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Rooftop Photovoltaic Systems – Windstorm Guidelines
Highly Protected Risk (HPR) Asset Protection “starts on the roof”
Overview
The roof is a building’s most critical and yet most vulnerable asset.
When the wind begins to blow, all elements of the roof must perform
uniformly including equipment that is installed on the roof. Similar to
how seatbelts function in a car, well designed rooftop equipment
securement will prevent equipment movement up to the limits of thestructure’s design. Roof mounted Photovoltaic (PV) electric power
generation systems present unique engineering design challenges ascompared to other roof mounted equipment. When subjected to highwinds, inadequately secured PV systems may become dislodged
resulting in severe damage system, roof cover and structure making
the building more vulnerable to the ongoing wind threat.
Typical rooftop PV system with panels near the roof
edges

PurposeCommon PV system installation practices
expose your roof to severe windstorm
damageThis guideline is intended to draw attention to typical rooftop PV System installation
practices and deficiencies. Despite close attention being paid to windstorm
resistance for roof structures and roof covers; rooftop equipment including mostPV systems are commonly installed without any means for securement other thanweight. Also, often there is less rigorous control over the methods used to secure
PV systems when the installation occurs in between new construction or re-roofing
projects. When improperly secured, PV system components may become
dislodged during high winds resulting in windborne debris damage to otherequipment and the roof cover. In addition, damaged PV systems have the potentialto become a significant rooftop fire ignition source. When rooftop equipment is notwell secured, damage to the roof makes all of the assets within the facility more
vulnerable to numerous hazards. From a risk assessment standpoint, a building’s
roof is a single point failure mode potential. Utilizing the approach outlined in thistechnical resource will equip the user to address PV system securement in bothconstruction and retrofit circumstance.

Rooftop Photovoltaic Systems – Windstorm Guidelines
Rooftop PV System Securement – General Guidelines
Tokio Marine America (TMA) HPR Property Loss Control recommends following Factory Mutual (FM) datasheets forbest protection against Natural Hazards. These windstorm guidelines adhere to the technical advice detailed in thereferenced documents. Whether considering new construction, major renovations, maintenance related roof
replacement or repairs or updating your risk management plan, follow the TMA HPR Loss Control “WIND” advice asa best practice.
Wherever your facility is located, all new important structures
should be designed to meet applicable standards

Investigate all existing important structures for conformance toappropriate standards

Necessary retrofit upgrades should be strategically consideredfollowing the advice of your Account Team

Decide in advance to meet these guidelines by inclusion incorporate design specifications
TMA HPR Loss Control Plan Review services areavailable to assist with your project

Equipment installed on roofs generally needs to be secured to the structure in a mannerequivalent to or exceeding the strength of the structure itself. If this is not the case,rooftop equipment will become dislodged at a lower wind speed than the roof and roof
cover. When rooftop PV equipment becomes dislodged, its components can damage
the roof cover and the damaged system may result in a fire involving roof above-deckcomponents. This may also cause premature failure of the roof cover or structure duringhigh wind exposure. Securing rooftop equipment protects the building, roof cover andWhile mechanically secured, thisits contents from unexpected additional damage.
system lacks fasteners at every seam

Rooftop PV Equipment Securement - Best Practices
Advanced planning during the design and installation of new roof mounted PV systems is the key method to help
prevent wind uplift damage to a PV system mounted on a roof. All new installations should adhere to the technicalguidance in this guideline and the applicable resources. Existing systems are difficult to modify once installed without
significant cost associated with a revised design and re-installation. However, in consultation with your TMA HPR
Property Account Team, existing systems should be considered for practical retrofits to limit the potential for severe
property damage and business interruption.

Tokio Marine Management, Inc. does not represent, warrant, or guarantee the appropriateness, validity or accuracy of this information in everysituation. This information does not necessarily cover every
possible condition, protection, hazard, situation or exposure and is not warranted to comply with laws, regulations, codes or standards in every jurisdiction. This information is representative of reasonable
practices in the industry. However, you may wish to investigate whether these recommendations are applicable to your specific operations. Loss control is the responsibility of your management.
© 2020 Tokio Marine America, All Rights Reserved.

