[RE-wrenches] Attaching Array To or Through Ply
Lloyd Hoffstatter
lloyd at sunstruckconsulting.com
Thu Mar 30 06:48:59 PDT 2023
System installed on Loggerhead Key in 2002 with spacing between subarrays and back bolted still there after much hurricane activity (John Calhoun design)[X]
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From: RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> on behalf of Christopher Warfel via RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Thursday, March 30, 2023 7:34:20 AM
To: re-wrenches at lists.re-wrenches.org <re-wrenches at lists.re-wrenches.org>
Cc: Christopher Warfel <cwarfel at entech-engineering.com>
Subject: Re: [RE-wrenches] Attaching Array To or Through Ply
If you look at FEMA's design guide for solar installations in FL and the Caribbean, the recommended module to rail attachment method is back to using the attachment holes in the solar module. Chris
On 3/30/2023 5:56 AM, Jason Szumlanski via RE-wrenches wrote:
This thread has morphed into more than it started as, and for good reason. I want to provide some practical/anecdotal information, having just gone through arguably the most catastrophic wind event in Florida's history (Ian) since the boom in solar energy started, and another major wind event (Irrma) just 5 years ago.
First, Aside from the Sunmodo and Quickbolt decking-only products, I would check out IronRidge's new entrant into the market, the IronRidge HUG. If you can't find info on it, ask your distributor or IronRidge sales rep. They have data on truss attachments and also missed truss installation procedures. It's a unique approach to a dual-purpose product, and they did a stellar job on the engineering documentation in my opinion.
Ok, now let's get to my most important point. Due to Hurricane Ian, the number of roofing PV attachments that I have witnessed that failed due to fastener pull-out (mine or competitors):
ZERO
The only building where we had any mounts fail was on a flat roof with pitched panels and Anchor Products mounts on TPO membrane, but the mounts themselves did not cause the failure. The roofing system itself failed, causing a small section of the PV system to fail. But even in that case, the following applies...
The weak point in a well-designed and installed system is not the fastener or flashing system. The module to rail connection is where we saw failures. These failures fell into a few categories:
* Windborne debris struck panel, panel frame failed, panel popped out of mid-clamps.
* Catastrophic wind forces popped panels out of mid-clamps (a good percentage of panels found INTACT and still functional on the ground!) I suspect the panels became covex in the wind, bending frames inward.
* Windborne debris struck mounting system components, panel dislodged, often still on the roof suspended by DC leads.
* Mid-clamp t-bolt tore out of aluminum rail channel (IronRidge UFO, Unirac SM).
* Mid-clamp sheared off (Quick Mount QRail).
* Unexplained module detachment failures.
On 9/28/22, while I stayed up all night bracing myself against my front door that I thought was about to fail, I was imagining how many roof leaks my clients were about to endure, and wondered about the efficacy of my business going forward. Those fears never materialized. Aside from a handful of minor panel dislodgements, there was no panic following the storm (with respect to solar panels). The bigger problem became all of the people needing to remove panels for roof replacements, but PV panels largely protected roofs in the areas where they were installed. Sadly, the rest of the roof often did not fare as well.
Anyway, back to the decking attachments. I have been skeptical of non-flashed products for comp shingle roofs for a long time. My thinking is coming around, particularly with the HUG (I trust IronRidge's testing regime). And sealants have come so far. This method will remain up for debate probably for a long time. Around here, I am pretty certain these products will outlast the shingles they are placed upon. We only get 15 years out of most shingle roofs around here.
About the pull-out fears... Mine are gone. We have done many flat roofs with long fasteners through steel decking or wood decking. These screws are usually something like #15 XHD screws in lengths from 5 - 12". Not a single failure. We have also used Quick Mount QBase Low-Slope bases on pitched tile roofs that were only screwed into decking with 4 fasteners each (due to horizontal truss transitions) in some cases. Zero failures. But the most relevant attachments I can think of that are germane to this discussion are the many thousands of S-5 SolarFoot that we have screwed into decking on 5V metal roofs around here. These have four screws per attachment, and S-5 load tests show something like 240 lbs of pull-out strength in OSB (adjusted for safety factor). When engineered for our wind loads, we usually get anywhere from 36-48 inch attachment spacing, sometimes 24 inches in certain roof zones. Again, not a single failure.
I have more solar installations on Sanibel Island and Fort Myers Beach (Hurricane Ian Ground zero) than anyone. Many of those have decking-only attachments, S-5 clamps, flat roofs, or other attachments other than trusses. I can tell you unequivocally that I trust decking-only attachments from a pull-out strength standpoint. When properly engineered, with cautious attachment spacing, these mounts work in both OSB and plywood. Because of the inconsistencies in OSB, we always err on the side of caution, if not in the engineering, then in the installation, by installing more attachments than prescribed. But the evidence is clear. It works.
Caveat to the above: I have zero experience with snow or seismic, and no experience on roofs exceeding 8:12 pitch, and few above 6:12.
And one more shout-out to S-5 clamps on standing seam roofs. Aside from one minor failure of the roof metal itself, not an S-5 failure, we had zero failures of S-5 clamps attachments to report.
I hope this anecdotal information helps and sets some fears aside. Please reach out to me off-list if you want any specifics or details about our experience with catastrophic wind events.
Sincerely,
Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
On Thu, Mar 30, 2023 at 2:47 AM William Miller via RE-wrenches <re-wrenches at lists.re-wrenches.org<mailto:re-wrenches at lists.re-wrenches.org>> wrote:
Friends:
Thanks for bringing up this scenario.
