SIST EN ISO 11855-1:2021

Building environment design - Embedded radiant heating and cooling systems - Part 1: Definitions, symbols, and comfort criteria (ISO 11855-1:2021)

This document specifies the basic definitions, symbols, and comfort criteria for embedded radiant
heating and cooling systems.

Umweltgerechte Gebäudeplanung - Flächenintegrierte Strahlheizungs- und -kühlsysteme - Teil 1: Begriffe, Symbole und Komfortkriterien (ISO 11855-1:2021)

Dieses Dokument legt grundlegende Definitionen, Symbole und Komfortkriterien für flächenintegrierte Strahlungsheiz- und  kühlsysteme fest.

Conception de l'environnement des bâtiments - Systèmes intégrés de chauffage et de refroidissement par rayonnement - Partie 1: Définitions, symboles et critères de confort (ISO 11855-1:2021)

Načrtovanje notranjega okolja v stavbah - Vgrajeni sevalni ogrevalni in hladilni sistemi - 1. del: Definicije, simboli in merila za ugodje (ISO 11855-1:2021)

General Information

• Status: Published
• Public Enquiry End Date: 02-Jun-2020
• Publication Date: 06-Oct-2021
• ICS: 91.140.10 - Central heating systems
• ICS: 91.140.30 - Ventilation and air-conditioning systems
• Technical Committee: OGS - Heating for buildings
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 02-Sep-2021
• Due Date: 07-Nov-2021
• Completion Date: 07-Oct-2021
• Ref Project: EN ISO 11855-1:2021 - Building environment design - Embedded radiant heating and cooling systems - Part 1: Definitions, symbols, and comfort criteria (ISO 11855-1:2021)

RELATIONS

• Replaces: SIST EN ISO 11855-1:2015 - Building environment design - Design, dimensioning, installation and control of embedded radiant heating and cooling systems - Part 1: Definition, symbols, and comfort criteria (ISO 11855-1:2012)
• Effective Date: 01-Nov-2021

Standards Content (sample)

SLOVENSKI STANDARD
SIST EN ISO 11855-1:2021
01-november-2021
Nadomešča:
SIST EN ISO 11855-1:2015
Načrtovanje notranjega okolja v stavbah - Vgrajeni sevalni ogrevalni in hladilni
sistemi - 1. del: Definicije, simboli in merila za ugodje (ISO 11855-1:2021)

Building environment design - Embedded radiant heating and cooling systems - Part 1:

Definitions, symbols, and comfort criteria (ISO 11855-1:2021)
Umweltgerechte Gebäudeplanung - Flächenintegrierte Strahlheizungs- und -
kühlsysteme - Teil 1: Begriffe, Symbole und Komfortkriterien (ISO 11855-1:2021)

Conception de l'environnement des bâtiments - Systèmes intégrés de chauffage et de

refroidissement par rayonnement - Partie 1: Définitions, symboles et critères de confort

(ISO 11855-1:2021)
Ta slovenski standard je istoveten z: EN ISO 11855-1:2021
ICS:
91.140.10 Sistemi centralnega Central heating systems
ogrevanja
91.140.30 Prezračevalni in klimatski Ventilation and air-
sistemi conditioning systems
SIST EN ISO 11855-1:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 11855-1:2021
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SIST EN ISO 11855-1:2021
EN ISO 11855-1
EUROPEAN STANDARD
NORME EUROPÉENNE
August 2021
EUROPÄISCHE NORM
ICS 91.040.01 Supersedes EN ISO 11855-1:2015
English Version
Building environment design - Embedded radiant heating
and cooling systems - Part 1: Definitions, symbols, and
comfort criteria (ISO 11855-1:2021)

Conception de l'environnement des bâtiments - Umweltgerechte Gebäudeplanung - Flächenintegrierte

Systèmes intégrés de chauffage et de refroidissement Strahlheizungs- und -kühlsysteme - Teil 1: Begriffe,

par rayonnement - Partie 1: Définitions, symboles et Symbole und Komfortkriterien (ISO 11855-1:2021)

critères de confort (ISO 11855-1:2021)
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 11855-1:2021 E

worldwide for CEN national Members.
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SIST EN ISO 11855-1:2021
EN ISO 11855-1:2021 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 11855-1:2021
EN ISO 11855-1:2021 (E)
European foreword

This document (EN ISO 11855-1:2021) 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 February 2022, and conflicting national standards

shall be withdrawn at the latest by February 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 11855-1:2015.

