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Community and Q&A

Re-roof prematurely (and fix insulation) when going solar?

Nola_Sweats | Posted in General Questions on

I have a simple gable roof that’s 12 years old, plywood covered with architectural shingles, presumably asphalt felt in the middle.  It all appears to be in good shape, roughly halfway through its realistic lifespan in our climate (Gulf Coast, Zone 2A).  I’m considering installing solar PV panels, and I’m wondering if it makes sense to re-roof now, so I won’t have to pull off the PV array to re-roof in 10-15 years.  Roof is just under 15 squares.

I may need to correct an existing design error: I have an unvented cathedral ceiling, insulated with fiberglass batts, with only a small area at the peak that may passively move moisture into the unconditioned main attic.  I’ve got a/c ductwork and machinery in the unconditioned attic, which I’d like to spray-foam, but comments on this site have dissuaded me from spray-foaming the main attic for fear of trapping moisture in the adjacent cathedral ceiling in its current state.  So I’m reluctantly considering re-roofing prematurely, adding R-5+ worth of foam board outside, then spray foam inside the main attic, trusting the exterior foam board to avoid winter moisture problems in the almost-unvented cathedral ceiling.

I don’t think I can partially re-roof to add exterior foam board only above the cathedral ceiling and not the whole roof, because that would make the roof uneven.  Does it make sense to re-roof the whole thing early if I’m getting solar panels?  If I put on solar panels without redoing the roof, I don’t think I could ever add exterior foam board, so the only solution to the cathedral ceiling would be to pull out the drywall ceiling and address it from inside with closed-cell foam or packed cellulose.

If the premature re-roofing is foolish, I can always have the drywall cathedral ceiling removed and the cathedral ceiling spray-foamed … but tearing out the bedroom ceiling is an option I’d pay extra to avoid, esp. since we’d have to move out while it’s being done.

I’ll take comments on the solar proposal, too: solar bid is about $17k after federal tax credits for a 6.03kw system.  Reputable company, LG 335 panels, Enphase microinverters, and we have the old (good) kind of net metering here.  Would love a backup battery, but the quoted $16k for one Tesla battery is scaring me off.  Thanks!! 

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  1. GBA Editor
    Brian Pontolilo | | #1

    Hi Nola,

    When I worked on an article on installing rooftop PV for FHB (Installing Rooftop PV) with a Colorado solar installer, they told me that they recommend only installing PV over roofs that have at least 10 years of life expectancy. When clients need to reroof, the company removes the panels and racking and stores it for them during the process as a service (at a cost, if I remember correctly). This is something worth asking your installer about.

  2. seabornman | | #2

    If it helps, you may be able to add the cost of re-roof to the amount of solar installation for tax credit purposes.

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