What is the best practice for attic air sealing when it's new construction?

In my jurisdiction I have to get my insulation HERS (California's new Home Energy Rating System) inspected before I can install the drywall, and the ceilings will get batt insulation, instead of blow-in. But proper attic air sealing requires that the drywall is already installed, since one of the places you need to hit with the expansion foam is where the ceiling drywall meets the plate. So then, it looks like I'll need to get my insulation inspected, then I will install the drywall, and then I'll have to get up in the attic and pull the insulation off again, so I can properly do the air sealing. That seems like an inefficient practice, and I'm wondering if there is an alternative work sequence that I'm not considering.

  • 1
    That does seem rather inefficient! You might want to call your local building inspector, explain to him what you've just explained to us, and see what he says/recommends.
    – FreeMan
    Feb 2, 2023 at 15:12
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    Please disambiguate "HERS" for those of us not in your jurisdiction. Assuming they have an office you can call, might want to ask them this question. I have vapor barrier between the drywall and the insulation above, so that's what I sealed.
    – Ecnerwal
    Feb 2, 2023 at 15:13
  • aerobarrier. spray foam cracks over time so while initially it will be air sealed give it a couple years and you'll be leaking air. I don't know how you'd install bat insulation without the drywall. Why can't you have it inspected after drywall? Sometimes you just get a deficiency on an inspection and they come back to see the piece that you needed to correct so maybe you get it all inspected and fail the attic, drywall, put the attic insulation up and then get the deficiency removed. Feb 3, 2023 at 4:45
  • OK, I just got off the phone with an energy consultant, and found the answer. Turns out the traditional sequence of construction isn't so good. The latest and best practice is to drywall ONLY the ceiling, tape it, and air seal the ceiling/attic BEFORE any insulation goes up, anywhere. Then we can do a blower door test, and catch any possible air sealing issues. So, the attic gets air sealed before the insulation. This sequence often isn't followed in production homes, and it requires an additional inspection just for the ceiling drywall nailing. But it really is the best way of doing it. Feb 17, 2023 at 17:54


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