Garage Vapor Barrier

Our attached 3 car garage has sheetrock on the ceiling and adjoining walls of the 2 car garage part. I would like to insulate and finish the garage, I would also be installing a garage heater. There was no vapor barrier installed before the sheetrock went up on the ceiling. Can I blow in fiberglass insulation in the attic without it? Or should I take down the sheetrock and put up the vapor barrier? I’m trying to avoid doing this. I’m planning to put up white pole barn tin on the ceiling.

Anyone have any experience with this situation?

My garage has blow in fiberglass directly over sheetrock in the ceiling. The attic space is your buffer. IMO, the benefit of vapor barrier is on the walls.

SuperDave1959 wrote:

My garage has blow in fiberglass directly over sheetrock in the ceiling. The attic space is your buffer. IMO, the benefit of vapor barrier is on the walls.

Humidity/moisture doesn’t care if it’s a wall, floor, or ceiling. If you have a conditioned space and an extreme temperature on the other side of that surface, moisture will start to accumulate and if it isnt allowed to dry will lead to mold.

OP – paint on vapor barriers are available and will likely be your simplest option.

I just did my third stall. Same situation. I just made sure all of the cracks we’re sealed. I took a foam spray can and sprayed all of the cracks. Sealed it up good. Will be fine.

I’d consult a professional, but…..

Since you’re putting steel over the sheetrock, I’d think a layer of poly between the two should be just fine.

Use some 1×4 firring strips to hold the poly up and create a little air space between the poly and the steel.

Another option besides a paint barrier or poly is to have spray foam sprayed to the rock from the top. spray foam is a vapor barrier. I believe all you need is an inch and then you can blow insulation on top of that.

If your planning on heating the garage all winter you’ll want that vapor barrier.
If your you’re only going to run the heater when your out there, you can get away without it.

If your attic has proper ventilation,you should be fine as is,the fiber blow is not going to hold moisture,it will pass through and be brought out of attic by ventilation,AS for the conditioned space below the cieling,i would mechanically ventilate with a exhaust fan vented out through the roof,a humidistat fan would be my choice,as you set humidity level where you want,leave switch on it will come on as needed.