Post Frame Building

Hi all, I have a dilema. I am about to build a post frame building (48 X 84), and in doing so I applied for a building permit. The site is @ my home on 35 acres and 17 Miles out of town, Butte, Montana. The problem is that I mentioned in the permit form that I plan to pour concrete (Floating Slab), and I also mentioned that I might put a heater in it sometime. Well I am being held "hostage", as he now wants to know how I plan to address the frost issue. Now, the post frame construction will be 6 x 6 treated posts on footers @ 48 inch depth. That's the foundation, as I have always known. The Building Official wants me to pour a 42 Inch stem wall to address the frost issue. I have never heard of such a thing. The contractor builds these all over the NW. Doesn't this defeat the purpose of post frame? I don't know how to answer this guy. The slab is nothing more than a parking pad, and not in any way tied to the building. It has no structural value as far as the building is concerned.

Thanks