SIST EN ISO 15927-3:2009
Hygrothermal performance of buildings - Calculation and presentation of climatic data - Part 3: Calculation of a driving rain index for vertical surfaces from hourly wind and rain data (ISO 15927-3:2009)
Hygrothermal performance of buildings - Calculation and presentation of climatic data - Part 3: Calculation of a driving rain index for vertical surfaces from hourly wind and rain data (ISO 15927-3:2009)
This part of ISO 15927 specifies two procedures for providing an estimate of the quantity of water likely to impact on a wall of any given orientation. It takes account of topography, local sheltering and the type of building and wall. The first method, given in Clause 3 and based on coincident hourly rainfall and wind data, defines a means of calculating - the annual average index, which influences the moisture content of an absorbent surface, such as masonry, and - the spell index, which influences the likelihood of rain penetration through masonry and joints in other walling systems. The second method, given in Clause 4 and based on average wind data and a qualitative recording of the presence and intensity of rain (the present weather code for rain), defines a means of calculating the spell length during which an absorbent material such as masonry is moistened, which has a 10 % probability of being exceeded in any year (commonly referred to as having a mean return period of 10 years). A comparison between the two methods is given in informative Annex D. Procedures are given to correct the results of both methods for topography, local sheltering and the type of building and wall. The methods included in this part of ISO 15927 do not apply in a) mountainous areas with sheer cliffs or deep gorges, b) areas in which more than 25 % of the annual rainfall comes from severe convective storms, c) areas and periods when a significant proportion of precipitation is made up of snow or hail.
Wärme- und feuchteschutztechnisches Verhalten von Gebäuden - Berechnung und Darstellung von Klimadaten - Teil 3: Berechnung des Schlagregenindexes für senkrechte Oberflächen aus stündlichen Wind- und Regendaten (ISO 15927-3:2009)
Dieser Teil der ISO 15927 legt zwei Verfahren fest, die eine Abschätzung der Wassermenge liefern, die wahrscheinlich auf eine Wand in beliebig gegebener Ausrichtung auftreffen wird. Berücksichtigt werden Topographie, örtlicher Windschutz sowie die Art des Gebäudes und der Wand.
Das erste Verfahren, das in Abschnitt 3 beschrieben ist und auf gleichzeitig gemessenen stündlichen Regen und Winddaten beruht, legt das Verfahren zur Berechnung folgender Größen fest:
Jahresdurchschnittsindex, der den Feuchtegehalt einer absorbierenden Oberfläche wie z. B. Mauerwerk beeinflusst;
Periodenindex, der die Wahrscheinlichkeit des Eindringens von Regen durch Mauerwerk und Verbin-dungs¬stellen in weiteren Wandsystemen beeinflusst.
Das zweite Verfahren, das in Abschnitt 4 beschrieben ist und auf den durchschnittlichen Winddaten und einer qualitativen Aufzeichnung des Auftretens und der Intensität von Regen (aktueller Wettercode für Regen) beruht, legt ein Verfahren zur Berechnung der Dauer der Periode fest, während der ein absorbierendes Material wie z. B. Mauerwerk befeuchtet wird und die mit 10%iger Wahrscheinlichkeit jedes beliebige Jahr überschritten wird (wird im Allgemeinen als mittlere Wiederkehrdauer von 10 Jahren bezeichnet).
Die beiden Verfahren werden im informativen Anhang D miteinander verglichen.
Darüber hinaus sind Verfahren zur Korrektur der Ergebnisse beider Verfahren in Bezug auf die Topographie, den örtlichen Windschutz sowie die Art des Gebäudes und der Wand angegeben.
Die in diesem Teil der ISO 15927 enthaltenen Verfahren gelten nicht für:
a) Gebirgsgegenden mit sehr steilen Klippen oder tiefen Schluchten;
b) Gebiete, in denen mehr als 25 % der jährlichen Regenmenge von schweren konvektiven Stark¬nieder-schlägen hervorgerufen werden;
c) Gebiete und Zeiträume, in denen ein wesentlicher Anteil des Niederschlags die Form von Schnee oder Hagel aufweist.
Performance hygrothermique des bâtiments - Calcul et présentation des données climatiques - Partie 3: Calcul d'un indice de pluie battante pour surfaces verticales à partir de données horaires de vent et de pluie (ISO 15927-3:2009)
L'ISO 15927-3:2009 spécifie deux modes opératoires permettant de fournir une estimation de la quantité d'eau susceptible de tomber sur un mur ayant une orientation donnée. Elle tient compte de la topographie, de la protection locale et du type de bâtiment et de mur.
