Solar Panel Fasteners?

Hey Y’all!

So I have my Renogy Solar kit and I’m working on affixing the panels with Z brackets to my roof.

The question is this: Should I use the fasteners from the kit which are self tapping screws, OR the second option that Renogy recommends for RV roofs but doesn’t provide which are Brass self expansion nuts.

Option 1, the screws will be biting into the fiberglass roof & maybe if I’m lucky I’ll hit a metal bar as structural element.

Option 2 is going to be the rubber nut that expands into the fiberglass when the machine screw is in.

My roof is a double walled fiberglass with insulation in between. There are a few steel roll bars throughout, but the placement of where they are may not be where the panels can fit.
Here is a photo of the roof cutout:

3/8" fiberglass
insulation / steel bars(unsure of locations)
3/8" fiberglass


Bookmarking this to come back to it for info! Wish I had info for you, but hopefully someone else can help out!


Same here unfortunately. But I just posted this on our IG story, hopefully someone who knows about this can help you out!

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Those well nuts in my experience haven’t worked well for me. I used them to fasten my door panels and literally tightening them by hand or with a drill they pop loose every once in a while.

Does your vehicle have rain gutters? What kind of van is it?

Right, I was worried about that, but that is what Renogy recommends for the RV’s. I don’t like the option 1 they gave me with either. Im not sure how well they’ll sit while driving and vibrations.
It is a '91 ford econoline with a fiberglass hightop, the rain gutters are where the high top connects to the van.

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Do you have access to the inside panel?

I have a fiberglass roof on my Vanagon which has thinner fiberglass than your van but they’re fastened with nuts.
I ran Yakima artificial rain gutters, towers, and round bars and attached my two renogy panels to the bars. A year and a half later of driving upward of 80mph driving I haven’t ever had an issue.

Something else you might be able to do is screw them down and silicone them to the roof.

Another idea that MIGHT work, is if you get a strong enough magnet you might be able to find where the studs run across the top.


This was a debate I had with myself when doing my van, spent hours trying to research and couldn’t find anything so just decided to go for it and hope for the best. But I have a 2009 high top Renault master with fiberglass roof and fixed my 350w solar panel on z brackets using self tapping screws and silaflex. 7 months in, Ive had no problems with it. Also my fiberglass roof is just that, no steel bars or anything else to fix to other than the fiberglass itself.


No access but the heavy duty magnet is a great idea. Thank you for your helpful response!!!

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This is a relief to hear. It is difficult and the fear of losing a panel is real lol. But I am glad to hear that what you went with is good. I will be definitely using sikaflex as well.

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Another idea that just struck me is a stud finder.


True! I definitely need to get one. Thanks!

So it has been a couple weeks now and I just wanted to update on the fasteners I went with.

I used a combination of half self tapping screws and half brass expansion nuts.

I’m not sure what the material was of the #10 self tapping screws that came with the renogy kit so I went to the hardware store and purchased #12 stainless steel.

I ended up finding the metal frame inside the high top so I was able to use the #12 self tapping SS screws in the outer holes of the Z brackets. The inner holes I had to use the brass expansion nuts.
I used loctite on almost all of SS screws.

I do have to say I’m pretty happy with how it turned out overall. HOWEVER, a tip about the brass expansion nuts*** make sure the machine screw threads into the nut before adding caulk and placing the nut into the pilot hole. Out of the 16 I used I think that 7 of them did not turn right and pushed the entire nut threw and just didn’t work until I replaced them. Very frustrating and it was definitely a challenge since I’ve never worked with them before either.

Also, I laid Eternabond down first before putting the Z brackets down and then on top of the fasteners as well. I just wanted to make it as waterproof as possible. When I went to use a polyurethane sika around the tape to really seal it up it did not stick to the top of the tape. So I will have to take that up and put down the self leveling dicor instead which is the only thing I’ve found to stick to the top side of the tape.

I recently installed a 600W Renogy Solar panel system to an RV with RV Roof tape. I cut 10 inch strips and taped down each of the four brackets on each panel. Once the sun melted the glue the tape won’t come off without a lot of yanking and cutting. It also holds up in the rain

Using the tape prevented having to drill holes into styrofoam roof and adding the to potential of leaking or mold.

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