Garage foundation insulation

[bagged89s10]

Starting to dig for my foundation in the next few weeks. Detached 36x24. Footings 42” deep to the frost line. I don’t plan to continuously heat the garage in the winter. I’ll probably only heat it with either a mini split electric heat pump, or natural gas if i get gas pulled to my property from the street. Heat would be only when plan to be out there for a few or more hours at a time. I will insulate the walls and ceiling. I’m not going to have running water out there so I’m not going to have radiant heat.

I’m thinking just to put rigid insulation around the exterior of the foundation walls down to the top of the footing.

I’m thinking no insulation under the slab will help keep the shop a little cooler in the summer by and a little warmer in the winter.

Does this sound reasonable and what thickness insulation do I need around the foundation? I’m in Connecticut.

 

[vekster]

I put 2" on the inside around the perimeter when i did mine last year.
The only reason it was on the inside is because i didnt want to see it on the outside as my grade is a little lower than my floor.

 

[bagged89s10]

I put 2" on the inside around the perimeter when i did mine last year.
The only reason it was on the inside is because i didnt want to see it on the outside as my grade is a little lower than my floor.

I guess inside the foundation would make more sense for a garage. I don’t want to deal with having to cover up insulation on the outside either.