ISO 11855-1:2012

INTERNATIONAL ISO
STANDARD 11855-1
First edition
2012-08-01
Building environment design — Design,
dimensioning, installation and control
of embedded radiant heating and
cooling systems —
Part 1:
Definition, symbols, and comfort criteria
Conception de l’environnement des bâtiments — Conception,
construction et fonctionnement des systèmes de chauffage et de
refroidissement par rayonnement —
Partie 1: Définition, symboles et critères de confort
Reference number
©
ISO 2012
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ii © ISO 2012 – All rights reserved

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 .15
5.2 Local thermal comfort .17
5.3 Acoustical comfort .20
Annex A (informative) Floor surface temperature for thermal comfort .22
Annex B (informative) Draught .25
Bibliography .26
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 and control of embedded radiant heating and cooling systems:
— Part 1: Definition, 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 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.
iv © ISO 2012 – All rights reserved

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, operation, and control method of embedded systems.
INTERNATIONAL STANDARD ISO 11855-1:2012(E)
Building environment design — Design, dimensioning,
installation and control of embedded radiant heating and
cooling systems —
Part 1:
Definition, symbols, and comfort criteria
1 Scope
This part of ISO 11855 specifies the basic definitions, symbols, and a comfort criteria for 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 13731:2003, Ergonomics of the thermal environment — Vocabulary and symbols
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
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.
2.2
average specific thermal capacity of the internal walls
thermal capacity related to one square metre of the internal walls
NOTE 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.
2.3
average surface temperature
θ
s,m
average value of all surface temperatures in the occupied or peripheral area
2.4
basic characteristic curve
curve or formula reflecting the relationship between the heat flux and the mean surface temperature difference
NOTE This depends on heating/cooling and surface (floor/wall/ceiling) but not on the type of embedded system.
2.5
calculation time step
length of time considered for the calculation of the temperatures and heat flows in the room and slab
NOTE This is typically assumed to equal 3 600 s.
2.6
circuit
section of system connected to a distributor which can be independently switched and controlled
2.7
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 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.
2.8
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 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 by the air layer around
2 2
the clothed body, and is expressed in the clo unit or in m K/W; 1 clo = 0,155 m K/W.
2.9
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 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.
2.10
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
2.11
convective heating and cooling system
system that directly conditions the air in the room for the purpose of heating and cooling
2.12
convective peak load
maximum cooling load to be extracted by a virtual convective system used to keep comfort conditions in the room
2.13
daily average temperature of the conductive region of the slab
average temperature of the conductive region of the slab during the day
2.14
design cooling capacity
Q
H,c
thermal output by a cooling surface at design conditions
2 © ISO 2012 – All rights reserved

2.15
design cooling load
Q
N,c
required thermal output necessary to achieve the specified design conditions in outside summer design conditions
2.16
design sensible cooling load
required sensible thermal output necessary to achieve the specified design conditions in outside summer
design conditions
2.17
design dew point
θ
Dp,des
dew point determined for the design
2.18
design supply temperature of heating/cooling medium
θ
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 The flow and the supply temperature are the same throughout the EN 1264 series.
2.19
design heat flux
q
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
H
of any supplementary heating or cooling equipment, if applicable
2.20
design heating capacity
Q
H,h
thermal output from a heating surface at design conditions
2.21
design heating load
Q
N,h
required thermal output necessary to achieve the specified design conditions in outside winter design conditions
NOTE When calculating the value of the design heat load, the heat flow from embedded heating systems into
neighbouring rooms is not taken into account.
2.22
design heating/cooling medium differential temperature
Δθ
H,des
temperature difference at design heat flux
2.23
design heating medium differential supply temperature
Δθ
V,des
temperature difference between the design supply medium temperature and indoor temperature at design heat flux
2.24
design heating/cooling medium flow rate
m
H
mass flow rate in a circuit which is needed to achieve the design heat flux
2.25
design indoor temperature
θ
i
operative temperature at the centre of the conditioned space used for calculation of the design load and capacity
NOTE The operative temperature is considered relevant for thermal comfort assessment and heat loss calculations.
This value
...