Foam vertical around perimeter of Barn

[camnick]

My pole barn is starting to go up this week. I am looking to put 2" of XPS foam under the slab. People at work have told me to put foam 3' down around the perimeter of the floor. So here's my questions. Shouldn't I put this foam on the outside of the 6x6 posts to stop the cold? How thick of a vapor barrier do I need under the foam on the floor?
Thanks

 

[tdkkart]

The only issue with putting the foam on the outside is keeping the top edge out of the weather. Ideally you need the foam to the top of the slab, which is usually above grade.

I've got mine around the inside of the posts, actually used the foam as the concrete forms. The top of the foam was exposed around the outside edge of my concrete, but because of the way I did my steel walls and baseboard it ended up concealed.

 

[camnick]

How far down did you go below grade with the perimeter foam?

 

[tdkkart]

How far down did you go below grade with the perimeter foam?

24" down from the top of the slab.

 

[rburke65]

So if you drill the holes for your posts, then install the posts, now you have to go back and, and what?, hand dig down 2 feet in order to install your foam board? Or does someone have an easier way? Can this be done with a backhoe?

 

[tdkkart]

So if you drill the holes for your posts, then install the posts, now you have to go back and, and what?, hand dig down 2 feet in order to install your foam board?

Yep, hand dug all the way around and once across the middle of a 30x40 building. Not alot of fun, but not all that bad.