My son lives in a 1930's cement block and brick construction house. It is in excellent shape and he would like to insulate without destroying the exterior appearance. Someone suggested pouring pearlite beads (or something similar) into the block and filling all the air space. There is about a 2" air space between the brick and the block and they are tied together with bricks into the block about every ten courses. Is anyone familiar with something like this and is it a good option. We have added insulation in the ceilings and are looking for more energy efficency. Any other ideas or suggestions are welcome. Thanks in advance for your ideas.