SIST-TP CEN/TR 16999:2019

Solar energy systems for roofs: Requirements for structural connections to solar panels

This Technical Report provides guidance on the principles and requirements of structural design for the safety and serviceability of the structural connection between solar energy panels (thermal or photovoltaic) that are mounted on flat or pitched roofs.
This Technical Report does not include requirements for:
-   weather tightness of the roof, solar panels and connections;
-   electrical, thermal or mechanical characteristics of the solar panels;
-   precautions against fire of the installation.

Solare Energiesysteme für Dächer: Anforderungen an konstruktive Verbindungen zu Sonnenkollektoren

Dieses Dokument enthält Leitlinien zu den Prinzipien für und Anforderungen an die Tragwerksplanung zur Sicherstellung der Sicherheit und Gebrauchstauglichkeit der konstruktiven Verbindung zwischen Sonnenkollektoren (thermisch oder photovoltaisch) und der Konstruktion von Flach  oder Schrägdächern.
Dieses Dokument enthält keine Anforderungen für:
- die Witterungsbeständigkeit des Daches, der Sonnenkollektoren und der Anschlüsse;
- elektrische, thermische oder mechanische Eigenschaften der Sonnenkollektoren;
- Vorkehrungen gegen einen Brand der Anlage.

Systèmes d'énergie solaire pour les toits : Exigences relatives aux raccordements des panneaux solaires à la charpente

Sončni energijski sistemi za strehe: zahteve za konstrukcijske povezave solarnih plošč

V tem tehničnem poročilu so podane smernice o načelih in zahtevah glede konstrukcijske zasnove za varnost in uporabnost konstrukcijske povezave med (toplotnimi ali fotonapetostnimi) solarnimi ploščami, ki so nameščene na ravnih ali poševnih strehah.
To tehnično poročilo ne vključuje zahtev za:
– odpornost strehe, solarnih plošč in priključkov na vremenske pogoje;
– električne, toplotne ali mehanske lastnosti solarnih plošč;
– varnostne ukrepe proti požaru v napeljavi.

General Information

• Status: Published
• Public Enquiry End Date: 19-May-2016
• Publication Date: 07-Apr-2019
• ICS: 27.160 - Solar energy engineering
• Technical Committee: IKER - Ceramics
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 18-Mar-2019
• Due Date: 23-May-2019
• Completion Date: 08-Apr-2019
• Ref Project: CEN/TR 16999:2019 - Solar energy systems for roofs - Requirements for structural connections to solar panels

Standards Content (Sample)

SLOVENSKI STANDARD
SIST-TP CEN/TR 16999:2019
01-maj-2019
6RQþQLHQHUJLMVNLVLVWHPL]DVWUHKH]DKWHYH]DNRQVWUXNFLMVNHSRYH]DYHVRODUQLK
SORãþ
Solar energy systems for roofs: Requirements for structural connections to solar panels
Solare Energiesysteme für Dächer: Anforderungen an konstruktive Verbindungen zu
Sonnenkollektoren
Systèmes d'énergie solaire pour les toits : Exigences relatives aux raccordements des
panneaux solaires à la charpente
Ta slovenski standard je istoveten z: CEN/TR 16999:2019
ICS:
27.160 6RQþQDHQHUJLMD Solar energy engineering
SIST-TP CEN/TR 16999:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TP CEN/TR 16999:2019

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SIST-TP CEN/TR 16999:2019


CEN/TR 16999
TECHNICAL REPORT

RAPPORT TECHNIQUE

February 2019
TECHNISCHER BERICHT
ICS 27.160
English Version

Solar energy systems for roofs - Requirements for
structural connections to solar panels
Systèmes d'énergie solaire pour les toits : Exigences Solare Energiesysteme für Dächer: Anforderungen an
relatives aux raccordements des panneaux solaires à la konstruktive Verbindungen zu Sonnenkollektoren
charpente


This Technical Report was approved by CEN on 26 November 2018. It has been drawn up by the Technical Committee CEN/TC
128.

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: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 16999:2019 E
worldwide for CEN national Members.