Le premier mode opératoire, fondé sur des données horaires concomitantes des précipitations et de la vitesse du vent, définit une méthode de calcul de l'indice moyen annuel qui influe sur la teneur en eau d'une surface absorbante, comme la maçonnerie, et l'indice de durée de mouillage qui influe sur la probabilité de pénétration de la pluie dans la maçonnerie et les joints dans d'autres systèmes d'enduits.
Le deuxième mode opératoire, fondé sur des données de vent moyennes et sur un enregistrement qualitatif de la présence et de l'intensité de pluie (le code du temps présent pour la pluie), définit une méthode de calcul de la durée de mouillage d'un matériau absorbant comme la maçonnerie, avec une probabilité de 10 % d'être dépassée en une année (ou, autrement dit, «avec une période de récurrence moyenne de 10 ans»).
L'ISO 15927-3:2009 fournit une comparaison entre les deux méthodes.
L'ISO 15927-3:2009 indique des modes opératoires pour corriger les résultats des deux méthodes en fonction de la topographie, de la protection locale et du type de bâtiment et de mur.
Les méthodes indiquées dans l'ISO 15927-3:2009 ne s'appliquent pas aux zones montagneuses avec des falaises abruptes ou des gorges profondes, aux zones où plus de 25 % des pluies annuelles proviennent de fortes tempêtes convectives, et aux zones et aux périodes où une proportion importante des précipitations est constituée de neige ou de grêle.
Higrotermalne značilnosti stavb - Izračun in predstavitev podnebnih podatkov - 3. del: Računanje indeksa padavin za navpične površine na podlagi hitrosti vetra in količine dežja (ISO 15927-3:2009)
General Information
Buy Standard
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 15927-3:2009
01-junij-2009
Higrotermalne značilnosti stavb - Izračun in predstavitev podnebnih podatkov - 3.
del: Računanje indeksa padavin za navpične površine na podlagi hitrosti vetra in
količine dežja (ISO 15927-3:2009)
Hygrothermal performance of buildings - Calculation and presentation of climatic data -
Part 3: Calculation of a driving rain index for vertical surfaces from hourly wind and rain
data (ISO 15927-3:2009)
Wärme- und feuchteschutztechnisches Verhalten von Gebäuden - Berechnung und
Darstellung von Klimadaten - Teil 3: Berechnung des Schlagregenindexes für senkrechte
Oberflächen aus stündlichen Wind- und Regendaten (ISO 15927-3:2009)
Performance hygrothermique des bâtiments - Calcul et présentation des données
climatiques - Partie 3: Calcul d'un indice de pluie battante pour surfaces verticales à
partir de données horaires de vent et de pluie (ISO 15927-3:2009)
Ta slovenski standard je istoveten z: EN ISO 15927-3:2009
ICS:
07.060 Geologija. Meteorologija. Geology. Meteorology.
Hidrologija Hydrology
91.120.10 Toplotna izolacija stavb Thermal insulation of
buildings
SIST EN ISO 15927-3:2009 en,fr
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 15927-3:2009
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SIST EN ISO 15927-3:2009
EUROPEAN STANDARD
EN ISO 15927-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2009
ICS 91.120.10; 07.060
English Version
Hygrothermal performance of buildings - Calculation and
presentation of climatic data - Part 3: Calculation of a driving
rain index for vertical surfaces from hourly wind and rain data
(ISO 15927-3:2009)
Performance hygrothermique des bâtiments - Calcul et Wärme- und feuchteschutztechnisches Verhalten von
présentation des données climatiques - Partie 3: Calcul Gebäuden - Berechnung und Darstellung von Klimadaten -
d'un indice de pluie battante pour surfaces verticales à Teil 3: Berechnung des Schlagregenindexes für senkrechte
partir de données horaires de vent et de pluie (ISO 15927- Oberflächen aus stündlichen Wind- und Regendaten (ISO
3:2009) 15927-3:2009)
This European Standard was approved by CEN on 31 January 2009.
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: Avenue Marnix 17, B-1000 Brussels
© 2009 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 15927-3:2009: E
worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 15927-3:2009
EN ISO 15927-3:2009 (E)
Contents Page
Foreword .3
2
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SIST EN ISO 15927-3:2009
EN ISO 15927-3:2009 (E)
Foreword
This document (EN ISO 15927-3:2009) 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 September 2009, and conflicting national standards shall be
withdrawn at the latest by September 2009.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
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.
