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I have a shed that was just built with the idea of being used as an entertainment shed. Although we call it a shed, it was built more like a 10x12 house. I currently am getting the electric installed and am trying to figure out what I need to use for insulation. It will be climate controlled. We live in southern Ohio so we have all 4 seasons and a fair bit of humidity with quickly changing temps from day to day.

The shed has vinyl siding with Tyvek wrap underneath and a metal roof. The floor has a layer of rigid insulating board already. My question is do I need to use faced or unfaced insulation? My main concern is development of mold. With the moisture barrier on the exterior and sealing up any openings with spray insulation, will having faced insulation create a problem with restricting air flow? Also, the ceiling is open (like a cathredral ceiling), so do I just install the insulation then drywall directly over it like we are the walls?

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    Pictures would help us give you better answers – Machavity Jun 16 '17 at 14:50
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Housewrap isn't a moisture barrier. It's an air blocker and drain plane that allows vaporized moisture to escape. Use either faced insulation or bare insulation with poly sheeting on the inside. Modern homes are build with poly sheeting sealed at all edges with specially-designed caulk.

I'm not sure I understand your ceiling question, but typically it's done the same way unless it's blown insulation, in which case that's done after drywall.

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    Just to be clear, you want the paper face of the insulation facing inwards, basically touching the back of your drywall. Your cathedral ceiling is treated the same as a wall, with insulation and no venting. Note that this means it's even more important that your roof doesn't leak, as even small leaks can quickly lead to sheathing rot and mold in your insulation, but that's just the tradeoff of having a cathedral ceiling. – Shimon Rura Jun 16 '17 at 15:52
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You can use faced or unfazed batt insulation, but make sure you fill the stud space...if it's a 2x4 stud then use 4" batts...if it's a 2x6 stud then use 6" batts. However, do not use poly sheeting.

Poly sheeting will allow VAPOR to pass, even if the sheets are taped, (I.e.: around switches, outlets, etc.) but does allow that same vapor to escape back into the room when it turns into MOISTURE. That vapor turns into moisture when it hits the dew point. If we find poly sheeting when we remodel, we cut it out.

Ceiling insulation needs to be vented if it's in an attic. If it's truest open beam and decking system, you need to install rigid insulation on the roof with a good peel and stick vapor barrier (like ice and water shield).

  • Polyethylene sheeting is essentially waterproof. And vapor is moisture. Moisture can be liquid or gas (vapor). – isherwood Jun 16 '17 at 15:58
  • @isherwood The type of vapor barrier or retarder depends on the location of the building. See Building Science Corp. at buildingscience.com for a complete discussion on this, but essentially there is a distinction between VAPOR BARRIER and VAPOR RETARDER. poly sheeting is a vapor barrier and is recommended in Hygro-Thermal zones 4-7, but not recommended in zones 1-3, which includes Ohio, which is where they said the shed is located. – Lee Sam Jun 17 '17 at 2:57
  • Fair enough, but that contradicts the second paragraph of your answer. You're describing poly as a retarder. – isherwood Jun 17 '17 at 13:10
  • @isherwood I've read the article twice and I still don't understand everything. I think it has to do with humidity and the changing seasons. It seems like when the season CAN change, then the process reverses and the moisture in the wall needs to escape...I think...and poly sheeting doesn't allow that. My second paragraph should read, "...but does NOT allow that same vapor to escape back into the room..." – Lee Sam Jun 17 '17 at 15:44

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