From what I have been told by a Monsignor when I asked about this, he said that only people can be possessed and objects, including houses, are obsessed. He said that a house would not really be exorcised, but more so blessed. Now I am sure that there may be special prayers in these instances, but from what I have been told, I believe that only people can be exocized. Of course, all of this is really just symantics.