I put up a similar building this summer, concrete floor, 3 rows of block and 18'x20' carport kit with enclosed end walls,9'w x8'tall overhead door. When it is real damp after a night of rain or frost, moisture condenses on the inside and drips. Insulation is a must, I will have to do this in the spring. My steel frame is spaced 5' apart, end walls are 2'x4' spaced 2' on center, easy to insulate. the steel frame is the problem, I priced spray foam, istalled at $1.25 per inch, per square foot. I also considered the white vinal faced pole barn insulation, have not priced it yet. I will cover the walls with7/16" OSB and leave ceiling with insulation exposed. This was saposed to be cheap storage for skidsteer, ATVs and lawn equipt. I would price a wood framed garage vs all steel, it may be cheaper to finish. The steel ribs do hold some dirt and water/snow. The steel frames go up quicker.
Dave