New Construction/Standoff/LowProfile Flashing [RE-wrenches]

Jeff Clearwater clrwater at earthlink.net
Fri Jun 4 08:20:37 PDT 2004


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Hi Graham, William, Nick and Bill and all,

I agree as well with Graham and Bill's assessment 
on this and did start this thread with saying 
that was the standard I've used on new 
construction.   I also see alot of installers 
refining thier methods and eliminating overkill 
to speed up the process and lower the price.  But 
this one feels like a place to stick to higher 
standards and not cut corners.

On this particular install they are using 
pre-made trusses that have only 2x4" rafters. 
The prosolar jacks have only one bolt hole as 
William pointed out and I've always used the rule 
to not have the lags go in more than half way 
into the rafter (weakens rafter's tensile 
strength fibers on bottom half of rafter).  So I 
usually use two lags per standoff to get the 
thread depth required for uplift (and hence use 
Unisolar standoffs)

But since it's new construction and only 2x4's 
I'm thinking of using  bolt and nut for the 
standoffs to blocking.  Perhaps 2x6's on their 
side offset as to allow screwing in from the ends 
to the rafters.  This will also allow the turning 
of the standoffs so the holes don't line up with 
the wood grain.  I figure the plywood/blocking 
combination should be strong enough even  if on 
their sides.

Any thoughts on this?

Thanks again.

Jeff

>
>William and Nick,
>
>I have to agree with Graham on his assessment of post and flashing. All new
>roofs should be done with post and flashing in my opinion. Drilling through
>shingles is okay on an existing comp roof in good shape with a single layer
>of shingles--that rules out and awful lot of roofs (like 80%).
>
>Not sure why you can't find rafters with your cathedral roof system. Are the
>rails running parallel to the rafters rather than perpendicular? 20" is
>pushing it for roof damming and 28" is too much in my understanding. If
>memory serves me correctly, our building code in North Carolina required a
>cricket (wedge-shaped waterway) above anything that was greater than 18"
>wide. I would think hard before making it a SOP so it won't FLOP;-).
>
>No offense to anyone personally, but I see too many contractors trying to
>leave the straight and narrow of flashed standoffs with well-designed
>aluminum rail systems that clamp the modules. This going to the "next level"
>often leads to repeating the mistakes of the past from both the PV and solar
>thermal industries in roof mounting. So many systems are going in these days
>that I think the tried and true methods are often found to be mundane,
>difficult, and slow, when in fact they are designed to last the life of the
>roof.
>
>Nick, I have never heard of anyone reroofing around a PV array. Although the
>roof under the array will last far longer that roof next to the array, I'm
>not sure of any roof that would be willing to feather in a new roof that
>way. I think your suggestion to the customer seems misleading to me. To be
>honest with them there should be an estimate for removing the array during
>reroofing so they can adequately assess whether a new roof with flashed
>penetrations is worth the investment today.
>
>Bill.
>
>
>-----Original Message-----
>From: William Miller [mailto:wrmiller at slonet.org]
>Sent: Friday, June 04, 2004 12:43 AM
>To: RE-wrenches at topica.com; RE-wrenches at topica.com
>Subject: Re: New Construction/Standoff/LowProfile Flashing [RE-wrenches]
>
>
>RE-roofing!  The million dollar question.  We are dedicated to "top-down"
>installations.  All (or darn near all) of our racks tilt up for back wiring
>in conduit.  Therefore, any rack can be lifted up for re-roofing.  We
>haven't done it yet, but we figure a comp roof can be re-roofed around our
>racks.  Lift the racks up and then the customer pays one of us to hang out
>and lift one foot at a time for new shingles to be slid underneath.  Like I
>said, we haven't actually tried it yet, but it would be many times cheaper
>than removing the whole shootin' match.
>
>Also, our "Cadillac" comp installs get DPW power posts with flashing.  I've
>tried the solar jacks, or whatever they are called, and I can't sanction a
>stand-off with only one lag.  I'd like to see the DPW power posts with a
>square flange, rather than rectangle, for more stability.  The only
>flashing that will clear the flange is the Oatey solar.
>
>Continuing with the creative process:  Just today we started an
>installation on a comp roof with cathedral ceiling.  Since we can't block,
>and we can't hit rafters (multiple 10 module racks, no consistent 48" foot
>spacing, variable roof framing, etc.), we are placing 20" to 28" sections
>of aluminum "Uni-strut" at each rack foot location.  Lots of caulk area
>under each strut and the feet placement is flexible.  Water can run off
>between sections of strut. So far, it looks like this may be a new SOP for
>us.  I'll keep you all posted.
>
>William Miller
>
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>
>
>
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--
~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design Associates
Sustainable Energy & Water Solutions for Home & Village
http://www.villagepower.com
gosolar at villagepower.com

877-SOLARVillage
413-256-6777,  Fax 413-825-0372
61 Baker Rd
Shutesbury, MA 01072

PO Box 115
Boonville, CA 95415
707-895-9015, Fax 707-897-0024
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`~

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Let University of Phoenix make 2004 your year. Evening, 
weekend or FlexNet® classes – over 130 locations. Look 
into our programs and get the degree that gets you going!
http://click.topica.com/caaciq1bz8Qcsbz9JC9f/UOP
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