[RE-wrenches] Stanchions for Comp Shingle Roofs

[North Texas Renewable Energy Inc]

Wrenches,
I have always used Peters #2 process. The reason being, in hot climates, asphalt shingles become very soft and susceptible to damage. We've all walked across one on a sunny >90f day. Anything mounted against one or more layers of 3 tab, and lagged firmly into a rafter, will compress the softened asphalt. 
So in the future, the flange that's flat against the shingles, is not as tight against the shingles as it would be if tourqued directly to the decking. And over the years, the minute movements of the stanchion and flange, from thermal stress, wood shrinkage, wild lift or load, will further compress the shingles under the increasingly loose fitting flange. 
Also, if a future roof pulloff & replacement is necessary, the entire array must be removed, including the standoffs. So when the new shingles are in place, all the mounting holes have disappeared. A complete array install is in order.
It is indeed a little more work to mount directly to the decking but that's what sealant is for. I get barely 4 standoffs per tube. It's cheap insurance in my book.
I also encourage every homeowner, during site surveys, to insist of others offering bids that flashing be used rather than angle aluminum brackets. 
Jim Duncan
North Texas Renewable Energy Inc
4029 Aragon Drive
Fort Worth, Texas 76133
817.917.0527
ntrei at earthlink.net
Serving North Texas since 1994.
For more information www.ntrei.com


  ----- Original Message ----- 
  From: Peter Parrish 
  To: 'RE-wrenches' 
  Sent: Monday, September 15, 2008 11:28 AM
  Subject: Re: [RE-wrenches] Stanchions for Comp Shingle Roofs


  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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