New Video=>How To Install Radiant Barrier Foil Into a Cathedral or Vaulted Ceiling

The hottest trend is construction is converting an attic space into a living space. Unfortunately the term “hot” usually describes the room once it is complete. One of the common challenges is to get a decent amount of insulation between the sheetrock and the roof deck. Typically roof rafters are 2”x6” and allow only about an R-19 level of batt fiberglass insulation. With only R-19 insulation it can be difficult to keep the new room comfortable when the roof is a dark color and can easily exceed 170 degrees.

Adding more insulation space between the roof deck and the sheetrock can be expensive, labor intensive and will reduce the ceiling height in the new room.

One option is to ventilate the roof deck and install a radiant barrier BEFORE you install insulation and sheetrock. This method helps keep the heat absorbed by the roof AWAY from the insulation by creating a THERMAL BREAK to reduce heat flow by conduction. This method also forces the energy absorbed by the roof to be converted into radiant energy. Radiant energy then can easily be reflected away with a radiant barrier.

Think of this method as a ONE-TWO Punch against heat gain. The radiant barrier is the 1st line of defense against radiant heat gain and regular type “R-Value” insulation is the 2nd layer of defense. This video shows a fast and effective way to install a radiant barrier into your roof assembly to maximize comfort and efficiency for your new attic room.

Looking for more videos on this topic? Check out my posts below.

  • Everything You Need to Know About AtticFoil Radiant Barrier
  • How Radiant Barrier Saves You Money
  • Should You Install Radiant Barrier on the Rafters AND Over Your Insulation?
  • Why I don’t recommend electric attic fans
  • BlueTex™ is the Ultimate Metal Building Insulation Vapor Barrier
  • 14 thoughts on “New Video=>How To Install Radiant Barrier Foil Into a Cathedral or Vaulted Ceiling

    1. i was watching your video on foil barrier and i have questions about the top and the bottom of the truss. right now there are holes in the board at the bottom of the truss (eve) (spacers) etc.. for air flow, should I seal the holes ??? and i used moure vents instead of pink 3/4 ” for an air channel and should I continue the airflow joining the moure vents at the top peak and back down the otherside ??? please help I am getting condensations coming through my batts and dripping on the floor, is that because of to much airflow????

      1. Possibly. Leaky warm moist air from inside your home can condense with cold attic air and form moisture molecules. The best way to stop moisture is to seal up any areas of leaking warm air (recessed lights, the attic door, windows, doors, etc. – any place air can get in to the attic) to stop moisture from accumulating. Then, once it is all sealed up, have proper air flow within the attic so keep air moving and moisture evaporating. You might benefit from having a professional coming out and doing a door blower test to see what areas need improvement. Good luck!

    2. Your site is very informative and I keep hoping to run across what I am about to ask. No luck yet. I have an 18×24 unfinished studio with open barn type roof using tech shield plywood on 2×6 rafters and a ridge vent. What type of insulation would best benefit this hot south texas weather allowing for air space and also your atticfoil to cover the rafters before the sheetrock is installed? That would mean the atticfoil would be in contact with the sheetrock and airspace would be included above the barrier. This is confusing to explain: Techshield ply>airspace>insulation?>airspace>Atticfoil contacting sheetrock. Should I use tech shield in combination with atticfoil? Do I need insulation inbetween? Is it cost effective? Should I leave out the Atticfoil? (rafter heat conduction is a concern). We have a loft I work in with short headroom from floor to ceiling/roof. How to eliminate or prevent most of the roof heat from radiating inside would help a soon to be installed ac unit and my half fried brain. Thanks

      1. Juan,

        You have a radiant barrier with the Techshield, however if you press insulation up against it (no airspace) you will loose the benefit it provides. I would recommend going the the cathedral ceiling method and using AtticFoil below the Techshield. Technically, this is doubling up on the Radiant Barrier, but you need a product to minimize air flow into the insulation below and be perforated so you do not have a vapor barrier. Another option you can do is put sheets of foam board across the rafters BEFORE you apply the sheetrock (3/4″ is great). Here is an example of Radiant Barrier In An Exterior Wall. You will basically do the same thing except on a ceiling. The foam board will take minimal space AND reduce thermal bridging through the rafters.

        You will end up with: Techshield>foam strips to create airspace>AtticFoil>Insulation>foamboard>sheetrock. Any other questions please call us on the 800 number at

    3. Can you use other types of insulation after creating what you show in this video? Spray foam or rigid foam right against the back of the AtticFoil?

      1. Yes, because the air space is between the deck and the foil, so the foil on the attic side can be touching other insulation. As far as which insulation you can use either but from feedback I have received, the spray foam does not adhere well directly to the foil. Therefore, if you are using spray foam I would recommend a thin sheet of foam board on the foil first, then spray the foam to that.

    4. Hi im finishing an attic in new england with the insulation and furring strips already installed on a cathedral ceiling. I was wondering if I should put a radiant barrier between the furring and drywall? Or is it too late. Thanks for your time and info.

      1. If you already have the furring strips up in between the rafters, then add the foil to them, foil facing the roof deck/air space and then continue on filling with insulation then finish with drywall.

    5. Good info…close to what I need. In new small addition, I have 2×8 ceiling joists, decked with 7/16 OSB, then felt, then metal roofing. Can my ceiling use 3/4 foam board w/ foil up against the 2x8s, giving a 7″ air space as needed for the radiant barrier…BUT…this in view that there will be NO air ventilation in the enclosed “box” I create by covering with foam board. The NO VENTILATION is what concerns me–is that a problem?

      1. The air will then be a “dead” air space which is fine and will work to allow the foil to reflect radiant heat from outside away from the interior. There is not really any risk involved in holding the hot air in the cavity (since it’s not vented).
        It’s worth noting that since this is presumably an addition to a CONDITIONED space, then you should include regular insulation in this cavity as well – for R-value. See how to do this type of installation on this page: Installing Radiant Barrier in a Cathedral Ceiling

    6. I have vaulted ceilings on half of my house, but I installed a radiant barrier on the side that my house has an attic and it works. The Problem is now I have half my house cooler than the other half. Is there any way I can slide attic foil into my vaulted rafters from the attic space. It’s already finished and the only thing between my roofs is one sided face insulation and a sheet of drywall. I was thinking using like a long PVC pipe and pushing a strip I cut into the space and just hope it leaves enough air from the weight of the pvc pipe holding the insulation down. Please help I dont plan to rip the ceilings out.

      1. Without seeing the space I can’t answer this. Only you can tell if there is a way to slide the foil in to the space since you can see what you are working with. If you want to send some photos of the area and get some advice, go to this page and submit your photos and info and we will be in touch: Submit a Radiant Barrier Question

    7. Hey Ed. , I am remodeling a small one bedroom turn of the century cottage. I’ve torn out the low, 7 ft ceiling to vault the interior ceiling. I only have a 2 / 4 roof rafter so only 4 inches at the most space for insulation. Also no soffit vents and no ridge vents. Any suggestions on how to insulate this shallow space? Also. I live in central Texas. Thanks.

      1. For this type of application, I would consider spray foam and fill up the rafters. Then, maybe put another 3/4″ foam board between the framing and the sheetrock. The foam board will provide extra R-value, noise reduction, minimize thermal bypass and won’t drop the ceiling too much.

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