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Insulation for a stick-frame roof — but we want the exposed beam look

A.J.W. | Posted in General Questions on

so we bought a house that was built in the 50s and we had take out the drop ceiling and old drywall ceiling above that to run new wiring.

Bottom line – wife saw the open ceiling and asked if we could keep it that way and ya’ll know that saying. Anyways – I look at the roof and it is just 1×6 boards laid across the rafters with a shingle roof on top. Roof nails piercing the wood all over.

So I would like to give my wife the look of exposed beams but I am thinking how do I insulate it. The roof is brand new on the outside, so I don’t want to disturb that.

My thought after doing some reading and watching some Utube videos is:

1 – attache a small piece of wood on the roof rafters and then sliding 1.5 inch Poly-ISO roofing insulation in-between the rafters. This will give some air space between the roof and insulation.

2 – then attach T&G on the underside of the small piece of wood to give my wife the look she wants and also another layer of open space for air to flow between the insulation and T&G.

So now my question – (we live in NE Florida and the house faces south):

Will this be enough insulation to keep the rooms warm and cool?

OR should I double up the insulation and apply it directly to the underside of the roof?

Thank you for your time – it is greatly appreciated.

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  1. GBA Editor
    Martin Holladay | | #1

    In northern Florida, most building codes require at least R-38 of ceiling insulation. You can call your local code authority (a) to see if your local code is different, and (b) to see if the code applies to retrofit work (it usually doesn't). Aiming for at least R-38 makes sense.

    You can either (1) add one or more layers of rigid foam above the roof sheathing -- an approach that requires you to install new roofing, and a solution that doesn't address the nail penetrations -- or (2) Thicken the roof framing so that you can add enough insulation on the interior.

    If you choose (1), you should read this article: How to Install Rigid Foam On Top of Roof Sheathing.

    If you choose (2), you should read this article: How to Build an Insulated Cathedral Ceiling.

    If you install your insulation on the interior, you can install any type of interior finish material you want once the insulation work is complete. If your wife likes tongue-and-groove boards, you can install tongue-and-groove boards. (You can even install fake beams under the tongue-and-groove boards to fool visitors.)

    Just remember that tongue-and-groove boards aren't an air barrier, so you'll need some type of interior air barrier (usually, taped drywall) above the tongue-and-groove boards, especially if you install a fluffy insulation like fiberglass.

  2. A.J.W. | | #2

    Thank you for your advice and recommended reading Martin. Much Appreciated.

  3. A.J.W. | | #3

    Mr. Holladay - Do I still need a space between the roof and insulation for airflow? I read an article on here that air flow space is not scientifically based and it's better to have it tight and sealed up.

  4. GBA Editor
    Martin Holladay | | #4

    If you are using a fluffy insulation like fiberglass batts, mineral wool, or cellulose, building codes require a ventilation gap between the top of the insulation and the underside of the roof sheathing, even in Florida.

    That said, there are two basic ways to create an unvented roof assembly. You can either (a) install an adequately thick layer of rigid foam above the roof sheathing, or (b) install an adequately thick layer of closed-cell spray foam on the underside of the roof sheathing. For a thorough discussion of unvented insulated roof assemblies, see How to Build an Insulated Cathedral Ceiling.

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