+ Reply to Thread
Results 1 to 9 of 9
  1. #1
    Join Date
    Jan 2014
    Location
    Northern Va.
    Posts
    5

    Default How to insulate a shed with metal roof?

    I am re-habbing a 14x28 foot wood frame shed. I would like to install an insulated ceiling to hide the metal roofing. The shed has a wooden floor, T1-11 uninsulated walls, four windows and a sloping metal roof using Master Rib metal roofing. I think the rafters are 2x6 set on 24" centers. The roof has a layer of vapor barrier material installed right up against the inside of the metal (more for leak prevention I think). There is a screened ridge vent the length of the roofing. The lower ends are closed off with T1-11 to prevent insects from free entry into the shed. I understand I need to provide for some airflow between the metal and whatever I use for insulation, and that I should have a good vapor barrier between the finished room and the insulation. I am wondering if I can use fiberglass roll insulation with a vapor barrier on the inside, then finish off the ceiling with some sort of thin wood paneling?

    I believe I will have to install some screened vents at the lower ends of the rafters to provide for some intake air, as I don't expect just the air flow from the ridge vent to be enough flow.

    To also ensure the air flow needed to prevent condensation I was thinking of installing something like Durovent plastic spacers between each rafter for the full length of the run. The idea is they would ensure the fiberglass does not directly touch the metal roofing. The Durovent would go up against the metal roofing, with the big dimples holding off the platic from the metal and providing space for air to flow between the plastic and the metal roof. We live in the foothills of the Blue Ridge mountains and it is very humid in the summer. The winters are not too bad, with not much snow. Not sure yet how to heat this room, but for now it would be electric heaters when the weather is cold enough. Eventually I would also insulate and finish the walls.

    From my reading it must be common to just install roll insulation against the metal roofing, but the reading also says that is not a good idea, as any water can collect in the insulation. Air flow and a vapor barrier is necessary to prevent the metal roof from condensing the plentiful moisture in the air on days when it is warmer inside the shed than outside.

    OK folks, am I on the right track?

  2. #2
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,969

    Default Re: How to insulate a shed with metal roof?

    I would install Celotex to the bottom of the rafters, tape the seams or use 2 overlapping layers, then cover with sheetrock.

  3. #3
    Join Date
    Jan 2014
    Location
    Northern Va.
    Posts
    5

    Default Re: How to insulate a shed with metal roof?

    I wanted to avoid the sheetrock part. It would take more than one person to work overhead on a ladder. The ceiling is sloped and the high point is like 12 feet overhead. The other methods use much lighter materials that I might have a chance of installing single handed. Celotex and similar materials need something to protect from fire, which is where the sheetrock comes in. Celotex in particular seems to have been made with asbestos, at least at one time. Is there something easier than sheetrock to use overhead?

  4. #4
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,969

    Default Re: How to insulate a shed with metal roof?

    Celotex hasn't been made with asbestos for 40 or 50 years. You're probably thinking of something else.

    You should have fire protection in there anyway.

    A drywall lift will make short work of holding any type of sheet goods overhead. They can be rented. HD has one on sale this week for $200

  5. #5
    Join Date
    Jan 2008
    Posts
    2,091

    Default Re: How to insulate a shed with metal roof?

    Ditto on covering Celotex- it is very prone to smoldering for long times if it begins combustion, then turning into flames an hour later. Even luan plywood will do for this purpose (even though it will burn, it's not as prone to ignition and smoldring), but you'll find the sheetrock a lot better in the end. Hire a helper (or a contractor who will let you help) and the hanging is easy. DIY and you'll need experience, endurance, and muscles to keep it all straight and nice. I could do it myself when I was younger but I don't even try it alone now- it's just not worth it.

    Do keep the moisture away from any insulation materials and maintain good ventilation under the roof sheathing. Celotex is very moisture-resistant but doesn't like being soaked.

    Phil

  6. #6
    Join Date
    Jan 2014
    Location
    Northern Va.
    Posts
    5

    Default Re: How to insulate a shed with metal roof?

    Those three items - experience, endurance and muscles are not in my asset set, unfortunately. Think I will check out the contractor suggestion. Walls look like fun, ceilings not so much. Thank you all for the suggestions.

  7. #7
    Join Date
    Jan 2014
    Location
    Northern Va.
    Posts
    5

    Default Re: How to insulate a shed with metal roof?

    One last question. Do the ceiling first or the walls? Seems to me I should work from the top down, but I am a rookie at this.

  8. #8
    Join Date
    Jan 2008
    Posts
    2,091

    Default Re: How to insulate a shed with metal roof?

    The usual practice is top down. This makes it easier to keep joints close-fitting since all you have to do is push up the wall panel till it hits the ceiling, then fasten. Gaps at the bottom are covered with baseboard anyway.

    Phil

  9. #9
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,607

    Default Re: How to insulate a shed with metal roof?

    A friend of mine faced a similar situation and had a contractor install closed-cell spray foam insulation. It will readily stick to the underside of the metal; you'll first want to remove the existing vapor barrier. The spray foam doesn't need an additional vapor barrier, and you won't need to provide any venting other than whatever you need to keep the interior of the shed dry. It can be applied as thin or as thick as you want, but you should have at least 1" of thickness to prevent condensation.

    Sure, it will probably be more expensive than installing something else yourself, but it will be a durable product that you won't have to worry about. Since you plan on heating the space, I would recommend a fire barrier of some sort on the ceiling.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •