Vapor barrier or not?

[dimarcelli]

I can't decide on whether i need a plastic vapor barrier or not. This is my garage layout. The three orange walls and single green wall make up the finished shop room. This room will be heated through the winter and cooled during the summer if need be. The orange walls are insulated with faced r-13 and covered with 6 mil poly. The interior green wall is insulated with faced r-13 but no poly. (Why i didn't use the plastic, i have no idea. In a hurry i guess when i did it) The next area i'm insulating will be the parking area. Those walls are blue. I bought some kraft faced r-13 for those, but what im wondering is, should i use the poly barrier here too? This area will not be heated through winter, maybe only three or four days out of the season.

I do plan on installing a drywall ceiling in this area as well, with blown in cellulose insulation, R-49. The grey lines indicate doors, and the garage door is insulated. During the summer i do plan on parking in here, but during winter if my truck is covered with snow it's going to stay outside. Id rather not have the water mess and additional moisture.

I forgot to add, the back rectangle is the back half of the garage, which is not insulated and i really don't plan on installing any in the future. I think i'll just leave that cold storage.

 

[Falcon67]

That really depends on your climate. I have a whole 960 sq/ft heated to varying temps and cooled when needed and no vapor barrier other than whats on R13 batts. BUT - we regularly have dew points in the single digits and I can run a 30K propane heater for a hour and not get condensate on the steel door because it's so dry here. We got an inch of snow last week and there are cracks in the ground you can drop pencils into. Humid in the summer is 60% RH. People start complaining at about 45%. RH sometimes goes low enough in summer that it won't register on my race weather station. So what works for me may well not work for you. From what I see and read about "those" regions, if you need 6 mil plastic, it best be sealed up air tight to the studs.

 

[dimarcelli]

Sorry that's one thing I forgot, my location. I live in northern indiana. Winter we usually see days with highs around 28-32F. The nights, in the middle of the season we can usually expect 10-15F. In the summer it can get quite warm, last year we saw 104 but that was only for a couple days. Dewpoint can run low 70s mid 60s in the summer.