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Old 03-18-2011, 04:37 PM   #1
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Sealing penetrations for solar installation


Hello,

I am in the process of installing a solar system on my roof. I am planning on doing most of the installation myself, and hiring a licensed electrician to wire everything together. I ran my plans by the permitting office, and so far everything seems to be in order for when I'm ready to start the installation (I haven't actually pulled the permits yet, just had them look it over).

This system will be installed on a low-slope (1/2 in 12) mod-bit roof. I'll be making 36 penetrations, in each case screwing a lag bolt directly into a joist.

However, I recognize that ensuring that these penetrations don't leak is, perhaps, the most important and most difficult part of this job. I have seen many professionally installed solar systems which simply use caulk or construction adhesive to seal the bolts, like this example (not my roof):


Something about that just doesn't sit right with me. It looks sloppy, and I worry about the long-term reliability of the seal.

My current plan (which I need some feedback on!) is to mount the brackets, like so:


I will use roofing cement (brand recommendation?) under each bracket to seal it to the membrane, add a little on the shaft of each lag screw before driving them in, and finally put a bead around the edge of each bracket and the bolt head for final waterproofing. However, I feel like I should also flash the penetrations to provide a second layer of waterproofing. Is this true, or is roofing cement on its own enough to provide a permanent seal?

Of course, while I could use Oatey flashings on the round standoffs, I'm not sure as to the best way to flash and seal those U-shaped brackets. Perhaps I could cut a rubber membrane to size? What about sealing the flashings themselves to the roof? The roof is torch-down, and I am, shall we say, hesitant to take a torch to my own roof. As such, more DIY-friendly methods are favored.

One thing that I have come across recently is the "ChemCurb/Minicurb" system. It looks something like this:


And has the advantage of being very easy, if not cheap (~$11 per penetration. I have 36). Furthermore, I wouldn't have to lay any membrane over the edges of the flashing and then seal it to my roof, which is nice.
Has anyone used something like this? How well does it work? Is there a cheaper/better way?

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Old 03-19-2011, 01:10 AM   #2
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Sealing penetrations for solar installation


No do not just put roof cement under the feet. They need to be in a Pitch Pan something like the chem curb but that is for single ply roofs. On hot roofs you use a metal pitch pan with a 3 in flange. The flange is covered with a layer of base sheet and a layer of mod bit. The middle is filled with mastic, or your choice of poorable sealer.

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Old 03-19-2011, 07:29 AM   #3
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Sealing penetrations for solar installation


Get 1/4" stainless steel brackets that'll accept 2-3 stainless lag bolts for the rafters, and the solar panel brackets.
Where they go, notch into the sheathing about a 1/4" so the roof doesn't get humped up. Just roof over them in so they self-flash, and or use lead or copper bibs if necessary.

Do this as you do the new roof. You aren't going to want to do this but once every 50 years. The roof and sloar system have to go on together, so to speak. ( Install the 50 year shingles)
I had pictures of the brackets, but can't find they. They're shaped like what I drew.

Doing anything else will likely have you uninstalling the panels every now and then to make repairs, or to replace the roof.

Well now! I need to read more thoroughly don't I???
I saw shingles and didn't read the post completely. I'll leave that up in case somebody needs to do the install on a shingle roof.

You need to install mounts and pitch boxes on the mod-bit roof.
Even doing this over a new mod-bit roof, you need to plan on taking it apart every now an then to recoat the roof surface. You might want to consider an .090 EPDM roof instead so you can possibly wait 30-40 years between uninstalling and reinstalling for roof work.
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Old 03-21-2011, 09:56 PM   #4
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Sealing penetrations for solar installation


Thanks for the tips, guys.

I'll try to post some pictures of the roof and the mounts (not installed, but it'll give you an idea of what I'm looking at) soon. If I do my own flashing, is there a product that will adhere well to my existing roof without the need for a torch? I want to do this job myself if I can, but I'm leery of burning my house down. That's why I liked the Chemcurb.
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Old 03-23-2011, 12:38 PM   #5
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Sealing penetrations for solar installation


Quote:
Originally Posted by jagec View Post
Thanks for the tips, guys.

I'll try to post some pictures of the roof and the mounts (not installed, but it'll give you an idea of what I'm looking at) soon. If I do my own flashing, is there a product that will adhere well to my existing roof without the need for a torch? I want to do this job myself if I can, but I'm leery of burning my house down. That's why I liked the Chemcurb.

No torch needed. Get the pitch pans. Square metal boxes with 3-4" flange. A roll of base sheet, and a roll of mineral surface modified. A bucket of cold app or flashing cement. put your brackets and pitch pans on, cut squares of base sheet to cover the pitch pan flanges atleast 6" past the edge of the flange, set them in cold app. Cut the mineral surface modified in squares to cover the base sheet go out past hte edge around 9" past set in cold app. roll the edges down and walla. I will try to draw up some pictures when I have more time.
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Old 03-24-2011, 02:55 PM   #6
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Sealing penetrations for solar installation


Here are some pictures of the current roof, with the un-attached mounts in place for scale, and some existing flashings.

If I can do the pitch pan cold, that works for me. I do want to install the mounts fairly close to the edge of the roof in some places...do I just roll the flashing and/or mod-bit covering it around the edge in that case?

Click to enlarge each pic.












