Radiant Floor Thermostats
Controlling the System
A radiant floor that uses a concrete slab takes many hours to heat up if it is allowed to become cold. This can be very inconvenient while waiting for the slab heat up so it can heat the space. Because of this, most radiant floor systems are not permitted to go into a very deep night setback. Depending on how the floor is constructed, the time it takes to re-heat the floor is sometimes longer than the occupant’s sleep period.
Heating ThermostatMany floor systems are also controlled by a floor thermostat instead of a wall thermostat. The system is also often designed to keep the circulation pump(s) running while the thermostat only controls the boiler’s burner. Other, more sophisticated, types of controls sense the floor temperature, outdoor temperature, and room temperature to keep the home comfortable. Such a system may also use less fuel.
Although radiant floor systems are usually heated by a boiler, they can also be heated with a geothermal heat pump. Such a system offers even greater energy savings in climates where the heating and cooling loads are similar in size. Another alternative for small houses, or those with small heating loads, is to use an ordinary gas water heater to supply the radiant floor system.
Source:http://www.radiant-heat-floor-methods.com/radiant-heat-thermostat.html
[...] heat during off-peak hours (approximately 9 p.m. to 6 a.m.), which can be done using a programmable radiant heat thermostat. If the floor’s thermal mass is large enough, the heat stored in it will keep the house [...]