[RE-wrenches] Stanchions for Comp Shingle Roofs
Glenn Burt
glenn.burt at glbcc.com
Mon Sep 15 10:02:02 PDT 2008
Quick item on Approach #1 bares repeating Sika is incompatible with
asphalt shingle roofing according to the manufacturer
Regards,
Glenn Burt
Technical Specialist
Renewable Power Systems, LLC
PO Box 967
Averill Park, NY 12018
V: 518-674-5808
C: 518-810-3174
F: 518-514-1175
E: <mailto:gburt at RPSPower.com> gburt at RPSPower.com
<http://www.RPSpower.com> www.RPSpower.com
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Peter
Parrish
Sent: Monday, September 15, 2008 12:28 PM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Stanchions for Comp Shingle Roofs
Im not sure if we have discussed this before, but I would like to get
opinions on the relative merits of the following two approaches to setting
stanchions and flashing them in for a roof mounted PV system:
Existing comp shingle roof in good condition. Professional Solar Fast-Jacks
(or similar stanchions that result in a ¾ to 1 post to which to attach
rails). I am not endorsing ProSolar products, I just wanted a specific
example to work with.
Approach #1: Lag stanchions directly onto existing comp shingle roof; cut a
inverted U into the top layer of shingle; slip in Oatey-style flashing
(9x12, with an elastomeric ring); seal exposed vertical edges of flashing
with a bead of high quality caulk (Sika 1A)
Approach #2: Remove shingles down to the felt; lag stanchion; replace
shingles incorporating full-sized (15x18) flashing and seal top of
flashing with high-quality caulk.
Obviously, approach #2 takes longer and costs more, but does it confer
commensurate benefit? If the resulting stanchion/flashing were exposed to
the elements, I would tend to favor the latter approach; and if we were
dealing with new construction the difference in time and money would not be
significant. However, if the stanchion/flashing lies directly underneath a
PV module, it will be shaded from the deleterious effects of UV sunlight and
will not receive any direct rain or snow accumulation. Under these specific
circumstances, I would argue that approach #1 should be more than adequate
and last at least as long as an existing comp shingle roof.
For those of you who havent seen the Fast-Jack/Oatey approach, you might
want to look at http://www.prosolar.com/Oateys.htm.
- Peter
Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com
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