SIST-TP CEN/TR 12831-2:2018

SLOVENSKI STANDARD
01-december-2016
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Energy performance of buildings - Method for calculation of the design heat load - Part 2:
Explanation and justification of EN 12831-1, Module M3-3
Gesamtenergieeffizienz von Gebäuden - Methode zur Berechnung der Norm-Heizlast -
Teil 2: Begleitender TR zur EN 12831-1, Modul M3
Performance énergétique des bâtiments - Méthode de calcul de la charge thermique
nominale - Partie 2 : Explication et justification de l’EN 12831-1, Module M3-3
Ta slovenski standard je istoveten z: CEN/TR 12831-2:2017
ICS:
91.120.10 Toplotna izolacija stavb Thermal insulation of
buildings
91.140.10 Sistemi centralnega Central heating systems
ogrevanja
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN/TR 12831-2
TECHNICAL REPORT
RAPPORT TECHNIQUE
April 2017
TECHNISCHER BERICHT
ICS 91.120.10; 91.140.10
English Version
Energy performance of buildings - Method for calculation
of the design heat load - Part 2: Explanation and
justification of EN 12831-1, Module M3-3
Performance énergétique des bâtiments - Méthode de Gesamtenergieeffizienz von Gebäuden - Methode zur
calcul de la charge thermique nominale - Partie 2 : Berechnung der Norm-Heizlast - Teil 2: Begleitender
Explication et justification de l'EN 12831-1, Module TR zur EN 12831-1, Modul M3
M3-3
This Technical Report was approved by CEN on 27 February 2017. It has been drawn up by the Technical Committee CEN/TC
228.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, 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: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 12831-2:2017 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and abbreviations . 5
4.1 Symbols . 5
4.2 Subscripts . 5
5 Information on the methods . 5
6 Method description . 6
6.1 Standard method . 6
6.1.1 Rationale, case of application . 6
6.1.2 Assumptions . 6
6.1.3 Data input . 7
6.2 Simplified method for the calculation of the design heat load of a heated space . 19
6.2.1 Rationale, case of application . 19
6.2.2 Assumptions . 19
6.2.3 Data input . 19
6.3 Simplified method for the calculation of the building design heat load . 19
6.3.1 Rationale, case of application . 19
6.3.2 Assumptions . 20
6.3.3 Data input . 20
7 Method selection . 20
8 Exemplary heat load calculation (standard method) . 20
8.1 Description . 20
8.2 Calculation details . 22
Annex A (informative) Calculation flowchart . 28
A.1 General . 28
A.2 Standard method . 28
A.3 Simplified method for the calculation of the design heat load of a heated space . 29
A.4 Simplified method for the calculation of the building design heat load . 29
Bibliography . 30

European foreword
This document (CEN/TR 12831-2:2017) has been prepared by Technical Committee CEN/TC 228
“Heating systems and water based cooling systems in buildings”, the secretariat of which is held by DIN.
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 has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
Introduction
In order to facilitate the necessary overall consistency and coherence, in terminology, approach,
input/output relations and formats, for the whole set of EPB-standards, the following documents and
tools are available:
a) a document with basic principles to be followed in drafting EPB-standards: CEN/TS 16628:2014,
Energy Performance of Buildings - Basic Principles for the set of EPB standards [1];
b) a document with detailed technical rules to be followed in drafting EPB-standards;
CEN/TS 16629:2014, Energy Performance of Buildings - Detailed Technical Rules for the set of
EPB-standards [2];
c) the detailed technical rules are the basis for the following tools:
1) a common template for each EPB-standard, including specific drafting instructions for the
relevant clauses;
2) a common template for each technical report that accompanies an EPB standard or a cluster of
EPB standards, including specific drafting instructions for the relevant clauses;
3) a common template for the spreadsheet that accompanies each EPB standard, to demonstrate
the correctness of the EPB calculation procedures.
Each EPB-standards follows the basic principles and the detailed technical rules and relates to the
overarching EPB-standard, EN ISO 52000-1 [3].
One of the main purposes of the revision of the EPB-standards is to enable that laws and regulations
directly refer to the EPB-standards and make compliance with them compulsory. This requires that the
set of EPB-standards consists of a systematic, clear, comprehensive and unambiguous set of energy
performance procedures. The number of options provided is kept as low as possible, taking into
account national and regional differences in climate, culture and building tradition, policy and legal
frameworks (subsidiarity principle). For each option, an informative default option is provided
(EN 12831-1:2017, Annex B).
Rationale behind the EPB technical reports
There is a risk that the purpose and limitations of the EPB standards will be misunderstood, unless the
background and context to their contents – and the thinking behind them – is explained in some detail
to readers of the standards. Consequently, various types of informative contents are recorded and made
available for users to properly understand, apply and nationally or regionally implement the EPB
standards.
If this explanation would have been attempted in the standards themselves, the result is likely to be
confusing and cumbersome, especially if the standards are implemented or referenced in national or
regional building codes.
Therefore, each EPB standard is accompanied by an informative technical report, like this one, where all
informative content is collected, to ensure a clear separation between normative and informative
contents (see CEN/TS 16629 [1]):
— to avoid flooding and confusing the actual normative part with informative content;
— to reduce the page count of the actual standard; and
— to facilitate understanding of the set of EPB standards.
This was also one of the main recommendations from the European CENSE project [2] that laid the
foundation for the preparation of the set of EPB standards.
1 Scope
This Technical Report refers to standard EN 12831, module M3-3 (EN 12831-1).
It contains information to support the correct understanding, use and national adaptation of standard
EN 12831-1.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN 12831-1:2017, Energy performance of buildings - Method for calculation of the design heat load - Part
1: Space heating load, Module M3-3
EN ISO 6946, Building components and building elements - Thermal resistance and thermal transmittance
- Calculation method (ISO 6946)
EN ISO 7345:1995, Thermal insulation - Physical quantities and definitions (ISO 7345:1987)
EN ISO 10077-1, Thermal performance of windows, doors and shutters - Calculation of thermal
transmittance - Part 1: General (ISO 10077-1)
EN ISO 52000-1:2017, Energy performance of buildings - Overarching EPB assessment - Part 1: General
framework and procedures (ISO 52000-1:2017)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 7345:1995,
EN ISO 52000-1:2017, EN 12831-1:2017 apply.
4 Symbols and abbreviations
4.1 Symbols
For the purposes of this Technical Report, the symbols given in EN ISO 52000-1:2017 and
EN 12831-1:2017 apply.
4.2 Subscripts
For the purposes of this Technical Report, subscripts given in EN ISO 52000-1:2017 and
EN 12831-1:2017 apply
5 Information on the methods
EN 12831-1 describes a method to calculate the design heat load of
— heated spaces (usually rooms);
— building entities (apartments etc.) or whole buildings containing heated spaces.
The design heat load is required in the sizing of several components of a heating systems, such as
— heat emission components (e.g. radiators);
— heat distribution components (tubing etc.); and
— heat generators (boilers etc.).
EN 12831-1 contains several methods for this purpose,
— a standard method that describes a versatile approach to calculate the design heat load of
— heated spaces / single rooms;
— building entities; and
— a whole building;
— a simplified method for the calculation of the design heat load of a building; and
— a simplified method for the calculation of the design heat load of heated spaces.
6 Method description
6.1 Standard method
6.1.1 Rationale, case of application
The standard method is a detailed approach for the calculation of the design heat load. The method is
based on design criteria, such as internal and external design temperatures, and detailed information
about the building or the heated spaces that the heat load shall be determined for. While the approach
itself is versatile in that it can be used for new (to-be-built) and existing or old buildings either way, it is
usually easier to apply to new ones than to old ones for several reasons, e.g.:
— detailed knowledge about the building, such as U-values, level of air tightness, etc., is required. In
new buildings, the knowledge of this information can be considered a given; in old buildings, often,
it cannot.
— in the process of constructing (new) buildings, usually, not only a single component of the heating
system but the heating system as a whole has to be designed/sized. Therefore, a detailed heat load
calculation is virtually mandatory. In the reconstruction of old/existing buildings, there are many
cases where only parts of the heating system are to be replaced; e.g. replacing only the heat
generator. Here, a detailed heat load calculation requires much more effort than is adequate for the
task given.
6.1.2 Assumptions
Considerations within EN 12831 are based on steady-state conditions, e.g.:
— assuming constant internal, external and ground temperatures;
— considering to-be-heated rooms as already heated to the required temperature – meaning that the
method basically determines how much power is required to maintain the required temperature
(although, a simplified approach for the determination of heating-up power is given in the standard
as well);
— assuming constant physical building properties (independent of time, temperature, etc.)
