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@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-boun...@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@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@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@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@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
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