Radiant floor heating under concrete.

ThermaRay panels go in below the slab and turn the concrete and the ground beneath it into a heat battery. It charges on cheaper off-peak power and gives the heat back all day.

Where it goes: Under a concrete slab
Best for: Slab-on-grade homes, basements, shops, warehouses, factories, farm buildings
Role: Primary heat

Where thermal mass floor heating goes. Choose another system to compare.

A heat battery two feet deep.

The panels are laid on the ground before the slab is poured. About 8 inches of sand goes over them, then the concrete. When the system runs, it warms a thermal mass 24 to 30 inches deep: the slab, the sand and the soil below.

The bigger the mass, the longer it holds heat and the less it costs to run. A large rock pulled from a fire stays warm long after a small one has cooled, and a deep slab works the same way.

Because the mass stores so much heat, the system can charge during off-peak hours and still keep the building warm through the day. Most Midwest power companies offer off-peak and dual-fuel rates for it.

ThermaRay thermal mass panels laid out on the ground before the slab is poured at McKenzie Electric Coop — Panels laid out before the pour at McKenzie Electric Coop.

What you get

35–70% less to operate than hydronic tubing or forced air
Qualifies for off-peak and dual-fuel electric rates
Typically 30–60% lower material cost
No foam insulation board needed under the slab
Installs in a fraction of the time of tubing
No boiler, pumps or moving parts to maintain
Takes no floor space and very little mechanical room
A 45+ year track record with no failed systems

Why it doesn’t need foam under the slab.

Heat only moves toward something colder. Put your hand on a table and your heat goes into the table; put it on a hot cup and the heat comes to you.

Hydronic tubing usually sits on 2 inches of foam so its heat doesn’t escape downward. That foam also limits how much mass the system can use, which raises the cost to run. A ThermaRay slab heats the deep mass on purpose, and once the ground below is as warm as the mass, heat stops moving down. It only rises into the room when the room is cooler than the floor.

Sand being spread over ThermaRay thermal mass heating panels — Sand goes over the panels before the concrete is poured.

Chart comparing the ideal heating curve with the radiant floor heating curve from floor to ceiling — Radiant floor heat follows the ideal curve closely: warmest at your feet, cooler at head height.

“We wanted a SMART and ENERGY efficient home. Part of that was having ThermaRay Heating Panels which created Thermal Mass and runs during off-peak hours. The savings is amazing.”

Homeowner, Durango, Colorado. A new home designed and built by the owners, heated with thermal mass panels on off-peak power.

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Specs and sizes.

Thermal Mass Floor Heating specifications
Heating element	Double Teflon-coated nickel-chromium heating wire embedded in a gypsum (sheetrock) panel. The panel just keeps the wire evenly spaced and makes it easy to ship and handle.
Panel thickness	1/2 inch
Panel width	18 inches
Panel lengths	4, 5, 7 or 8 feet
Connections	Two hot-to-cold feed connections, with two 6-inch leads at one end of each panel
Covered by	About 8 inches of fill sand, then the concrete slab
Thermal mass depth	24 to 30 inches
Insulation under panels	Not required

Downloads

Every system can be paired with a control package, from a simple wall thermostat to full building automation. See the controls

From the job site.

Rows of thermal mass panels across the floor of a large building with overhead doors — Panels across a large building floor before the slab.

Thermal mass panels laid out on gravel inside a basement foundation — Panels laid out for a basement slab.

Thermal mass panels on sand inside a new foundation on a residential street — Panels on sand before the pour.

See it installed.

Thermal mass floor heat installationAn onsite technician shows the panels and how they go in.

Why a developer chose thermal massA developer explains the system in a Brooklyn Park, Minnesota building.

Installed and working.

Manufacturing floor heated by a ThermaRay thermal mass system

Industrial

Thermal mass under a factory floor

“Down the road, our client is going to get a lot of benefits. When he realizes it’s thirty years later and he hasn’t had any maintenance costs, and you didn’t have to replace eight rooftop units … My attitude is this is the right solution.”

Mike Faber, on choosing thermal mass floor heat for a commercial building.

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