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New construction With new Solar system

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  • New construction With new Solar system

    Hello, what is the best way to install the solar panels on new construction. Should the feet go on after sheathing, then roofing, then install the rail and panels?

    Looking for the best install method and most water tight system since its new construction.


  • #2
    Not entirely tongue in cheek, the best way to keep a roof watertight with respect to solar installations is to put the array somewhere other than on a roof. Roof mounts are usually cheaper than ground mounts, but a ground mount won't cause leaks into your living room.

    If an array is roof mounted as most are, the method of mounting will be dictated to a large degree but not entirely by the mounting method. For example,tile hooks, if used will go on at or with the tile. Conventional attachment via posts can be done before or contemporaneous with the roof work, but before shingles/tile. Sometimes it's possible to do post type supports when the roof is being finished but that takes a fair amount of coordination between the builder and the PV installer.

    FWIW, I prefer posts that allow at least 6" of clearance between top of shingle/tile and bottom of panel. that allows more air circulation around the array making for lower array temperatures and thus better (more) output, a way to at laest peek under the array and maybe spot problems a bit sooner and the ability to double flash the supports - a method that has stood the test of time.as being pretty reliable and well known.

    Adding PV to new construction has some advantages but some of them come from being able to consider adding PV at the design stage rather than after design but before construction. On a tract home, that's less important. On a custom home, not doing so is losing out on a golden opportunity to really get it right.

    Either or any way, I'd suggest you get any PV system separately from the builder. You'll get a better product and better value. Also, use a reasonable, that is, not to liberal or conservative a value for annual electrical usage for the new house. If you have an EV add that usage, but if you don't, consider that many people getting PV claim to be getting an EV soon. Seems to me few do. Size a PV system accordingly and know that offsetting b100 % of an electrical load may not be the most cost effective way to the lowest long term electrical costs.

    If you have room, consider keeping the array open enough so that it's possible to get at every panel for service, particularly if you will be using micros or optimizers. Someday, you or some other owner will need to get at a panel that's perhaps in the middle of an array. Serviceability will then begin to take on more importance as arrays age and access issues not thought about at installation begin taking on more importance and get higher visibility.

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    • #3
      My standard recommendation is cover the entire roof deck with WR Grace Ice and water shield. It seals penetrations and acts as a long term water proof barrier. The only problem with it, is UV degrades it so thats what the roofing you put on afterward takes care of. If you are going with shingles go with one of the various flashed in mounts and hand them to whomever is doing the roofing so its covered by the warranty. Its not that hard to lift up shingles and add them after the fact but that usually voids any roof guarantees. It is a lot easier to hit the center of the joists with mounting bolts if the shingles are off. If you are planning to put a junction box on the roof make sure you buy a roof box that can be flashed in.

      Note with respect to JPMs 6" gap recommendation, its good idea if your mounting system design will let you do it. Just be aware that wind uplift may be an issue in high wind zones, I could not get a off the shelf system design for my racking with a 6" gap and had to live with a 4" gap as I am in high wind zone.

      BTW make sure you have some steel conduits installed from the basement to the attic for the wiring runs .

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      • #4
        The plan is to have the solar attachment post put on first then.

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        • #5
          If you are doing asphalt shingles, then the L-feet and flashing is best installed as the roofing is installed. The flashing still needs to be in between layers of shingles in order to properly shed water.
          Have your solar designer send the plans to the roofer. They will install the mounts as they would any other flashed opening.

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