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

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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

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?


> From: "David Cohen (Baran Raviv)" <dcohen(--nospam--at)>

> 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

>> From: Milo Zabala [mailto:milozabala(--nospam--at)]=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)> 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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