Oh figured it out. It's the pressure thank for water I believe.

 

Yes,the round tank in the lower left of the photo is the expansion tank.

 

beers4all garage is insane...

I did mine on more of a 'budget'. All walls and ceiling are fully finished (drywall, tape, mud, primer, paint) and I did spray foam behind all walls and ceiling. The garage doors are insulated and also have extra insulation on them (rigid foam).

I had epoxy done on the floor so its nice to walk on even barefoot, but if you do a garage floor tile system that would help warm it up a little too. My garage never goes below 5 deg C even on the coldest winter days. If I pull in, all the ice on my car is melted by the next morning.

I've thought about adding heaters but whenever I work in my garage I just throw on an old pair of jeans, hoodie and keep the door closed and its never been an issue in the winter. Just make sure your overhead doors are installed properly and that there are no gaps so you don't have cold air finding its way in. I have flashing (probably not the right word) with a rubber seal installed around 3 sides, and a very thick rubber on the bottom so there's no gaps or anywhere for cold air to come in.

since it's more of a storage/projects garage, I wouldn't bother with heat but I didn't price it out so I can't really comment on that.