One of the goals of this article is to enable installers to make better decisions on the job site. These decisions can range from modifying the layout to account for changes in the room to determining the effect of adding windows on heat loss from the room. To better solve these problems, you must understand how radiation systems work. All forms of heating are based on three basic modes of heat transfer: convection, conduction and radiation.

Convective heat transfer is the most common type of heat. All forced ventilation systems are convection heat transfer systems. This includes circulation base plates and fan coil units.

Conductive heat transfer is the movement of energy in an object. Put a metal pan on the stove and in a few minutes the handle will be hot.

Radiant heat transfer is the least known, yet the most important in our everyday lives. Radiant heat transfer is the exchange of energy from a heat source to a cold source. The sun is often used to illustrate this shift.

Regardless of the type of heating system used, there is one basic rule to follow. Heat always turns cold. Put your hand under the light and your hand will start to warm. This is because the lamp is hotter than your hand and is trying to transfer energy to a cooler environment. In most cases, all three forms of energy transfer are present in radiant floor heating systems.


The heat transfer plate is attached to the subfloor, and the radiant PEX is inserted into the plate. This separates the PEX from the floor, eliminating the noise issues mentioned earlier.

However, this separation raises concerns about the conductive transfer of energy required to deliver the desired heat into the space.

The aluminum transfer plate provides this contact, allowing conduction to continue from the radiating PEX to the subfloor. In most cases, a PEX system with heat transfer plates installed will still deliver the required BTU load to the space. The maximum thermal unit is usually about 45 thermal units/square foot.