GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

How to Insulate a vaulted ceilng (w/ odd roof add on)

kaynekonecny | Posted in Energy Efficiency and Durability on

So I’m doing some major renovation to my brewpub and will be opening up a vaulted ceiling. This is an old road house style building, I think a residential home at one time with many additions, most done very poorly over the last probably 80-100 years. And now it’s all one large restaurant/brewery. This in the NY Catskill area, just making zone 6. I’ve been gut renovating sections at a time and now is the entire front of the building where I need to vault the ceiling. It’s about 50×23 with conventionally framed single gable roof with 2×6 rafters 24oc. What gets complicated is that a larger roof was added over the original roof. They sistered rafter add-ons to one side of the gable and then there is a series of rafters that go up and over the other gable side with purlins and such all the way over the rear addition. So what I’m left with is this smaller gable framing within the attic of this newer system. One gable is part of the (newly) roofed exterior and the other gable is in the attic. I cannot figure out how to best insulate this vaulted ceiling. Initially I was going to install baffles and build down the rafters to fit R30C fiberglass and then a continuous layer of foil faced polyiso on the interior.  But the ridge of these gables would just vent into the attic, not outside. Or I can skip batt insulation and just install staggered layers of rigid foam on the inside? I have a few sources for reclaimed foam. There will be no lighting or mechanicals in the bays so I can be done pretty airtight. Spray foam is really out due to cost. I am not looking for the absolute best insulation value in the world as anything is better than what has essentially been zero in this building. I just don’t want to cause any problems. I’ve attached a crude pdf to better illustrate the construction. Thanks so much for any direction.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    Akos | | #1

    You can use the larger vented attic as an exhaust vent for for the new celling baffles. Just make sure you cut the roof deck there to allow for air flow from both sides.

    Since you say it is a brew pub, I'm guess you want T&G ceiling. In that case, the easiest would to furr down for R24 batts+vent space and install 1" of rigid insulation with taped seams underneath as your air barrier. You can nail your T&G with 2.5" nails through the foam.

    If you have a lot of cheap rigid, it might be cheaper to skip the furr down, just go for 2x4 batts and add enough rigid underneath for the R value you want. You can than strap this out with 1x4s for attaching your finished ceiling.

    P.S. Generally, with old houses and complicated roofs, SPF is the simplest option. Not cheap but hard to get a well sealed assembly any other way.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |