Hi Mike
I'm thinking of building a pole barn too so your question caught my eye. I'm in zone 5b so insulation is important, the possiblity of using some kind of earth
berm system like
Oehler's psp, strawbale, clay slip are the main ones I've looked at. If I do build a good size one (40 x 30) i'll probably go with putting the posts on concrete pads, siding with green oak and doing a straw-clay slip insulation, then terracing into the hill to hold the hill since it's into a hill. I am still intrigued with the psp system and have been since i met oehler in 1982 but i mostly worry about termites so i might build a small, say, 15 x 15 structure and bury it to see how it holds up.
What are you using the pole barn for? What zone are you in? rainfall? what kind of roof?
good luck, keep us posted on how you're doing.