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 11855-1:2021 has been approved by CEN as EN ISO 11855-1:2021 without any

modification.
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SIST EN ISO 11855-1:2021
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SIST EN ISO 11855-1:2021
INTERNATIONAL ISO
STANDARD 11855-1
Second edition
2021-08
Building environment design —
Embedded radiant heating and cooling
systems —
Part 1:
Definitions, symbols, and comfort
criteria
Conception de l'environnement des bâtiments — Systèmes intégrés de
chauffage et de refroidissement par rayonnement —
Partie 1: Définitions, symboles et critères de confort
Reference number
ISO 11855-1:2021(E)
ISO 2021
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SIST EN ISO 11855-1:2021
ISO 11855-1:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
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SIST EN ISO 11855-1:2021
ISO 11855-1:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................11

5 Comfort criteria ..................................................................................................................................................................................................16

5.1 General ........................................................................................................................................................................................................16

5.2 General thermal comfort .............................................................................................................................................................16

5.2.1 Operative temperature ............................................................................................................................................17

5.2.2 PMV (predicted mean vote) and PPD (predicted percentage of dissatisfied) .........17

5.3 Local thermal discomfort ............................................................................................................................................................18

5.3.1 Surface temperature limit .....................................................................................................................................18

5.3.2 Radiant temperature asymmetry ...................................................................................................................19

5.3.3 Vertical air temperature difference ..............................................................................................................19

5.4 Acoustical comfort ............................................................................................................................................................................20

5.4.1 Water velocity and noise ........................................................................................................................................20

5.4.2 Acoustical comfort in water-based heating and cooling systems .......................................20

5.4.3 Acoustical comfort in thermally active building systems (TABS) .......................................21

Annex A (informative) Floor surface temperature for thermal comfort ......................................................................22

Annex B (informative) Draught ...............................................................................................................................................................................25

Bibliography .............................................................................................................................................................................................................................26

© ISO 2021 – All rights reserved iii
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SIST EN ISO 11855-1:2021
ISO 11855-1:2021(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 11855-1:2012), which has been technically

revised.
The main changes compared to the previous edition are as follows:

— only references cited normatively were kept in Clause 2, the others were moved to Bibliography;

— in Clause 3, self-explanatory terms were removed, two similar terms representing the same concept

were unified into one term, and one term explaining two concepts were divided into two terms each

having one concept;
— editorial changes were performed.
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
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SIST EN ISO 11855-1:2021
ISO 11855-1:2021(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, this document, 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 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.
© ISO 2021 – All rights reserved v
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SIST EN ISO 11855-1:2021
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SIST EN ISO 11855-1:2021
INTERNATIONAL STANDARD ISO 11855-1:2021(E)
Building environment design — Embedded radiant heating
and cooling systems —
Part 1:
Definitions, symbols, and comfort criteria
1 Scope

This document specifies the basic definitions, symbols, and comfort criteria for embedded 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 11855-5:2021, Building environment design —Embedded radiant heating and cooling systems — Part 5:

Installation
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
3.1
additional thermal resistance

thermal resistance representing layers added to the building structure and acting mostly as thermal

resistances because of their own low thermal inertia
EXAMPLE Carpets, moquette, and suspended ceilings.
3.2
average specific thermal capacity of the internal walls
thermal capacity related to one square metre of the internal walls

Note 1 to entry: Since internal walls are shared with other rooms, then just half of the total specific thermal

capacity of the wall shall be taken into account, since the second half is influenced by the opposite rooms that are

considered to be at the same thermal conditions as the one under consideration.
3.3
average surface temperature
s,m

average value of all surface temperatures in the occupied or peripheral area (3.62)

© ISO 2021 – All rights reserved 1
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SIST EN ISO 11855-1:2021
ISO 11855-1:2021(E)
3.4
basic characteristic curve

curve reflecting the relationship between the heat flux (3.31) and the mean surface temperature

difference (3.47)

Note 1 to entry: This depends on the heating or cooling and the surface (floor, wall or ceiling) but not on the type

of embedded system.
3.5
calculation time step
length of time considered for the calculation
Note 1 to entry: This is typically assumed to equal 3 600 s.
3.6
circuit

section of system connected to a distributor (3.25) which can be independently switched and controlled

3.7
circuit total thermal resistance

thermal resistance representing the circuit (3.6) as a whole, determining a straight connection between

the water inlet temperature and the mean temperature at the pipe level (3.63)

Note 1 to entry: It includes the water flow thermal resistance (3.92), the convection thermal resistance at the pipe

inner side (3.10), the pipe thickness thermal resistance (3.66), and the pipe level thermal resistance (3.64).

