garage

Hello! I've got a garage in thr garden built by the previous owner in 1991. It has a sloping (gable?) roof with a couple of veluxes. It's a cold roof design, with some insulation between the joists, but I want to add some more insulation to the walls and ceiling as i plan to use it as a wfh...

I'd like to insulate my concrete garage and I'm not sure if I need more insulation? Internally I plan to: 1. Paint the concrete slabs and roof with anti condensation concrete paint 2. Use DIY spray foam insulation kit on the ceiling and walls ( Link Removed ) 3. Fit plyboard 4. Fit sound...