I'd just build a function to handle each subsystem & call them all unconditionally from loop. Let each of them keep track of time using millis to see if it's time to do something.
Unless you're using one of the sleep modes though, the Arduino is going to be running at full speed/power so you won't get much benefit power wise from doing things less frequently.
You can get the arduino to sleep, see Nick Gammon's site: Gammon Forum : Electronics : Microprocessors : Power saving techniques for microprocessors. This will introduce an additional complication because of your communication with the house unit. You may need to arrange external circuitry to wake the arduino when data transmission is detected and you'll likely need to arrange for the sending unit to send some discardable data to wake the receiver before sending real data.