I have heard of people tearing out the sheetrock of one room - the studio/practice room - putting in chicken wire between the studs, and replacing the sheet rock. They also make sheets of thin lead especially for this purpose but I don't know where you find it. I would think you would have to do the ceiling too and maybe under the floor if you want to get serious. I honestly have no idea how effective this is but I remember reading that synthesist Wendy Carlos did something like this to a home studio to cut rf interference.