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SIST-TP CEN/TR 16999:2019
CEN/TR 16999:2019 (E)
Contents Page

European foreword . 7
Introduction . 8
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 10
4 Symbols . 10
5 Configuration of solar panel installation . 10
6 Design responsibility . 10
7 Thermal solar collectors and PV solar panels . 10
8 Principles of limit state structural design . 11
8.1 General . 11
8.2 Design situations . 11
8.3 Ultimate limit state . 11
8.4 Serviceability limit state . 11
9 Determination of actions . 11
9.1 Permanent actions (G) . 11
9.2 Variable actions (Q) . 11
9.2.1 General . 11
9.2.2 Imposed loads . 12
9.2.3 Snow loads . 12
9.2.4 Wind loads . 12
9.2.5 Critical load combinations . 13
9.2.6 Load combination factor ψ . 13
9.2.7 Partial safety factors for actions . 13
9.2.8 Consequence of structural failure . 13
10 Structural resistance of connections . 14
10.1 Configuration and type of connectors . 14
10.2 Design by calculation . 14
10.3 Design assisted by testing . 14
11 Design for accidental action . 15
12 Design for seismic action . 15
Annex A (informative) Examples of connection design . 17
A.1 Fixing hook for PV solar panels mounted above tiled roof . 17
A.1.1 Description of the system . 17
A.1.2 Climate zone . 17
A.1.3 Loads . 17
A.1.3.1 Dead loads. 17
2

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A.1.3.2 Imposed load . 18
A.1.3.3 Wind and snow loads . 18
A.1.3.4 Calculation of the wind load acting on the panels . 18
A.1.3.5 Snow loads . 19
A.1.3.6 Summary of loads acting on a single panel, in directions normal to the roof and down the
roof . 19
A.1.4 Factored load combinations for the ultimate limit state . 20
A.1.5 Factored load combinations for the serviceability limit state . 21
A.1.6 Structural resistance (by test) . 22
A.1.6.1 General . 22
A.1.6.2 Characteristic Resistance . 23
A.1.6.3 Safety factors and design resistance . 24
A.1.6.3.1 General . 24
A.1.6.3.2 Ultimate Limit State for characteristic resistance by test . 24
A.1.6.3.3 Serviceability Limit State for resistance by test . 24
A.1.6.3.4 Design structural resistance values: . 24
A.1.7 Design verification – derivation of the number of hooks required . 25
A.2 Thermal solar collector on flat roof stabilized with dead weight . 27
A.2.1 Description of the system . 27
A.2.2 Climate zone . 27
A.2.3 Loads . 27
A.2.3.1 Dead loads . 27
A.2.3.2 Wind load at roof height Z . 27
A.2.4 Ultimate load case for uplift and sliding . 28
A.2.5 Serviceability limit state . 28
A.2.6 Ultimate resistance to uplift and sliding . 28
A.2.7 Design downward load on roof (concrete blocks + collector + downward wind + snow,
excluding self weight of roof structureConcrete blocks: 14x0,35x1,35 = 6,62kN
(γ = 1,35) . 29
G
A.2.8 Verify the design load and compression strength of the aluminium member BD . 30
A.2.8.1 Critical load case: Snow + downward wind . 30
A.2.8.1.1 Snow: In accordance with EN 1991-1-3: . 30
A.2.8.1.2 Wind: Downward pressure coefficient c = +1,2 . 30
p,net
A.2.8.1.3 Factored snow, wind and dead loads . 30
A.2.8.2 Compression strength of member BD . 33
A.2.9 Summary of design verification for compression member BD . 34
A.3 Connections for an in-roof solar PV system. 35
3

