Batten roofs [RE-wrenches]

[Steve Fain]

Hi Andrew,
	There are special alloys of stainless steel ok for direct contact
with copper (probably expensive), but standard procedure recommends that
brass be used as the interface metal between copper and aluminum.  I've also
seen rubber and vinyl membranes used to isolate dissimilar metals, but these
may lose their insulating properties in time with exposure to the elements.

	Toggle bolts for holding a PV rack to a roof?  We have a mantra here
at UniRac:  "Firmly attached to structural members, Firmly attached to
structural members, Firmly attached to structural members..."  Your battens
are probably nailed to the sheathing, which is probably nailed to the
rafters.  What is the pull-out strength of each nail?  What's their spacing?
What kind of nails are they?  See where I'm going with this?  Without clear
knowledge of the holding strengths of all the fasteners involved, you'd
never be sure about how much live load the system would be able to
withstand.  It's a similar problem with a standing seam metal roof and S-5!
clamps.  I know the S-5! clamps aren't going to come off the standing seams
in a wind storm, but I have no idea how strongly the roof is attached to the
structure.  (We always recommend, if it's at all possible, that the standing
seam connections to the sheathing beneath the array be reinforced with
screws, not nails.)  Nope, sorry.  No toggle bolts, please. We want to see a
nice, beefy lag screw with at least a couple of inches of thread imbedded
into a rafter, that has a pull-out strength and a safety factor that we can
quantify.  Or a thru-bolt, if you have steel purlins.  Any other way and
you'd just be guessing and hoping.

Steve Fain
Customer Service/ Tech Support
UniRac, Inc.
1411 Broadway Blvd. NE
Albuquerque, NM   87102-1545
Ph:  505-242-6411 ext. 21
Fx:  505-242-6412
Email:  sfain at unirac.com
Web:   http://www.unirac.com
 
 
-----Original Message-----
From: Andrew Truitt [mailto:atruitt at gmail.com] 
Sent: Wednesday, February 28, 2007 7:55 PM
To: RE-wrenches at topica.com
Subject: Re: Batten roofs [RE-wrenches]

Great information, Steve. Thanks.  Is stainless steel is o.k. in
permanent contact with copper?

Also, if we decide to try to anchor through the battens, would Unirac
warranty any type of Toggle bolt anchoring system since the rafters
are off-set from the battens?  We would of course have to isolate the
aluminum L-feet from the copper battens.

Nice to have a Unirac staffer here on the wrenches list!

Andrew Truitt
Standard Solar Inc.



On 2/28/07, Steve Fain <sfain at unirac.com> wrote:
>
> Hi Andrew,
>         If those battens have any open space inside, crimping something
> (like an S-5! clamp) onto them would cause distortion, probably pulling
the
> copper roof strips on either side of the batten together.  To my knowledge
> the S-5! folks don't make a clamp that can accommodate 2" standing seams,
> and I haven't heard of anything that will.  At any rate, you'd need to use
> brass  between the copper and the racks or module frames----aluminum in
> direct contact with copper would melt away in no time from galvanic
> corrosion.  Custom brass clamps for 2" standing seams might end up costing
> around $60 to $80 each if UniRac made them.  You'd use at least 25 or 30
> clamps---more if you're in a higher wind area.  I'll bet those welded
> flashings are looking better to you now!
>
> Steve Fain
> Customer Service/ Tech Support
> UniRac, Inc.
> 1411 Broadway Blvd. NE
> Albuquerque, NM   87102-1545
> Ph:  505-242-6411 ext. 21
> Fx:  505-242-6412
> Email:  sfain at unirac.com
> Web:   http://www.unirac.com
>
>
> -----Original Message-----
> From: Andrew Truitt [mailto:atruitt at gmail.com]
> Sent: Tuesday, February 27, 2007 8:14 PM
> To: RE-wrenches at topica.com
> Subject: Batten roofs [RE-wrenches]
>
> Does anyone know of a non-invasive method for mounting L-feet to a
> copper batten roof?  The battens are 2" x 2", 22" o.c. and sit on 3/4"
> ply with 2" x 4", 24" o.c. framing.  Our roofer will only warranty
> roof penetrations if he can use 6" welded flashings which would cost a
> lot (10 kW system) and would raise the profile more than we would
> like.  We are basically looking for the equivalent of S-5! clips for
> 2" wide standing seams.
>
> Thanks in advance for any help because I am stumped!
>
> --
> Andrew Truitt
> System Designer/Lead Installer
> Standard Solar Inc.
> 15200 Shady Grove Rd. Ste. 202
> Rockville, MD 20850
> Office: (301) 296 - 4373
> Cell: (415) 290 - 8240
> Fax: (301) 296 - 4548
> andrewtruitt at standardsolar.com
>
>
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>


-- 
Andrew Truitt
System Designer/Lead Installer
Standard Solar Inc.
15200 Shady Grove Rd. Ste. 202
Rockville, MD 20850
Office: (301) 296 - 4373
Cell: (415) 290 - 8240
Fax: (301) 296 - 4548
andrewtruitt at standardsolar.com


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