The setback temperature is the temperature you would like the property to remain at during out of hours operation. A setback temperature is important as it allows the property to heat up to the desired temperature during active hours without using as much energy as heating the property from a lower temperature.
Secondly, the setback temperature prevents moisture developing in properties, which could otherwise lead to the development of damp patches. Moisture forms at temperatures below 14° so a typical setback temperature is 16°.