I have been blessed with a recent remodel before moving in to a house. This blessing has turned in to project after project because shortcuts(no code violations to speak of). The house is one of that added rooms as needed and has various construction styles in use. During the remodel in areas where block was the outside wall surface a separate 2x4 wall was built in front of the block (about a 2x4 width away from it). When they put up the wallboard they didn't insulate behind it. Now that Summer has hit full tilt here I need advice. I know these walls need insulation(infrared thermometer indicates that the wall surface is only about 10 to 20 % less than the outdoor temp) but what is going to be the least intrusive mode of installation(trying to avoid tearing out walls and redoing).