Radiant floor heat costs less to operate than other forms of heat. Because radiant floors offer more comfort at lower thermostat settings, most people find that they're comfortable at lower room temperatures.

Affordable, Efficient Comfort for Cold Feet

John Vastyan | Common Ground

Affordable, Efficient Comfort for Cold Feet
Radiant floor heat costs less to operate than other forms of heat. Because radiant floors offer more comfort at lower thermostat settings, most people find that they're comfortable at lower room temperatures. 
Affordable, Efficient Comfort for Cold Feet
By John Vastyan

We'd never experienced a winter squall like this one.  Sub-zero temperatures and high winds set the stage for a heavy snowfall.  The eight-foot drift beyond our living room window looked like a menacing grin.  Yet, looking out at the storm in shorts and bare feet, we experienced a giddy comfort that's hard to describe. 

That first warm floor experience was the beginning of our enduring romance with radiant heat.  But until you've experienced it, you can only imagine the unexpectedly luxurious sensation it delivers.

Without question, consumer interest in radiant heat has thrust builders, architects, home designers and flooring pros into the "radiant realm." 

Radiant floor heating works by using water-filled tubes or electric heating elements to warm interior mass.  The surface of a floor or wall then gently emits energy that moves gracefully to all the objects in the room, making them - and your feet - cozy warm. 

Radiant heat delivers uncompromised comfort, the highest energy efficiency available (typically, 25% to 30% better that forced air), and - with no air grates, radiators or baseboard to factor-in - there's no interference with room function or furniture layout.  Radiant heat systems can also be fueled by many different energy sources, and sometimes even a combination of two or more, including fuel oil, gas, electric, solar, ground source heat, and solid fuels. 

Today, there are also many ways to deliver radiant heat to existing, and new, floors.  These systems also offer snowmelting options for safe access to a home or commercial facility. 

Here's to your health, and greater comfort

Without question, warm floors are the most comfortable form of heat you can have.  The radiant heat from your floor will warm all the mass in your rooms, giving every surface an inviting sensation that you can feel. Surprisingly, those surfaces most uncomfortable without radiant heat - stone, tile and hardwood floors - become the most comfortable with radiant because they transfer the heat so well. 

Allergy sufferers love radiant.  In many instances, allergy problems are eliminated in homes with radiant heat.  Anyone with arthritis or poor circulation will enjoy the warmth of radiant. 

Lower operating costs

Radiant floor heat costs less to operate than other forms of heat. Because radiant floors offer more comfort at lower thermostat settings, most people find that they're comfortable at lower room temperatures.  And, radiant heat doesn't stratify at the ceiling as it does with forced air.  Another advantage is the zonability of radiant heat - thermostatically controlled zones are the essence of control. 

Hydronic (water based) radiant floor systems are used in larger areas or for an entire home or commercial facility.  Generally, hot water radiant is best for spaces of 500 square feet or more, or in a building where hot water is already used as a heat source.  Hydronic tubing can be embedded in concrete slabs, in thin-slabs over frame floors, stapled up between floor joists, or installed on top of the subfloor. 

An electric system may be the best choice for small areas like a single master bathroom (be sure to see the "Where Green Goes Wrong" sidebar, below - sadly, danger lurks within some electric radiant heat products).  Of course, if electric energy is cheap, it could be used to heat, or provide floor warming, to an entire home.  Typically, low-profile electric floor radiant systems are installed right in the thinset used to set a finished tile or stone floor.  Warm solid surface floors are popular for master bathrooms, entries, kitchens and sunrooms.

SunTouch offers mats that come in 12", 24", 30" and 36" wide rolls with lengths up to 80 feet.  These are shaped on the jobsite to fit any floorplan.  The mats contain a woven-in heating element.  In most instances, installers of electric radiant products first attach a cementous backer board over the subfloor.  The mats are then stapled or taped to the backerboard and thinset mortar is applied with a notched trowel just prior to setting tile or stone. 

Where can you put radiant heat?

When building a home or addition, radiant heat can be applied anywhere - floors, walls and ceilings.  One technique is to staple radiant tubing to the top of the plywood subfloor.  It's then covered with a thin slab of lightweight concrete or gypsum based masonry.  Joist bay staple-up is also popular for new construction and retrofits. 

