SIST EN ISO 15927-6:2008

SLOVENSKI STANDARD
SIST EN ISO 15927-6:2008
01-januar-2008
+LJURWHUPDOQH]QDþLOQRVWLVWDYE5DþXQDQMHLQSUHGVWDYLWHYNOLPDWVNLKSRGDWNRY
GHO9VRWDWHPSHUDWXUQLKUD]OLNGQHYQHVWRSLQMH,62
Hygrothermal performance of buildings — Calculation and presentation of climatic data
— Part 6: Accumulated temperature differences (degree days) (ISO 15927-6:2007)
Wärme und feuchteschutztechnisches Verhalten von Gebäuden — Berechnung und
Darstellung von Klimadaten — Teil 6: Akkumulierte Temperaturdifferenzen (Gradtage)
(ISO 15927 6:2007)
Performance hygrothermique des bâtiments — Calcul et présentation des données
climatiques — Partie 6: Différences accumulées de la température (en degrés par jour)
(ISO 15927 6:2007)
Ta slovenski standard je istoveten z: EN ISO 15927-6:2007
ICS:
07.060 Geologija. Meteorologija. Geology. Meteorology.
Hidrologija Hydrology
91.120.10 Toplotna izolacija stavb Thermal insulation
SIST EN ISO 15927-6:2008 en,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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EUROPEAN STANDARD
EN ISO 15927-6
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2007
ICS 07.060; 91.120.10

English Version
Hygrothermal performance of buildings - Calculation and
presentation of climatic data - Part 6: Accumulated temperature
differences (degree-days) (ISO 15927-6:2007)
Performance hygrothermique des bâtiments - Calcul et Wärme- und feuchteschutztechnisches Verhalten von
présentation des données climatiques - Partie 6: Écarts de Gebäuden - Berechnung und Darstellung von Klimadaten -
température cumulés (degrés-jour) (ISO 15927-6:2007) Teil 6: Akkumulierte Temperaturdifferenzen (Gradtage)
(ISO 15927-6:2007)
This European Standard was approved by CEN on 30 June 2007.
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 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 Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2007 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 15927-6:2007: E
worldwide for CEN national Members.

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EN ISO 15927-6:2007 (E)
Contents Page
Foreword.3

2

---------------------- Page: 3 ----------------------

EN ISO 15927-6:2007 (E)
Foreword
This document (EN ISO 15927-6:2007) has been prepared by Technical Committee ISO/TC 163 "Thermal
performance and energy use in the built environment" in collaboration with Technical Committee CEN/TC 89
"Thermal performance of buildings and building components", the secretariat of which is held by SIS.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by March 2008, and conflicting national standards shall be withdrawn at
the latest by March 2008.
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, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 15927-6:2007 has been approved by CEN as a EN ISO 15927-6:2007 without any
modification.

3

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INTERNATIONAL ISO
STANDARD 15927-6
First edition
2007-09-01

Hygrothermal performance of
buildings — Calculation and presentation
of climatic data —
Part 6:
Accumulated temperature differences
(degree days)
Performance hygrothermique des bâtiments — Calcul et présentation
des données climatiques —
Partie 6: Différences accumulées de la température (en degrés par jour)




Reference number
ISO 15927-6:2007(E)
©
ISO 2007

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ISO 15927-6:2007(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.


COPYRIGHT PROTECTED DOCUMENT


©  ISO 2007
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland

ii © ISO 2007 – All rights reserved

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ISO 15927-6:2007(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and units . 1
4 Direct calculation of accumulated temperature differences . 3
5 Estimation of totals. 6
6 Reference altitude. 7
7 Accuracy and presentation of data. 8
Annex A (informative) Estimation of monthly accumulated temperature differences from
climatological statistics . 10
Bibliography . 13

