Insulate between the joists?  The front entrance was initially recessed under a concrete slab front porch covered by the overhanging second floor. I have pushed the front entrance out to extend straight down from the second floor. The new entryway is six feet by six feet.  The finished slab was 7″ below the finished hardwood of the former entrance so the floor level was raised using 2×8 sleepers.  I have not closed anything in yet, but today is the day.  I have insulated the 2×4 walls from top plate to bottom plate. The bottom plate has been sealed to the concrete slab to prevent air leaks. The ceiling is under an existing finished space, so insulation in no an issue there.  What about the floor?  Do I need to insulate between the joists before installing the subfloor?