Thermostat

A thermostat can be added. However, several comments. First, there may already be an in-floor sensing thermostat to control the floor temperature. If there is, it may or may not be adjustable -- and may or may not be in an obvious location. Second, the last thing you want to do with radiant heat is to be turning the heat on and off. Radiant responds very slowly, so any thermostat should be set to a constant temperature. And the last comment: note that I said "a thermostat can be added". Electric radiant heat is either at 110 volts or 220 -- most likely the latter -- and you may need a contactor -- high power rated relay -- controlled by a thermostat instead of just a thermostat. Even if it is just a thermostat, it has to be rated for 220 and interrupt both sides of the circuit and have an appropriate amperage rating. This is really a job for an electrician.

A section of my house has electric baseboard heat. It used to run on on cheap mechanical thermostat switch and led to big temperature swings of +/- 5degrees of teh setponit. We swapped it out for a Mysa smart thermostat last year and have been very happy with the temp stability and energy savings and have been mostly happy with the stability of the smartphone app it connects with (it can also be used without an app, you just lose the scheduling ability. And I think the newer generation they sell has improved the stability. and customer service has been exceptional)

I mention this because I think i read in the documentation that it is also suited for many electric radiant systems too. It might be an option for you if you're interested in scheduling setbacks and being able to turn it on/off remotely. It's for line voltage, though, so while I was comfortable swapping it out from an existing thermostat...I would not have felt safe or qualified to fish new wires and do a from scratch install myself with it. Electric anything, and especially high voltage, can start fires if done wrong, I'd consult an electrician!