[RE-wrenches] Structural Review for Residential PV Systems

[Glenn Burt]

Hi Bruce,

 

As a starting point, I'd recommend reviewing the sections of the SolarABC's
Expedited Permit Process Report - REV 2.

http://solarabcs.org/about/publications/reports/expedited-permit/index.html

 

In it Bill has a section on structural reviews and possible reassurances
that may be relevant for you.

 

Good Luck,

Glenn Burt

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Bruce
Leininger
Sent: Saturday, July 06, 2013 6:04 PM
To: RE-wrenches at lists.re-wrenches.org
Subject: [RE-wrenches] Structural Review for Residential PV Systems

 

A local jurisdiction is starting to require that we document non-truss
rafter dimensions, span and attachment points.  This seems to be a fad that
other jurisdictions have required at times, and other times not.  When the
existing structure was deemed insufficient, we've either paid a structural
engineer to do some calcs and recommend more attachment points, or sistered
the rafters to match the spacing given in the 20 psf table in the UBC.

Would the dead load from the PV modules ever be more than that from adding a
second layer of comp roofing, which does not require a structural analysis?
Would the live point loads from the PV system ever be greater than the point
load of a person walking on the roof?  If the answers are "no" and "no",
then it seems that a roof that supports a person walking on it would not be
adversely affected by the installation of a non-ballasted residential PV
system.

I looking for help with the following:

1.  Has there been an occasion when a residential PV system (non-ballasted),
that was installed per the manufacturer's instructions, detached from a roof
or caused damage to the structure of the roof?
2.  Is there a good explanation for why structural review for residential PV
systems is necessary?
3.  Are there studies or resources that I can present to building officials
to explain why structural review for residential PV systems is not
necessary?

Thanks for your help.

Bruce

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