6.1.3 Data input
6.1.3.1 General
An extensive list of all input parameters and sources that shall be used to obtain them is given in the
standard. In what follows, some items are named that may require some more explanation than is given
in the standard.
6.1.3.2 Space allocation / partitioning of buildings
EN 12831-1 uses the following terms to describe scope(s) of the heat balance:
— Building (Build)
A whole building.
— Building entity (BE)
A portion of the building that can contain one or more rooms. A building entity is defined by use as
a portion of the building that belongs to one user (owner(s), tenant(s), etc.) in a way that if one
room of the entity is heated, it may be assumed that the other rooms of that entity are – give or take
– heated as well. Typical examples are:
a) an apartment / a flat;
b) an office unit, etc.
In the scope of EN 12831-1, each building entity has an internal temperature that is a property of
the building entity as a whole. That temperature is required to calculate heat loss from other rooms
to that building entity.
— Zone / Ventilation zone (z)
A zone is a portion of the building that can contain one or more rooms. It is defined as an entity
where all contained rooms are air-connected by design (through internal ATDs / shortened door
leafs, etc.). By design, there is no air transfer between several ventilation zones. Usually, a zone is
also a building entity.
— Heated space (i)
Each space heated to uniform conditions is considered a heated space. A heated space is separated
from other spaces by building elements, such as walls etc. Usually each room is a heated space. The
terms heated space and (heated) room are used synonymously in the standard.
6.1.3.3 Climatic data
The following climate data shall be provided through national standardization bodies:
— Reference external design temperature in [°C]: nationally defined default value(s) of the external
temperature; can be transformed into the external temperature at the building site by means of the
temperature gradient.
— Reference height in [m]: the mean height level that corresponds with the given reference external
design temperature (e.g. height of the weather station whose measurements the reference external
temperature is based on).
— Reference Temperature gradient in [K/m]: the rate of height-dependent temperature in- or
decrease; together with the reference external temperature and the height of the building site, it
shall be used to determine the external temperature at the building site and allows adjustment in
case of significant height differences between the building site and the place the reference external
temperature refers to.
— Annual mean external temperature in [°C]: annual mean value of the external temperature;
distinction between different reference sites, height levels, etc. is not necessarily required, but may
be implemented nationally.
— Parameters for the determination of the influence of the thermal storage capacity: a linear function
to determine a temperature correction term (Δθ) that allows for the influence of the building’s
thermal storage capacity on the heat loss. The following parameters are required:
a) basic value in [K];
b) slope in [K/h];
c) optionally, lower and upper limit of the correction function in [K].
In using this temperature adjustment, the external design temperature takes building properties into
account and, therefore, becomes a calculation value that may differ from the actual external
temperature on the building site.
That data can be given either as a single set of default values, to be applied nation-wide, or – with a
higher degree of geographical distinction – for several reference sites. A reference site is a defined area
of equal or similar climate conditions. The number and sizes of reference sites shall be set according to
the given geographical variance of climate conditions. The geographical scope to each reference site
shall be defined, e.g. by reference to cities, regions, etc.
Either adjustment may be nullified on a national basis.
6.1.3.4 Internal design temperature
The internal design temperature is the temperature that is required for a certain kind of use of a heated
space. Within EN 12831-1, the term is understood as an operative temperature. It is usually agreed
upon by the customer that orders the installation of a heating system and the contractor planning or
installing the heating system. For calculation purposes, normative default values shall be provided
nationally (e.g. 20 °C in residential rooms, etc.). In the absence of national values, EN 12831 provides
default values in an informative annex.
The internal design temperature is required in the calculation of design heat losses. It is fully
independent from room height and heat transport mechanisms. The internal design temperature does
not factor in effects as air temperature gradients, significantly differing air and radiant temperature, etc.
If however necessary, adjustments to consider such effects are done by means of a temperature
adjustment factor and the effective internal temperature θ* , e.g. in calculating temperature adjusted
int
heat loss coefficients after EN 12831-1:2017, 6.3.2/6.3.8. Therefore, in order to correctly consider the
abovementioned effects, the internal design temperature θ shall not be manipulated.
int,i
Additional information on internal temperatures can be found in the international standards
EN ISO 7730 and EN 15251.