Last edited by jagec; 03-24-2011 at 03:08 PM.
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Old 03-24-2011, 07:15 PM   #7
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Sealing penetrations for solar installation


Tear off the existing roof which is in need of replacement.
I think I'd go with .090 EPDM. Get a supervisor's manual from a roof supply house. Use 1/2" ISO insulation board. Cut 12" pieces from a 1" x 12" board and screw them down at each bracket location. Use the 1/2" ISO on the rest of the roof. Put your roof on, put the pockets over the pieces of wood, flash and seal with appropiate EPDM glues, Cover tapes, etc, and you'll be good to go.
( The 14" thicker wood will prevent ponding around the brackets.)
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Old 04-04-2011, 06:09 PM   #8
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Sealing penetrations for solar installation


Quote:
Originally Posted by tinner666 View Post
Tear off the existing roof which is in need of replacement.
I think I'd go with .090 EPDM. Get a supervisor's manual from a roof supply house. Use 1/2" ISO insulation board. Cut 12" pieces from a 1" x 12" board and screw them down at each bracket location. Use the 1/2" ISO on the rest of the roof. Put your roof on, put the pockets over the pieces of wood, flash and seal with appropiate EPDM glues, Cover tapes, etc, and you'll be good to go.
( The 14" thicker wood will prevent ponding around the brackets.)
Well, that's not exactly what I wanted to hear! The house inspector thought that the roof was in good shape and should last for years when he looked at it...but he's not a roofer.

At least putting on a new roof would give me a chance to add a bit more insulation.
Given that I'd have to flash and seal no fewer than 41 penetrations, though, I'm a little tempted to contract out this job. I'm a pretty confident DIYer, but I've never roofed before. Or is it actually easy enough to flash with EPDM that a DIYer can get seals that last for decades? If I go to the professionals, would EPDM still be the best material?
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Old 04-04-2011, 07:55 PM   #9
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Sealing penetrations for solar installation


With 41 penetrations, I'd think you'll be out of your league. Most good DIY EPDM jobs had no, or very few penetrations, and were shed-roof shaped.
I believe you need a PRO.

As for best product, I have doubts about TPO and you'd need special tools.
You'll find out most residential contrators want to sell you mod-bit like you have, or .045 EPDM which is considered fine for residential roofing. I wouldn't use it in this application either.
I always spec .060 reinforced as my min and will upgrade to .090. The .090 should be good for 30 years, imho. Or more.
I know nothing about PVC, so I can't advise you. I do varieties of mod-bit like you have and SBS which is similar. I wouldn't advise either in this case.

You owe it to yourself to put this roof and equipment on the roof once, and to be done with it.
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Old 04-05-2011, 08:53 PM   #10
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Sealing penetrations for solar installation


That roof may or may not last for years, hard to tell. The one thing for sure is none is going to be cheap roofing it after its covered in solar panels. I wouldnt recomend a DIY person with the penetrations. A Fully Ahered 60mil is a good roof and will last a good long time. 90 with 6" seams will last a little longer. TPO would be fine or PVC again not DIY friendly. I would spec 1.5 ISO, picture frame the roof edges with 2x's and 1 1/2 Iso the rest. Cut out 2x8's in to 8" blocks to rest the feet. These would be flush with the ISO. Would leave you agood solid base for the feet. I would also recomend taking off hte old roof.
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Old 04-06-2011, 02:23 PM   #11
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Sealing penetrations for solar installation


All right, I'll probably do the tear-off myself, install the ISO and wood blocks, lag bolt the solar brackets in place, and then have a contractor install the EPDM and flash everything. I just found out that I have to move my AC unit off the roof so that I can shift the array further away from the front of the house to comply with a historical district regulation (the first time that I heard that I was in a historical district...they are tearing down houses right and left around here!). So, I'll have to get an HVAC guy to pump out the refrigerant and relocate/reattach the unit. At least that will be one less penetration to worry about. This is getting to be more expensive than I'd planned...the eternal lament of the homeowner.
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Old 04-06-2011, 05:14 PM   #12
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Sealing penetrations for solar installation


Don't feel too bad. Most of us contractors and roofers have the same issues with our own projects. Sure is true in my case.
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Old 04-07-2011, 12:21 AM   #13
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Yeah we all have them, this year paint ext of house and rebuild chimney chase (putting up corten standing seam Horisontal) New patio door and rebuild and stain deck. Along with poor driveway wider and pad in the back yard. lets not forget still have to plant and care for the garden. I hope this summer is long enough!

Next year shingle my own roof and what ever else my wife comes up with.

Some times it sucks to be handy, but then again I cant imagion my self paying my self what I would charge to do all this work.

Good luck on your project as you will be much happier then if you got it all done and the flipping roof leaked!
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Old 04-21-2011, 05:03 PM   #14
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Sealing penetrations for solar installation


OK, I had a roofer come out and look at the roof, and give me an estimate for a replacement.

He said that the roof itself was in OK shape, but that some of those flashings had been added after the fact and needed replacement.

He recommended installing another layer of Ruberoid smooth torch-down over the top of the existing, re-flashing all 4 vent pipes, and flashing in the 36 solar brackets. That AC unit will be moved down to the backyard by someone else (turns out it was just sitting on top of the roof, no fasteners or penetrations at all). The new roof would then be aluminum coated. He quoted about $3k for the whole deal, which was less than I was expecting. (13' x 43' roof, single slope). This would carry a 15-year guarantee.

The alternative would be to simply re-flash the 4 vent pipes, flash the 36 solar brackets, and coat the entire roof with aluminum. This cost $1100 and had no guarantee.

Thoughts? I'll probably get another estimate to compare, but that re-roofing cost is fairly affordable and right now it seems like a decent option, unless there is a powerful reason why EPDM is just that much better.

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Old 04-21-2011, 09:14 PM   #15
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Well thats not a new roof that a cover over a old one. A 15 year waranty is pretty optomistic for just torching down another layer and reflashing.

I wouldnt say EPDM is better then a mod bit roof, better then an old roof yes, but new to new no. By new I mean tear off and redo. For giggles have them price a tear off and redo it shouldnt cost you anything and honestly for a little more you could get a brand new roof. Have a couple of people give you a bid also. That would be my thoughts.

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