I am converting a detached garage into a workshop/office, the garage will be
partitioned so half can be used for storing junk and then a separate room
for the office. The garage walls are single skin brick with about a half
inch of render on the outside, the DPC looks to be in good condition with no
rising or penetrating damp the garage has a flat roof with timber joists and
felted roof. I have put rockwool insulation between the joists and
plasterboarded it over, i have also made a stud work floor with polystyrene
insulation and then a plywood top sheet arrangement. The task this weekend
is to make the stud walls and batten the external walls to receive the
insulation and plasterboard. My question is as follows: for the stud walls
i intend to use rockwool fibreglass as they will not be faced against
brickwork. As for the two wall that will be against the brickwork can i
still use fibreglass or should i use kingspan which is much more expensive
bearing in mind there is no damp or condensation? Anything else i have
forgotten?

Thanks for any help given.

Tom