We have a 1960’s 2-story detached garage.It has poured in place concrete walls and a on-way structural concrete garage floor slab supported ½ way the width of the garage with a steel beam and 2 steel posts.The space below the garage is currently just used for storage and is a ‘walk out’. It only has 7’-2” clear between the floor and underside of concrete slab above.The beam cuts that to 6’-5” clear.

We are about to have part of the structural slab repaired by demoing out a portion, shoring, splicing in new reinforcing steel and pour new concrete due to moisture issues and corrosion.A new floor coating would then be installed to control the water & salt issues.We are in zone 5 of Michigan. We are hoping to move our workshop to part of the space below the garage to get more space inside our house. I am considering installing a split system to help making the shop comfortable with the temperature swings & hopefully condensation?The garage space above is unheated and not insulated.

The question is how to insulate the ceiling and walls.I am not going to occupy it for more than a few hours on the weekend but am not thrilled by the idea of leaving my tools in an unconditioned space. Mainly concerned about condensation & rust with temperature swings. I am considering 2” of closed cell foam on the ceiling to keep 7’-0” building code clear.I am also considering finishing out just half of the space.

Any comments are welcome! Right now we are trying to figure out if this makes any sense.I don’t need perfection but I don’t want to make a big mistake either. Thanks!