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CEN/TR 16999:2019 (E)
A.3.1 Description of the system . 35
A.3.2 Climate zone . 35
A.3.3 Loads . 35
A.3.3.1 Dead load . 35
A.3.3.2 Imposed loads . 35
A.3.3.3 Wind loads . 35
A.3.3.3.1 General . 35
A.3.3.3.2 External pressure coefficient . 35
A.3.3.4 Snow loads . 36
A.3.3.5 Thermal loads . 36
A.3.4 Vector load components . 37
A.3.5 Ultimate limit state load combinations . 37
A.3.5.1 Ultimate limit state criteria . 37
A.3.5.2 Load cases . 37
A.3.5.3 Vectorial load . 38
A.3.6 Serviceability limit state load combinations . 39
A.3.6.1 Serviceability limit state criteria . 39
A.3.7 Structural resistance of connections . 39
A.3.7.1 Lower side of module . 39
A.3.7.1.1 General . 39
A.3.7.1.2 Axial load . 39
A.3.7.1.3 Shear Load . 40
A.3.7.2 Upper edge of module . 41
A.3.8 Design verification (resistance ≥ loads) . 42
A.3.8.1 Lower edge of module . 42
A.3.8.2 Upper interlocking profile . 43
A.4 Earthquake resistant design of solar PV panel connections . 43
A.4.1 Description of the system . 43
A.4.2 Seismic zone . 43
A.4.3 Calculation of the seismic load acting on the panels . 43
A.4.4 Seismic load and other loads acting on a single panel . 45
A.4.5 Load Combination . 45
Annex B (normative) Supplementary information on wind actions . 47
B.1 General . 47
B.2 Terms and definitions (NEN 7250:2014/A1:2015 3.0) . 47
B.2.1 back panel (NEN 7250:2014/A1:2015 3.1) . 47
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B.2.2 building construction (NEN 7250:2014/A1:2015 3.2) . 47
B.2.3 eave height (NEN 7250:2014/A1:2015 3.3) . 47
B.2.4 photovoltaic element (NEN 7250:2014/A1:2015 3.4) . 47
B.2.5 combined element (NEN 7250:2014/A1:2015 3.5) . 47
B.2.6 closed substructure (NEN 7250:2014/A1:2015 3.6) . 47
B.2.7 façade (NEN 7250:2014/A1:2015 3.7) . 47
B.2.8 sloping roof (NEN 7250:2014/A1:2015 3.8) . 48
B.2.9 high side (NEN 7250:2014/A1:2015 3.9) . 48
B.2.10 mounting method (NEN 7250:2014/A1:2015 3.10) . 48
B.2.11 mounting method 1 (NEN 7250:2014/A1:2015 3.11) . 48
B.2.12 mounting method 2 (NEN 7250:2014/A1:2015 3.12) . 49
B.2.13 mounting method 3 (NEN 7250:2014/A1:2015 3.13) . 50
B.2.14 mounting method 4 (NEN 7250:2014/A1:2015 3.14) . 51
B.2.15 mounting method 5 (NEN 7250:2014/A1:2015 3.15) . 52
B.2.16 low side (NEN 7250:2014/A1:2015 3.16) . 53
B.2.17 substructure (NEN 7250:2014/A1:2015 3.17) . 53
B.2.18 open substructure (NEN 7250:2014/A1:2015 3.18) . 53
B.2.19 flat roof (NEN 7250:2014/A1:2015 3.19) . 53
B.2.20 thermal element (NEN 7250:2014/A1:2015 3.20) . 53
B.2.21 external dividing construction (NEN 7250:2014/A1:2015 3.21) . 54
B.2.22 solar element (NEN 7250:2014/A1:2015 3.22) . 54
B.2.23 solar energy system (NEN 7250:2014/A1:2015 3.23) . 54
B.3 Requirements for the construction (NEN 7250:2014/A1:2015 6) . 54
B.3.1 General (NEN 7250:2014/A1:2015 6.1). 54
B.3.2 Wind load (NEN 7250:2014/A1:2015 6.2) . 54
B.3.2.1 General (NEN 7250:2014/A1:2015 6.2.1) . 54
B.3.2.2 Net pressure coefficient for mounting method 1 (NEN 7250:2014/A1:2015 6.2.2) . 55
B.3.2.2.1 External pressure coefficient c , mounting method 1 (NEN 7250:2014/A1:2015
pe
6.2.2.1) . 55
B.3.2.2.2 Internal pressure coefficient, c , mounting method 1 (NEN 7250:2014/A1:2015
pi
6.2.2.2) . 55
B.3.2.2.3 Pressure equalization factor c mounting method 1, sloping roof (NEN 6.2.2.3) . 55
eq
B.3.2.2.4 Pressure equalization factor c , mounting method 1, wall (NEN 7250:2014/A1:2015
eq
6.2.2.4) . 57
B.3.2.3 Net pressure coefficients for mounting method 2 (NEN 7250:2014/A1:2015 6.2.3) . 59
B.3.2.3.1 Net Pressure Coefficient, cp,net, pitched roof, parallel (NEN 7250:2014/A1:2015
6.2.3.1) . 59
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CEN/TR 16999:2019 (E)
B.3.2.3.2 Net Pressure Coefficient, c , pitched roof, not-parallel (NEN 7250:2014/A1:2015
p net
6.2.3.2) . 60
B.3.2.3.3 Net Pressure Coefficient, c , of Mounting method 2, façade (NEN
p net
7250:2014/A1:2015 6.2.3.3) . 61
B.3.2.3.4 Net Pressure coefficient c , for mounting method 2, flat roof (NEN
p, net
7250:2014/A1:2015 6.2.3.4) . 61
B.3.2.4 Net pressure coefficient c , for mounting method 3 (NEN 7250:2014/A1:2015 6.2.4) 62
p net
B.3.2.4.1 General (NEN 7250:2014/A1:2015 6.2.4.1) . 62
B.3.2.4.2 Open support structure (NEN 7250:2014/A1:2015 6.2.4.2) . 62
B.3.2.4.3 Closed under construction (NEN 7250:2014/A1:2015 6.2.4.3) . 65
B.3.2.4.4 Load Zones (NEN 7250:2014/A1:2015 6.2.4.4) . 66
B.3.2.4.5 Roof areas (NEN 7250:2014/A1:2015 6.2.4.5) . 67
B.3.2.5 Net pressure coefficient mounting methods 4 and 5 (NEN 7250:2014/A1:2015 6.2.5) . 69
B.3.3 Determination of the design value for wind load resistance of solar energy systems
according to assembly method1 and 2 by testing (research prototype) (NEN
7250:2014/A1:2015 11.2) . 69
B.3.3.1 General (NEN 7250:2014/A1:2015 11.2.1) . 69
B.3.3.2 Principle (NEN 7250:2014/A1:2015 11.2.2) . 70
B.3.3.3 Sampling (NEN 7250:2014/A1:2015 11.2.3) . 70
B.3.3.4 Test Conditions (NEN 7250:2014/A1:2015 11.2.4) . 70
B.3.3.5 Specimen (NEN 7250:2014/A1:2015 11.2.5) . 70
B.3.3.5.1 Test Samples (NEN 7250:2014/A1:2015 11.2.5.1) . 70
B.3.3.5.2 Dimensions of the test specimen (NEN 7250:2014/A1:2015 11.2.5.2) . 70
B.3.3.5.3 Number of tests (NEN 7250:2014/A1:2015 11.2.5.3) . 70
B.3.3.5.4 Composition of the test piece (NEN 7250:2014/A1:2015 11.2.5.4) . 70
B.3.3.5.5 Equipment and apparatus (NEN 7250:2014/A1:2015 11.2.6) . 70
. 70
B.3.3.5.6 Test Procedure and evaluation (NEN 7250:2014/A1:2015 11.2.7) .
Bibliography . 73


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SIST-TP CEN/TR 16999:2019
CEN/TR 16999:2019 (E)
European foreword
This document (CEN/TR 16999:2019) has been prepared by Technical Committee CEN/TC 128 “Roof
covering products for discontinuous laying and products for wall cladding”, the secretariat of which is held by
NBN in co-operation with CEN/TC250 “Structural Eurocodes”, CEN/TC254 “Flexible sheets for
waterproofing”; CEN/TC312 “Thermal solar systems and components” and CLC/TC82 “Solar photovoltaic
energy systems”.
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.
7

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SIST-TP CEN/TR 16999:2019
CEN/TR 16999:2019 (E)
Introduction
The following is a summary of the requirements for structural design of the structural connection between
solar energy panels and the roof structure as detailed in this Technical Report.
a) Type of solar panel: Thermal or photovoltaic solar panels which comply with the mechanical resistance
requirements of EN 12975-1 (solar thermal collectors) or EN 61215 (solar PV panels).
b) Determining of the loads and load combinations: self-weight of the solar panels and relevant imposed
snow and wind actions in accordance with EN 1991-1-1, EN 1991-1-3 and EN 1991-1-4. Referring to
French Standard NF P78−116 and Dutch Standard NEN 7250 for additional data on snow and wind loads
on solar panels.
c) Determining the design loads for the solar panels: multiplication of each of the loads by their respective
partial factor γ or γ for the ultimate limit state, and separately for the serviceability limit state in
G Q
accordance with EN 1990.
d) Identifying combinations of most unfavourable design loads which act together at the same time, for the
ultimate and serviceability limit states. Modifying the loads by applying a load combination factor ψ to
one of the two variable loads which act at the same time.
e) Determining of the structural resistance of the connections between the solar panels and the roof
structure in accordance wit
...

SLOVENSKI STANDARD
kSIST-TP FprCEN/TR 16999:2016
01-maj-2016
6RQþQLHQHUJLMVNLVLVWHPL]DVWUHKH]DKWHYH]DNRQVWUXNFLMVNHSRYH]DYHVRODUQLK
SORãþ
Solar energy systems for roofs: Requirements for structural connections to solar panels
Solare Energiesysteme für Dächer: Anforderungen an konstruktive Verbindungen zu
Sonnenkollektoren
Systèmes d'énergie solaire pour les toits : Exigences relatives aux raccordements des
panneaux solaires à la charpente
Ta slovenski standard je istoveten z: FprCEN/TR 16999
ICS:
27.160 6RQþQDHQHUJLMD Solar energy engineering
kSIST-TP FprCEN/TR 16999:2016 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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kSIST-TP FprCEN/TR 16999:2016

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kSIST-TP FprCEN/TR 16999:2016


FINAL DRAFT
TECHNICAL REPORT
FprCEN/TR 16999
RAPPORT TECHNIQUE

TECHNISCHER BERICHT

March 2016
ICS 27.160
English Version

Solar energy systems for roofs: Requirements for
structural connections to solar panels
Systèmes d'énergie solaire pour les toits : Exigences Solare Energiesysteme für Dächer: Anforderungen an
relatives aux raccordements des panneaux solaires à la konstruktive Verbindungen zu Sonnenkollektoren
charpente


This draft Technical Report is submitted to CEN members for Vote. It has been drawn up by the Technical Committee CEN/TC
128.

