Indoor-Outdoor Radiant

Learn about the perfect companion to commercial renovation or construction when it comes to melting snow. 

During the winter months, all variety of tools are used to combat winter across Canada.  The goal: to eliminate snow and ice.  Salt, chemicals, shovels and plows with heavy blades are frequently the first line of defense.  Though, in the process, many exterior concrete surfaces are chipped, cracked and chemically attacked.  Nearby garden plants aren’t very fond of the stuff, either.  

The result? Sometimes, it’s marginal at best.  Meanwhile, accumulation continues.  

It doesn’t have to be that way.  Snowmelt systems, similar to, but not the same as radiant heat systems, are a great way to eliminate winter precipitation from driveways and walkways.  

Snowmelt technology can be used to heat concrete, stone and brick pavers, and even asphalt, keeping surfaces safe and clear of icy accumulations.  

“The key function of a snowmelt system is to keep walkways, driveways and other areas dry and clear,” says Rich McNally, eastern regional sales manager, Watts Water Technologies.  “For commercial applications, especially those deemed critical areas — such as hospitals and senior housing entry areas and helicopter pads — snowmelt warmth performs a valuable, even life-saving function.” 


Indoors, radiant heat works by using warm water-filled tubes or electric heating elements to warm the mass of a floor, wall or ceiling.  The surfaces then gently emit radiant energy to warm all the objects in the room — heat goes to cold.    

“Modern hydronic radiant heat systems use a closed loop design,” says Dave Yates, president of York, Pennsylvania-based F.  W.  Behler Inc., a full-service mechanical contracting firm that specializes in radiant heat and snowmelt systems.  “Water is heated by a heat source, typically a boiler, and then is circulated through the tubing to all areas of the building.  Warmth is then delivered to each zone as thermostats call for it.”

Hydronic radiant floor heating operates on low pressure (usually below 20 psi) with low temperatures often in the 90° F to 130° F range.   
Surprisingly, those surfaces most uncomfortable without radiant heat — concrete, stone and tile — become the most comfortable with radiant because they transfer the heat so well.  

“Ever wonder why your lower legs ache after standing on cold concrete for too long?” asks McNally.  “Your muscles contract to replace the heat that left you for the concrete.  Now there’s a comfortable thought, huh?”

An electric system may be the best choice for small interior areas like a bathroom or a foyer.  Of course, if electric energy is locally affordable, it could be used to heat, or provide floor warming, for an entire building.  

“Occasionally, people refer to snowmelt technology as ‘radiant heat.’ That’s really not the case because snow and ice are melted through convective and conductive heat transfer; there’s a key difference,” says John Sweaney general manager, Watts Radiant.  

One thing’s for sure: 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.  

The most likely uses for heated concrete inside a structure are for on-grade, high-mass slabs and finished basements.  Though, today there’s growing interest in suspended, thin-slab and lightweight concrete applications that stiffen, isolate sound, fireproof or level floors.  Radiant heat works just fine in these slabs too.  

All this and snowmelting too?

While designing a radiant heat system, look at the floor plan carefully to see if there might be a door, a sidewalk or a garage entrance that faces north or is exposed to ice and snow build-up.  Perhaps the home or building owner should consider snowmelting zones.  

This entails moving heated water/antifreeze solutions, underground, from a heat exchanger to cold surfaces outside.  Snowmelting zones can be activated when weather reports calls for freezing precipitation, or a microprocessor control could be employed to do the job.   

Snowmelt systems 

For snowmelt systems, system designers must consider the influence of local weather from snowfall records kept at nearby airports.  

To speed up melting of icy accumulations, some installers use blanket type insulation.  High-density foam board can also be considered, but caution must be taken so to not affect slab stability.  

Pipe spacing of six, nine, or 12 inches on center help determine how much energy is delivered, depending on a client’s needs.  Pipe diameter is decided by circuit length, which depends on the slab size and manifold locations.  PEX (cross-linked polyethylene) or EPDM tubing should have at least two inches of concrete over the top of the tubing — this depends on traffic weight.  Usually, building codes provide exact specifications for this.  

Snowmelting has several benefits.  Icy surfaces are no longer a concern; the areas are maintenance-free.  Facility costs can be reduced because ice-melting chemicals aren’t required.  These chemicals kill landscaping and increase building cleanup as they are tracked inside, which can ruin expensive floor coverings.  They can also degrade concrete and asphalt.  

PEX tubing is a great product for radiant heat and snowmelting applications.  Some care must be taken to protect it from jobsite puncture, crushing or exposure to the sun’s light.  

“That’s why we use a lot of Onix EPDM tubing with aluminum oxygen barrier and layers of Kevlar; it’s much more resistant to jobsite abuse and UV radiation,” says Yates.  “And for winter installations, it stays flexible — meaning we can work with it easily — even at below-freezing temperatures.”  

Miles of PEX

A good example of exterior slab-warming is a snowmelt system installed for the 40,000-square-foot, two-level West Friendship Volunteer Fire Department headquarters in Maryland.  During construction a few years ago, an 18,000-square-foot snowmelt system was installed.  

When fire and EMS personnel need to make a quick break from base camp, the last thing they need to contend with are the hazards of snow and ice.  “Around here, we can now say that fire and ice are dealt with accordingly,” says Fire Chief Mickey Day.    

The L-shaped facility is home to EMS personnel and equipment on one side, and large fire equipment bays on the other.  Common areas include food service, office and training areas.  In the enclosed, radiantly-heated bays, 10 pieces of equipment are kept in mint condition.  
The West Friendship Fire Company job — typical of the commercial work done by Gaithersburg, Maryland-based Mallick Plumbing & Heating, Inc.  — billed-out at about $1.5 million.  

According to Mike Mallick, general superintendent and project manager, the job entailed installation of a large hydronic system with radiant heat, snowmelt and hydro-air heat for the common and bunk areas.  

Mallick professionals installed 32,000 lineal feet of Watts Radiant EPDM synthetic rubber Onix tubing and manifolds, two pre-engineered, prepackaged HydroNex system panels from Watts Radiant for equipment bay radiant heating and one larger, custom-built HydroSkid package built specifically for the project to control the snow-melting operation outside.  

“We prefer working with Onix because of its flexibility and ruggedness,” says Mallick.  “It doesn’t kink and bounces right back if it’s crushed.  It’s also uneffected by exposure to the sun.  We also appreciate its greater tensile strength.”  

For snowmelting, the uninsulated, eight-inch concrete slab was divided into three separate, 6,000-square-foot slabs, all operating off of one or more outdoor temperature-and-precipitation-sensitive sensor.

“Facility managers can over-ride automatic activation of the system if they know that a winter storm’s coming in,” adds Mallick.  “The snowmelt operation is actually quite simple.  When the snowmelt system is activated, all loops are warmed at once.”  

Where to get started?

The key is to involve the talents of a professional installer who knows and has experience with radiant heat and snowmelt, preferably a member of the Radiant Professionals Alliance.  Be sure to visit the organization at  

Also, visit two of the best sites in the industry: and

But hurry.  Your customers’ toes deserve the happiness only radiant heat, and clear melted walkways can deliver.


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