The problem is the home was built in 1970 and has 2x4 walls. The inside walls are finished and the exterior walls are sided. I am willing to take off the siding and insulate the home from that point on. However, I am wondering what would be the best way to do that. Attach some studs and use fiberglass or Styrofoam and what thickness. I would appreciate any and all info if someone has ever tackled this type of project.