How do I replace insulation in the corner?

Question

I'm re-insulating a room in my house, and have come to the corner. The studs are arranged like so:

x| | |
-
-

x = the space I'm talking about, | = studs of an interior wall, - = studs of an exterior wall.

Peeking in, I can see there is some loose fibreglass insulation in there.

Question: What should I do about that space? I can see 3 possibilities

1. Try to rip out as much of the existing insulation as possible (maybe with a linoleum knife?), and try to re-fill with Roxul (the insulation I'm using for the rest of the project.
2. Same as 1, but fill the space with Big Gap Filler
3. Don't try to remove the existing insulation, and just stuff a little more Roxul in there.

What would people who actually know what they're doing suggest?

Answer 1

I wouldn't attempt to remove the existing insulation unless there's a health hazard (e.g. mold). It was put there during the middle of framing because of how difficult the space is to access. My personal solution would be to spray a little big gap filler in there because it's designed to expand and provide an airtight seal. Other types of insulation, like fiberglass and Roxul lose their effectiveness when compressed. Much of the insulation in them comes from trapping air in pockets. So you'd get less efficiency after cramming it through a small crack.