© ISO 2007 – All rights reserved iii

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ISO 15927-6:2007(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 15927-6 was prepared by the European Committee for Standardization (CEN) Technical Committee
CEN/TC 89, Thermal performance of buildings and building components, in collaboration with Technical
Committee ISO/TC 163, Thermal performance and energy use in the built environment, Subcommittee SC 2,
Calculation methods, in accordance with the Agreement on technical cooperation between ISO and CEN
(Vienna Agreement).
ISO 15927 consists of the following parts, under the general title Hygrothermal performance of buildings —
Calculation and presentation of climatic data:
⎯ Part 1: Monthly means of single meteorological elements
⎯ Part 2: Hourly data for design cooling load
⎯ Part 3: Calculation of a driving rain index for vertical surfaces from hourly wind and rain data
⎯ Part 4: Hourly data for assessing the annual energy use for heating and cooling
⎯ Part 5: Data for design heat load for space heating
⎯ Part 6: Accumulated temperature differences (degree days)

iv © ISO 2007 – All rights reserved

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ISO 15927-6:2007(E)
Introduction
Accumulated temperature differences are a relatively simple form of climatic data, useful as an index of
climate severity as it affects energy use for space heating.
Calculation or estimation of accumulated temperature differences in this part of ISO 15927 is based on the
concept of a base temperature. The base temperature reflects the point at which buildings begin to need
heating to maintain the required internal temperatures. This is the external temperature below which the
heating plant is assumed to come into operation. For some purposes, such as development of energy policy,
the need is for a single base temperature that can be taken to represent an average value for the whole built
stock and overall climate. For other purposes, it is better to determine a base temperature appropriate to an
individual building and time of year.
This part of ISO 15927 meets these needs by including both exact and approximate methods of determining
accumulated temperature differences to both standard and variable base temperatures. Some methods
include the possibility of a threshold temperature (e.g. a daily mean air temperature lower than the base
temperature, above which accumulated temperature differences are not counted). This approach is found in
certain national methods of computation. It is, however, not covered in this part of ISO 15927 because it is
considered to be less flexible than the methods given, in which accumulated temperature differences are
assessed for a base temperature appropriate to the thermal performance of the building (taking account of
other climatic conditions such as solar irradiation).
Accumulated temperature differences computed and presented in accordance with this part of ISO 15927 are
suitable for various purposes including the following:
a) providing an index of climatic severity as it affects energy use for space heating (the comparison use);
b) monitoring the amount of energy used by a heating plant, and thus its efficiency (the energy management
use);
c) comparing the actual energy consumption for heating in a specific period with the consumption in a
standardized period in order to determine the measured rating (the energy modelling use);
d) predicting the economic consequences of different levels of energy efficiency (e.g. through thermal
insulation) for the building stock as a whole or for different classes of building (the energy policy use).
Energy management [list item b)] requires new accumulated temperature difference data at regular intervals,
such as meteorological station data or data representative of a climatic region, calculated to standard base
temperatures, published for each month of the heating season as soon as these can be computed from
verified meteorological observations.
Comparison, energy modelling and energy policy [list items a), c) and d)] require meteorological station data,
data representative of a climatic region or mapped data, collected over many years (possibly giving extremes
as well as mean values), to typify the severity of the climate of a locality, area or region. For list item b),
accumulated temperature differences are best suited to modelling the energy performance of relatively small
buildings with simple heating systems and controls, using “steady-state” thermal analysis. Modelling the
performance of larger or more complex buildings can require more extensive climatological data sets, such as
full or short “test reference years” which are outside the scope of this part of ISO 15927.
In principle the equations in this part of ISO 15927 can be reversed to deal with accumulated temperature
differences for assessing energy use in cooling or air-conditioning buildings (“cooling degree-hours” or
“cooling degree-days”). However, as the air conditioning demand depends as much on solar gain and external
humidity as temperature, the results are not a reliable index of energy demand.

