Programmable thermostats can be used, but consider this: Radiant
systems are designed to maintain a constant temperature. It can take
quite a while to warm a room from a cold start and the system is going
to use a lot of energy to heat the room. Digital thermostats are more
precise than standard mercury-bulb thermostats and may cause the system
to cycle too frequently. Mercury-bulb thermostats are generally the
best choice for radiant systems.