3
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SIST EN ISO 15927-3:2009
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SIST EN ISO 15927-3:2009
INTERNATIONAL ISO
STANDARD 15927-3
First edition
2009-03-15
Hygrothermal performance of
buildings — Calculation and presentation
of climatic data —
Part 3:
Calculation of a driving rain index for
vertical surfaces from hourly wind and
rain data
Performance hygrothermique des bâtiments — Calcul et présentation
des données climatiques —
Partie 3: Calcul d'un indice de pluie battante pour surfaces verticales à
partir de données horaires de vent et de pluie
Reference number
ISO 15927-3:2009(E)
©
ISO 2009
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SIST EN ISO 15927-3:2009
ISO 15927-3:2009(E)
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Published in Switzerland
ii © ISO 2009 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 15927-3:2009
ISO 15927-3:2009(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Terms, definitions, symbols and units . 2
3 Calculation of airfield indices from hourly wind and rain data. 4
4 Estimation of the effect of driving rain from average wind and present weather code for
rain. 4
5 Calculation of wall indices. 5
Annex A (informative) Limits to the validity of the calculated indices . 11
Annex B (informative) The nature of a “spell” of driving rain . 12
Annex C (informative) The procedure for generating the driving-rain maps. 13
Annex D (informative) Comparison of methods specified in Clauses 3 and 4 . 15
Bibliography . 17
© ISO 2009 – All rights reserved iii
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SIST EN ISO 15927-3:2009
ISO 15927-3:2009(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 15927-3 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 2009 – All rights reserved
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SIST EN ISO 15927-3:2009
ISO 15927-3:2009(E)
Introduction
This part of ISO 15927 specifies two procedures for analysing data derived from hourly observations of wind
and rainfall so as to provide an estimate in terms of both an annual average and short-term spells of the
quantity of water likely to impact on a wall of any given orientation.
[1]
The first method, which uses hourly observations of wind and rainfall, is based closely on BS 8104 , which
originated from a long series of measurements of driving rain on buildings in a wide range of locations within
the UK. As such, the method applies to climates similar to those in the UK; in other regions, with very different
climates, it is recommended that confirmation of its applicability be obtained by measurements of driving rain
on representative buildings.
Where hourly observations of wind and rain are not available, the second procedure, based on the present
weather code for rain and average wind speeds can be used.
In all cases, especially in mountainous areas, it is important that direct measurements of the rain impacting on
building façades be made wherever possible.
Rain penetration around the edges of doors and windows or similar cracks in building façades depends on
shorter periods of heavy rain and strong winds.
© ISO 2009 – All rights reserved v
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SIST EN ISO 15927-3:2009
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SIST EN ISO 15927-3:2009
INTERNATIONAL STANDARD ISO 15927-3:2009(E)
Hygrothermal performance of buildings — Calculation and
presentation of climatic data —
Part 3:
Calculation of a driving rain index for vertical surfaces from
hourly wind and rain data
1 Scope
This part of ISO 15927 specifies two procedures for providing an estimate of the quantity of water likely to
impact on a wall of any given orientation. It takes account of topography, local sheltering and the type of
building and wall.
The first method, given in Clause 3 and based on coincident hourly rainfall and wind data, defines a means of
calculating
⎯ the annual average index, which influences the moisture content of an absorbent surface, such as
masonry, and
⎯ the spell index, which influences the likelihood of rain penetration through masonry and joints in other
walling systems.
The second method, given in Clause 4 and based on average wind data and a qualitative recording of the
presence and intensity of rain (the present weather code for rain), defines a means of calculating the spell
length during which an absorbent material such as masonry is moistened, which has a 10 % probability of
being exceeded in any year (commonly referred to as having a mean return period of 10 years).
A comparison between the two methods is given in informative Annex D.
Procedures are given to correct the results of both methods for topography, local sheltering and the type of
building and wall.
The methods included in this part of ISO 15927 do not apply in
a) mountainous areas with sheer cliffs or deep gorges,
b) areas in which more than 25 % of the annual rainfall comes from severe convective storms,
c) areas and periods when a significant proportion of precipitation is made up of snow or hail.
© ISO 2009 – All rights reserved 1
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SIST EN ISO 15927-3:2009
ISO 15927-3:2009(E)
2 Terms, definitions, symbols and units
For the purposes of this document, the following terms, definitions, symbols and units apply.
