In my opinion, and in this climate, pole barns have there place. Not doubt. I would never build one onto my house (my dad did and 30 years later had to cut in a foundation because the pole rotted off.). I've seen people insulate them with spray foam. Just spray the underside of the steel, purlins, girts, and poles. Something I would never to. NOW. We have designed a few buildings that were pole buildings, but they had full footings/foundations. Poles sat on the foundation. It is still cheaper than traditional stick framed, but not the short comings of a pole barn.
While I'm a big fan of spray foam, I haven't had the opportunity to experiment with spraying the back side of Tyvek wrap. That would allow the exterior panels to be replace if necessary and not develop condensation on the bottom side to rust.