Interior Vapor Barrier

[Danno]

Hello :-)

I'm looking at what type of vapor barrier to use on the inside of my workshop I'm building. Please see an earlier post, http://www.construction-resource.com/forum/ftopic4554.html for details. I've nailed panel siding directly to the outside of the studs and will insulate with FG, not sure if it will be kraft, foil, or bare faced.

I've got a bunch of 4-6mil visqueen that I used to cover the roofing for the last several months. There's plenty of it, but there's lots of staple holes and small rips in it.

So could I use #15 felt, #30 felt, my used visqueen, or new visqueen or what? I also understand there's a difference between #30 felt and 30# felt, depending on where the '#' is placed.

Thanks!

PS: If it makes a difference, I'm north of Seattle. Lots of rain but not much snow or persistent sub-freezing weather. Summer rarely hits 80.

[danh]

To be honest, whether or not the visqueen has holes in it doesn't change its performance as a vapor barrier. However it does change it's performance as an air barrier. And generally with fiberglass insulation, condensation problems are air leakage related.

In your climate, a vapor barrier may not be justifiable, especially if you are planning on running A/C in the shop during the summer. In that case, any building paper, felt, etc will work - pick the material that is the easiest to tape and seal.

And generally if you had wanted to prevent moisture problems with the visqueen, you would need to be just as diligent with the taping and sealing.

[Danno]

Thanks, danh.


I'm a bit confused by your answer. Maybe I'm using the wrong terms?

As I understand it, a vapor barrier is needed on the warm side of the insulation to prevent condensation of the water vapor on the cooler parts of the insulation and interior side of the exterior wall. So I wonder if my holey visqueen would allow too much water vapor through.

I definately won't be having A/C.

As far as what's easiest, I'd think putting up visqueen would be the one. Get a 10x25 roll to cover almost a whole wall without splices. I'd do the same to the bottom of the ceiling, too, I suppose.

So I'd duct tape around all the edges? Stapling wouldn't be enough?

Cheers!