Flair will work alongside ANY thermostat. You do not need a smart thermostat to reap the benefits of the Flair system.
We integrate with ecobee, Honeywell Home, Honeywell TCC, Google Nest, Carrier Infinity, Bryant Evolution, Sensi (all models), Daikin (One+, One Touch, and One Lite), Goodman (Connected GTST), and Amana (Amana Brand Smart Thermostat) smart thermostats. This allows us to communicate with them directly. For the full list of supported brands and models, see our thermostat compatibility article.
We have many users who use Flair alongside Smart Thermostats such as the Lennox iComfort, Amazon Smart Thermostat, and Trane ComfortLink for which we do not have integrations as well as legacy thermostats that don't connect to the internet.
When using one of the integrated thermostats above we are notified when the system is heating, cooling, idle, or running a fan cycle.
When using a non-integrated thermostat your Flair Smart Vents will read the duct temperature to determine when the system is heating or cooling.
In both cases, our Smart Vents will open and close as the room temperature dictates keeping the room at or near the comfortable temperature you have defined.