3.8
clothing insulation

resistance of a uniform layer of insulation covering the entire body that has the same effect on sensible

heat flow as the actual clothing under standardized (static, wind-still) conditions

Note 1 to entry: The definition of clothing insulation also includes the uncovered parts of the body, e.g. the head. It

is specified as the intrinsic insulation from the skin to the clothing surface, not including the resistance provided

2 2

by the air layer around the clothed body, and is expressed in the clo unit or in m K/W; 1 clo = 0,155 m K/W.

3.9
conductive region of the slab

region of the slab (3.75) that includes the pipes with thermal conductivities of the layers higher than

0,8 W/(m·K)

Note 1 to entry: Due to the subdivision of the slab into an upper slab and a lower slab, the conductive region is

also subdivided into an upper conductive region and a lower conductive region.
3.10
convection thermal resistance at the pipe inner side

thermal resistance associated to the convection heat transfer taking place between the water flowing

in the pipe and the pipe inner side, thus connecting the mean water temperature along the circuit (3.6)

with the mean temperature of the pipe inner side
3.11
convective heating and cooling system

system that directly conditions the air in the room for the purpose of heating and cooling

3.12
convective peak load

maximum cooling load to be extracted by a virtual convective system used to keep comfort conditions

in the room
3.13
design cooling capacity
H,c
thermal output by a cooling surface at design conditions
2 © ISO 2021 – All rights reserved
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SIST EN ISO 11855-1:2021
ISO 11855-1:2021(E)
3.14
design cooling load
N,c

required thermal output necessary to achieve the specified design conditions in outside summer design

conditions
3.15
design sensible cooling load

required sensible thermal output necessary to achieve the specified design conditions in outside

summer design conditions
3.16
design supply temperature of heating medium
V,des

value of flow water temperature with the thermal resistance of the chosen floor covering, at maximum

value of heat flux q
max

Note 1 to entry: The flow and the supply temperature are the same throughout the EN 1264 series.

Note 2 to entry: For the radiant cooling system, the design supply temperature of cooling medium applies instead

of design supply temperature of heating medium.
3.17
design heat flux
des

heat flow divided by the heating or cooling surface, taking into account the surface temperature

required to reach the design thermal capacity of a surface heated or cooled space, Q , reduced by the

thermal capacity of any supplementary heating or cooling equipment, if applicable

3.18
design heating capacity
H,h
thermal output from a heating surface (3.33) at design conditions
3.19
design heating load
N,h

required thermal output necessary to achieve the specified design conditions in outside winter design

conditions

Note 1 to entry: When calculating the value of the design heat load, the heat flow from embedded heating systems

into neighbouring rooms is not taken into account.
3.20
design heating medium differential temperature
H,des
temperature difference of heating medium at design heat flux (3.17)
3.21
design cooling medium differential temperature
C,des
temperature difference of cooling medium at design heat flux (3.17)
3.22
design heating medium differential supply temperature
V,des

temperature difference between the design supply medium temperature and indoor temperature at

design heat flux (3.17)
© ISO 2021 – All rights reserved 3
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SIST EN ISO 11855-1:2021
ISO 11855-1:2021(E)
3.23
design heating medium flow rate

mass flow rate in a circuit (3.6) which is needed to achieve the design heat flux (3.17)

Note 1 to entry: The design cooling medium flow rate is similar with the only difference being that it has an

embedded radiant cooling system.
3.24
design indoor temperature

operative temperature (3.58) at the centre of the conditioned space used for calculation of the design

load and capacity

Note 1 to entry: The operative temperature is considered relevant for thermal comfort assessment and heat loss

calculations. This value of internal temperature is used for the calculation method.

3.25
distributor
common connection point for several circuits (3.6)
3.26
draught

unwanted local cooling of a body caused by movement of air and related to temperature

3.27
electric heating system

several panel systems that convert electrical energy to heat, raising the temperature of conditioned

indoor surfaces and the indoor air

Note 1 to entry: The electric heating system can be applied to floor, walls and ceiling.

