House wide automation network: CAN or Ethernet?
Although you could use Ethernet and implement a TCP/IP Stack on each controller, and surely use UDP to broadcast sensor readings/commands/etc. I would recommend the use of CAN for the following factors:


Easier to Implement/Code
Very, very lightweight. You can integrate with smaller controllers. A MCP2515 can be used if the MCU doesn't have CAN.
You could use CAT5/CAT6 and use the spare wires and carry 24V or 36V to power the nodes.
The small message frame can be easily fitted inside a sub-1Ghz RF frame if you decide to extend the Bus over RF. You just need to code a CAN to RF gateway, maybe using el-cheapo RFM69 modules.


There's a blog that explore the use of CAN bus for similar use, might worth checking it out: talk2.wisen.com.au

Anyway, if you decide go with Ethernet, UDP would be better so you don't need to worry much with node addressing.

All the best!