2.1 Definitions
2.1.1
spell
period, or sequence of periods, of wind-driven rain on a vertical surface of given orientation
NOTE Further information about spells is given in Annex B.
2.1.2
airfield hourly index
quantity of driving rain that would occur on a vertical wall of given orientation per square metre of wall during
1 h at a height of 10 m above ground level in the middle of an airfield, at the geographical location of the wall
2.1.3
airfield annual index
airfield index for a given wall orientation totalled over one year
2.1.4
airfield spell index
airfield index for a given wall orientation totalled over the worst spell likely to occur in any three-year period
2.1.5
wall annual index
quantity of wind-driven rain per square metre at a point on a wall of given orientation, based on the airfield
annual index and corrections for roughness, topography, obstruction and wall factors
2.1.6
wall spell index
quantity of wind-driven rain per square metre at a point on a given wall, based on the airfield spell index and
corrections for roughness, topography, obstruction and wall factors
2.1.7
line of sight
horizontal view away from the wall, over a sector spanning about 25° either side of the normal to the wall
2.1.8
terrain roughness category
classification of the surface roughness upwind in terms of the average height and spacing of obstructions such
as buildings, trees or hedges
2.1.9
roughness coefficient
factor that allows for the modification of the wind speed by the roughness of the terrain upwind of a wall
2.1.10
topography coefficient
factor that allows for the effect of local topography on the wind speed
2.1.11
obstruction factor
factor that relates to shelter from the very local environment and allows for obstructions such as buildings,
fences and trees close to, and upwind of, the wall
2.1.12
wall factor
ratio of the quantity of water hitting a wall to the quantity passing through an equivalent unobstructed space,
allowing for the characteristics of the wall
2 © ISO 2009 – All rights reserved
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SIST EN ISO 15927-3:2009
ISO 15927-3:2009(E)
2.1.13
wall orientation
angle between north and line normal to a wall
2.1.14
convective storm
heavy precipitation in the form of showers or thunderstorms generally lasting less than 1 h
2.1.15
reference spell
period during which a wall oriented in any given direction is moistened, having a 10 % probability of being
exceeded in any year
2.1.16
present weather code
numerical code used by meteorological observers to assess the weather conditions at the time of an
observation
[2]
NOTE Present weather codes are given in the WMO Guide .
2.1.17
half day
twelve-hour period including the hours from 07:00 to 18:00 or from 19:00 to 06:00
2.2 Symbols and units
Symbol Quantity Unit
C roughness coefficient —
R
C topography coefficient —
T
D hourly mean wind direction from north °
H effective height of feature m
2
I airfield annual index l/m
A
2
I airfield spell index l/m
S
2
I wall annual index l/m
WA
2
I wall spell index l/m
WS
K terrain factor —
R
L length m
N number of years of available data —
O obstruction factor —
r hourly rainfall total mm
v hourly mean wind speed m/s
W wall factor —
x horizontal distance m
z height above ground m
z roughness length m
0
z minimum height m
min
Θ wall orientation relative to north °
© ISO 2009 – All rights reserved 3
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SIST EN ISO 15927-3:2009
ISO 15927-3:2009(E)
3 Calculation of airfield indices from hourly wind and rain data
3.1 Sources of data
Data used for calculations according to this part of
...
SLOVENSKI STANDARD
SIST EN ISO 15927-3:2009
01-junij-2009
+LJURWHUPDOQHNDUDNWHULVWLNHVWDYE5DþXQDQMHLQSUHGVWDYLWHYNOLPDWVNLK
SRGDWNRYGHO 5DþXQDQMHLQGHNVDSDGDYLQ]DQDYSLþQHSRYUãLQHQDSRGODJL
KLWURVWLYHWUDLQNROLþLQHGHåMD ,62
Hygrothermal performance of buildings - Calculation and presentation of climatic data -
Part 3: Calculation of a driving rain index for vertical surfaces from hourly wind and rain
data (ISO 15927-3:2009)
Wärme- und feuchteschutztechnisches Verhalten von Gebäuden - Berechnung und
Darstellung von Klimadaten - Teil 3: Berechnung des Schlagregenindexes für senkrechte
Oberflächen aus stündlichen Wind- und Regendaten (ISO 15927-3:2009)
Performance hygrothermique des bâtiments - Calcul et présentation des données
climatiques - Partie 3: Calcul d'un indice de pluie battante pour surfaces verticales à
partir de données horaires de vent et de pluie (ISO 15927-3:2009)
Ta slovenski standard je istoveten z: EN ISO 15927-3:2009
ICS:
