EN ISO 11855-3:2021

SLOVENSKI STANDARD
01-november-2021
Nadomešča:
SIST EN ISO 11855-3:2015
Načrtovanje notranjega okolja v stavbah - Vgrajeni sevalni ogrevalni in hladilni
sistemi - 3. del: Načrtovanje in dimenzioniranje (ISO 11855-3:2021)
Building environment design - Embedded radiant heating and cooling systems - Part 3:
Design and dimensioning (ISO 11855-3:2021)
Umweltgerechte Gebäudeplanung - Flächenintegrierte Strahlheizungs- und -
kühlsysteme - Teil 3: Planung und Auslegung (ISO 11855-3:2021)
Conception de l'environnement des bâtiments - Systèmes intégrés de chauffage et de
refroidissement par rayonnement - Partie 3: Conception et dimensionnement (ISO 11855
-3:2021)
Ta slovenski standard je istoveten z: EN ISO 11855-3:2021
ICS:
91.140.10 Sistemi centralnega Central heating systems
ogrevanja
91.140.30 Prezračevalni in klimatski Ventilation and air-
sistemi conditioning systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 11855-3
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2021
EUROPÄISCHE NORM
ICS 91.040.01 Supersedes EN ISO 11855-3:2015
English Version
Building environment design - Embedded radiant heating
and cooling systems - Part 3: Design and dimensioning
(ISO 11855-3:2021)
Conception de l'environnement des bâtiments - Umweltgerechte Gebäudeplanung - Flächenintegrierte
Systèmes intégrés de chauffage et de refroidissement Strahlheizungs- und -kühlsysteme - Teil 3: Planung und
par rayonnement - Partie 3: Conception et Auslegung (ISO 11855-3:2021)
dimensionnement (ISO 11855-3:2021)
This European Standard was approved by CEN on 29 July 2021.

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

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

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 11855-3:2021 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 11855-3:2021) has been prepared by Technical Committee ISO/TC 205
"Building environment design" in collaboration with Technical Committee CEN/TC 228 “Heating
systems and water based cooling systems in buildings” the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by March 2022, and conflicting national standards shall
be withdrawn at the latest by March 2022.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 11855-3:2015.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN websites.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 11855-3:2021 has been approved by CEN as EN ISO 11855-3:2021 without any
modification.
INTERNATIONAL ISO
STANDARD 11855-3
Second edition
2021-08
Building environment design —
Embedded radiant heating and cooling
systems —
Part 3:
Design and dimensioning
Conception de l'environnement des bâtiments — Systèmes intégrés de
chauffage et de refroidissement par rayonnement —
Partie 3: Conception et dimensionnement
Reference number
ISO 11855-3:2021(E)
©
ISO 2021
ISO 11855-3:2021(E)
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Email: copyright@iso.org
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Published in Switzerland
ii © ISO 2021 – All rights reserved

ISO 11855-3:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 1
5 Radiant panel . 3
5.1 Floor heating systems . 3
5.1.1 Design procedure . 3
5.1.2 Heating medium differential temperature . 4
5.1.3 Characteristic curve . 4
5.1.4 Field of characteristic curves . 4
5.1.5 Limit curves . 4
5.1.6 Downwards thermal insulation . 5
5.1.7 Procedure for determining the design supply temperature of the heating
medium .10
5.1.8 Procedure for determining the design heating medium flow rate .13
5.1.9 Peripheral areas.14
5.2 Ceiling heating systems .14
5.2.1 General.14
5.2.2 Limit curves .14
5.2.3 Procedure for determining the design heating medium flow rate .15
5.3 Wall heating systems .15
5.3.1 General.15
5.3.2 Limit curves .15
5.3.3 Procedure for determining the design heating medium flow rate .15
5.4 Floor cooling systems . .16
5.4.1 Design procedure .16
5.4.2 Cooling medium differential temperature .16
5.4.3 Characteristic curve .17
5.4.4 Field of characteristic curves .17
5.4.5 Limit curves .17
5.4.6 Downwards thermal insulation .17
5.4.7 Procedure for determining the supply design temperature of cooling medium .17
5.4.8 Procedure for determining the design cooling medium flow rate .17
5.5 Ceiling cooling systems .17
5.6 Wall cooling systems .17
Annex A (normative) Thermal insulation for type A and C .18
Bibliography .19
ISO 11855-3:2021(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 205, Building environment design, in
collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC
228, Heating systems and water based cooling systems in buildings, in accordance with the Agreement on
technical cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 11855-3:2012), which has been
technically revised.
The main changes compared to the previous edition are as follows:
— the Scope clause was modified, series-related information has been moved to the Introduction
section;
— normative references were modified;
— informative references have been moved to the Bibliography;
— Annex A was added for the calculation of the thermal resistance of the insulating layers.
A list of all parts in the ISO 11855 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved

ISO 11855-3:2021(E)
Introduction
The radiant heating and cooling system consists of heat emitting/absorbing, heat supply, distribution,
and control systems. The ISO 11855 series deals with the embedded surface heating and cooling system
that directly controls heat exchange within the space. It does not include the system equipment itself,
such as heat source, distribution system and controller.
The ISO 11855 series addresses an embedded system that is integrated with the building structure.
Therefore, the panel system with open air gap, which is not integrated with the building structure, is
not covered by this series.
The ISO 11855 series is applicable to water-based embedded surface heating and cooling systems
in buildings. The ISO 11855 series is applied to systems using not only water but also other fluids or
electricity as a heating or cooling medium. The ISO 11855 series is not applicable for testing of systems.
The methods do not apply to heated or chilled ceiling panels or beams.
The object of the ISO 11855 series is to provide criteria to effectively design embedded systems. To do
this, it presents comfort criteria for the space served by embedded systems, heat output calculation,
dimensioning, dynamic analysis, installation, control method of embedded systems, and input
parameters for the energy calculations.
The ISO 11855 series consists of the following parts, under the general title Building environment
design — Embedded radiant heating and cooling systems:
— Part 1: Definitions, symbols, and comfort criteria
— Part 2: Determination of the design heating and cooling capacity
— Part 3: Design and dimensioning
— Part 4: Dimensioning and calculation of the dynamic heating and cooling capacity of Thermo Active
Building Systems (TABS)
— Part 5: Installation
— Part 6: Control
— Part 7: Input parameters for the energy calculation
ISO 11855-1 specifies the comfort criteria which should be considered in designing embedded radiant
heating and cooling systems, since the main objective of the radiant heating and cooling system is
to satisfy thermal comfort of the occupants. ISO 11855-2 provides steady-state calculation methods
for determination of the heating and cooling capacity. ISO 11855-3, this document, specifies design
and dimensioning methods of radiant heating and cooling systems to ensure the heating and cooling
capacity. ISO 11855-4 provides a dimensioning and calculation method to design Thermo Active
Building Systems (TABS) for energy saving purposes, since radiant heating and cooling systems can
reduce energy consumption and heat source size by using renewable energy. ISO 11855-5 addresses the
installation process for the system to operate as intended. ISO 11855-6 shows a proper control method
of the radiant heating and cooling systems to ensure the maximum performance which was intended
in the design stage when the system is actually being operated in a building. ISO 11855-7 presents a
calculation method for input parameters to ISO 52031.
INTERNATIONAL STANDARD ISO 11855-3:2021(E)
Building environment design — Embedded radiant heating
and cooling systems —
Part 3:
Design and dimensioning
1 Scope
This document establishes a system design and dimensioning method to ensure the heating and cooling
capacity of the radiant heating and cooling systems.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 11855-1, Building environment design —Embedded radiant heating and cooling systems — Part 1:
Definition, symbols, and comfort criteria
ISO 11855-2:2021, Building environment design — Embedded radiant heating and cooling systems —
Part 2: Determination of the design heating and cooling capacity
ISO 11855-5:2021, Building environment design —Embedded radiant heating and cooling systems —
Part 5: Installation
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11855-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Symbols
For the purposes of this document, the symbols in Table 1 apply.
Table 1 — Symbols
Symbol Unit Quantity
A m Area of the heating or cooling surface
F
A m Area of the occupied heating or cooling surface
A
A m Area of the peripheral heating or cooling surface
R
C J/(kg·K) Specific heat of water
Wa
K W/(m ⋅K) Equivalent heat transmission coefficient
H
l m Distance between the joists
p
l m Thickness of the joist
W
ISO 11855-3:2021(E)
Table 1 (continued)
Symbol Unit Quantity
m kg/s Design cooling medium flow rate
C
m kg/s Design heating medium flow rate
H
q W/m Design heat flux
des
q W/m Design heat flux in the occupied area
des,A
q W/m Design heat flux in the peripheral area
des,R
q W/m Limit heat flux
G
q W/m Maximum design heat flux
max
Q W Design heating/cooling capacity
des
Q W Design heating/cooling load
N
Q W Design sensible cooling load
N,s
Q W Design latent cooling load
N,l
Q W Heat output of supplementary heating equipment
out
R
(m K)/W Thermal resistance on the surface of the back side of the wall
h,bk
R (m K)/W Thermal resistance on ceiling surface under the floor heated room
h,c
R (m K)/W Partial inwards thermal resistance of the surface structure
o
R (m K)/W Partial outwards thermal resistance of the surface structure
u
R
(m ⋅K)/W Thermal resistance of surface covering
λ,B
R (m ⋅K)/W Thermal resistance of ceiling slab structure
λ ,c
R
(m ⋅K)/W Back side thermal resistance of insulating layer
λ,ins
R
(m ⋅K)/W Thermal resistance of plaster layer
λ ,pl
s m Effective thickness of thermal insulating layer
ins
W m Pipe spacing
h W/(m K) Heat transfer coefficient at ceiling heating surface
C
h W/(m K) Heat transfer coefficient at floor heating surface
F
h W/(m K) Heat transfer coefficient at wall heating surface
W
λ W/(m⋅K) Effective thermal conductivity of the thermal insulation layer
ins
λ W/(mK) Thermal conductivity of the thermal insulation layer between the joists
i
λ W/(mK) Thermal conductivity of the joist
w
θ °C Maximum surface temperature
F,max
θ °C Minimum surface temperature
F,min
θ °C Design indoor temperature
i
θ °C Return temperature of heating or cooling medium
R
θ °C Supply temperature of heating or cooling medium
V
θ °C Design supply temperature of heating/cooling medium
V,des
Δθ K Heating or cooling medium differential temperature
H
Δθ K Design cooling medium differential temperature
C,des
Δθ K Design heating medium differential temperature
H,des
Δθ K Limit of heating/cooling medium differential temperature
H,G
Δθ K Design heating/cooling medium differential supply temperature
V,des
σ K Temperature drop/rise between supply and return medium
2 © ISO 2021 – All rights reserved

