That looks like a very nice piece of work.
I too am building a home automation system having moved into a new house. You can see it at http://219.88.69.69/2WG/
I use ethernet for input and output and to use its world wide connectivity.
I am planning to pull excess heat out of the roof space in winter to reduce heater use. Hence I have thermometers in the roof space to measure the resource and will need to implement a fan controlled by the Arduino.
My focus is just on lounge heating - we do not spend enough time anywhere else to want the whole house at the same temperature and since we can open or close internal doors as required we can keep other areas at a reasonable temperature if required and can make occasional use of electric heaters when needed.
Good luck with your project.
Cheers
Catweazle NZ