2|P a g eRooftop Photovoltaic Systems – Windstorm Guidelines
Ballasted PV solar panel systems: PV solar panels systems that are not mechanically secured to thestructure should only be installed as follows:o Do not install a ballasted PV solar panel system on a roof
where a ballasted roof cover would not be permitted due to theexposure (e.g. > 110 mph).
o Ballasted PV solar panel systems should only be installed on
roofs with a slope not exceeding ½ in. per foot.
o Do not consider installing a PV solar panel system over a roof
cover with aggregate such as pea gravel or stone ballast.
o A ballasted roof cover that utilizes a complete paver block
surface such as an ‘inverted membrane’ roof cover may be suitable
for the installation of a ballasted PV solar panel system.
o Utilize concrete paver blocks that meet the specifications ofASTM C1491 and tested in accordance with ASTM C1262.
o Concrete paver blocks used for ballast should be well secured
using slotted or flanged pedestals or paver trays.
This installation violates several “best practices” making it
o A PV solar panel system should not be installed above single
more vulnerable to wind damage
ply, mechanically secured roof covers such as TPO, EPDM, PVC,etc.
o In lower wind speed zones, entirely ballasted systems are tolerable.
 Install ballasted systems in the ‘field’ of the roof away from the edges and corners.
 Increase the ballast rate prescriptively by 50 % for all PV solar panels along all edges of thearrays including edges located in the middle of the roof.
o All related equipment such as combiner and junction boxes, conduits, etc. should be mechanicallyattached to the structure. The dead weight of this related equipment is not sufficient to withstand windforces even when the array itself may be.
o The manufacturer’s windstorm testing should be completed using a Boundary Layer Wind Tunnel(BLWT) test that better simulates wind flow towards a building.
 A manufacturer’s windstorm test conducted using an Aerospace Wind Tunnel (AWT) or
computational fluid dynamics modeling is not considered acceptable.
o Installation of a ballasted PV solar panel system should be designed to meet the requirements of thereferenced guidelines.
Mechanically Secured PV Solar Panel Systems: Complete or partial mechanical securement alone or in
combination with ballast offers far superior protection against wind forces. When a fully ballasted arrangement
does not offer sufficient protection based upon the above guidelines, utilize the options below for bestprotection.
o Install an entirely mechanically secured PV Solar Panel System utilizing the services of a licensed
structural engineer. The system should be designed using the effective wind area for each anchor per
the referenced documents.

Secure panels within the array perimeter zone using anchors designed using the services of a licensed structuralengineer. The perimeter zone is two times the height of the building as measured from the edge of the roof. Allpanels within the interior zones may be ballasted.

Tokio Marine Management, Inc. does not represent, warrant, or guarantee the appropriateness, validity or accuracy of this information in everysituation. This information does not necessarily cover every
possible condition, protection, hazard, situation or exposure and is not warranted to comply with laws, regulations, codes or standards in every jurisdiction. This information is representative of reasonable
practices in the industry. However, you may wish to investigate whether these recommendations are applicable to your specific operations. Loss control is the responsibility of your management.
© 2020 Tokio Marine America, All Rights Reserved.

3|P a g eRooftop Photovoltaic Systems – Windstorm Guidelineso

Provide additional setback for the array from the edge of the roof to reduce the effective wind load on
the array to permit more feasible ballast or anchor design. This approach may be especiallyappropriate in high basic wind speed zones where it may be very difficult to effectively secure panelsin the corner and perimeter zones.

PV Solar Panel Systems on Standing Seam Roofs (SSR): Install rigid PV solar panels on a standing seamroof (SSR) using external seam clamps (ESC’s).
o An ESC should be installed at every seam to ensure that theinstallation will match the load path of the SSR as designed by themanufacturer.
o Ideally, the ESC’s utilized should be approved for the SSR on which
they are used when available.
o The ESC’s should be torqued per the SSR manufacturer’s instructions
and inspected prior to acceptance and periodically during systeminspections.
 Hail Hazards: The PV solar panels chosen should specifically be rated
for the hail exposure present at the location of installation. When the hail
exposure exceeds the rating of the PV solar panels installed, all of thepanels are likely to be damaged when the predicted hail event occurs.

PV solar panels are highly susceptible to hail

Summary of the Risk
The risk of damage to your facility during a windstorm is significant and may result from many factors. Windstorms,
hail and other natural perils have the potential to severely damage rooftop mounted PV Solar Panel Systems. Thereis also the added potential for a fire originating within damaged equipment following the storm. The best risk
management approach is to ensure adequate protection during the design process because retrofits may be costly.
Prior to considering adding a rooftop mounted PV Solar Panel System, begin outside on the roof with a windstorm
risk engineering assessment. The most effective means to protect the assets located both within and on your facility
is to take the necessary steps during new construction, re-roofing and renovations to ensure your investments arewell protected when nature strikes.

Summary of the Risk Reference Documents
FM Data Sheet 1-15 “Roof Mounted Solar PV Panels”
FM Data Sheet 1-28 “Wind Design”
FM Data Sheet 1-31 “Panel Roof Systems”
FEMA Document “Rooftop Solar Panel Attachment: Design, Installation, and Maintenance”

A service of the Tokio Marine America Loss Control Department.
TMM is committed to the highest customer trust.
We exist to deliver ANSHIN (safety, security and peace of mind) to our customers by providing the highest quality services.
This information is provided solely as a client service. Tokio Marine Management, Inc. does not represent, warrant, or guarantee the appropriateness, validity or accuracy of this information in every situation.
This information does not necessarily cover every possible condition, protection, hazard, situation or exposure and is not warranted to comply with laws, regulations, codes or standards in every jurisdiction.
This information is representative of reasonable practices in the industry. However, you may wish to investigate whether these recommendations are applicable to your specific operations. Loss control is theresponsibility of your management. | © 2020 Tokio Marine America, All Rights Reserved.
Tokio Marine America (TMA) is the marketing name for Tokio Marine America Insurance Company (TMAIC), Trans Pacific Insurance Company (TPI), and TNUS Insurance Company (TNUS).

Revised 4/28/2021