Insulating the ceiling of my shed, gonna put two layers of faced insulation. Shed will be heated in the winter, cooled in the summer.
Which way should the insulation faces be?
Double layer of faced insulation
Insulating the ceiling of my shed, gonna put two layers of faced insulation. Shed will be heated in the winter, cooled in the summer.
Which way should the insulation faces be?
winter is what matters. vapor barrier on the warm side.
ok, so which option should I do? two faces together in the middle? or both faces toward the warm side? or sandwich the insulation in the middle between two faces?
>two faces together in the middle?
yeah, i guess you're right, vapor barrier away from the warm side.
> or both faces toward the warm side?
why would you do that
>or sandwich the insulation in the middle between two faces?
yeah, gotta block all that humidity coming through the roof
I don't understand, are you saying option A) in the OP pic is best? There are only 4 possibilities.
the faces on the insulation don't even do anything, they're mostly just for stapling it to studs. The amount of vapor blocking they do is minimal to nonexistent so the orientation doesn't really matter
this. Moisture ingress to a walls structure generally occurs from bulk air movement through walls and the moisture deposition that occurs then, not primarily from vapor drive itself. This is a result of imbalanced forced ventilation.
doubling up on paper backed pink stuff is pointless. if anything go with option B. you're going to want to do a proper plastic vapour barrier too or else you WILL run into real bad mold and mildew issues in the not too distant future. that paper backing is food, any little bit of moisture will frick it right away.
I already put up drywall on the walls without a plastic vapor barrier, am I fricked? is it even worth putting a plastic sheet on the ceiling if there's none on the walls or floor? The space is just a shed that I'll turn into a gym/workshop and use/heat a couple hours a day max
Put the plastic on the side that faces the higher relative humidity. The warm side, as constructionanon said. Your roof and such should be dry areas; you want to stop the higher moisture in the living space from saturating the insulation.
The paper is there, to only have something to staple it up with.
The inner layer should have the facing on the inside so it acts as a vapor barrier. For the outer layer, peel off the facing paper so it's just the fiberglass batting, because you don't want two vapor barriers trapping moisture between them.
>peel off the facing paper
This is a fricking disaster.
>This is a fricking disaster.
Better than the disaster that would happen with 2 separated layers of vapor moronant in a wall. It would eventually become a moisture trap that would breed mold. Either that or spend an hour or two pulling the paper off 1 layer of insulation.
Related question, is it ok to have a ridge vent without soffit vents for a sealed off small garage attic in a northern climate?
Buy insulation made for the depth of your ceiling joists, and leave a 2 inch air gap between the roof sheathing and the insulation.