3.28
embedded surface heating and cooling system

system consisting of circuits (3.6) of pipes embedded in floor, wall or ceiling construction, distributors

(3.25) and control equipment
3.29
equivalent heat transmission coefficient

coefficient describing the relationship between the heat flux (3.31) from the surface and the heating

medium differential temperature (3.36)

Note 1 to entry: For the radiant cooling system, the cooling medium differential temperature applies instead of

heating medium differential temperature.
3.30
family of characteristic curves

curves denoting the system-specific relationship between the heat flux (q) (3.31) and the required

heating medium differential temperature (ΔθH) (3.36) for conduction resistance of various floor

coverings
3.31
heat flux
heat flow between the space and surface divided by the heated or cooled surface

Note 1 to entry: For heating it is a positive value and for cooling it is a negative value.

4 © ISO 2021 – All rights reserved
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SIST EN ISO 11855-1:2021
ISO 11855-1:2021(E)
3.32
heat transfer coefficient

combined convective and radiative heat transfer coefficient between the heated or cooled surface and

the space operative temperature (3.58) [design indoor temperature (3.24)]
3.33
heating surface

surface (floor, wall, ceiling) covered by the embedded surface heating system between the pipes at the

outer edges of the system with the addition of a strip at each edge of width equal to half the pipe spacing

(3.65), but not exceeding 0,15 m

Note 1 to entry: The cooling surface is similar with the only difference being that it has an embedded surface

cooling system.
3.34
heating surface area

area of surface (floor, wall, ceiling) covered by the embedded surface heating system between the pipes

at the outer edges of the system with the addition of a strip at each edge of width equal to half the pipe

spacing (3.65), but not exceeding 0,15 m

Note 1 to entry: The same concept of cooling surface area applies to the embedded cooling system.

3.35
heating capacity for circuit
heat exchange between a pipe circuit (3.6) and the conditioned room

Note 1 to entry: The same concept of cooling capacity for circuit applies to the embedded cooling system.

3.36
heating medium differential temperature

logarithmically determined average difference between the temperature of the heating medium (3.83)

and the design indoor temperature (3.24)

Note 1 to entry: The same concept of cooling medium differential temperature applies to the embedded cooling

system.
3.37
internal convective heat gain
convective contributions by internal heat gains acting in the room
Note 1 to entry: Mainly due to people or electrical equipment.
3.38
internal radiant heat gain
radiant contributions by internal heat gains acting in the room
Note 1 to entry: This is mainly due to people or electrical equipment.
3.39
internal thermal resistance of the slab conductive region

total thermal resistance connecting the pipe level (3.63) with the middle points of the upper conductive

region and lower conductive region of the slab (3.9)
3.40
limit curve

curve in the field of characteristic curves showing the pattern of the limit heat flux (3.41) depending on

the heating medium differential temperature (3.36) and the floor covering
© ISO 2021 – All rights reserved 5
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SIST EN ISO 11855-1:2021
ISO 11855-1:2021(E)
3.41
limit heat flux

heat flux (3.31) at which the maximum (3.45) or minimum permissible surface temperature (3.49) is

achieved
3.42
limit heating medium temperature difference
H,G
intersection of the system characteristic curve with the limit curve (3.40)
3.43
maximum cooling power

maximum thermal power of the cooling equipment, referring only to the room under consideration

3.44
maximum design heat flux
max

required design heat flux (3.17) in the room in order to design supply medium temperature

3.45
maximum permissible surface temperature
S,max

maximum temperature permissible for physiological reasons or for the physical building, for calculation

of the limit curves (3.40), which may occur at a point on the surface (floor, wall, ceiling) in the occupied

or peripheral area (3.62) depending on the particular usage at a temperature drop (σ) (3.82) of the

heating medium equal to 0
3.46
mean radiant temperature

uniform surface temperature of an imaginary black enclosure in which an occupant would exchange

the same amount of radiant heat as in the actual non-uniform enclosure
...

SLOVENSKI STANDARD
oSIST prEN ISO 11855-1:2020
01-maj-2020
Načrtovanje okolja v stavbah - Vgrajeni hladilni in ogrevalni sistemi - 1. del:
Definicije, simboli in merila za ugodje (ISO/DIS 11855-1:2020)

Building environment design - Embedded radiant heating and cooling systems - Part 1:

Definitions, symbols, and comfort criteria (ISO/DIS 11855-1:2020)
Umweltgerechte Gebäudeplanung - Flächenintegrierte Strahlheizungs- und -

kühlsysteme - Teil 1: Begriffe, Symbole und Komfortkriterien (ISO/DIS 11855-1:2020)

