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Installing A Vapor Barrier Over Insulated Concrete Walls

I am insulating my garage and need to know if I need to apply a vapor barrier between the concrete walls and the wool batting. The walls are poured concrete and have been framed out. I received a supply of wool batting but although the manufacturer says it resists the moisture, I live on Orcas Island in Washington and moisture is out life out here. I will also be putting it in the ceiling. So I wanted to be sure about the layering before getting started. I am doing it myself to cut costs so I would appreciate any free advice you pass along to me. Thank you so much.

K.M.
Orcas Island, WA

Vapor barriers - to add on or not. Everyone has an opinion on this one and that includes me. My experience tells me that unless you live in a desert climate you need a vapor barrier. Many builders don't add vapor barriers to garage walls as they are not considered a living space. The purpose of the vapor barrier on concrete garage walls is to prevent warm air from condensing on the cooler garage concrete walls. If that happens moisture can run down the garage concrete walls and you may experience dry rot, mildew or mold.  

So based on where you live I'd definitely recommend applying a vapor barrier. In your question you stated you would apply it between the concrete and the wool batting. You would actually want to attach it over the insulation towards the heated area where the drywall would be installed.

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If you placed the vapor barrier over the concrete you would possibly have condensation building up on it. So, make sure you have it installed in the correct place.  If not installed correctly the vapor barrier won't be as effective. Your best bet would be using a 4 mil plastic sheeting continuous vapor barrier.

Good luck with your project.

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