07.060 Geologija. Meteorologija. Geology. Meteorology.
Hidrologija Hydrology
91.120.10 Toplotna izolacija stavb Thermal insulation
SIST EN ISO 15927-3:2009 en,fr
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST EN ISO 15927-3:2009
---------------------- Page: 2 ----------------------
SIST EN ISO 15927-3:2009
EUROPEAN STANDARD
EN ISO 15927-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2009
ICS 91.120.10; 07.060
English Version
Hygrothermal performance of buildings - Calculation and
presentation of climatic data - Part 3: Calculation of a driving
rain index for vertical surfaces from hourly wind and rain data
(ISO 15927-3:2009)
Performance hygrothermique des bâtiments - Calcul et Wärme- und feuchteschutztechnisches Verhalten von
présentation des données climatiques - Partie 3: Calcul Gebäuden - Berechnung und Darstellung von Klimadaten -
d'un indice de pluie battante pour surfaces verticales à Teil 3: Berechnung des Schlagregenindexes für senkrechte
partir de données horaires de vent et de pluie (ISO 15927- Oberflächen aus stündlichen Wind- und Regendaten (ISO
3:2009) 15927-3:2009)
This European Standard was approved by CEN on 31 January 2009.
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: Avenue Marnix 17, B-1000 Brussels
© 2009 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 15927-3:2009: E
worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 15927-3:2009
EN ISO 15927-3:2009 (E)
Contents Page
Foreword .3
2
---------------------- Page: 4 ----------------------
SIST EN ISO 15927-3:2009
EN ISO 15927-3:2009 (E)
Foreword
This document (EN ISO 15927-3:2009) 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 September 2009, and conflicting national standards shall be
withdrawn at the latest by September 2009.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
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.
3
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SIST EN ISO 15927-3:2009
---------------------- Page: 6 ----------------------
SIST EN ISO 15927-3:2009
INTERNATIONAL ISO
STANDARD 15927-3
First edition
2009-03-15
Hygrothermal performance of
buildings — Calculation and presentation
of climatic data —
Part 3:
Calculation of a driving rain index for
vertical surfaces from hourly wind and
rain data
Performance hygrothermique des bâtiments — Calcul et présentation
des données climatiques —
Partie 3: Calcul d'un indice de pluie battante pour surfaces verticales à
partir de données horaires de vent et de pluie
Reference number
ISO 15927-3:2009(E)
©
ISO 2009
---------------------- Page: 7 ----------------------
SIST EN ISO 15927-3:2009
ISO 15927-3:2009(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 2009
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
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
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Web www.iso.org
Published in Switzerland
ii © ISO 2009 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 15927-3:2009
ISO 15927-3:2009(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Terms, definitions, symbols and units . 2
3 Calculation of airfield indices from hourly wind and rain data. 4
4 Estimation of the effect of driving rain from average wind and present weather code for
rain. 4
5 Calculation of wall indices. 5
Annex A (informative) Limits to the validity of the calculated indices . 11
Annex B (informative) The nature of a “spell” of driving rain . 12
Annex C (informative) The procedure for generating the driving-rain maps. 13
Annex D (informative) Comparison of methods specified in Clauses 3 and 4 . 15
Bibliography . 17
© ISO 2009 – All rights reserved iii
---------------------- Page: 9 ----------------------
SIST EN ISO 15927-3:2009
ISO 15927-3:2009(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 15927-3 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 2009 – All rights reserved
---------------------- Page: 10 ----------------------
SIST EN ISO 15927-3:2009
ISO 15927-3:2009(E)
Introduction
This part of ISO 15927 specifies two procedures for analysing data derived from hourly observations of wind
and rainfall so as to provide an estimate in terms of both an annual average and short-term spells of the
quantity of water likely to impact on a wall of any given orientation.
[1]
The first method, which uses hourly observations of wind and rainfall, is based closely on BS 8104 , which
originated from a long series of measurements of driving rain on buildings in a wide range of locations within
the UK. As such, the method applies to climates similar to those in the UK; in other regions, with very different
climates, it is recommended that confirmation of its applicability be obtained by measurements of driving rain
on representative buildings.
Where hourly observations of wind and rain are not available, the second procedure, based on the present
weather code for rain and average wind speeds can be used.
In all cases, especially in mountainous areas, it is important that direct measurements of the rain impacting on
building façades be made wherever possible.
Rain penetration around the edges of doors and windows or similar cracks in building façades depends on
shorter periods of heavy rain and strong winds.
