What Is a Slab Sensor in HVAC & BMS — And Why Is It So Important?
The Slab Temperature Sensor
Unlike a wall thermostat that measures air temperature, a slab sensor measures the actual temperature inside the concrete floor.
This matters because the floor itself is the thermal mass - it heats and cools slowly, stores energy, and directly affects comfort.
Why Do We Use a Slab Sensor?
1. Prevents Floors from Overheating (especially wood/vinyl)
2. Improves Comfort by maintaining consistent radiant temperature
3. Enhances Energy Efficiency – no over-heating or over-cooling
4. Protects the System with freeze protection (snow-melt)
5. Ensures Safe Radiant Cooling by preventing condensation (dew point)
Where Is It Installed?
1. Embedded within the concrete slab
Usually inside a protective conduit for serviceability Installed near radiant PEX piping
Used in:
▪ Bathrooms
▪ Living rooms
▪ Outdoor ramps
▪ Parking areas with snow-melt
How Does BMS Use Slab Sensor Feedback?
The controller uses slab temperature to:
1. Limit floor temperature (prevent too hot/cold floors)
2. Maintain stable comfort even after thermostat is satisfied
3. Activate freeze protection in snow-melt
4. Control radiant cooling with dew-point lockout logic
This avoids common issues like “cold floors in winter” or “sweating floors in cooling.”
Sensor Type (Common)
1. 10k NTC thermistor, Waterproof, epoxy-coated, Simple 2-wire connection
Why Consultants Specify It
Because room temperature alone can mislead the controller, especially with high thermal mass floors. A slab sensor gives the BMS the true thermal picture.
Summary
A slab sensor may look like a small component, but in radiant systems it is a mission-critical feedback device for safety, comfort, and energy savings.