Insulating a house that has Plank walls.

House was built around 1870. The original wood siding was left on the house. What happened , is that Fan fold insulation board was placed over that old siding, and then Vinyl siding on top of that. Would like to have blown in insulation in the walls, but was told that might not be possible because of the plank walls.

Can this be done ? I know that when the electric outlets were replaced, there was enough space for those blue plastic boxes that the new outlets set in. That should be enough room to blow in at least some insulation.

(.-.)

Insulating a house that has Plank walls.