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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey 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 Technical Report. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a Technical Report.


EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprCEN/TR 16999:2016 E
worldwide for CEN national Members.

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kSIST-TP FprCEN/TR 16999:2016
FprCEN/TR 16999:2016 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols . 6
5 Configuration of solar panel installation . 6
6 Design responsibility . 6
7 Thermal solar collectors and PV solar panels . 6
8 Principles of limit state structural design . 6
8.1 General . 6
8.2 Design situations . 7
8.3 Ultimate limit state . 7
8.4 Serviceability limit state . 7
9 Determination of actions . 7
9.1 Permanent actions (G) . 7
9.2 Variable actions (Q) . 7
9.2.1 General . 7
9.2.2 Imposed loads . 7
9.2.3 Snow loads . 7
9.2.4 Wind loads . 8
9.2.5 Critical load combinations . 8
9.2.6 Load combination factor ψ . 9
9.2.7 Partial safety factors for actions . 9
9.2.8 Consequence of structural failure . 9
10 Structural resistance of connections . 9
10.1 Configuration and type of connectors . 9
10.2 Design by calculation . 9
10.3 Design assisted by testing . 10
11 Design for accidental action . 11
12 Design for seismic action . 11
Annex A (informative) Examples of connection design . 13
A.1 Fixing hook for PV solar panels mounted above tiled roof . 13
A.2 Thermal solar collector on flat roof stabilized with dead weight . 23
A.3 Connections for an in-roof solar PV system . 31
A.4 Earthquake resistant design of solar PV panel connections . 39
Bibliography . 43

2

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kSIST-TP FprCEN/TR 16999:2016
FprCEN/TR 16999:2016 (E)
European foreword
This document (FprCEN/TR 16999:2016) has been prepared by Technical Committee CEN/TC 128 “Roof
covering products for discontinuous laying and products for wall cladding”, the secretariat of which is held
by NBN in co-operation with CEN/TC250 “Structural Eurocodes”, CEN/TC254 “Flexible sheets for
waterproofing”; CEN/TC312 “Thermal solar systems and components” and CLC/TC82 “Solar photovoltaic
energy systems”.
This document is currently submitted to the vote on TR.
3

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kSIST-TP FprCEN/TR 16999:2016
FprCEN/TR 16999:2016 (E)
Introduction
The following is a summary of the requirements for structural design of the structural connection between
solar energy panels and the roof structure as detailed in this Technical Report.
a) Type of solar panel: Thermal or photovoltaic solar panels which comply with the mechanical resistance
requirements of EN 12975-1 (solar thermal collectors) or EN 61215 (solar PV panels).
b) Determining of the loads and load combinations: self-weight of the solar panels and relevant imposed
snow and wind actions in accordance with EN 1991-1-1, EN 1991-1-3 and EN 1991-1-4. Referring to
French Standard NF P78−116 and Dutch Standard NEN 7250for additional data on snow and wind loads
on solar panels.
c) Determining the design loads for the solar panels: multiplication of each of the loads by their respective
partial factor γ γ for the ultimate limit state, and separately for the serviceability limit state in
G or Q
accordance with EN 1990.
d) Identifying combinations of most unfavourable design loads which act together at the same time, for the
ultimate and serviceability limit states. Modifying the loads by applying a load combination factor ψ to
one of the two variable loads which act at the same time.
e) Determining of the structural resistance of the connections between the solar panels and the roof
structure in accordance with calculation methods of one or more of the following European Standards:
— EN 1992 series to EN 1996 series, and EN 1999 series for the ultimate and serviceability limit
states;
— For the serviceability limit state, determining of the resistance at the specified maximum
deformation limiting the function of the connection;
or
— determine the resistance by serviceability and ultimate load tests.
f) Verifying the design by confirming that the factored structural resistance is not less than the critical
combinations of factored actions for both limit states.
Four examples of design calculations for different solar panel connections are given in Annex A.
4