ISO 11855-3:2021(E)
5 Radiant panel
5.1 Floor heating systems
5.1.1 Design procedure
Floor heating system design requires determining heating surface area, type, pipe size, pipe spacing,
supply temperature of the heating medium, and design heating medium flow rate. The design steps are
as follows.
Step 1: Calculate the design heating load Q . The design heating load Q shall not include the adjacent
N N
heat losses. This step should be conducted in accordance with a standard for heating load calcula-
tion, such as EN 12831, based on an index such as operative temperature (OT) (see ISO 11855-1).
Step 2: Determine the area of the heating surface A , excluding any area covered by immovable objects
F
or objects fixed to the building structure.
Step 3: Establish a maximum permissible surface temperature in accordance with ISO 11855-1.
Step 4: Determine the design heat flux q according to Formula (1). For floor heating systems including
des
a peripheral area, the design heat flux of peripheral area q and the design heat flux of occu-
des,R
pied area q shall be calculated respectively on the area of the peripheral heating surface A
des,A R
and on the area of the occupied heating surface A complying with Formula (2).
A
Q
N
(1)
q =
des
A
F
Qq=×Aq+×A (2)
Ndes,R Rdes,A A
Step 5: For the design of the floor heating systems, determine the room used for design with the max-
imum design heat flux q = q .
max des
Step 6: Determine the floor heating system such as the pipe spacing and the covering type, and design
heating medium differential temperature Δθ based on the maximum design heat flux q
H,des max
and the maximum surface temperature θ from the field of characteristic curves according
F,max
to ISO 11855-2 and 5.1.7.
Step 7: If the design heat flux q cannot be obtained by any pipe spacing for the room used for the
des
design, it is recommended to include a peripheral area and/or to provide supplementary heating
equipment. In this case, the maximum design heat flux q for the embedded system may now
max
occur in another room. The amount of heat output of supplementary heating equipment Q is
out
determined by Formula (3):
QQ=−Q (3)
outN des
where design heating capacity Q is calculated by Formula (4):
des
...