[RE-wrenches] Attaching Array To or Through Ply
Christopher Warfel
cwarfel at entech-engineering.com
Fri Mar 31 05:46:33 PDT 2023
I had worked in USVI after those two hurricanes and I don't think FEMA
is overkill. Their design manual is very thorough. It considers the
factors mentioned here. Having done a fair amount of high wind
compliance engineering for structures, the FEMA approach is just
something you have to organize to install. Yes it will take longer. Chris
On 3/30/2023 6:34 PM, Jason Szumlanski via RE-wrenches wrote:
> That would be great if it were possible! I'm not sure how you bottom
> mount a flush mount array. For a brief period many years ago, I was
> building solar trailers. I would bottom mount 4-6 panel arrays on
> rails in my warehouse and then hoist them up and through-bolt the
> whole array on the top of a trailer. I wasn't about to allow a trailer
> going 80 mph on the interstate to have panels mounted on the roof with
> mid-clamps! I had no idea what I was doing, but I had enough sense to
> know that would have been a bad idea!
>
> I did provide feedback to IronRidge regarding a handful of failures
> from Hurricane Ian, but most of the issues we saw were most likely
> related to catastrophic module failure. After all, they are only
> tested to 5600 Pa uplift for even the best options we have on the
> market and 2400 Pa for some (which I refuse to use). The mid-clamp
> T-bolts tearing out of the rail are slightly concerning, but this was
> pretty rare, and honestly it could be related to installation torque
> issues, misalignment, or coupled with module failure. There was no
> widespread or definitive reason for rail failures at the clamp locations.
>
> I would suggest that FEMA's recommendation is overkill and not based
> on much science, but conclusions based on anecdotal information
> without statistical data. It should be scrutinized. I think it would
> be a good idea to consider bottom mount for ground racks and tilt
> mounts that allow it, but it's just not practical or possible in the
> vast majority of residential installation cases. On that note, I am
> not aware of any ground mount failures around here from Hurricane Ian
> except for submerged arrays that were washed away from storm surge
> (Yikes!). And the handful of failures that we observed were a drop in
> the bucket relative to the installed numbers here.
>
> One other thing. Wind direction, upwind obstructions/windbreaks, and
> luck have a huge amount to do with failures (of both PV and roofs
> themselves). These storms pick winners and losers. You will have ten
> houses in a row with pool enclosures mangled, and one in the middle
> that is unscathed. It's crazy to see. We have lots of gated
> communities with houses close together. When wind accelerates between
> houses, it can topple air conditioning units and pool equipment. If
> you look hard enough at where the wind was coming from and the
> surrounding area, you can really see how there are so many factors
> that come into play.
>
> 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 7:35 AM Christopher Warfel via RE-wrenches
> <re-wrenches at lists.re-wrenches.org> wrote:
>
> 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> 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] *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> wrote:
>>
>> We like Spider Rax… with the flashing!
>>
>> *Spider-Rax PV Solar Mounting <https://spiderrax.com/>*
>>
>> *spiderrax.com <https://spiderrax.com/>*
>>
>>
>>
>> *Error! Filename not specified.* <https://spiderrax.com/>
>>
>> *Andrew Koyaanisqatsi*
>>
>> President
>>
>> *Solar Energy Solutions, Inc.
>> /The BRIGHT CHOICE/*
>>
>> *Since 1987, helping you and your *
>>
>> *Portland neighbors move towards an environmentally
>> sustainable future.*
>>
>> *503-238-4502 <tel:503-238-4502>
>> www.SolarEnergyOregon.com
>> <http://www.solarenergyoregon.com/>*
>>
>>
>>
>> On Mar 29, 2023, at 11:04 AM, Jerry Shafer via
>> RE-wrenches <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> 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> 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
>>
>>
>> --
>>
>> Matt Sherald
>>
>> PIMBY Energy, LLC
>>
>> 304-704-5943
>>
>>
>>
>> _______________________________________________
>> List sponsored by Redwood Alliance
>>
>>
>>
>> _______________________________________________
>>
> --
> Christopher Warfel
> ENTECH Engineering, Inc.
> PO Box 871, Block Island, RI 02807
> 401-466-8978
> <http://entech-engineering.com>
>
>
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--
Christopher Warfel
ENTECH Engineering, Inc.
PO Box 871, Block Island, RI 02807
401-466-8978
<http://entech-engineering.com>
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