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kSIST-TP FprCEN/TR 16999:2016
FprCEN/TR 16999:2016 (E)
1 Scope
This Technical Report provides guidance on the principles and requirements of structural design for the
safety and serviceability of the structural connection between solar energy panels (thermal or photovoltaic)
that are mounted on flat or pitched roofs.
This Technical Report does not include requirements for:
— weather tightness of the roof, solar panels and connections;
— electrical, thermal or mechanical characteristics of the solar panels;
— precautions against fire of the installation.
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 1990:2002/A1:2005, Eurocode - Basis of structural design
EN 1991 (all parts), Eurocode 1 - Actions on structures
EN 1992 (all parts), Eurocode 2 - Design of concrete structures
EN 1993 (all parts), Eurocode 3 - Design of steel structures
EN 1994 (all parts), Eurocode 4 - Design of composite steel and concrete structures
EN 1995 (all parts), Eurocode 5 - Design of timber structures
EN 1995-1-1:2004/A2:2014 Eurocode 5 - Design of timber structures - Part 1-1: General - Common rules and
rules for buildings
EN 1996 (all parts), Eurocode 6 - Design of masonry structures
EN 1997 (all parts), Eurocode 7 - Geotechnical design
EN 1998 (all parts), Eurocode 8: Design of structures for earthquake resistance
EN 1998-1:2004/A1:2013, Eurocode 8: Design of structures for earthquake resistance - Part 1: General rules,
seismic actions and rules for buildings.
EN 1999 (all parts), Eurocode 9: Design of aluminium structures
EN 1999-1-1:2007/A2:2013, Eurocode 9: Design of aluminium structures - Part 1-1: General structural rules
NEN 7250:2014, Zonne-energiesystemen - Integratie in daken en gevels - Bouwkundige aspecten
3 Terms and definitions
For the purposes of this document, the terms and definitions for structural design given in EN 1990, the
EN 1991 series, the EN 1992 series, the EN 1993 series, the EN 1994 series, the EN 1995 series, the EN 1996
series, the EN 1997 series, the EN 1998 series, and the EN 1999 series apply.
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4 Symbols
For the purposes of this document, the symbols for structural design given in EN 1990, the EN 1991 series,
the EN 1992 series, the EN 1993 series, the EN 1994 series, the EN 1995 series, the EN 1996 series, the
EN 1997 series, the EN 1998 series, and the EN 1999 series apply.
5 Configuration of solar panel installation
The configuration of solar panel installations is classified by the method of mounting on the roof structure,
as given in NEN 7250:2014, Clause 3.
6 Design responsibility
The designer should ensure that:
— The choice of the structural system and the design of the structural connections are made by
appropriately qualified and experienced personnel.
— Adequate supervision and quality control are provided in design offices, factories and on site.
— The structure will be adequately maintained.
— The structure will be used according to the design assumptions.
— The building structure can safely support the solar panels according to Eurocode standards of design;
building retrofitted with solar panels should also be checked.
7 Thermal solar collectors and PV solar panels
Thermal solar collectors and PV solar panels are collectively called solar panels in this Technical Report.
Thermal solar collectors should comply with EN 12975–1, according to the manufacturer’s declared
requirements.
PV solar panels should comply with the requirements of EN 61215 or EN 61646.
The structural resistance of the body of solar panels is not considered in this Technical Report. It is assumed
that their structural resistance is adequate. Attention is drawn to high snow loads in certain areas of Central
and Northern Europe (see EN 1991–1-3:2003/A1:2015, Annex C), acting together with downward wind
loads, which should be compared with the structural resistance of solar panels determined by ‘mechanical
load tests’ incorporating adequate safety factors.
8 Principles of limit state structural design
8.1 General
Structural design should be carried out according to the principles of limit states of EN 1990. The ultimate
limit state and the serviceability limit state should both be considered, for relevant design situations.
For each limit state:
— the design value of an action is its characteristic value multiplied by the appropriate partial safety factor
for the action;
— the design value of the resistance is its characteristic value divided by the appropriate partial safety
factor for the material, which should be not less than the design value of the action.
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8.2 Design situations
Design situations to be considered are actions which are:
— persistent (conditions of normal use, from dead loads, wind and snow loads, and other imposed loads);
— induced loads from thermal action due to temperature variation (e.g. for mounting beams of solar
panels);
— transient loads (e.g. during execution or repair);
— accidental actions (for exceptional conditions e.g. explosion, impact, disproportionate consequence of
local failure);
— seismic actions (in seismic locations only).
The most unfavourable combinations of actions which act together at the same time should be considered in
design. They may include loads which are applied in different directions.
8.3 Ultimate limit state
The ultimate limit state concerns the safety of people and/or the structure when failure of the structure
occurs by excessive deformation, transformation into a mechanism or loss of stability.
8.4 Serviceability limit state
The serviceability limit state concerns the deformation, vibration or damage of the structure under normal
