[RE-wrenches] The perfect solar ready roof

Thu Oct 21 11:52:09 PDT 2010

andrew,a few comments added to your last email...
You Wrote.... If you ask me this is a dream scenario.  The scary thing about S-5!s is that you rarely know how often the roofing panels are attached to the decking and how well the decking is attached to the framing. i'm not overly familiar with standing seam metal roofs (and i know they are not all created equal) but aren't the screws holding the metal roof panel to the decking visible at the bottom, at the top under the vent cap and anywhere along the length of said panel?  i agree about the 'unknown' attachments btwn the decking and the framing   In this case you can direct the roofer to fasten the roof as often as you want.  I had a PE do an analysis for a sure-fire acceptable attachment method for a standing seam roof given: 90 mph wind zone, 18" wide standing seam roofing panels, flush-mounted PV array (modules to rail to S-5!s, no tilt legs), and his result was that if the roofing panels are fastened every 4" along each seam you are in the clear.  No doubt, that seems like quite a few fasteners.  He did not address the decking-to-framing attachment, So worst case scenario, you get a 90+ mph wind that takes the array, the metal roof and the decking for a ride to the ground, (HAS ANYONE SEEN OR HAD THIS HAPPEN?) when it is determined that the decking wasn't properly attached to the framing, who do ya call?  PV installer, PE who stamped it, roofer?  I'm not looking for a place to point fingers, I'm just looking for some insight on this so i understand our responsibilities a bit better.  I realize that it would be onerous to confirm the number and placement of decking to framing attachments)  but while the roof is off you could add as many fasteners as you want.  If the structure of the roof is in question I would definitely have a PE look at it and stamp the plans before proceeding, but once you have everything under the roof robust and approved, you are primed and ready for a worry-free, penetration-free S-5!-to-standing-seam array install.In another email string someone mentioned issues with S-5!s slipping down the roof due to snow which is why I recommend attaching at every seam and breaking out that torque-wrench when installing.  Good luck!...end of your msg
in response to Kris' suggestion, don't the 2x6's need to be toe-nailed into the 'rafters' on either side? or in this case toe-nailed into the beams? which probably wouldn't be much different than the 'inadvisable' lag bolting into them.
cheers,benn
DayStar Renewable Energy Inc. benn at daystarsolar.ca780-906-7807 HAVE A SUNNY DAY

From: atruitt at gmail.com
Date: Thu, 21 Oct 2010 11:30:40 -0600
To: re-wrenches at lists.re-wrenches.org
Subject: Re: [RE-wrenches] The perfect solar ready roof

If you ask me this is a dream scenario.  The scary thing about S-5!s is that you rarely know how often the roofing panels are attached to the decking and how well the decking is attached to the framing.  In this case you can direct the roofer to fasten the roof as often as you want.  I had a PE do an analysis for a sure-fire acceptable attachment method for a standing seam roof given: 90 mph wind zone, 18" wide standing seam roofing panels, flush-mounted PV array (modules to rail to S-5!s, no tilt legs), and his result was that if the roofing panels are fastened every 4" along each seam you are in the clear.  He did not address the decking-to-framing attachment, but while the roof is off you could add as many fasteners as you want.  If the structure of the roof is in question I would definitely have a PE look at it and stamp the plans before proceeding, but once you have everything under the roof robust and approved, you are primed and ready for a worry-free, penetration-free S-5!-to-standing-seam array install.

In another email string someone mentioned issues with S-5!s slipping down the roof due to snow which is why I recommend attaching at every seam and breaking out that torque-wrench when installing.  
Good luck!

Andrew Truitt
NABCEP Certified PV Installer™ (ID# 032407-66)

Truitt Renewable Energy Consulting

(202) 486-7507

http://www.linkedin.com/pub/andrew-truitt/8/622/713

"Don't get me wrong: I love nuclear energy! It's just that I prefer 
fusion to fission. And it just so happens that there's an enormous 
fusion reactor safely banked a few million miles from us. It delivers 
more than we could ever use in just about 8 minutes. And it's wireless!"

~William McDonough

On Wed, Oct 20, 2010 at 2:32 PM, Kristopher Schmid <solman at legacysolar.com> wrote:
What about screwing in double 2x6s flush to the roof deck between the beams where your feet will attach and lag bolting into that?  Definitely check with the beam manufacturer first, though.

Kris
Legacy Solar

864 Clam Falls Trail

Frederic, WI 54837

715-653-4295

solman at legacysolar.com

www.legacysolar.com 

-----Original Message-----

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Scott McCalmont

Sent: Wednesday, October 20, 2010 12:00 AM

To: RE-wrenches

Subject: Re: [RE-wrenches] The perfect solar ready roof
In general, you shouldn't drill or cut the flanges on engineered wood beams. I think that eliminates lag screws into the rafters. They probably wouldn't have the same pull-out strength as a lag screw into a conventional rafter, either. 

Scott

On Oct 19, 2010, at 7:58 PM, Chris Daum wrote:

    Dear Wrenches:

    I have a composite (shingle) roof at hand, and the 
    owner wants to upgrade it to a metal roof and install a 5kw+ array on 
    it.   The rafters are those (sort of) particle board I-beams 
    covered with 1/2" plywood (and shingles).  What's the best metal 
    roofing you could suggest--and would you beef up the wood to lag 
    into?

    Thanks for all your 
input.

    Chris 
    Daum
    Oasis 
    Montana Inc.
    406-777-4309
    406-777-0830 
    fax_______________________________________________
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