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Thread: Metal Roof Insulation

  1. #1
    Member AK_Mark's Avatar
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    Default Metal Roof Insulation

    I have a small cabin with a loft (12x20) in Willow AK. Question; Do I need to put anything between the metal and insulation? Or do I just insulate and seal like any other wall. I plan to use sheetrock on the walls. Thanks in advance! I have already gotten a lot of great information here.

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    Member CaptNemo's Avatar
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    Mark,
    I talked to a lot of people about this with as many answers. What I decided on was to tack up 1" styrofoam board to the bottom of (2x4)perlins and then fill with the pink stuff. I'm hoping that will give enough room for some airflow under the metal. Also used vented ridge cap. I'll find out how well it works this winter. Good luck. CN
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  3. #3

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    Mark, I'd leave an airspace large enough for airflow between the metal and the insulation. Vent the ridge.

    I know of a guy that ran his metal on 2x4 nailers on the rafters, then had a spray foam company come in, spray it filling the voids without any airspace in the vaulted ceiling. He's got a vapor barrier under the sheetrock, that to date has kept the mold and moisture at bay from entering the living space. But, if you pull back the soffit board or the facia on the exterior, it's a wet, moldy mess inside the roof cavity.

    I keep expecting the guy to have a complete failure of the roof on the vaulted ceiling any day now. It's surprised me how long it's lasted so far.

  4. #4
    Member AK_Mark's Avatar
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    Default Metal Roof Insulation

    Thanks for the help! I like the Styrofoam idea. I kind of thought I needed some kind of ventilation. I did not build the cabin I bought it. Itís unfinished on the inside. My wife and I are going work on it this summer.
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    Member AKDoug's Avatar
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    I would just insulate it with R21 fiberglass (those look like 2x6 rafters) with a good vapor barrier on the inside. Almost all the moisture that collects on the bottom surface of a metal roof leaks from the inside of the house. A super tight vapor barrier of a minimum of 6mil visqueen with ALL the seams taped and preferably glued with Tremco accoustical sealant will go a long way to never having any issues. Even though you would end up filling the entire rafter, there should be enough ventilation since the steel is sitting on the 2x4 nailers. Remember that roof ventilation starts with air entering the facia and when it picks up heat along the way it rises and exits the ridge or gable end vents. 2x4 nailers will block some of that flow, but the ribs of the steel will often allow enough air to pass.

    With a cabin that small you will find it tough to find a heater that won't overheat the place anyway. The extra expense of the styrofoam and it's extra insulation value is probably not needed in your case.

  6. #6

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    Quote Originally Posted by AK_Mark View Post
    Thanks for the help! I like the Styrofoam idea. I kind of thought I needed some kind of ventilation. I did not build the cabin I bought it. Itís unfinished on the inside. My wife and I are going work on it this summer.

    Nice place!!!!

  7. #7
    Member AK_Mark's Avatar
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    Thanks! Hopefully we can get it wired, insulated, and sheetrocked in the two weeks that we will be up there this summer.

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