0K . 36
1 1
Table A.2 – ϑ – ϑ′ = 5K . 36
1 1
Table A.3 – ϑ – ϑ′ = 10K . 37
1 1
Table A.4 – ϑ – ϑ′ = 15K . 37
1 1
Table A.5 – ϑ – ϑ′ = 20K . 38
1 1
Table A.6 – ϑ – ϑ′ = 30K . 38
1 1
Table A.7 – ϑ – ϑ′ = 35K . 39
1 1
Table A.8 – ϑ – ϑ′ = 38K . 39
1 1
Table B.1 – Determination of heat conductivity coefficient U . 49
o
Table B.2 – Determination of heat conductivity coefficient U . 50
u
Table C.1 – Determination of heat conductivity coefficient U . 54
o
Table C.2 – Determination of heat conductivity coefficient U . 55
u
– 6 – IEC 62999:2016+AMD1:2021 CSV
© IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRIC ROOM HEATING – UNDERFLOOR HEATING –
PERFORMANCE CHARACTERISTICS – DEFINITIONS, METHOD
OF TESTING, SIZING AND FORMULA SYMBOLS

FOREWORD
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This consolidated version of the official IEC Standard and its amendment has been
prepared for user convenience.
IEC 62999 edition 1.1 contains the first edition (2016-02) [documents 59C/193/CDV and
59C/197/RVC] and its amendment 1 (2021-10) [documents 59C/250/CDV and
59C/197/RVC].
In this Redline version, a vertical line in the margin shows where the technical content
is modified by amendment 1. Additions are in green text, deletions are in strikethrough
red text. A separate Final version with all changes accepted is available in this
publication.
© IEC 2021
International Standard IEC 62999 has been prepared by subcommittee 59C: Heating
appliances, of IEC technical committee 59: Performance of household and similar electrical
appliances.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of the base publication and its amendment will
remain unchanged until the stability date indicated on the IEC web site under webstore.iec.ch
in the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 8 – IEC 62999:2016+AMD1:2021 CSV
© IEC 2021
ELECTRIC ROOM HEATING – UNDERFLOOR HEATING –
PERFORMANCE CHARACTERISTICS – DEFINITIONS, METHOD
OF TESTING, SIZING AND FORMULA SYMBOLS

1 Scope
This International Standard applies to electrical underfloor heating of dwellings and all other
buildings whose use corresponds to dwellings or is at least similar, having a maximum load
bearing in use of 4 kN/m .
This Standard defines the main characteristics of electrical underfloor heating and establishes
the method of testing of these characteristics as information for the user.
This Standard does not deal with:
– installation and safety requirements.
Annexes D and E are added for information purposes about performance testing according to
the European Commission Regulation (EU) 2015/1188.
2 Normative references
IEC 60335-2-96, Household and similar electrical appliances – Safety – Part 2-96: Particular
requirements for flexible sheet heating elements for room heating
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
electrical underfloor heating system
electrical underfloor heating, switching, control and regulation appliances and electrical
installation
3.1.1
underfloor heating
in situ flooring constructed as an electrical underfloor heating system
Note 1 to entry: It is generally laid on a dry, level, load-bearing substructure.
3.1.2
underfloor direct heating
underfloor direct heating, by which the heat generated from electrical energy is transferred
with the least possible time lag to the room to be heated mainly via the surface of the floor
Note 1 to entry: There is no restriction on the amount of time electrical energy can be converted into heat.
3.1.3
underfloor warming
underfloor warming increases comfort by means of pleasant warmth on the feet
Note 1 to entry: It is not necessary to calculate the heat load of the room, and the insulating layers as the
underfloor warming are not considered when calculating the heat load of the room.

© IEC 2021
3.1.4
controlled underfloor heating
underfloor direct heating, by which the conversion of electricity into heat may be interrupted
according to the provisions laid out in Note 1
Note 1 to entry: The conversion of electricity into heat may be interrupted – for no longer than 2 h continuously –
no longer than 8 h total in a 24 h period. The period of use will be equivalent to at least the previous period of
interruption.
3.1.5
underfloor storage heating
underfloor heating, by which the electrical energy is converted into heat and transferred with
an intended time lag to the room to be heated mainly via the surface of the floor
Note 1 to entry: The charging takes place during the charging time period t and, as a rule, during an additional
F
charging time t of minimum 2 h.
ZF
3.1.6
underfloor storage heating system
underfloor heating, auxiliary heating, switching, control and regulation appliances and
electrical installation
3.1.7
electrical auxiliary heating
necessary heating equipment with a rating Q in the room being heated, additional to, and
Z
different from, the underfloor heating (e.g. periphery heating, convector panels, etc.)
3.1.8
heating circuit
independently switched, regulated or controlled section of an underfloor heating system
3.2
duration of design charge
duration of the charge for which the storage heating system is designed and which is
determined as the basis for testing
Note 1 to entry: It constitutes the largest continuous charging time within a period of 24 h.
3.3
auxiliary charge
sum of the auxiliary charging times occurring between two design charge times
3.4
designed rating of a heating element
manufacturer’s stated power rating for the heating element in W at the design voltage
3.5
capacity of a room
capacity in W of underfloor heating in a room is the sum of the measured power ratings of the
installed heating elements of an underfloor heating system in that room
3.6
design temperature
ϑ
N
highest permissible heating cable nominal temperature in °C, taking into consideration the
specific operating properties, such as heat resistance of heat and sound insulation materials
Note 1 to entry: The design limiting temperature is the highest permissible temperature which is allowed by the
manufacturer of the surface heating element.

– 10 – IEC 62999:2016+AMD1:2021 CSV
© IEC 2021
3.7
maximum surface temtperature
temperature which, for physiological purposes, cannot be exceeded on the uncovered upper
surface of the flooring
Note 1 to entry: This temperature may be exceeded in peripheral areas.
3.8
standard internal temperature
value of the room temperature necessary for the calculation, ϑ in °C; it is the resulting
i
temperature, defined as the mean of the dry air temperature and the mean radiant
temperature
3.9
standard heat load of an underfloor heated room
 ∗
Q
N
standard heat load of an underfloor heated room, it is used only to size the underfloor

heating
 ∗
Note 1 to entry: Its value (as with that of the standard heat load of an underfloor heated room Q ) in W, is
N
calculated, taking into account the partially limited heating of the rooms in the dwelling. Areas of the room which
are equipped with surface heating elements (flooring, ceiling) remain unconsidered. To differentiate between the
  ∗
standard heat load Q in W this value will be denoted as the standard heat load of an underfloor heated room, Q
N N
in W.
3.10
standard heat load per unit surface area

∗

q
N

standard heat load Q related to the area of the flooring surface A of the room to be heated, in
N
W/m

Q
∗
N

q =
N
A
3.11
design heating capacity of a room with an underfloor direct heating system

 ∗
Q
H
 ∗
design heating capacity of a room with underfloor direct heating Q in W
N
3.12
design heating capacity per unit area of a room with an underfloor direct heating
∗

system q
H
 ∗
design heating capacity of a room with underfloor direct heating Q in relation to its floor area
H
2 2
A in m , in W/m
 ∗
Q
∗ H

q =
H
A
© IEC 2021
3.13
maximum capacity per unit area
P
F
largest possible capacity in W/m which can be installed, taking into account the maximum
surface temperature, the construction of the underfloor heating system and the energy supply
charging time
3.14
capacity per unit area
capacity P in W in relation to the floor area to be heated A
F
P
P =
IN
A
F
3.15
mean heating capacity
average heating capacity in W of the heating floor area for a given time, taking into account
the floor upper surface temperature, the standard room temperature and the mean
temperature on the inside surfaces of walls and ceilings
3.16
mean heat flow density

q
F
heat flow per surface area in W/m from the floor to the heated room
3.17
localised hot spots
occur when the floor area is covered with a highly insulating material (such as cushions or
mattresses) or by defective switching, regulation or control apparatus. This results in an
undue thermal strain on the underfloor heating
3.18
effective heat storage capacity for underfloor storage heating
partial amount of the heat storage capacity of a building (room) in W/m K, having an influence
on the heat load
3.19
storage mass of a heated room in relation to external surface
m/∑A in kg/m is the quotient of the storage mass of the room m in kg and the sum of the
a
external surfaces of the room ∑A in m
a
3.20
permanent fixture area
non-heating area of the floor surface which is designated for full-surface mounting or the
installation of furnishings
Note 1 to entry: The floor areas in WC, shower or bathroom, on which bathroom fittings such as WC, shower or
bathtub are to be installed, count as permanent fixture areas.
3.21
peripheral zone area
A
R
floor area with a maximum width of 1 m which heats at a higher temperature, generally in front
of glazed external walls or external doors
Note 1 to entry: This is not deemed to be an area of permanent dwelling; in m .

