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What is True Radiant?

True Radiant is a Nest Learning Thermostat feature that keeps homes with in-floor radiant or boiler-and-radiator systems more comfortable. It reduces temperature swings and starts heating early so you get the temperature you want when you want it.

True Radiant is a feature that the Nest Learning Thermostat automatically activates for radiant systems. It keeps you more comfortable without using any more energy and gives you a predictable temperature on schedule.

What is radiant heat?

Most conventional heating systems send warm air through vents. These forced air systems change the temperature fast. Radiant systems are more efficient, but take much longer to heat up and cool down. Instead of air, underfloor radiant systems heat your home using tubes filled with liquid or electric coils under the floor, and boiler systems send hot water to radiators in each room.

Because radiant systems take so long to heat up, it can be difficult to set a schedule - you may need to start heating at 4am to get to the temperature you want at 7am. With other thermostats, underfloor radiant systems also overshoot your target temperature by an average of 2.2ºF/1.2ºC since radiant pipes stay hot even after the boiler has stopped heating.

How does True Radiant work?

Although radiant systems work very differently than forced air systems, most thermostats treat them the same.

True Radiant will make your radiant system run like it always should have - according to your schedule. No more guessing and turning the heat on hours earlier than you need it. Tell your Nest Thermostat what temperature you want and True Radiant will take care of the rest.

With True Radiant, your Nest Thermostat learns how long your radiant system takes to heat up. It’ll turn the heat on early to reach your target temperature, then turn it off early so you won’t go beyond the temperature you want. For example, the Nest Thermostat may learn that to reach 70ºF/20ºC, it should turn the boiler off when the room hits 65ºF/18ºC because the already hot radiators will take you the rest of the way to 70ºF/20ºC. The Nest Thermostat will also maintain that temperature by turning your system back on before the temperature gets too low.

How do I enable True Radiant?

True Radiant is enabled automatically. To confirm or turn it off, follow these steps:

  • On your Nest Thermostat, go to Settings > Nest Sense > True Radiant and choose ON to enable it.
  • On the Nest Mobile app, choose your thermostat in landscape mode and go to Settings > Nest Sense > True Radiant and choose ON to enable it.

If you were already using the Nest Thermostat before the October 2012 update, you’ll probably want to edit or reset your schedule to use True Radiant properly.

Note that True Radiant is only available if you’ve selected that your system type is in-floor radiant or uses radiators.

* Numbers from the 2012 Nest Simulation