ZigBee, Z-wave and other domestic systems operate in the licence free spectrum, but this might or might not be the same unlicensed frequency bands used for Bluetooth and Wi-Fi. Z-wave uses 868.42 MHz in Europe and 908.42 MHz in the USA, which are not used for Wi-Fi or Bluetooth. Frequencies such as these are below 1 GHz, and propagate around buildings much better than the 2.4 and 5 GHz bands used for Wi-Fi.
Given the transmission power, frequencies below 1 GHz travel further than those above 1 GHz. Usually, above 1GHz, higher frequencies propagate less well than lower frequencies.
Whatever band is used, non-Wifi systems require a separate hub or gateway from that used for Wi-Fi. Devices are controlled by the hub, either from a remote connected device or from a wifi-enabled controller in the same location. The hub or gateway is then connected to a domestic broadband router by either wired connection or wirelessly.
This hub is also called the ‘protocol translation gateway’ This is because instructions need to be translated and conveyed to the broadband route, and then any response sent back is also translated by the hub before it reaches the device.
In mesh networks with nodes of devices designed for battery operation, it is common for the device to go into standby or low energy mode. They need to be woken from this mode to send data or act on instructions. Because waking up takes time, standby mode contributes to the relatively long latency of low energy mesh networks compared with high power hub and spoke networks such as Wi-Fi.
A delay of a second or two would not be critical for most devices, although I can imagine in our society lots of humans would find it irritating if light didn’t come on immediately when entering a room. A more crucial issue might be a stove that didn’t turn off immediately when requested if it became a potential hazard because of its hot surface.