© ISO 2009 – All rights reserved v
---------------------- Page: 11 ----------------------
SIST EN ISO 15927-3:2009
---------------------- Page: 12 ----------------------
SIST EN ISO 15927-3:2009
INTERNATIONAL STANDARD ISO 15927-3:2009(E)
Hygrothermal performance of buildings — Calculation and
presentation of climatic data —
Part 3:
Calculation of a driving rain index for vertical surfaces from
hourly wind and rain data
1 Scope
This part of ISO 15927 specifies two procedures for providing an estimate of the quantity of water likely to
impact on a wall of any given orientation. It takes account of topography, local sheltering and the type of
building and wall.
The first method, given in Clause 3 and based on coincident hourly rainfall and wind data, defines a means of
calculating
⎯ the annual average index, which influences the moisture content of an absorbent surface, such as
masonry, and
⎯ the spell index, which influences the likelihood of rain penetration through masonry and joints in other
walling systems.
The second method, given in Clause 4 and based on average wind data and a qualitative recording of the
presence and intensity of rain (the present weather code for rain), defines a means of calculating the spell
length during which an absorbent material such as masonry is moistened, which has a 10 % probability of
being exceeded in any year (commonly referred to as having a mean return period of 10 years).
A comparison between the two methods is given in informative Annex D.
Procedures are given to correct the results of both methods for topography, local sheltering and the type of
building and wall.
The methods included in this part of ISO 15927 do not apply in
a) mountainous areas with sheer cliffs or deep gorges,
b) areas in which more than 25 % of the annual rainfall comes from severe convective storms,
c) areas and periods when a significant proportion of precipitation is made up of snow or hail.
© ISO 2009 – All rights reserved 1
---------------------- Page: 13 ----------------------
SIST EN ISO 15927-3:2009
ISO 15927-3:2009(E)
2 Terms, definitions, symbols and units
For the purposes of this document, the following terms, definitions, symbols and units apply.
2.1 Definitions
2.1.1
spell
period, or sequence of periods, of wind-driven rain on a vertical surface of given orientation
NOTE Further information about spells is given in Annex B.
2.1.2
airfield hourly index
quantity of driving rain that would occur on a vertical wall of given orientation per square metre of wall during
1 h at a height of 10 m above ground level in the middle of an airfield, at the geographical location of the wall
2.1.3
airfield annual index
airfield index for a given wall orientation totalled over one year
2.1.4
airfield spell index
airfield index for a given wall orientation totalled over the worst spell likely to occur in any three-year period
2.1.5
wall annual index
quantity of wind-driven rain per square metre at a point on a wall of given orientation, based on the airfield
annual index and corrections for roughness, topography, obstruction and wall factors
2.1.6
wall spell index
quantity of wind-driven rain per square metre at a point on a given wall, based on the airfield spell index and
corrections for roughness, topography, obstruction and wall factors
2.1.7
line of sight
horizontal view away from the wall, over a sector spanning about 25° either side of the normal to the wall
2.1.8
terrain roughness category
classification of the surface roughness upwind in terms of the average height and spacing of obstructions such
as buildings, trees or hedges
2.1.9
roughness coefficient
factor that allows for the modification of the wind speed by the roughness of the terrain upwind of a wall
2.1.10
topography coefficient
factor that allows for the effect of local topography on the wind speed
2.1.11
obstruction factor
factor that relates to shelter from the very local environment and allows for obstructions such as buildings,
fences and trees close to, and upwind of, the wall
2.1.12
wall factor
ratio of the quantity of water hitting a wall to the quantity passing through an equivalent unobstructed space,
allowing for the characteristics of the wall
2 © ISO 2009 – All rights reserved
---------------------- Page: 14 ----------------------
SIST EN ISO 15927-3:2009
ISO 15927-3:2009(E)
2.1.13
wall orientation
angle between north and line normal to a wall
2.1.14
convective storm
heavy precipitation in the form of showers or thunderstorms generally lasting less than 1 h
2.1.15
reference spell
period during which a wall oriented in any given direction is moistened, having a 10 % probability of being
exceeded in any year
2.1.16
present weather code
numerical code used by meteorological observers to assess the weather conditions at the time of an
observation
[2]
NOTE Present weather codes are given in the WMO Guide .