– 12 – IEC 62999:2016+AMD1:2021 CSV
© IEC 2021
3.22
dwelling area
A
V
area of permanent residing within the heating floor area
Note 1 to entry: It is the product of the heating floor area minus the border area, in m .
3.23
components of electric underfloor heating
• insulating layer (for heat- and soundproofing);
• damp proofing;
• heating element;
• heat and load distribution layer;
• floor covering
3.24
insulating layer
heat insulation below the flooring, which can also serve as sound proofing
3.25
damp proofing
layer of material that serves to prevent the insulating layer becoming damp from the water
used to mix the flooring screed and also to prevent mortar pollution
Note 1 to entry: At the same time it prevents the heating cables from sinking into open joints in the insulation.
3.26
heating element
combination of a heating cable or laminar heating element and, if applicable, its cold tails
which connect it to the terminals of the electrical installation
3.26.1
heating conductor
electrically conducting component of the heating cable in which electrical energy is directly
converted into heat
3.26.2
heating cable
insulated heating conductor
3.26.3
laminar heating conductor
electrically conducting planar component of a laminar heating element allowing the direct
conversion of electrical energy into heat
3.26.4
laminar heating element
insulated laminar heating conductor. Contact strips provide power supply
3.26.5
heating loop
heating element comprising a heating cable and its connected cold tails, whose geometric
fixing takes place during the installation of the system
3.26.6
heating mat
combination of one or more heating elements, geometrically fixed by the manufacturer using
suitable equipment
© IEC 2021
3.26.7
cold tail
insulated conductor providing the connection between the heating cable and the terminals of
the electrical installation, at the same time preventing an undue warming of the terminals on
the supply side
3.26.8
point of connection
connection (e.g. coupling sleeve) between a heating cable or laminar heating element and its
cold tail
3.27
load distribution layer in electric underfloor heating
for example heating screed
3.28
storage layer
comprises the heating screed, floor covering and all other construction elements above the
heating layer which have heat conductivity values of λ ≥ 1,0 W/(m ⋅ K)
3.29
floor covering
upper layer of the underfloor heating able to be walked upon
3.30
laying methods (see Figure 1)
3.30.1
bedding in heating screed
the heating element is bedded directly in the freshly laid heating screed as shown in Figure 2
construction A
3.30.2
bedding below heating screed
the heating element is bedded directly below, or only partially in the fresh heating screed as
shown in Figure 3, construction B. The heating screed can have a separating layer
d
A
d
2d
B
Heating cable
Connection
Cold cable
IEC
Key
d depth of heating screed
Figure 1 – Layout diagram of an underfloor heating system

– 14 – IEC 62999:2016+AMD1:2021 CSV
© IEC 2021
Floor
Screed
Heating cable
Conductor
Cover
Insulation
Base ground
IEC
Figure 2 – Construction A, cross-section A – B
3.30.3
dry laying of electrical heating elements
the heating element is laid in pre-fabricated, grooved slabs, tubes or canals below, or in the
heating screed. The heating element does not come into contact with the heating screed
3.30.4
bedding directly below the floor covering
the heating element is laid on the existing sub-structure (e.g. screeding) as shown in Figure 4,
construction C. It is normally fixed to the sub-structure with grouting
Note 1 to entry: It is normally fixed to the sub-structure with grouting.
3.31
pulsation factor
∆ϑ
F
maximum temperature difference in Kelvin which can occur on the upper surface of a flooring
within the dwelling area
Floor
Screed
Separating layer
Screed
Heating cable
Cover
Insulation
Base ground
IEC
Figure 3 – Construction B, cross-section A – B
Floor
Tile glue
Heating cable
Mortar
Screed
Cover
Insulation
Base ground
IEC
Figure 4 – Construction C, cross-section A – B

© IEC 2021
3.32
control and regulation equipment

3.32.1
weather sensor
component which measures prevailing weather conditions (e.g. outside temperatures) and
transmits these values as reference input to other components of the charge control
3.32.2
floor temperature sensor
component which measures the temperature of a fixed point in the heating floor surface and
transmits this value as a reference input to other components of the charge control/regulator
3.32.3
floor temperature limiter
operating temperature limiter as defin
...