© ISO 2007 – All rights reserved v

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INTERNATIONAL STANDARD ISO 15927-6:2007(E)

Hygrothermal performance of buildings — Calculation
and presentation of climatic data —
Part 6:
Accumulated temperature differences (degree days)
1 Scope
This part of ISO 15927 specifies the definition, method of computation and method of presentation of data on
accumulated temperature differences, used for assessing the energy used for space heating in buildings.
These are normally expressed in degree-hours or degree-days, and such data are often referred to simply as
“heating degree-hours” or “heating degree-days”.
This part of ISO 15927 includes approximate methods for calculating accumulated temperature differences
based on hourly or daily mean temperatures and for estimating monthly values to any base temperature, for
use when data computed directly from meteorological air temperature records are not available.
In some countries, a threshold temperature different from the base temperature is used. This part of
ISO 15927 does not cover this.
2 Normative references
The following referenced documents are indispensable for the application 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 6243, Climatic data for building design — Proposed system of symbols
th 1)
WMO Guide to Meteorological Instruments and Methods of Observation, No. 8., 6 Edition, 1996
3 Terms, definitions, symbols and units
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
hourly temperature difference
difference between a specified base temperature and the external air temperature during a given hour when
the difference is positive, otherwise zero

1) World Meterorological Organization: http://www.wmo.ch/pages/catalogue/New%20HTML/frame/engfil/8.html
© ISO 2007 – All rights reserved 1

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ISO 15927-6:2007(E)
3.1.2
daily temperature difference
difference between a specified base temperature and the mean external air temperature during a given day
when the difference is positive, otherwise zero
3.1.3
accumulated hourly temperature difference
sum of all hourly temperature differences over a given period, e.g. day, month, season, year
3.1.4
accumulated daily temperature difference
sum of all daily temperature differences over a given period, e.g. day, month, season, year
3.1.5
base temperature
any conventional temperature, for instance the internal design temperature less decrements due to internal
and solar gains
3.1.6
daily maximum and daily minimum temperatures
maximum and minimum external dry-bulb temperatures during a day, which may be taken either as the
highest and lowest of the 24 hourly mean temperatures, recorded f
...

SLOVENSKI oSIST prEN ISO 15927-6:2005

PREDSTANDARD
januar 2005
Higrotermalne karakteristike stavb – Računanje in predstavitev klimatskih
podatkov – 6. del: Vsota temperaturnih razlik (dnevne stopinje) (ISO/DIS
15927-6:2004)
(istoveten prEN ISO 15927-6:2004)
Hygrothermal performance of buildings - Calculation and presentation of climatic
data - Part 6: Accumulated temperature differences (degree days) (ISO/DIS 15927-
6:2004)
ICS 07.060; 91.120.10 Referenčna številka
oSIST prEN ISO 15927-6:2005(en)
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

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EUROPEAN STANDARD
DRAFT
prEN ISO 15927-6
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2004
ICS
English version
Hygrothermal performance of buildings - Calculation and
presentation of climatic data - Part 6: Accumulated temperature
differences (degree days) (ISO/DIS 15927-6:2004)
Performance hygrothermique des bâtiments - Calcul et
présentation des données climatiques - Partie 6:
Différences accumulées de la température (en degrés par
jour) (ISO/DIS 15927-6:2004)
This draft European Standard is submitted to CEN members for parallel enquiry. It has been drawn up by the Technical Committee
CEN/TC 89.
If this draft becomes a European Standard, 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.
This draft European Standard was established by CEN 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 Management Centre has the same
status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2004 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN ISO 15927-6:2004: E
worldwide for CEN national Members.

---------------------- Page: 2 ----------------------
prEN ISO 15927-6:2004 (E)




Foreword

This document (prEN ISO 15927-6:2004) has been prepared by Technical Committee
CEN/TC 89 "Thermal performance of buildings and building components", the secretariat of
which is held by SIS, in collaboration with Technical Committee ISO/TC 163 "Thermal
insulation".

This document is currently submitted to the parallel Enquiry.