I have two problems with using a product such as the easy-feet or other deck-fastened brackets, particularly on a rigid foam-above-sheeting roof:
1. I worry about compression of the foam material over time. This could leave a void under the bracket which could lead to leaks or wobbly brackets.
2. I don’t believe in chemical solutions for sloped-roof rain-proofing. By that I mean the use of caulks, gaskets, etc. Since roofs were first thatched, the overriding wisdom is that gravity is the only way to reliably shed water. Overlapping, seamless material is the only method to use. Caulks degrade, roof surfaces become powdery, and the rafter is often under an architectural feature or seam in the shingles.
I researched the PLP EZ foot back when the company was DPW. The fasteners provided were not rated for the application, according to the fastener manufacturer. If you can match the fasteners to the decking and the forces, then maybe you have a start to a mounting solution.
Whatever product you use, I would install it on a section of flashing metal, lapped under the next course up. The flashing gives a flat, seamless surface to caulk or gasket to. The thicker and wider the flashing, the more you distribute the downward force
applied to the bracket by weight and fasteners. Any voids under the bracket will have an overlapped flashing above it.
I hope these musings help you find a solution.
William Miller
PS: I have encountered this roof configuration a few times on flat, built-up roofing (BUR<https://homeinspectioninsider.com/built-up-roofing/>). We have dealt with it by cutting through the foam, installing blocking on top of the sheeting and having a roofer feather the blocks into the roofing with cant strips<https://www.blueridgefiberboard.com/cant-strip-tapered-edge-smoothes-roof-drainage-slope/>. A pitched roof is a different situation, however.
Wm
Miller Solar
17395 Oak Road, Atascadero, CA 93422
805-438-5600
www.millersolar.com<http://www.millersolar.com/>
CA Lic. 773985
From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org<mailto:re-wrenches-bounces at lists.re-wrenches.org>] On Behalf Of August Goers via RE-wrenches
Sent: Wednesday, March 29, 2023 11:47 AM
To: RE-wrenches
Cc: August Goers
Subject: Re: [RE-wrenches] Attaching Array To or Through Ply
We've found that in the Bay Area that deck-mount solutions typically pencil out structurally (via a structural professional engineer) as long as the deck is 1/2" plywood or thicker, assuming we have all the info on how the roof is constructed. The big assumption is that we can get all that roof construction info, which can be difficult for existing structures.
We haven't taken the plunge yet on the flahingless deck mount products like the Sunmodo Nanomount or Unirac Flashloc Duo. I do think that they offer several significant advantages including not needing to find rafters, thus virtually eliminating missed pilot holes, and not disturbing the comp shingle by eliminating prying up the courses to insert the flashing.
August
Luminalt
On Wed, Mar 29, 2023 at 11:34 AM Solar Energy Solutions via RE-wrenches <re-wrenches at lists.re-wrenches.org<mailto:re-wrenches at lists.re-wrenches.org>> wrote:
We like Spider Rax… with the flashing!
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On Mar 29, 2023, at 11:04 AM, Jerry Shafer via RE-wrenches <re-wrenches at lists.re-wrenches.org<mailto:re-wrenches at lists.re-wrenches.org>> wrote:
Wrenches
Sounds like a SIP's type product, there are quite a few multi hole attachment bases that are designed for SIP's. Most will have a larger base, lots of holes for screws to attach that do not require rafters underneath to attach.
Fun times
On Wed, Mar 29, 2023, 8:30 AM frenergy via RE-wrenches <re-wrenches at lists.re-wrenches.org<mailto:re-wrenches at lists.re-wrenches.org>> wrote:
Matt,
I guess my questions are 1/2" plywood or 5/8" and how thick is the foam? Oh and I assume its nominal 2X6 T&G? Do you know how the plywood is attached?.....through the foam into the T&G?... to stringers, nailers or whatever they're called?
Bill
Feather River Solar Electric
Bill Battagin, Owner
4291 Nelson St.(shipping)
5575 Genesee Rd. (USPS, UPS)
Taylorsville, CA 95983
530.284.1925 Office/ 530.258.1641 Cell
CA Lic 874049
Solar powered since 1982
On 3/29/2023 7:53 AM, Dave Tedeyan via RE-wrenches wrote:
Hi Matt,
I've used these in the past when on a comp roof and there was no good way to get into the rafters (or TJI's in this case)
https://sunmodo.com/nanomount/
You might want to replace the screws with something shorter and beefier though to get more grip if you are only going into 1/2" plywood.
Cheers,
Dave
On Wed, Mar 29, 2023 at 10:38 AM Matt Sherald via RE-wrenches <re-wrenches at lists.re-wrenches.org<mailto:re-wrenches at lists.re-wrenches.org>> wrote:
Hi All,
I've run into a roof-mounted job where the roof is built-up with the following:
Comp shingle
Plywood
Foam board
T&G (roof deck, but also interior ceiling)
The beams that hold the t&g up are wide-spaced and not convenient for fastening the full extent of the array.
This being the case, I was considering other fastening options and am writing to pick the collective brain of the Wrenches to see how others have addressed similar situations.
One thought I had was to use the PLP Easy Mounting Foot and I'd be glad for any opinions on that or another solution.
-Matt
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Matt Sherald
PIMBY Energy, LLC
304-704-5943
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