Conception de l'environnement des bâtiments - Systèmes intégrés de chauffage et de

refroidissement par rayonnement - Partie 1: Définitions, symboles et critères de confort

(ISO/DIS 11855-1:2020)
Ta slovenski standard je istoveten z: prEN ISO 11855-1
ICS:
91.140.10 Sistemi centralnega Central heating systems
ogrevanja
91.140.30 Prezračevalni in klimatski Ventilation and air-
sistemi conditioning systems
oSIST prEN ISO 11855-1:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN ISO 11855-1:2020
---------------------- Page: 2 ----------------------
oSIST prEN ISO 11855-1:2020
DRAFT INTERNATIONAL STANDARD
ISO/DIS 11855-1
ISO/TC 205 Secretariat: ANSI
Voting begins on: Voting terminates on:
2020-03-16 2020-06-08
Building environment design — Embedded radiant heating
and cooling systems —
Part 1:
Definitions, symbols, and comfort criteria

Conception de l'environnement des bâtiments — Systèmes intégrés de chauffage et de refroidissement par

rayonnement —
Partie 1: Définitions, symboles et critères de confort
ICS: 91.040.01
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
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STANDARD UNTIL PUBLISHED AS SUCH.
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BE CONSIDERED IN THE LIGHT OF THEIR
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ISO/DIS 11855-1:2020(E)
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NOTIFICATION OF ANY RELEVANT PATENT
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PROVIDE SUPPORTING DOCUMENTATION. ISO 2020
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oSIST prEN ISO 11855-1:2020
ISO/DIS 11855-1:2020(E)
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© ISO 2020

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ii © ISO 2020 – All rights reserved
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oSIST prEN ISO 11855-1:2020
ISO/DIS 11855-1:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviations ....................................................................................................................................................................10

5 Comfort criteria ..................................................................................................................................................................................................15

5.1 General thermal comfort .............................................................................................................................................................16

5.1.1 Operative temperature ............................................................................................................................................16

5.1.2 PMV (predicted mean vote)/PPD (predicted percentage of dissatisfied) ...................17

5.2 Local thermal discomfort ............................................................................................................................................................17

5.2.1 Surface temperature limit .....................................................................................................................................17

5.2.2 Radiant temperature asymmetry ...................................................................................................................18

5.2.3 Vertical air temperature difference ..............................................................................................................19

5.3 Acoustical comfort ............................................................................................................................................................................19

5.3.1 Water velocity and noise ........................................................................................................................................19

5.3.2 Acoustical comfort in water based heating and cooling systems .......................................20

5.3.3 Acoustical comfort in Thermally Active Building Systems (TABS) ....................................20

Annex A (informative) Floor surface temperature for thermal comfort ......................................................................21

Annex B (informative) Draught ...............................................................................................................................................................................24

Bibliography .............................................................................................................................................................................................................................25

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oSIST prEN ISO 11855-1:2020
ISO/DIS 11855-1:2020(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.

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 11855-1 was prepared by Technical Committee ISO/TC 205, Building environment design.

ISO 11855 consists of the following parts, under the general title Building environment design —

Design, dimensioning, installation, control and input parameters for the energy calculation of embedded

radiant heating and cooling systems:
— Part 1: Definitions, symbols, and comfort criteria
— Part 2: Determination of the design and 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

Part 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. Part 2 provides steady-state calculation methods for determination

of the heating and cooling capacity. Part 3 specifies design and dimensioning methods of radiant

heating and cooling systems to ensure the heating and cooling capacity. Part 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. Part 5 addresses the installation process for the system to operate as intended. Part

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. Part 7 presents a calculation method for input parameters to ISO 52031.

iv © ISO 2020 – All rights reserved
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oSIST prEN ISO 11855-1:2020
ISO/DIS 11855-1:2020(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 shall be applied to systems using not only water but also other fluids or electricity

as a heating or cooling medium.

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.
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oSIST prEN ISO 11855-1:2020
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oSIST prEN ISO 11855-1:2020
DRAFT INTERNATIONAL STANDARD ISO/DIS 11855-1:2020(E)
Building environment design — Embedded radiant heating
and cooling systems —
Part 1:
Definitions, symbols, and comfort criteria
1 Scope

This part of ISO 11855 specifies the basic definitions, symbols, and comfort criteria for embedded

radiant heating and cooling systems.

The ISO 11855 series is applicable to water based embedded surface heating and cooling systems in

residential, commercial and industrial buildings. The methods apply to systems integrated into the

wall, floor or ceiling construction without any open air gaps. It does not apply to panel systems with

open air gaps which are not integrated into the building structure.

