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Insulation question

tom-ky | Posted in General Questions on

New to here and this forum was suggested for a question I have about insulation.

We have a garage that is built using pole construction. We want to finish a area of it for man cave type area that will be heated and cooled.

The building is metal siding and when built had the double bubble reflective insulation put on the walls. We want to frame out the room and insulate it. I was concerned about what type insulation to use because of the vapor barrier. Could un-faced insulation be used ? I did not want to create a moisture problem in doing this. Any suggestions?

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  1. GBA Editor
    Martin Holladay | | #1

    First of all, we need to know your geographical location or climate zone.

    Where is the bubble wrap? Is it between the nailers (framing) and the steel cladding? Or was it installed on the interior side of the posts? (If it's on the interior side of the posts, it should be easy to remove.)

    This type of building is always tricky to insulate, with or without bubble wrap. My guess is that you will need to erect 2x4 or 2x6 walls in the interior side of the existing framing, and that these walls will need to be sheathed with OSB or plywood before the walls are raised. If you take that route, you'll have enough air movement between the existing cladding and the new walls to prevent any problems from your wrong-side vapor barrier.

  2. tom-ky | | #2

    I am in Kentucky. The bubble wrap is in between the metal and the 2x6's. When it was built part of it was already framed out so there is basically a 6 inch wall there, so the osb would be hard to do.

    Thanks for the response.

  3. GBA Editor
    Martin Holladay | | #3

    The steel cladding is also a vapor barrier, like the bubble wrap. To make this assembly safe, you either need to ensure a pretty generous ventilated air gap between the bubble wrap and the exterior air barrier, or you have to insulate the wall with spray polyurethane foam.

    If you want to insulate the walls with an air-permeable insulation like fiberglass, mineral wool, or cellulose, you're going to have to figure out a way to install an exterior air barrier. That's going to be tough, unless you frame up a new wall. And as I said, you'll need a ventilated air gap between the exterior air barrier and the bubble wrap. It's challenging.

    Spray foam may be your best bet.

  4. tom-ky | | #4

    It is basically framed out to the posts already. So what do you mean by framing up a new wall? there is the metal siding with the reflective insulation under it attached to horizontal 2x6's. Then there is a framed up wall in between the post that is approximately a 6" wall. Really don't want to take out any existing framing, willing to take out the bubble wrap if needed. Is there anything we can install ourselves that can be put up against the metal?

  5. GBA Editor
    Martin Holladay | | #5

    Option 1: Install spray foam insulation between the existing 2x6 studs, right against the existing bubble wrap.

    Option 2: Build a new 2x4 or 2x6 framed wall, properly detailed, on the interior side of the existing framing. The main disadvantage of this approach (besides cost) is that you lose interior area.

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