making a waterproof roof out of solar panels



  • rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
    Re: making a waterproof roof out of solar panels

    you could just put a thin piece of aluminum flashing over the "joints" to prevent UV exposure, the top and bottom "H" shaped metal would have the silicon covered by the aluminum anyways. 804 is used for frame sealing, junction box sealing and stuff like that it sticks very well to anodized aluminum, tedlar, plastic, pretty much everything!
  • michael kmichael k Registered Users Posts: 6
    Re: making a waterproof roof out of solar panels

    roland, seen this? Cick on "open structure" - how's THAT work?

    Also, a "SolarMount Bottom Up Module Clip" would help achieve tite spacing like you want?

    (ps: i have a cost/supplier problem and need to make a decision about mounting method! Does anyone know a good retail/wholesaler where i can just walk in and buy 100" plus mounting rails, probably Unirac, thus avoiding excessive shipping charges? I live in Atlanta GA area but any major US city will do!! )
  • rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
    Re: making a waterproof roof out of solar panels

    I am still surpriosed there apparently are no more integral roof mounting systems available?they were available in 1983. by the looks of the pictures below the perpendicular rails are exactly the same as the ones I linked to before from Polygal. Has anyone seen one of these systems in place? Seems like a bit of caulk and aluminum flashing would easily cover up the horizontal seams. though if they leaked 20years down the road, fixing the leak without being able to step on the roof would be a challenge.
  • rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
    Re: making a waterproof roof out of solar panels

    Opps this image was supposed to be first.
  • rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
    Re: making a waterproof roof out of solar panels

    By not having to spend $0.80 to a dollar pre square foot on roofing the cost of the solar panels is reduced by about 20%

    In today's market I think that is significant.

    Just look at how fast the bankrupt Evergreen panels at 78 cents a watt sold out in a few weeks, while for only 25 cents more one could get regular solar panels for about a $1 each.

    Furthermore if manufacturer's sold panels with out the aluminum frame the cost per watt would go down even more.

    Of course retrofitting an exsisting structure this way is unpractical, but for new construction I wonder why it is not used more!
  • Shane JacksonShane Jackson Solar Expert Posts: 49
    Re: making a waterproof roof out of solar panels

    Your numbers don't add up. I know here (not too far from you) the cost of roofing is around .80sqft installed. Your numbers are fine here. However the for this to equal 20% of the cost of solar panels you would have to be paying roughly $4 per sqft of solar panels. That just isn't going to happen. Even if you use a price of .50/watt for laminates from sunelec that still works out to approx $5.50 per sqft (148watt panel 51x38 or 11watt per sqft). That is not counting freight, adding a junction box, or any labor for installing everything.
  • rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
    Re: making a waterproof roof out of solar panels

    you are overlooking the fact that you no longer need a racking system at around 15 cents per watt.

    If a 3x5' panel makes 200 watts and you save 3x5x.80 cents for no roofing that is $12 plus no racking savings of $30 or so which is $42 or 20% of 200watt panel which costs $200. Assuming cost is $1/watt which is the current selling price for panels my math works out quite well.

    furthermore if solar manufacturers sold the panels with out the frames this would reduce the price of a panel even more around 10 cents a watt, assuming cost of aluminum is $1.40 a foot. I have not been able to find it cheaper, though I'm sure big panel manufacturer's pay less than that, but not a whole lot less.
  • miscrmsmiscrms Registered Users Posts: 15 ✭✭
    Re: making a waterproof roof out of solar panels

    Anyone tried the Unirac Sunframe racks? Like the idea of the shared rails between the panels with the cap strip that screws in over the top. I'm sure they are not completely water proof, but curious how good a job they do of keeping out the rain. Not the cheapest system, but when you factor in the reduction in number of rails it doesn't seem too bad.

    Working on a solar shade structure over our patio, and also like the idea of going gap-less to improve the protection below from sun and weather.

  • muskratmuskrat Registered Users Posts: 3
    edited July 2017 #40
    I have done this and the roof is about 9 months old ,has gone through a Missouri winter and does not leak. The panels are fastened from the rear with stainless steel bolts to a dip galvanized uni-strut frame. I used 50 year ultracaulk not silicone because it sticks better and does not completely harden.I used 1/4 inch backer rod between the panels and caulked each panel as installed. I used an opaque caulk so I could find any missed spots which I fixed with a plastic spatula on a long stick. the panels themselves depending on the brand may not be completely waterproof. The small amount of leakage through the panels can be captured with a gutter made of aluminum fascia along the bottom of each row and run out the sides. It is important to get the uni-strut runs parallel and the ends square.I overbuilt this somewhat as only 2 rails per panel were required and I used 3 . Don't forget the panels all need a separate ground and ground the uni-strut also .Galvanized uni-strut against aluminum panel frames is acceptable in rural areas like mine but might be iffy in seaside or polluted industrial areas.In my area all wiring must be 9 ft above the floor if exposed, this would also minimize any chance of breaking the panels from underneath. I structure is open on any side wind load uplift must be taken into account.You may note I have left room for latter expansion.This is a line tie system and Ameren UE will not allow  more capacity than yearly net zero plus 5% .Someday there will be an electric car though and I will need more panels. The main reason I built this the way I did ,other than savings on materials, was this design allowed me to build everything but the foundation with one person, as I had time; working from a ladder rather than standing on a steep roof trying to handle full sheets of plywood and roofing metal.
  • wellbuiltwellbuilt Solar Expert Posts: 479 ✭✭✭
    Why not just build a roof and cover it with 2'x10 ' Metal roof and place the solar panels on top? 
    Out back  flex power one  with out back 3648 inverter fm80 charge controler  flex net  mate 16 gc215 battery’s 4425 Watts solar .
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,279 ✭✭✭✭✭
    How about a picture Muskrat.

    If anyone is interested I have used these American made and very pricey bi-facial panels. They definitely are water tight and can be used for projects that require it. I would never use them as a roof though on a home. They look beautiful underneath and the gain in power is pretty amazing with a bi-facial solar panel. See them at the show today!  Bill are you going?

    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
    E-mail [email protected]

  • BB.BB. Super Moderators, Administrators Posts: 30,721 admin
    Hi Dave,

    No, not going.

    Take care,
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • muskratmuskrat Registered Users Posts: 3
    I was just out in my solar panel only roof during a heavy rainstorm and there is an occasional drip.It's not a problem for the tool shed but I think I will check the next sunny day to see if there are any breaks in the caulking or if it is coming through the panel seams.I hadn't found any leaks before when I checked the day after it rained so what little had leaked in had probably evaporated.
  • mcgivormcgivor Solar Expert Posts: 3,436 ✭✭✭✭✭
    Could it be condensation forming on the underside of the panels dripping down? Heat trapped underneath with cooler rain water temperatures. 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • muskratmuskrat Registered Users Posts: 3
    possible but the drops were coming from the panel frames and not from the glass and I didn't see any condensation on the glass
  • rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
    edited July 2019 #47
    I texted schletter and asked if they can sell me 20' long pieces of mid rail clamp extrusion to be used as a gutter between solar panel columns and they said no, unirac said same thing. Good thing they are only 20 minutes away. I will probably just use these
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