use which affect its function, appearance, or discomfort to people.
9 Determination of actions
9.1 Permanent actions (G)
The characteristic value of self-weight of the solar panel and its structural connection should be taken as its
mean value.
Indirect actions, e.g. caused by irreversible deformation, are also classed as permanent actions.
9.2 Variable actions (Q)
9.2.1 General
Variable actions are imposed loads, wind and snow loads, and loads induced by thermal movement (e.g. for
mounting beams)
The characteristic load values for snow and wind speeds may vary with location and may be given in
National Annexes to the standard.
9.2.2 Imposed loads
Imposed loads are in accordance with EN 1991-1-1.
9.2.3 Snow loads
9.2.3.1 General
Snow loads are in accordance with EN 1991-1-3 and the relevant National Annex. Supplementary
information on increased snow load on solar panels at the eaves of pitched roofs in climatic conditions
where melting, sliding and re-freezing of snow can occur, is given in NF P78-116.
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9.2.3.2 Return period
The ground snow load value may be adjusted according to the return period adopted (see EN 1991-1-
3:2003/A1:2015, Annex D), if specified by the National Annex. The return period may be based on the
expected design life of the solar panel connections.
9.2.3.3 Sliding snow loads on pitched roofs
Sliding snow loads which act on the framework and connections of solar panels which project above the
pitched roof surface should be determined according to EN 1991-1-3:2003/A1:2015, 6.4. They may occur at
the same time as vertical snow loads and snow drift loads. Solar panel elements are not designed to resist
sliding snow load.
To protect solar panels projecting above the roof surface from heavy sliding snow loads from a long length
of pitched roof, snow guards are recommended to be installed up-slope of the solar panels. Where the
projected height of the solar panels is greater than that of the snow guard, snow drift loads should be
assumed to act on the difference in projected height.
9.2.4 Wind loads
9.2.4.1 General
The modelling of wind velocity and peak velocity pressure is given in EN 1991-1-4. For site-specific data on
climatic information, wind speed distribution maps and altitudes, refer to the relevant National Annex to
EN 1991-1-4.
The dynamic pressure of the wind should be derived in accordance with EN 1991-1-4 based on the peak
velocity pressure. The characteristic wind load is the dynamic pressure modified by terrain, height and wind
pressure coefficients according to the shape and orientation of the structure.
Pressure coefficients for roofs of certain building configurations are given in EN 1991-1-4. Information on
pressure coefficients for various mounting configurations of solar panels on roofs and façades is given in
NEN 7250.
The effect of wind loads on the roof surface with solar panels installed above it should be considered.
9.2.4.2 Return period
The wind speed may be adjusted according to the return period adopted (see EN 1991-1-4), which is
normally assumed to be not less than 25 years, unless otherwise specified by the National Annex.
9.2.5 Critical load combinations
The following are load combinations which may act together at the same time on solar panels and their
connections:
— dead load + imposed load;
— dead load + snow load (including sliding snow for pitched roofs) + wind (downward);
— dead load + wind load (upward);
— loads induced by thermal action [for mounting beams].
The most unfavourable load combinations in magnitude and load direction should be adopted for design.
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9.2.6 Load combination factor ψ
Where the leading variable action occurs at the same time as other variable actions, the value of the other
variable actions may be reduced by multiplying by combination factors ψ (See EN 1990 and design
examples in A.1 and A.2).
9.2.7 Partial safety factors for actions
The design value of an action is the characteristic value multiplied by partial safety factor γ or γ
G Q.
For the ultimate limit state:
— permanent actions: in favourable load combination γ = 1,0;
G
— in equilibrium condition, e.g. dead load solely providing stability γG = 0,9;
= 1,35;
— in unfavourable load combination γG
— variable actions: γ = 1,50.
Q
Where design is assisted by wind tunnel testing using an appropriate model of the structure and of the
natural wind (see EN 1991–1-4), the value of γ for wind action may be taken as 1,35.
Q
For the serviceability limit state:
— permanent and variable actions, γ = 1,0; γ = 1,0.
G Q
9.2.8 Consequence of structural failure
Where permitted nationally, solar panels installed on buildings in normal conditions of use may be
designated with a consequence class CC1 (EN 1990:2002/A1:2005, Table B.1) corresponding to Reliability
Class RC1.
For RC1, a multiplying consequence factor K = 0,9 should be applied to unfavourable actions (ultimate limit
FI
state only).
For installations requiring consideration of higher risk, see EN 1990:2002/A1:2005, B.3.
10 Structural resistance of connections
10.1 Configuration and type of connectors
The arrangement in number, position and spacing of connectors to solar panels should be not less
favourable than the arrangement adopted in the mechanical load test for the body of the solar panel.
10.2 Design by calculation
The structural resistance should be determined by calculation in accordance with one or more Eurocodes
the EN 1992 series, the EN 1993 series, the EN 1994 series, the EN 1995 series, the EN 1996 series and the
EN 1999 series, for both the ultimate and serviceability limit states, to support adequately the most
unfavourable load combinations.
