Shop / Tools insulation for old construction heated workshop

[Wulf]

i have a heated shop space which is stick construction built 1950ish (not sure just a ball park). It is built with clapboard siding over studs with no sheathing behind the siding.

the shop has a gas furnace and that itself does enough to keep it warm but I'd like to add some insulation on the cheap.

I understand the ideal solution is to pull all siding, add insulation/sheathing/vapor barrier as needed, and install siding over it. unfortunately that's not in the budget.

Can I use foam board or reflective bubble insulation directly over the drywall in the interior for a temporary solution?

 

[The_Lobbster]

As long as the siding is watertight, I would see no problem just using foam board. One of my friends used foam board that has a reflective layer on both sides in his car port type structure, with about a 3" air gap between the board and the metal siding.

Spray foam would be an option as well, but again, need to make sure there isn't any water leaking by.

 

[Wulf]

I was thinking about this a bit -- maybe I throw up some firring strips to attach the foam board to so there's another air gap?

I'm not planning to do the entire thing at this point, just the south wall and south west corner to create a home office space.