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PV panels on a flat roof

user-6610113 | Posted in General Questions on

I am retrofitting a flat roof – new insulation and water control layer.  I would like to have PV panels installed in the future.  Any details and/or recommendations on how I can prepare to house/attach the panels?



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  1. Expert Member
    Michael Maines | | #1

    Matt, usually PV systems on low-slope roofs are ballasted, not permanently attached. But you could install metal fins installed above the roof membrane. Either way, there is no reason to take special steps now regarding the structure, as long as your structure meets or exceeds code requirements. The one item that might be good to install now is a conduit for electrical conductors, if you don't want them installed on the exterior of the walls. You need to use galvanized steel conduit for this, not plastic, in most places.

  2. Expert Member
    BILL WICHERS | | #2

    I would have rails installed on the roof to support the future solar system. I used to use the ballasted “non-penetrating” roof mounts commercially for antennas but we stopped due to problems with them blowing over in wind when improperly installed. Many commercial landlords won’t allow their use either.

    For conduits, run two — one sized for power conductors and the other a small 3/4” conduit for control conductors. Have a solar contractor quote you a system and ask them to spec the power cabling gauge and type so that you can install the correct size conduit. I’d put the conduit through the roof using a commercial style stepped rubber boot, and not a pitch pot. Use metal conduit and continue it all the way to wherever you’ll install the electronics in the future. Have electricians install the conduit so that it’s done correctly without an excessive number of bends.


  3. Expert Member
    Peter Yost | | #3

    Right on Michael -

    My colleague and GBA contributing editor Steve Baczek has a "flat-roofed" Passive House with ballasted PV system:


  4. tommay | | #4

    What kind of flat roof?

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