you mean that because the cables are spread all over the house over too long distances, I will have problems with the operation?
Yes, for example a temp sensor may only produce 1v if it's cold, you don't need much noise to stuff that up and also if there is a voltage drop in the line you could read a much different value.
RS-485 doesn't fix the problem as such, what I (and I think marklar) am suggesting is that you have several processors (or "nodes", could be Arduinos or any other processor/board type) distributed around the house, each taking local readings and feeding the information back to a central controller.
RS-485 is probably the best medium to feed this data between nodes and the controller.
Rob