Heat Transfer Plates Basics
Heat transfer plates were developed to resolve two main issues previously associated with radiant heated floors: noise and cold spots (uneven heat distribution). These issues commonly arise in installations, when tubing is stapled directly to the subfloor, or installed in pre-manufactured plywood panels.
When PEX tubing is stapled/secured directly to the subfloor, or is in direct contact with the mounting surface (such as the groves on the plywood panels) it is likely to create noise, as tubing expands and contracts, responding to the thermal changes in the system. The expanded length can be as high at 30”, given appropriate conditions.
The Omega-like shape of the heat transfer plate’s channel minimizes the contact of tubing with the mounting surface, thus reducing, or eliminating the noise. Some manufacturers also recommend the use of silicone sealant in the tubing channels of the heat transfer plates to further reduce the noise.
Installing heat transfer plates may also dramatically increase the response time and heat distribution properties of the radiant heating system. In conventional installations, described above, ½” PEX tubing is installed at 8-10” on center spacing. Such installation creates an uneven distribution of heat, as the tubing provides the greatest amount of heat directly to the surface above it, leaving the center between the tubing runs as a coldest spot. To avoid this, the system is usually operated at prolonged time periods, to allow the coldest area to heat thoroughly. Furthermore, the water supply temperature is also increased, which may inflict damage to several flooring types (such as hardwood) and inevitably increases the heating costs.
Aluminum heat transfer plates maximize the heat transfer area of the tubing with the flooring surface, acting as a medium between the two, which allows for greater and more even heat transfer than by using PEX tubing alone.
Depending on the thickness, plate type/design, heat transfer plates can deliver a BTU load as high as 40-50 BTU/sq. ft.
There is a wide variety of heat transfer plates available today, and it is important to understand the differences between them prior to selecting the type for your project.
Generally, heat transfer plates are available in two types – extruded and stamped (or rolled). Extruded version is a thicker one (~0.05”), while stamped is thinner (~0.019”). It is a misconception to think that one type is better than the other simply judging by the thickness of the plate.
Thicker heat transfer plates are generally designed for below subfloor installations only, when PEX tubing and plates are secured to the bottom of the subfloor between the joists. A newer design implements a reversed Omega-shaped tubing channel, which completely eliminates the noise problem and allows for a faster and easier installation.
Thinner heat transfer plates are mostly designed for use in sandwich-type installations, where PEX tubing is placed between the subfloor and finished floor.
As seen above, thickness of the plates usually corresponds with the thickness of the flooring above.
Common lengths of the aluminum plates is 2’, 4’ and 8’, with the first two being more popular, since they are easier to handle and install by a single person.
Thinner plates (stamped/rolled) are usually secured to the surface with regular wood fasteners (not shorter tan ½”), while thicker ones (extruded) will require the use of self-drilling screws, if not supplied by manufacturer with pre-drilled holes.