The house is made of a double brick wall and the joists are sitting on those walls. So basically the current wall that is there is not holding anything, it is just finishing. ( lathe and plaster) So once i remove that i am left with a bare concrete wall.You could, but aren't your above grade walls wood framed? Don't you want to insulate the wall stud cavities? If you use the metal channels to hold the foam make sure you aren't going to need the wall's wood framing strengh later on down the road. All your interior wall coverings will have to be anchored to those narrow metal channels you see in the pictures.