The ISO 11855 series also applies, as appropriate, to the use of fluids other than water 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.
2 Normative references

ISO 7726:1998, Ergonomics of the thermal environment — Instruments for measuring physical quantities

ISO 7730:2005, Ergonomics of the thermal environment — Analytical determination and interpretation of

thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria

ISO 13731:2001, Ergonomics of the thermal environment — Vocabulary and symbols
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
additional thermal resistance

thermal resistance representing layers added to the building structure and acting mostly as thermal

resistances because of their own low thermal inertia
EXAMPLE Carpets, moquette, and suspended ceilings.
3.2
average specific thermal capacity of the internal walls
thermal capacity related to one square metre of the internal walls

Note 1 to entry: Since internal walls are shared with other rooms, then just half of the total specific thermal

capacity of the wall must be taken into account, since the second half is influenced by the opposite rooms that are

considered to be at the same thermal conditions as the one under consideration.
3.3
average surface temperature
s,m
average value of all surface temperatures in the occupied or peripheral area
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3.4
basic characteristic curve

curve or formula reflecting the relationship between the heat flux and the mean surface temperature

difference

Note 1 to entry: This depends on heating/cooling and surface (floor/wall/ceiling) but not on the type of

embedded system.
3.5
calculation time step

length of time considered for the calculation of the temperatures and heat flows in the room and slab

Note 1 to entry: This is typically assumed to equal 3 600 s.
3.6
circuit

section of system connected to a distributor which can be independently switched and controlled

3.7
circuit total thermal resistance

thermal resistance representing the circuit as a whole, determining a straight connection between the

water inlet temperature and the mean temperature at the pipe level

Note 1 to entry: It includes the water flow thermal resistance, the convection thermal resistance at the pipe inner

side, the pipe thickness thermal resistance, and the pipe level thermal resistance.

3.8
clothing insulation

basic clothing insulation that is the resistance of a uniform layer of insulation covering the entire body

that has the same effect on sensible heat flow as the actual clothing under standardized (static, wind-

still) conditions

Note 1 to entry: The definition of clothing insulation also includes the uncovered parts of the body, e.g. the head. It

is described as the intrinsic insulation from the skin to the clothing surface, not including the resistance provided

2 2

by the air layer around the clothed body, and is expressed in the clo unit or in m K/W; 1 clo = 0,155 m K/W.

3.9
conductive region of the slab

region of the slab that includes the pipes with thermal conductivities of the layers higher than 0,8 W/(m·K)

Note 1 to entry: Due to the subdivision of the slab into an upper slab and a lower slab, the conductive region is

also subdivided into an upper conductive region and a lower conductive region.
3.10
convection thermal resistance at the pipe inner side

thermal resistance associated to the convection heat transfer taking place between the water flowing

in the pipe and the pipe inner side, thus connecting the mean water temperature along the circuit with

the mean temperature of the pipe inner side
3.11
convective heating and cooling system

system that directly conditions the air in the room for the purpose of heating and cooling

3.12
convective peak load

maximum cooling load to be extracted by a virtual convective system used to keep comfort conditions

in the room
3.13
daily average temperature of the conductive region of the slab
average temperature of the conductive region of the slab during the day
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3.14
design cooling capacity
H,c
thermal output by a cooling surface at design conditions
3.15
design cooling load
N,c

required thermal output necessary to achieve the specified design conditions in outside summer design

conditions
3.16
design sensible cooling load

required sensible thermal output necessary to achieve the specified design conditions in outside

summer design conditions
3.17
design dew point
Dp,des
dew point determined for the design
3.18
design supply temperature of heating/cooling medium
V,des

value of flow water temperature with the thermal resistance of the chosen floor covering, at maximum

value of heat flux q
max

Note 1 to entry: The flow and the supply temperature are the same throughout the EN 1264 series.

