Radiant floors are most commonly used for heating a room but may also be used for cooling. A heated or chilled fluid, typically water, is passed through the floor inside Pex tubing embedded in the slab. The tubing material is highly durable, flexible and an excellent thermal conductor. During heating the heat from the fluid is passed on to the floor and then radiated into the room. During cooling mode the heat absorbed by the cool floor is transferred to the fluid and carried back to the conditioning equipment; that then conducts heat energy through the floor surface. Radiant energy is felt by all exposed objects (including people), similar to the radiant energy felt by the Sun and radiant ceiling panels.

The floor is usually a material with a high emissivity that absorbs heat and radiates it evenly over a period of time beyond a conditioned fluid passing through, such as concrete. This concrete can serve as the foundation or as a thin layer over a wood-framed floor with the tubing embedded inside and out of view. Other layers of floor may be installed over the slab such as wood or even carpet, though this will reduce the efficiency of the system. Insulation is placed between the floor and the Earth so the Earth does not act as a heat sink.

Radiant floors distribute heat much more evenly than a central radiator or forced air system. Radiant floors also distribute the heat much closer to an ideal human body-heating curve as opposed to a forced air conditioning system. This curve was developed based on ASHRAE standard 55.