DYI attic buildout newby

[Deleted member 32]

I've purchased a new (to me) home recently. It has 2000 sq attic space that is already wire/sub-floored and has the HVAC lines and electric ran by builder. I also have similar space in the detached garage. I want to build and office, then 2 bedrooms and bathroom in the house attic space. Probably a 1 room apartment over garage. Looking at insulation options now. I was given 2 large pallets of foam board I'm trying to determine if I can use.