3.19
design heat flux
des

heat flow divided by the heating or cooling surface, taking into account the surface temperature

required to reach the design thermal capacity of a surface heated or cooled space, Q , reduced by the

thermal capacity of any supplementary heating or cooling equipment, if applicable

3.20
design heating capacity
H,h
thermal output from a heating surface at design conditions
3.21
design heating load
N,h

required thermal output necessary to achieve the specified design conditions in outside winter design

conditions

Note 1 to entry: When calculating the value of the design heat load, the heat flow from embedded heating systems

into neighbouring rooms is not taken into account.
3.22
design heating/cooling medium differential temperature
Δθ /Δθ
H,des C,des
temperature difference at design heat flux
3.23
design heating medium differential supply temperature
V,des

temperature difference between the design supply medium temperature and indoor temperature at

design heat flux
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oSIST prEN ISO 11855-1:2020
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3.24
design heating/cooling medium flow rate
mass flow rate in a circuit which is needed to achieve the design heat flux
3.25
design indoor temperature

operative temperature at the centre of the conditioned space used for calculation of the design load and

capacity

Note 1 to entry: The operative temperature is considered relevant for thermal comfort assessment and heat loss

calculations. This value of internal temperature is used for the calculation method.

3.26
distributor
common connection point for several circuits
3.27
draught

unwanted local cooling of a body caused by movement of air and related to temperature

3.28
electric floor (wall, ceiling) heating system

several panel systems that convert electrical energy to heat, raising the temperature of conditioned

indoor surfaces and the indoor air
3.29
embedded surface heating and cooling system

system consisting of circuits of pipes embedded in floor, wall or ceiling construction, distributors and

control equipments
3.30
equivalent heat transmission coefficient

coefficient describing the relationship between the heat flux from the surface and the heating/cooling

medium differential temperature
3.31
family of characteristic curves

curves denoting the system-specific relationship between the heat flux, q, and the required heating

medium differential temperature Δθ for conduction resistance of various floor coverings

3.32
heat flux
heat flow between the space and surface divided by the heated/cooled surface

Note 1 to entry: For heating it is a positive value and for cooling it is a negative value.

3.33
heat transfer coefficient

combined convective and radiative heat transfer coefficient between the heated or cooled surface and

the space operative temperature (design indoor temperature)
3.34
heating or cooling surface

surface (floor, wall, ceiling) covered by the embedded surface heating/cooling system between the

pipes at the outer edges of the system with the addition of a strip at each edge of width equal to half the

pipe spacing, but not exceeding 0,15 m
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3.35
heating or cooling surface area

area of surface (floor, wall, ceiling) covered by the embedded surface heating/cooling system between

the pipes at the outer edges of the system with the addition of a strip at each edge of width equal to half

the pipe spacing, but not exceeding 0,15 m
3.36
heating/cooling capacity for circuit
heat exchange between a pipe circuit and the conditioned room
3.37
heating/cooling medium differential temperature

logarithmically determined average difference between the temperature of the heating/cooling

medium and the design indoor temperature
3.38
internal convective heat gains
convective contributions by internal heat gains acting in the room
Note 1 to entry: Mainly due to people or electrical equipment.
3.39
internal radiant heat gains
radiant contributions by internal heat gains acting in the room
Note 1 to entry: Mainly due to people or electrical equipment.
3.40
internal thermal resistance of the slab conductive region

total thermal resistance connecting the pipe level with the middle points of the upper conductive region

and lower conductive region of the slab
3.41
limit curves

curves in the field of characteristic curves showing the pattern of the limit heat flux depending on the

heating medium differential temperature and the floor covering
3.42
limit heat flux

heat flux at which the maximum or minimum permissible surface temperature is achieved

3.43
limit heating medium temperature difference
H,G
intersection of the system characteristic curve with the limit curve
3.44
maximum cooling power

maximum thermal power of the cooling equipment, referring only to the room under consideration

3.45
maximum permissible surface temperature
max

required design heat flux in the room in order to design supply medium temperature

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3.46
maximum operative temperature allowed for comfort conditions

maximum operative temperature allowed in the room according to comfort requirements in cooling

conditions
3.47
maximum operative temperature drift allowed for comfort conditions

maximum drift in operative temperature allowed in the room according to comfort requirements

3.48
maximum permissible surface temperature
S,max

maximum temperature permissible for physiological reasons or for the physical building, for calculation

of the limit curves, which may occur at a point on the surface (floor, wall, ceiling) in the occupied or

peripheral area depending on the particular usage at a temperature drop σ of the heating medium

equal to 0
3.49
mean radiant temperature

uniform surface temperature of an imaginary black enclosure in which an occupant would exchange

the same amount of radiant heat as in the actual non-uniform enclosure
3.50
mean surface temperature difference

difference between the average surface temperature θ and the design indoor temperature θ

