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Thread: Roof mounts on commercial building

  1. #1
    Join Date
    Mar 2016
    Location
    Washington State
    Posts
    46

    Roof mounts on commercial building

    Hi all,

    I have installed many PV systems over the years but never once on a flat, commercial building. The building of interest has torch-down on it.

    Is there a preferred method for installing and flashing the standoffs. I know there are commonly large systems done on roofs like these so there must be a fairly established method.

    What about ballast?

    Also. Is it typical to give the modules any pitch or is it not worth the extra cost? I supposed if they are flat they will get dirty pretty easily.

    Any thoughts on these topics are appreciated. Thanks.

  2. #2
    Join Date
    Oct 2009
    Location
    Austin, TX, USA
    Posts
    8,489
    Quote Originally Posted by bbartmasse r View Post
    Hi all,

    I have installed many PV systems over the years but never once on a flat, commercial building. The building of interest has torch-down on it.

    Is there a preferred method for installing and flashing the standoffs. I know there are commonly large systems done on roofs like these so there must be a fairly established method.

    What about ballast?

    Also. Is it typical to give the modules any pitch or is it not worth the extra cost? I supposed if they are flat they will get dirty pretty easily.

    Any thoughts on these topics are appreciated. Thanks.
    There are many ballasted roof mount systems out there; lately we have been using Unirac and Ironridge; both of them have array planners on their websites. Yes, it's a good idea to tilt the modules; it lets them drain and even a little tilt helps with production. If the roof cannot stand the weight and penetrations are not possible, consider U-Anchor attachments (they aren't cheap). Good luck with your project.

  3. #3
    Join Date
    May 2013
    Location
    Massachusetts
    Posts
    2,269
    Quote Originally Posted by bbartmasse r View Post
    Hi all,

    I have installed many PV systems over the years but never once on a flat, commercial building. The building of interest has torch-down on it.

    Is there a preferred method for installing and flashing the standoffs. I know there are commonly large systems done on roofs like these so there must be a fairly established method.

    What about ballast?

    Also. Is it typical to give the modules any pitch or is it not worth the extra cost? I supposed if they are flat they will get dirty pretty easily.

    Any thoughts on these topics are appreciated. Thanks.
    Rigidly fastened solar arrays on flat roofs, will need to have a flashing method approved by the roofing manufacturer, and installed by a roofing contractor who is certified by the roofing manufacturer. Even if you had all the tools and parts to do it yourself, you void the warranty if you do. In any case, it is in your interest to reduce the penetration count as much as possible. Some attachment methods, like those made by OMG roofing, can be installed close to the roof level with an integrated sheet of membrane that is adhered or welded. Others would be a standoff with a roofing wrap, flashing conical boot, or pitch pocket. This standoff will have to go through the insulation layers and be tall enough to meet the large roofing boots, so it likely will be much taller than the standard products available from Ironridge and Unirac.

    Ballasted solar arrays either need to have a footprint material approved by the roofing manufacturer, or have a brand-specific slip sheet that matches the membrane. Some manufacturers, like Firestone, are OK with a competitor's roofing material for the slipsheet as long as it is the same material. Other manufacturers, like Carlisle, requrie a brand-specific match. The membrane manufacturer will also likely have a paperwork process and fees associated with approving your instalation to not void the warranty.

    Generally speaking, ballasted arrays are more economical to install than rigidly fastened solar arrays.

  4. #4
    Join Date
    Oct 2009
    Location
    Austin, TX, USA
    Posts
    8,489
    +1 on consulting with the roofer (or whoever is standing behind the roof warranty). Different roofing material manufacturers have different requirements. Some, for example, require that the slip sheets under a ballasted racking system be their EXACT brand name material, not an equivalent material of the same type. Some will require that their own contracted personnel install them. Some will require that the slip sheets be attached to the roof and some won't.

    Voiding the roof warranty would be a big problem for you. Avoid roof penetrations if you possibly can; penetrations make the job a whole lot more complicated.
    Last edited by ggunn; 08-25-17 at 11:08 AM.

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