Are You ‘PV Ready’?

Therefore, the chance of sharp tools dropping onto the roof surface or impact damage from heavy traffic or equipment installation is increased. That’s why enhancing the puncture resistance of membranes used with rooftop PV systems can be so important. Solutions may include protective coverboards when practical or other options for existing roofs, such as roof walkway pads.

In fact, some roof system manufacturers require an approved insulation board with a minimum thickness and compressive strength, the addition of an approved coverboard to enhance insulation protection, and/or an approved protection/separation sheet installed between the PV components and the membrane. Protection pads should be large enough and properly secured so they do not move during expansion and contraction of the roof membrane.

Membrane Type and Thickness

The roof on Old Dominion Freight Line Inc.’s vault logistics facility in Thomasville, N.C., features almost 7,700 solar panels. The panels produce enough power (1.8 megawatts) to offset more than 90 percent of the building’s annual energy costs. Photo courtesy of Old Dominion Freight Line Inc., Thomasville, N.C.

The roof on Old Dominion Freight Line Inc.’s vault logistics facility in Thomasville, N.C., features almost 7,700 solar panels. The panels produce enough power (1.8 megawatts) to offset more than 90 percent of the building’s annual energy costs. Photo courtesy of Old Dominion Freight Line Inc., Thomasville, N.C.


A broad selection of membranes and thicknesses are available for consideration when a PV installation is planned.
For example:

  • • EPDM, PVC, TPO, KEE and CPA smooth and fleece-back membranes
    • APP and SBS modified bitumen membranes
    • Certain types of “enhanced” membranes engineered for use with PV. These membranes may include special formulations designed to accommodate the additional heat generated by the PV array or other sources. Your roofing manufacturer’s representative or regional sales manager will have more information about these specially formulated single-ply membranes.

In approving the installation of a PV system upon an existing warranted roof and maintaining the warranty, membrane manufacturers may have PV-system-specific requirements the existing roof must meet, such as:

  • • Limitations on the current age of the existing roof system
    • Restrictions on the method of roof system attachment to the structural deck
    • Restrictions for a minimum approved roof membrane thickness
    • Pre-solar and post-solar system installation roof inspections
    • A requirement that the building owner make any needed repairs at his expense

As you’ve probably guessed by now, it’s generally best to contact the roofing manufacturer for help deciding on a membrane, its thickness and/or existing roof requirements.

Paperwork

Roofing manufacturers frequently require project documentation forms be completed before installing a PV system over an existing warranted roof to maintain warranty coverage. For example:

  • • A Standard Pre-Installation Notice with Roof Drawings
    • A PV Post Warranty Alteration Form
    • Completed Inspection Reports (before and after PV installation)
    • “Overburden (O/B) Waiver Form” completed by the building owner, wherein the owner
  • 1. Describes the PV materials to be installed (the “overburden”)
  • 2. Agrees to pay for the overburden removal when leak repairs are necessary
  • 3. Agrees to pay for repairs caused by the overburden removal and replacement

There are a variety of other general terms, conditions and suggestions that should be considered when installing PV systems on existing roofs:

  • • Racks should have enough clearance above the membrane to allow for roof servicing.
    • Set PV arrays so all field seams and penetrations are accessible for repair.
    • Staging areas for PV materials for installation should be identified and protected.

Many roofing system manufacturers offer certain services to building owners in addition to the sale of roofing system products. For example:

  • • Solar products
    • Financial analyses to show returnon- investment payback period for a planned solar installation
    • Specifications and details for the roofing and solar system installations
    • Solar roof layouts
    • A single-source warranty for the roof system and the solar integration
    • Warranty insurance that pays for the cost of overburden removal, if needed

There is no question that partnering with a roof system manufacturer that offers PV-ready roofing systems can be a big benefit to the roofing contractor. However, it is important to remember that each SPRI member may have its own PV-ready program and no SPRI member may necessarily have all the previously mentioned program elements. Always consult the manufacturer
of the roof system specified for your new construction or reroofing project prior to the installation of a PV system on a warranted roof.

More Information

Visit SPRI’s website or email the association.

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About Mike Ennis, RRC

Mike Ennis joined SPRI in 1993. He has chaired a variety of SPRI committees and task forces and served as president from 2004-06. He became technical director of SPRI in 2007.

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