cable connection between 2 Arduino long distance

Hello everybody,

I just learn to work with Arduino tu update controls in my home. For dataexchange I want to connect local controlers like heating system with the central controler that will be supposed to connect to internet.
I tested connection between 2 Arduino by I2C, it seems limited at about 20m.
What type of wire communication to use for longer distances?

Thanks for your help

Armin

Try RS485;

https://arduino-info.wikispaces.com/SoftwareSerialRS485Example