Heat Transfer Basics
One of the goals of this artical is to enable installers to make better decisions on the job site. These decisions can range from modifying a layout to account for a room change to determining what effect added windows have on a room heat loss. To better address these types of concerns, you must understand how a radiant system works. All forms of heating work on three basic modes of heat transfer: Convection, Conduction and Radiant.
Convective Heat Transfer is the most familiar type of heat. All forced-air systems are convective heat transfer systems. This includes hydronic baseboards and fan coils.
Conductive Heat Transfer is energy moving through an object. Place a metal pot on the stove and in a few minutes the handle is hot.
Radiant Heat Transfer is the least understood, but is the one that is most important in our daily lives. Radiant heat transfer is the exchange of energy from a hot source to a cold source. The sun is typically used to illustrate this mode of transfer.
Regardless of the type of heating system used, all follow one basic rule. Hot always moves to cold. Place your hand under a lamp and your hand begins to get warm. This is because the lamp is hotter than your hand and is trying to lose energy to its cooler surroundings. 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 then inserted into the plate. This allows the PEX to be separated from the subfloor, eliminating the noise issue before mentioned.
However, this separation raises concerns relative to the conductive transfer of energy needed to deliver the required heat to a space.
The aluminum transfer plates offer this contact, allowing for conduction to continue from the Radiant PEX to the subfloor. In most cases a PEX system installed with heat transfer plates will still deliver the required BTU load to a space. The maximum BTU delivered will typically be around 45 BTU/sq.ft.