Self-flashing mounts for solar PV systems explained

Roof Tech mount

Point of entry. Photo courtesy of Roof Tech.

“Self-flashing mounts” is perhaps a new term for the PV mounting industry. It is a unique concept, so let’s look at how it should be interpreted.

Flashing defined

Perhaps we begin by interpreting the word “flashing” from the IRC (International Residential Code):

IRC R903.2 FLASHING

Flashings shall be installed in a manner that prevents moisture from entering the wall and roof through joints in copings, through moisture permeable materials and at intersections with parapet walls and other penetrations through the roof plane.

There is no specific standard about flashing for solar attachments to a roof.

So the real question as far as flashing goes, or as I’d like to say “where rubber meets the road” is how is the roof penetration being sealed up? The penetration being the very point of entry through the roof, the underlayment and into the wood by the lag or wood screw.

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With that in mind, one will realize that flashing really is nothing more than the sealant used on the very point of entry. Which brings us to the concept of “flexible flashing,” which is simply a synthetic material produced and tested for durability and water resistance used to seal the penetration on a roof in the case of our industry.

Self-flashing, then, is defined as the self-sealing of the penetration as the mounting gets fastened to the roof. So, the idea of self-flashing not only addresses the sealing of the penetration but usually avoids the breaking or disturbing the seal on roof asphalt shingles (steep slope roof).

flashing test Roof Tech

ASTM 2140 (Immersion test, 6 inches of water for 6 hours). Photo Courtesy of Roof Tech.

Unlike “pipe flashings” or metal flashings, flexible flashing can be tested beyond the UL 441 standard for pipe flashing. Because of its flexibility and being 100 percent weatherproof, flexible flashing is tested under a column of water (hydrostatic pressure).

roof tech water immersion

ICC –ES AC 75 (5” of water immersion for three days at 4° Celsius). Photo Courtesy of Roof Tech

There are different types or formulations and all must be provided with an MSDS (Material Safety Data Sheet). The following is a list of mounts that are fastened with woodscrews right and a flexible flashing.

  • Dynoraxx — Butyl tape
  • Preformed Line Products — Butyl Tape
  • ROOF TECH — Butyl Tape
  • S-5 — Butyl Tape
  • Sol Attach — Butyl Tape

To further evaluate products among manufacturers with flexible flashing, we recommend looking at the documentation provided and third party testing/certification. Roof Tech for instance has an ICC evaluation report maintained by the ICC Evaluation Services with yearly factory inspections for quality.

Milton Nogueira is the senior business development manager at Roof Tech, a wholly subsidiary of Yanegiken, a pioneer of self-flashing solar mounting systems since 1994 in Japan.

— Solar Builder magazine

[source: https://solarbuildermag.com/mounting-solutions-guide/self-flashing-mounts-for-solar-pv-systems-explained/]

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