[RE-wrenches] Stanchions for Comp Shingle Roofs

[Peter Parrish]

I’m 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
(9”x12”, 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 (15”x18”) 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 haven’t 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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