I have a one and one-half story house. I want to put some additional insulation behind the upstairs walls. The walls are 2x4, 8' tall, 16" on center, with sheetrock on the interior side. The voids between the 2x4's are filled with R-13 insulation. The new insulation is to be connected to the exposed backside of the 2x4's which I can get to in the attic space under the roof behind the walls. How do I connect insulation to the back edge of the 2x4's. I've always put insulation between studs, before never on them. There must be some common practice on how this is done. Thanks for your help.
Mike
Mike