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RE: "Non-penetrating" roof support for Solar PV

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Many years ago, I worked on systems for a department store chain for ballasted antennas all over the US.  Building officials will be satisfied if the system (PV, antennas, etc.) do not cause a hazard if they are restrained in some fashion.  They can move all over the place.  But they should be "anchored" to avoid the equipment from becoming a falling or wind borne debris hazard.  That can be done with a cable that can be anchored to the under side of an eave, or other rigidly attached roof equipment.  

Regards, Harold Sprague


 
> Date: Sun, 23 Jan 2011 09:32:34 -0500
> Subject: Re: "Non-penetrating" roof support for Solar PV
> From: ad026(--nospam--at)rpransom.ca
> To: seaint(--nospam--at)seaint.org
>
> David,
> Very plausible but possibly not acceptable to building authorities and
> owners considering the (fragile) nature of roof systems (e.g. shear load
> transfer through membrane, insulation, drainage layer, vapour barrier to
> deck) and the dynamic nature of the load effects. It is possible that it is
> not appropriate to transfer wind loads by friction.
>
> Is anyone aware of any tests that have been done to confirm this approach?
> Should special precautions be taken to fasten the BUR in the area of the
> load? Is retro-fit fastening the BUR any less expensive than
> through-fastening the PV assembly?
>
> Which leads to my next thought ...
> Who is responsible for determining the wind load on a PV assembly - either
> laying "flat" near the roof surface or elevated on stands? Okay, I know that
> I am ultimately responsible for the loads that I consider but I haven't met
> a PV installer who knows what a wind tunnel looks like. There are a lot of
> these roof-mounted PV assemblies being installed and it appears that we are
> currently relying on "it hasn't failed, yet" to justify our individual
> practices.
>
> Is anyone aware of any publicly accessible guidance on PV assembly wind load
> effects? Any work in progress on research or industry "standards", etc? Any
> private work that you are willing to discuss?
>
> Regards
> Paul
> --
> PRansom(--nospam--at)PaulRansom.ca
>
> > From: "David Cohen (Baran Raviv)" <dcohen(--nospam--at)barviv.co.il>
>
> >
> > Hi Milo
> > I don't think you will have a real problem with seismic forces, even in
> > high seismic region.
> > The weight of PV panels that stay the seismic force,in comparison to the
> > wind forces that they generate is generaly very negligeable.
> > If by the usually used ballast system you are able to give a resistance
> > to the Uplift and drag forces due to wind, it will give also a good
> > response to seismic forces.
> >
> > David Cohen
> > Baran Raviv, Israel
> > www.barangroup.com
>
>
> >> From: Milo Zabala [mailto:milozabala(--nospam--at)yahoo.com]=20
> >
> >>
> >> In high seismic region, ballast alone may not be enough to resist
> >> lateral forces. There must be some way to anchor the panels to some
> >> external wall system. Recall that friction resistance is not allowed to
> >> counter seismic force.=20
> >
> >> Milo Zabala, PE
> >>>
> >>>
> >>> On Jan 21, 2011, at 9:46 AM, Krupakaran Kolandaivelu
> >>> <krupk(--nospam--at)advantageengineers.com> wrote:
> >>>
> >>> Non-Penetrating roof support for Solar PV is achieved by ballast
> >>> loading, for resisting wind (uplift & drag) forces. Usually the wind
> >>> forces for the solar modules are calculated by method 3 of ASCE7-05
> >>> section 6.6 wind tunnel procedure. Typically concrete pavers on paver
> >>> trays are used on the roof.
> >>>
> >>> Krup Kolandaivelu, P.E.
> >>> Lansdale, PA.
>
>
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