Solar panel underlayment

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gsf4726

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Mar 9, 2013
27
Tampa, FL
Recently was given a set of 4 year old solar direct Vortex panels from a friend that no longer wanted them after getting a new roof. They look in good shape and I plan on installing them on my house soon.

The panels were previously installed with thin, corrugated fiberglass sheets under each solar collector. My friend says he had the system installed professionally. However, I believe he previously had the Fafco panels and these may have been a holdover from those. The Vortex installation manual makes no mention of putting anything under the panels. I have the sheets, so question is, should I use them?

Thanks!
 
@Dirk you have thoughts about these solar panels?

Hmmm, dumb question, @Dirk has thoughts about anything and everything. :poke:
 
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I don't even know if "solar direct Vortex panels" are for electricity or for heating pool water. And you don't mention what kind of roof you have. A lot of roofs need to breath. Others not as much. Solar panels can trap leaves and debris under them. Adding another layer of material between panels and roof could just make that possibility worse. If the Vortex installation instructions don't specifically call for any sort of underlayment, fiberglass or otherwise, I would say don't use any.

I just looked. Solar Direct is still around and seems to have robust support. They also have excellent installation instructions that cover just about everything you need to know and do to get your system working, including plumbing and adjusting. You could always give them a call to double check if the fiberglass underlayment is required.
 
@Dirk thanks for taking the time. It's a good idea to contact them directly. Also, after searching the forum and seeing results for those panels, I had a bit of selection bias and just assumed everyone knew what they were, my fault.

And it's a pretty standard sloped residential roof with asphalt shingles.
 
Ah, no worries. I'm no solar expert. I installed my own system, so that's the scope of my experience.

What was the roofing material of your friend's house (his old roof) where they used the fiberglass sheets?
 
gsf4726 said:
Same type of roof, with asphalt shingles. I suppose they could help with wear on the underside of the panels against the shingles during expansion.
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My bad, I should have thought of that. That's probably why the fiberglass was there. My panels have components that align the tubes and keep them from touching the roof: spacers, every foot or so. It was quite a chore to get them to align perfectly with the high points of my concrete tile roof. Without them, the tubes would scrape across the concrete as the entire array expands and contracts in all directions.

I think your panels are solid, so dragging them across an asphalt shingle roof would definitely affect the wear on the underside. But maybe they're thick enough where that isn't an issue? That's a good question for Solar Direct. I didn't see a mention of that in the quick scan I did of the installation instructions.
 
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I do really like the construction and assembly of Heliocol. Ideally I'd have chosen them. These panels just fell into my lap, so with about $200 in replacement hardware I'll have what I think is a decent solar heater. Plus I estimate that my roof only has about 3 - 5 years left on it, and it seemed not that great to spend a bunch of money on a new system just to take it off and put it on again in a few years. Hopefully it's the right call.
 
I fell into an incredible deal on my Heliocols. One which no longer exists. I used to send local TPFers to "my guy" for the same deal, but I just spoke to him a few days ago and he stopped offering it. Otherwise they're pretty expensive. I certainly wouldn't have turned my nose up at $50 panels! That's for sure. Sounds to me like you're on the right track. The various brands all brag about their heating efficiency, blah, blah, blah. To me: they're all just black tubes on a roof, one way or another!

I think determining the correct flow for the panels is one of the most important parts of the installation: which optimizes how well the system can heat water. I think I saw a section about that in the Vortex installation manual, so have a look. I installed a FlowVis flow meter just for my solar system, so I could dial in the perfect flow rate and maintain it year round. Because I clean my filter so infrequently (once, in Spring), the flow through my plumbing sort'a degrades throughout the year. The FlowVis allows me to adjust my VS pump quickly to maintain the flow needed, so I'm always getting the best heating possible. (Optimizes my suction-side vac, too.) Your solar system's plumbing will require at least one check valve, maybe two. If you have to buy a check valve, consider a FlowVis, which doubles as both a flow meter and a check valve.

The following page describes how tilting your panels will help with the heating efficiency and the draining of the panels (important for freezing temps, if you get any down there), something that might not be addressed in your installation instructions. I did this on my system. On an asphalt roof it'd be especially easy. The whole page, and this whole site, has some incredible installation tips you might find handy. The tilting is described part way down the page in the section "Tilting Solar Collectors to Release Air."

www.h2otsun.com

Hot Sun Solar Pool Heating l How Does a Solar Pool Heater Function?

Detailed plumbing and operating instructions of solar swimming pool heaters.
www.h2otsun.com www.h2otsun.com
 
@Dirk thanks again. Couldn't agree more about h2otsun.com, really good and clear information there. I have been using that website to plan out my install.

Also, in case it helps anyone else in the future, Solar Direct technical support confirmed that underlayment is not required on shingle roofs, only on metal roofs with exposed screw heads. The Vortex panels can sit directly on asphalt shingles and even be walked on.
 
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