The design resistance is the lesser of the characteristic strength at the ultimate limit state, or at the
serviceability limit state, divided by a material partial factor γ
M.
Values of γ at the ultimate limit state are specified in the relevant Eurocode for structural materials: the
M
EN 1992 series, the EN 1993 series, the EN 1994 series, the EN 1995 series, the EN 1996 series and the
EN 1999 series (see design examples C1 and C2). The value of γ for the serviceability limit state is 1,0.
M
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10.3 Design assisted by testing
In accordance with EN 1990:2002/A1:2005, Annex D, design may be based on a combination of tests and
calculations.
Testing to determine the resistance of the structure or part of the structure may be carried out, for example,
in the following circumstances if:
— adequate calculation models are not available;
— a large number of components are to be used;
— it is necessary to confirm, by control checks, assumptions made in the design.
Test specimens should be specified or obtained by sampling in such a way as to represent the conditions of
the real structure, and to obtain a statistically representative sample.
The rate of loading should where possible reflect actual conditions. Where the material of the structure has
significant time dependent effects on strength and deformation (e.g. timber – see EN 1995-1-1), the test
results should be modified to take into account the difference in load durations between testing and the
design conditions. Tests should be continued until failure occurs, recording load increments and deflections.
The characteristic strength should be the 5 % characteristic value based statistically on the Normal
Distribution of a population of test results (EN 1990:2002/A1:2005, Table D1). The minimum population of
tests results should be 3.
The design resistance value for the ultimate load condition is the characteristic value divided by γ > 1, 0.
M
Values of γ vary according to the type of structural material (See relevant Eurocode: EN 1990, the EN 1991
M
series, the EN 1992 series, the EN 1993 series, the EN 1994 series, the EN 1995 series, the EN 1996 series,
the EN 1997 series, the EN 1998 series, or the EN 1999 series).
The design resistance at the limit of serviceability should also be the 5 % characteristic value.
The design resistance at the limit of serviceability is the characteristic value divided by γM = 1,0.
The minimum design resistance is the lesser of the ultimate load and serviceability conditions.
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Figure 1 — Resultant value for the load
Where separate tests are carried out on two loads each acting in different directions, the resultant value for
the loads acting together may be obtained vectorally by Formula (1):
1
F = (1)
rd
2 2
(cosαα/VN) +(sin / )
 rd  rd
where
N is the design resistance of the anchor point acting normal to the roof;
rd
V is the design resistance of the anchor point acting parallel to the roof;
rd
F is the resultant design resistance acting at an angle α.
rd
For a test method to determine the wind uplift resistance, see NEN 7250:2014, 11.2.
11 Design for accidental action
Solar panel installations normally would not induce progressive collapse of the building to which they are
attached, therefore no special measures are required against accidental actions for the structural
connections.
In exceptional conditions of high consequence of failure, EN 1991-1-7 provides design advice.
12 Design for seismic action
Design for seismic action should be in accordance with the EN 1998 series and is required only in
earthquake areas as indicated in relevant National Annexes to the EN 1998 series, or in national building
regulations.
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National seismic design requirements and standards should also be adopted. The design should validate
both seismic and non-seismic design situations.
Solar panels connected to the roof structure should normally be regarded as ‘non-structural elements’ or
’appendages’ of buildings as defined in the EN 1998 series.
Unless otherwise specified, the effect of seismic action may be determined by applying to the non-structural
element a horizontal force Fa, defined in the EN 1998 series as:
F = SW y / g (2)
a a aa a
S αS 3 1+ z(/ / 1+−1 T /T 2−0,5 but SS≥α (3)
( ) ( )
( ( ) )
a a i a
where
F is the horizontal seismic force, acting at the centre of mass of the non-structural elements in the
a
most unfavourable direction;
W is the weight of the element;
a
S is the seismic coefficient for non-structural elements, defined in Formula 3.
a
γ is the importance factor of the element, taken as 1,0;
a
q is the behaviour factor of the element, taken as 1,0;
a
α is the ratio of the design ground acceleration on type A ground, ag, to the acceleration of gravity g
S is the soil factor;
T is the fundamental vibration period of the non-structural element;
a
T is the fundamental vibration period of the building in the relevant direction;
i
z is the height of the non-structural element above the level of application of the seismic action
(foundation or top of a rigid basement);
H is the building height measured from the foundation or from top of a rigid  basement.
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Annex A
(informative)

Examples of connection design
A.1 Fixing hook for PV solar panels mounted above tiled roof
A.1.1 Description of the system
A solar roof hook is used to connect solar panels above a covering of roof tiles. Different generic types of
connection are shown in Figure A.1. The base of the roof hooks in Figures A.1a and A.1b are screwed to the
rafters. The hook then passes around the roof tiles, usually via the h
...