2.1.17
half day
twelve-hour period including the hours from 07:00 to 18:00 or from 19:00 to 06:00
2.2 Symbols and units
Symbol Quantity Unit
C roughness coefficient —
R
C topography coefficient —
T
D hourly mean wind direction from north °
H effective height of feature m
2
I airfield annual index l/m
A
2
I airfield spell index l/m
S
2
I wall annual index l/m
WA
2
I wall spell index l/m
WS
K terrain factor —
R
L length m
N number of years of available data —
O obstruction factor —
r hourly rainfall total mm
v hourly mean wind speed m/s
W wall factor —
x horizontal distance m
z height above ground m
z roughness length m
0
z minimum height m
min
Θ wall orientation relative to north °
© ISO 2009 – All rights reserved 3
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SIST EN ISO 15927-3:2009
ISO 15927-3:2009(E)
3 Calculation of airfield indices from hourly wind and rain data
3.1 Sources of data
Data used for calculations according to this part of ISO 1
...
SLOVENSKI oSIST prEN ISO 15927-3:2006
PREDSTANDARD
oct 2006
Higrotermalne karakteristike stavb – Računanje in predstavitev klimatskih
podatkov – 3. del: Računanje indeksa padavin za navpične površine glede na
hitrost vetra in količino dežja (ISO/DIS 15927-3:2003)
Hygrothermal performance of buildings - Calculation and presentation of climatic
data - Part 3: Calculation of a driving rain index for vertical surfaces from hourly
wind and rain data (ISO/DIS 15927-3:2006)
ICS 07.060; 91.120.10 Referenčna številka
oSIST prEN ISO 15927-3:2006(en)
© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno
---------------------- Page: 1 ----------------------
EUROPEAN STANDARD
DRAFT
prEN ISO 15927-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2006
ICS 91.120.10; 07.060
English Version
Hygrothermal performance of buildings - Calculation and
presentation of climatic data - Part 3: Calculation of a driving
rain index for vertical surfaces from hourly wind and rain data
(ISO/DIS 15927-3:2006)
Performance hygrothermique des bâtiments - Calcul et Wärme- und feuchteschutztechnisches Verhalten von
présentation des données climatiques - Partie 3: Calcul Gebäuden - Berechnung und Darstellung von Klimadaten -
d'un index de pluie battante pour les surfaces verticales à Teil 3: Berechnung des Schlagregenindexes für senkrechte
partir de données horaires de vent et de pluie (ISO/DIS Oberflächen aus stündlichen Wind- und Regendaten
15927-3:2006) (ISO/DIS 15927-3:2006)
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, Romania,
Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to
provide supporting documentation.
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
© 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN ISO 15927-3:2006: E
worldwide for CEN national Members.
---------------------- Page: 2 ----------------------
prEN ISO 15927-3 :2006
Foreword
This document (prEN ISO 15927-3 :2006) 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 15927-3
ISO/TC 163/SC 2 Secretariat: SN
Voting begins on: Voting terminates on:
2006-07-27 2006-12-27
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION
Hygrothermal performance of buildings - Calculation and
presentation of climatic data —
Part 3:
Calculation of a driving rain index for vertical surfaces from
hourly wind and rain data
Performance hygrothermique des bâtiments — Calcul et présentation des données climatiques —
Partie 3: Calcul d'un index de pluie battante pour les surfaces verticales à partir de données horaires de vent et
de pluie
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, 2006
---------------------- Page: 4 ----------------------
ISO/DIS 15927-3
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 2006 – All rights reserved
---------------------- Page: 5 ----------------------
ISO/DIS 15927-3
Contents Page
Introduction.iv
1 Scope.1
2 Normative references.1
3 Definitions, symbols and units .1
3.1 Definitions .1
3.2 Symbols and units.3
4 Calculation of airfield indices from hourly wind and rain data .3
4.1 Sources of data.3
4.2 Airfield annual index .3
4.3 Airfield spell index.4
5 Estimation of the effect of driving rain from average wind and present weather code for
rain .4
6 Calculation of wall indices .5
6.1 General .5
6.2 The roughness coefficient.5
6.3 Topography coefficient.6
6.4 Obstruction factor .9
6.5 The wall factor W .9
Annex A (informative) Limits to the validity of the calculated indices.11
Annex B (informative) The nature of a ‘spell’ of driving rain.12
Annex C (informative) The procedure for generating the driving rain maps in the British Standard
BS 8104:1992 .13
Annex D (informative) Comparison of methods specified in Clauses 4 and 5 .15
Bibliography.17
© ISO 2006 – All rights reserved iii
---------------------- Page: 6 ----------------------
ISO/DIS 15927-3
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 15927-3 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 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).