2

---------------------- Page: 3 ----------------------
DRAFT INTERNATIONAL STANDARD ISO/DIS 15927-6
ISO/TC 163/SC 2 Secretariat: SN
Voting begins on: Voting terminates on:
2004-11-11 2005-04-11
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION
Hygrothermal performance of buildings — Calculation and
presentation of climatic data —
Part 6:
Accumulated temperature differences (degree days)
Performance hygrothermique des bâtiments — Calcul et présentation des données climatiques —
Partie 6: Différences accumulées de la température (en degrés par jour)
ICS 07.060; 91.120.10

ISO/CEN PARALLEL ENQUIRY
This draft International Standard is a draft standard developed within the European Committee for
Standardization (CEN) and processed under the CEN-lead mode of collaboration as defined in the
Vienna Agreement. The document has been transmitted by CEN to ISO for circulation for ISO member
body voting in parallel with CEN enquiry. Comments received from ISO member bodies, including those
from non-CEN members, will be considered by the appropriate CEN technical body. Should this DIS be
accepted, a final draft, established on the basis of comments received, will be submitted to a parallel two-
month FDIS vote in ISO and formal vote in CEN.
In accordance with the provisions of Council Resolution 15/1993 this document is circulated in
the English language only.
Conformément aux dispositions de la Résolution du Conseil 15/1993, ce document est distribué
en version anglaise seulement.
To expedite distribution, this document is circulated as received from the committee secretariat.
ISO Central Secretariat work of editing and text composition will be undertaken at publication
stage.
Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du
secrétariat du comité. Le travail de rédaction et de composition de texte sera effectué au
Secrétariat central de l'ISO au stade de publication.
THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE
REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.
© International Organization for Standardization, 2004

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ISO/DIS 15927-6
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall
not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the
unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
Copyright notice
This ISO document is a Draft International Standard and is copyright-protected by ISO. Except as permitted
under the applicable laws of the user's country, neither this ISO draft nor any extract from it may be
reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, photocopying,
recording or otherwise, without prior written permission being secured.
Requests for permission to reproduce should be addressed to either ISO at the address below or ISO's
member body in the country of the requester.
ISO copyright office
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Reproduction may be subject to royalty payments or a licensing agreement.
Violators may be prosecuted.
©
ii ISO 2004 – All rights reserved

---------------------- Page: 5 ----------------------
ISO/DIS 15927-6
Contents Page
1 Scope . 6
2 Normative references . 6
3 Terms and definitions. 6
3.1 Definitions . 6
3.2 Symbols and units. 8
4 Direct calculation of accumulated temperature differences . 9
4.1 General. 9
4.2 Sources of data . 9
4.3 Standard base temperatures . 9
4.4 Calculation of hourly temperature differences and accumulated hourly temperature
differences. 9
4.5 Estimation of accumulated hourly temperature differences from daily maximum and
minimum temperatures . 10
4.6 Calculation of accumulated daily temperature differences. 11
5 Estimation of totals. 12
5.1 Estimation of accumulated temperature differences to various base temperatures . 12
5.2 Interpolation . 12
5.3 Estimation from climatological statistics. 12
6 Reference altitude. 13
7 Accuracy and presentation of data. 13
7.1 Information to be given with all accumulated temperature difference data. 13
7.2 Correction for altitude . 13
7.3 Other information to be given as appropriate. 14
Annex A (informative) Alternative methods for estimating monthly accumulated temperature
differences. 15
© ISO 2004 – All rights reserved iii

---------------------- Page: 6 ----------------------
ISO/DIS 15927-6
Foreword
ISO 15927-6 was prepared by Technical Committee CEN/TC 89, Thermal performance of buildings and
building components, in cooperation with Technical Committee ISO/TC 163, Thermal performance and energy
use in the built environment, Subcommittee SC 2, Calculation methods.
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 15927 consists of the following parts, under the general title Hygrothermal performance of buildings —
Calculation and presentation of climatic data:
 Part 1: Monthly means of single meteorological elements
 Part 2: Hourly data for design cooling load
 Part 3: Calculation of a driving rain index for vertical surfaces from hourly wind and rain data
 Part 4: Hourly data for assessing the annual energy for heating and cooling
 Part 5: Data for design heat load for space heating
 Part 6: Accumulated temperature differences (degree days)
iv © ISO 2004 – All rights reserved