S,m i
Note 1 to entry: It determines the heat flux.
3.51
metabolic rate

rate of transformation of chemical energy into heat and mechanical work by aerobic and anaerobic

metabolic activities within an organism, usually expressed in terms of unir area of the total body

surfaces

Note 1 to entry: The metabolic rate varies with each activity. It is expressed in the met unit or in W/m ;

1 met = 58,2 W/m . 1 met is the energy produced per unit surface area of a sedentary person at rest. The surface

area of an average person can be determined by Dubois Equation, Body Surface Area (m ) = 0,20 247 × Height

0,725 0,425
(m) × Weight (kg) .
3.52
minimum permissible surface temperature
S,min

minimum temperature permissible for physiological reasons or for the physical building, for calculation

of the limit curves, which may occur at a point on the surface (floor, wall, ceiling) in the occupied or

peripheral area depending on the particular usage at a temperature drop σ of the heating medium

equal to 0
3.53
nominal heat flux
limit heat flux achieved without surface covering
3.54
nominal heating/cooling medium differential temperature
absolute temperature difference at nominal heat flux q
3.55
non-active area
area of the surface not covered by a heating/cooling system
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3.56
number of active surfaces

number of surfaces in straight thermal connection with the pipe level, so that it distinguishes whether

the slab transfers heat both through the floor side and through the ceiling side or whether the ceiling

side is much more active than the floor side

Note 1 to entry: Two active surfaces when the conductive region extends from the floor to the ceiling, one active

surface otherwise.
3.57
number of operation hours of the circuit
length of time during which the system runs in the day
3.58
occupied area
surface area which is heated or cooled, excluding peripheral area
3.59
occupied zone

part of the conditioned zone in which persons normally reside and where requirements as to the

internal environment are satisfied

Note 1 to entry: Normally, the zone between the floor and 1,8 m above the floor and 1,0 m from outside walls/

windows and heating/cooling appliances, 0,5 m from internal surfaces.
3.60
open air gap

air gap in the floor, wall, or ceiling construction, where air exchange with space or the outside may occur

3.61
operative temperature

uniform temperature of an imaginary black enclosure in which an occupant exchanges the same amount

of heat by radiation and convection as in the actual non-uniform environment
3.62
orientation of the room
orientation of the main windowed external wall: East, South or West

Note 1 to entry: It is used to determine when the peak load from heat gains happens, since internal heat gains are

considered almost constant and the widest variation is expected to happen in solar heat gains.

3.63
outward heat flux

heat flow which is exchanged through the construction with unconditioned spaces, another building

entity, the ground or outdoor air
3.64
peak load

maximum cooling load to be extracted by the system used to keep comfort conditions in the room

3.65
peripheral area
surface area which is heated or cooled to a higher or lower temperature

Note 1 to entry: It is generally an area of 1 m maximum in width along exterior walls. It is not an occupied area.

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oSIST prEN ISO 11855-1:2020
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3.66
pipe level
virtual plane where the pipe circuit lies
3.67
pipe level thermal resistance

thermal resistance associated to the 2-D conduction heat transfer taking place between the pipes and

the embedding layer, virtually referred to the pipe level, thus connecting the mean temperature of the

pipe outer side with the mean temperature at the pipe level
3.68
pipe spacing
spacing or distance between pipes embedded in the surface
3.69
pipe thickness thermal resistance

thermal resistance associated to the conduction heat transfer taking place through the pipe wall, thus

connecting the mean temperature of the pipe inner side with the mean temperature of the pipe outer side

3.70
predicted mean vote

PMVindex that predicts the mean value of the thermal sensation votes of a large group of persons on a

7-point thermal sensation scale
3.71
predicted percentage of dissatisfied

PPDindex that establishes a quantitative prediction of the percentage of thermally dissatisfied people

who are either too warm of too cool
3.72
primary air convective heat gains
heat gains acting in the room due to the infiltration or primary air inflow
3.73
radiant surface heating and cooling system

heating and cooling system that controls the temperature of indoor surfaces on the floor, walls, or ceiling

3.74
radiant temperature asymmetry

difference between the plane radiant temperature of the two opposite sides of a small plane element

3.75
relative air velocity
air velocity relative to the occupant, including body movements
3.76
regional dew point
Dp,R
dew point specified depending on the climatic conditions of the region
3.77
running mode

running mode of the circuit that defines whether the system is currently switched on or off

3.78
slab

horizontal building structure separating two rooms placed one below the other, hence being the ceiling

for one and the floor for the other
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3.79
solar heat gains
sol
...