Introduction
This standard specifies two procedures for analysing data derived from hourly observations of wind and
rainfall so as to provide an estimate of the quantity of water likely to impact on a wall of any given orientation
in terms of both an annual average and short term spells.
The first method, which uses hourly observations of wind and rainfall, is based closely on the British Standard
method (see [1] in the Bibliography), which originated from a long series of measurements of driving rain on
buildings in a wide range of locations within the UK. As such, the method will apply to climates similar to the
UK; in other regions, with very different climates, it is recommended that confirmation of its applicability is
obtained by measurements of driving rain on representative buildings.
iv © ISO 2006 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/DIS 15927-3
Where hourly observations of wind and rain are not available, the second procedure, based on the present
weather code for rain and average wind speeds may be used.
In all cases, especially in mountainous areas, direct measurements of the rain impacting on building facades
should be made wherever possible.
Rain penetration around the edges of doors and windows or similar cracks in building façades, depends on
shorter periods of heavy rain and strong winds.
© ISO 2006 – All rights reserved v
---------------------- Page: 8 ----------------------
DRAFT INTERNATIONAL STANDARD ISO/DIS 15927-3
Hygrothermal performance of buildings — Calculation and
presentation of climatic data — Part 3: Calculation of a driving
rain index for vertical surfaces from hourly wind and rain data
1 Scope
This standard specifies two procedures for providing an estimate of the quantity of water likely to impact on a
wall of any given orientation. It takes account of topography, local sheltering and the type of building and wall.
The first method, given in Clause 4 and based on coincident hourly rainfall and wind data, defines the method
of calculation of:
⎯ the annual average index, which influences the moisture content of masonry;
⎯ the spell index, which influences the likelihood of rain penetration through masonry.
The second method, given in Clause 5 and based on average wind data and a qualitative recording of the
presence and intensity of rain (the present weather code for rain), defines a method for calculating the spell
length during which masonry is moistened, having a 10 % probability of being exceeded in any year
(commonly referred to having a mean return period of 10 years).
A comparison between the two methods is given in informative Annex D.
Procedures are given to correct the results of both methods for topography, local sheltering and the type of
building and wall.
The methods included in this standard do not apply in:
a) mountainous areas with sheer cliffs or deep gorges;
b) areas in which more than 25 % of the annual rainfall comes from severe convective storms.
2 Normative references
This standard contains no normative references.
3 Definitions, symbols and units
3.1 Definitions
3.1.1
spell
period, or sequence of periods, of wind driven rain on a vertical surface of given orientation
NOTE Further information about spells is given in Annex B.
© ISO 2006 – All rights reserved 1
---------------------- Page: 9 ----------------------
ISO/DIS 15927-3
3.1.2
airfield hourly index
quantity of driving rain that would occur on a vertical wall of given orientation per square metre of wall during
one hour at a height of 10 m above ground level in the middle of an airfield, at the geographical location of the
wall
3.1.3
airfield annual index
airfield index for a given wall orientation totalled over one year
3.1.4
airfield spell index
airfield index for a given wall orientation totalled over the worst spell likely to occur in any 3 year period
3.1.5
wall annual index
quantity of wind driven rain per square metre at a point on a wall of given orientation based on the airfield
annual index and corrections for roughness, topography, obstruction and wall factors
3.1.6
wall spell index
quantity of wind driven rain per square metre at a point on a given wall, based on the airfield spell index and
corrections for roughness, topography, obstruction and wall factors
3.1.7
line of sight
horizontal view away from the wall, over a sector spanning about 25° either side of the normal to the wall
3.1.8
terrain roughness category
classification of the surface roughness upwind in terms of the average height and spacing of obstructions such
as buildings, trees or hedges
3.1.9
roughness coefficient
factor which allows for the modification of the wind speed by the roughness of the terrain upwind of a wall
3.1.10
topography coefficient
factor which allows for the effect of local topography on the wind speed
3.1.11
obstruction factor
factor which relates to shelter from the very local environment, and allows for obstructions such as buildings,
fences and trees close to and upwind of the wall
3.1.12
wall factor
ratio of the quantity of water hitting a wall to the quantity passing through an equivalent unobstructed space,
allowing for the characteristics of the wall
3.1.13
convective storm
heavy precipitation in the form of showers or thunderstorms generally lasting less than an hour
3.1.14
reference spell
period during which a wall oriented in any given direction is moistened having an a 10 % probabili
...
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