The only retrofit fan speed controller I know of is Visia RF. There is supposedly an Insteon version, but I dont know how good it is and it won integrate with OP. I have a couple fantech fans and a fireplace blower that I control from Centralite elegance, it's a hard wired system. So if you plan to have other zwave devices like door locks, you may consider investing in Vizia RF, it plays well with HAI controller.