6.1.3.5 Thermal transmittance
6.1.3.5.1 General
Thermal transmittances of the building elements of the thermal envelope shall be determined in
accordance with:
— EN ISO 6946 (opaque elements);
— EN ISO 10077-1 (doors and windows); or
— information given in European Technical Approvals.
Note that U-values determined after methods differing significantly from EN ISO 6946 / EN ISO 10077-1
may require an additional adjustment in order to be applied within EN 12831. This is done through a
correction factor for the influence of building part properties and meteorological conditions […] e (see
k
chapter input data).
6.1.3.5.2 Simplified determination of U-values based on the referred standards
On the basis of the methods described in the abovementioned standards, U-values may also be
determined in a simplified way (e.g. for teaching materials), exemplarily shown in the following
nomograms.
External and internal walls (vertical)

Key
Wall material Axes
a Solid concrete d1 wall thickness without insulation
b Sand-lime brick d2 thickness of the insulation
c Solid brick λ thermal conductivity
d Hollow brick U thermal transmittance
e Concrete with crushed brick
f Light concrete
g Drywall/plasteboard
h Wood
i Light/cellular concrete or insulation brick
Reading example:
1 36 cm masonry (solid brick) with
2 4 cm thermal insulation
U approximately 0,6 W/m K
total
Figure 1 — Estimation of U-values based on structure, walls
The nomograph is based on the following equation and boundary conditions.
(1)
U=
dd
1 2
RR+ ++
si se
λλ
1 2
where
U is the thermal transmittance of the building element [W/(m ∙K)]
R is the internal heat transmission resistance [m K/W]
si
R is the external heat transmission resistance [m K/W]
se
is the with Σ(R ) approximately 0,17
s
d is the thickness of the wall structure (without thermal insulation) [m]
λ is the thermal conductivity of the wall structure (without thermal insulation) [W/mK]
d is the thickness of the thermal insulation [m]
λ is the thermal conductivity of the thermal insulation with λ = 0,04 [W/mK]
2 2
Ceilings and floors
Key
Ceiling/floor material Axes
a Natural stone floor d1 wall thickness without insulation
b Sand, gravel (floor) d2 thickness of the
c Mud floor λ thermal conductivity
d Reinforced concrete U thermal transmittance
e Arched ceiling, filled
f Wooden beam ceiling, no filling
Reading example:
1 20 cm concrete ceiling with
2 4 cm thermal insulation
Utotal approximately 0,6 W/m K
Figure 2 — Estimation of U-values based on structure, ceilings/floor
The nomograph is based on the following equation and boundary conditions.
(2)
U=
dd
1 2
RR+ ++
si se
λλ
1 2
where
U is the thermal transmittance of the building element [W/(m ∙K)]
R is the internal heat transmission resistance [m K/W]
si
R is the external heat transmission resistance [m K/W]
se
is the with Σ(R ) approximately 0,17
s
d is the thickness of the wall structure (without thermal insulation) [m]
λ is the thermal conductivity of the wall structure (without thermal insulation) [W/mK]
d is the thickness of the thermal insulation [m]
λ is the thermal conductivity of the thermal insulation with λ = 0,04 [W/mK]
2 2
Roofs
Key
Roof material Axes
a Flat roof (concrete) d1 wall thickness without insulation
b Rafter roof with roofing d2 thickness of the insulation
c Flat roof (concrete) wit static air layer λ thermal conductivity
U thermal transmittance
Reading example:
1 18 cm rafter roof with
2 6 cm thermal insulation
U approximately 0,55 W/m K
total
Figure 3 — Estimation of U-values based on structure, roofs
The nomograph is based on the following equation and boundary conditions.
(3)
U=
dd
1 2
RR+ ++
si se
λλ
1 2
where
U is the thermal transmittance of the building element [W/(m ∙K)]
R is the internal heat transmission resistance [m K/W]
si
R is the external heat transmission resistance [m K/W]
se
is the with Σ(R ) approximately 0,14
s
d is the thickness of the wall structure (without thermal insulation) [m]
λ is the thermal conductivity of the wall structure (without thermal insulation) [W/mK]
d is the thickness of the thermal insulation [m]
λ is the thermal conductivity of the thermal insulation [W/mK]
with λ = 0,04
Windows
The follow
...