If you have access to the floor from below, you can staple radiant tubing directly to the underside of the subfloor. If PEX tubing is used, aluminum heat emission plates can be used to improve heat transfer; these sheet metal pieces attach to the pipe and are stapled to the subfloor. Or, if EPDM rubber radiant heat tubing is used - one of the best methods I know of for under-floor applications - the plates aren't necessary. Typically, batting insulation is then attached two inches below the pipe. This method works for any type of floor covering and does not affect the finished floor height.

There are a variety of other products suitable for new construction or remodeling.  One method offered by a few manufacturers provides excellent BTU output per square foot.  For example, SubRay plywood sleepers are screwed to the subfloor and tubing is laid between them.  A floor installer then bridges over the system with any finished floor using hardwood, a laminated product, tile or stone.  This method adds 1/2" to 3/4" to the finished floor height.

When Green Goes Wrong

Another emerging issue within the electric radiant heat industry is the issue of EMF (electromagnetic frequency) radiation.  The idyllic scene so many suppliers of this technology prefer are women and children relaxing on a warm floor, saving energy at the same time.  They're helping to drive sales of electric radiant systems at levels never seen before. But there's trouble brewing below.  Some companies have made sacrifices over the years to pioneer dual wire EMF-canceling technology.  Others - offering only single-wire systems - are selling products that release very high levels of EMF. 

Electromagnetic fields (EMF) come from all electrical appliances, but studies show an average American's daily exposure is less than 1 unit (mG) of EMF. When you sit on an unshielded electric radiant floor, however, you may be exposed to 20, 40, or more times this level.

Shockingly, some electric floor products expose homeowners to about the same electromagnetic field radiation as putting your nose up against the door of a microwave oven.  

Know your exposure

Today, there is only one scientific and independent third party test to measure electromagnetic fields produced by electric radiant floor heating systems.

The new test is known as "REET" or Radiant Electric Emissions Test and it was developed by Watts Radiant and the ETL Semko division of Intertek, the global leader in the testing, inspection, and certification of products for manufacturers and retailers around the world.

Unlike unverifiable claims made by some companies the REET test measures each product according to standard procedures.

The test protocol by ETL Semco specifies exact descriptions and model numbers for test equipment, test configuration and test procedures for twenty points of measurement across a grid that typically covers a four square foot area of warm tile.  Those point measurements are averaged together to yield a radiation value for each product for both electric and magnetic field radiation.  Health care concerns have focused on the magnetic, or H-field, measured in milligaus or mG.

The first series of test results for Watts Radiant products and for other manufacturers showed a startling variation in H-field exposure.  In one notable head-to-head comparison of electric mats of similar size and amp rating, a competitive product emitted 462 times the H-field radiation as the Watts Radiant mat.

The difference is in the wire

Watts Radiant uses a complex wire that is actually two sets of heating element constructions that run in parallel with a patented helical twist.

There is no practical technology for covering a heating element to minimize H-field EMF.  The only successful approach is "active shielding" which means each set of heating elements cancel the H-field of the other.  This is the design of Watts Radiant (SunTouch) tile warming wires, an approach that costs somewhat more to produce

If we select five radiant floor products that cover 35-40 square feet of heated area that represents the most common size for residential bathroom installations.  The Watts Radiant mat in that size range emits a mG value that is 20 times lower than the average US exposure.

Watts Radiant recently selecting four competing products in that size range, the REET test, as conducted by the prestigious ETL Semco Laboratory, produced these values:

  • Product A: 42.38 times the U.S. average exposure
  • Product B: 45.74 times the U.S. average exposure
  • Product C: 71.34 times the U.S. average exposure
  • Product D: 92.54 times the U.S. average exposure

Where to get started?

The key to a successful first venture into radiant heat is to involve the talents of a professional installer who knows and has experience with radiant heat, preferably a member of the Radiant Panel Association.  

Leading industry references:

The Radiant Panel Association


SunTouch (electric products)


Watts Radiant (hydronic & electric products)


The Green Mechanical Council

Dan Holohan's Heating Help forum

Author bio:

John Vastyan is president of Common Ground, based in Manheim, PA. He specializes in communications for the radiant heat, hydronics, plumbing and mechanical, HVAC & geothermal industries.  He can be reached at cground@ptd.net

The content & opinions in this article are the author’s and do not necessarily represent the views of AltEnergyMag

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