Rebecca:
I am not a structural engineer, nor would I second guess a structural
engineer's findings. The audacity here is that your inspector posture's
him/herself as knowing more than a licensed engineer and is imposing unfair
demands. Your maximum responsibility ends with an engineer's project
specific wet stamp.
My complaint is when I receive impromptu demands from a building
inspector. I insist that every requirement be published and equally
enforced. If the AHJ wants an engineering report on every roof mount
installation, so be it -- as long as every contractor and owner-builder has
the exact same requirement and the requirement is in writing in a publicly
accessible forum. Then at least the playing field is level and all
contractor's know what to expect when bidding a job.
The down side to heightened requirements imposed by an AHJ is that it makes
all installs more expensive, allowing fewer projects to be completed and
leaving your area with a larger carbon foot print.
I have a clause in my contract that allows extra charges if a standard
permit package proves inadequate. This requires a change order signed by
the client. The client will be informed immediately if the project gets
bogged down with unfair or arbitrary demands. This way the client can get
involved politically, if appropriate. If it becomes necessary, the more
angry calls your county elected officials receive, the better.
I hope this is helpful information. I think you can tell I have had some
bad experiences!
William Miller
At 04:03 AM 12/5/2009, you wrote:
Hi William,
Thanks for responding. We have three long rows of modules, with rails
attached every other rafter, every 4'. The inspector's argument is that
two attachments for one row might be fine, but that the wind load for the
entire array theoretically could be born by one rafter, and therefore it
would pull the rafter right out of the house. This is only my year 3 as an
installer, and while I'm not afraid to push the inspector if needed, I
admit I want to be sure he isn't right, even though an engineer says so
(because I'm not an engineer :-). So in your experience, is there a limit
to an array size that would be 'safe' for a home if the array is within
the edges of the roof and flush-mounted? I feel like that's the real
argument, you might safely attach one module, but he is saying when you
multiply the modules you multiply the wind load to the house by the same
factor.
Rebecca
Message: 3
Date: Fri, 04 Dec 2009 22:21:43 -0800
From: William Miller
<<mailto:[email protected]>[email protected]>
To: RE-wrenches
<<mailto:[email protected]>[email protected]>
Subject: Re: [RE-wrenches] PV wind load
Message-ID:
<<mailto:[email protected]>[email protected]>
Content-Type: text/plain; charset="us-ascii"; Format="flowed"
Rebecca:
It sounds like you have made an air-tight case (pun intended) and you have
still not been able to convince this thick-headed inspector. I have had a
similar experience last summer that might be relevant: After being pushed
around beyond my patience, I fought back. I worked up the chain of
command, stayed professional and put it all in writing.
I won the battle and set a precedent. I have forbidden the building
department from assigning the problem inspector to my projects and, to my
amazement, the department obeys my request!
Good luck, and let us know how it turns out
William Miller
At 05:55 PM 12/4/2009, you wrote:
>Solar is somewhat 'new technology' where I live. :-) I have a building
>inspector that feels that (32) Sanyo modules (6.88 kW array) mounted to a
>house roof is going to cause undue stress to the roof truss (it is a
>regular house in a Minnesota suburb, building height is 26', 30 degree
>roof angle, in a suburban neighborhood. 2" x 4" manufactured truss). We
>are leaving 12-24" on each edge with no PV, and are careful to attach to
>the center of each rafter.
>
>The inspector is not that concerned with dead load, but is especially
>concerned with wind load. We have provided an engineering letter that
>ascertains that a solar array mounted parallel to the roof surface is well
>within the parameters of what a typical roof truss can handle. We were
>required to have an engineer look at this address specifically, so we then
>provided an additional engineer's letter that affirmed that yes, solar
>mounted in the manner we proposed (with Quick-Mount attachment and Unirac
>SolarMount rails, all installed according to manufacturers' instructions)
>would be fine on this home. The building inspector insists that the wind
>load is excessive, and wants more analysis. Do any of you have ideas,
>experience, or data that might help me?
>
>Rebecca Lundberg
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