Murphy Brothers Blog

Radiant Heating 102: Types of Installation

“Wet” floor installation Methods

Cables or tubing are embedded within a solid floor, either in a thick concrete foundation slab (commonly used in “slab” ranch houses that don’t have basements) or a thin layer of concrete, gypsum, or other material installed on top of a subfloor. If concrete is used and the new floor is not on solid earth, additional floor support may be necessary because of the added weight. Consult a professional engineer to determine the floor’s carrying capacity. An electric radiant floor “wet installation” is a supplemental rather than primary heating system. It is used to heat the floor but would not produce enough heat to replace other primary sources, such as a radiator or forced air heat source.


Thick concrete slab systems have high heat capacity and are ideal for storing heat from solar energy systems, which have a fluctuating heat output.


The downside of the thick slabs is their slow thermal response time, which makes strategies such as night or daytime setbacks difficult if not impossible. Most experts recommend maintaining a constant temperature in homes with these heating systems.

Dry floor installations

Cables or tubing are run in an air space beneath the floor or underneath the subfloor between the joists. This method usually requires drilling through the floor joists in order to install the tubing.

Installation of reflective insulation must also be installed under the tubes to direct the heat upward.


Alternative method: Tubing or cables may also be installed from above the floor, between two layers of subfloor.  In these instances, liquid tubing is often fitted into aluminum diffusers that spread the water’s heat across the floor in order to heat the floor more evenly.

The tubing and heat diffusers are secured between furring strips (sleepers), which carry the weight of the new subfloor and finished floor surface.


Advantage: A “dry” floor is faster and less expensive to build than a “wet” floor

Disadvantage: Because dry floors involve heating an air space, the radiant heating system needs to operate at a higher temperature.


Compatible Floor Coverings


Ceramic tile is the most common and effective floor covering for radiant floor heating because it conducts heat well from the floor and adds thermal storage because of its high heat capacity

Vinyl and linoleum sheet goods, carpeting, or wood: can be used, but because they help to insulate the floor, will result in a decrease of the efficiency of the system.

If using carpeting, select a thin carpet with dense padding and install as little carpeting as possible.


If some rooms, but not all, will have a floor covering, then those rooms should have a separate tubing loop to make the system heat these spaces more efficiently. This is because the water flowing under the covered floor will need to be hotter to compensate for the floor covering.

Wood laminate floor should be used instead of solid wood. This reduces the possibility of the wood shrinking and cracking from the drying effects of the heat.

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