---------------------- Page: 7 ----------------------
ISO/DIS 15927-6
Introduction
Accumulated temperature differences are a relatively simple form of climatic data, useful as an index of
climate severity as it affects energy use for space heating.
Calculation or estimation of accumulated temperature differences reflects the point at which buildings begin to
need heating to maintain the required internal temperatures. In common with all methods, this standard uses
the concept of a base temperature. This is the external temperature below which heating plant is assumed to
come into operation. For some purposes, such as development of energy policy the need is for a single base
temperature that can be taken to represent an average value for the whole built stock and overall climate. For
other purposes, it is better to determine a base temperature appropriate to an individual building and time of
year.
This standard meets these needs by including both exact and approximate methods of determining
accumulated temperature differences, to both standard and variable base temperatures. The methods include
the possibility of a threshold temperature (e.g. a daily mean air temperature higher than the base temperature,
above which accumulated temperature differences are not counted). This approach is found in certain
national methods of computation. It is, however, considered to be less flexible than the methods given in this
standard, in which accumulated temperature differences are assessed for a base temperature appropriate to
the thermal performance of the building (taking account of other climatic conditions such as solar irradiation).
Accumulated temperature differences computed and presented in accordance with this standard are a
measure of climatic severity as it affects the energy used for the space heating of buildings. The data may be
used for the following purposes:
a) monitoring the amount of energy used by heating plant, and thus its efficiency (the energy management
use);
b) predicting and/or comparing the relative energy performance of space heating in buildings at the design
stage (the energy modelling use); and
c) predicting the economic consequences of different levels of energy efficiency (e.g. through thermal
insulation), for the building stock as a whole or for different classes of building (the energy policy use).
Energy management (purpose a)) requires new accumulated temperature difference data at regular intervals,
such as meteorological station or zone data, calculated to standard base temperatures, published for each
month of the heating season, as soon as these can be computed from verified meteorological observations.
Energy modelling and energy policy (purposes b) and c)), require meteorological station, zone or mapped
data collected over many years (possibly giving extremes as well as mean values), to typify the severity of the
climate of a locality, area or region. For purpose b), accumulated temperature differences are best suited to
modelling the energy performance of relatively small buildings with simple heating systems and controls, using
“steady-state” thermal analysis. Modelling the performance of larger or more complex buildings may require
more extensive climatological data sets, such as full or short ‘test reference years’, which are outside the
scope of this standard.
In principle the equations in this standard could be reversed to deal with accumulated temperature differences
for assessing energy use in cooling or air-conditioning buildings (“cooling degree-hours” or “cooling degree-
days”). However, as the air conditioning demand depends as much on solar gain and external humidity as
temperature, the results will not be a reliable index of energy demand.
© ISO 2004 – All rights reserved v

---------------------- Page: 8 ----------------------
ISO/DIS 15927-6
Hygrothermal performance of buildings — Calculation and
presentation of climatic data — Part 6: Accumulated temperature
differences (degree days)
1 Scope
This standard specifies the definition, method of computation and method of presentation of data on accumulated
temperature differences, used for assessing the energy used for space heating in buildings. These are normally
expressed in degree-hours or degree-days, and such data are often referred to simply as “heating degree-hours” or
“heating degree-days”.
The standard includes approximate methods for calculating accumulated temperature differences based on hourly or
daily mean temperatures and for estimating monthly values to any base temperature, for use when data computed
directly from meteorological air temperature records are not available.
In some countries a threshold temperature different from the base temperature is used. This standard allows for this,
but it is assumed that for many uses the threshold and base temperatures will be equal.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated refe
...