Whether you're placing concrete or installing stamped concrete or pavers, snowmelting systems secure the beauty and integrity of the surface by safely melting snow without using chemicals. The ability to install snowmelting systems—a capability that can differentiate your firm—also means a substantial upsell: more income with each job sold.
A snowmelting system works by heating a mass or surface so that walkways, driveways, and other areas remain dry and clear. Most snowmelting systems are "hydronic," using circulated fluids to heat these outdoor masses, although some use electric heat.
Snowmelting systems are ideal for commercial and residential applications—especially critical areas such as hospital and senior housing entry areas, helicopter pads, and delivery ramps. A snowmelting system performs a valuable, and sometimes lifesaving, function.
Typically, most of the components of a snowmelting system, especially the heating plant, sensors, and controls, are installed by a plumbing and mechanical contractor. Concrete contractors often, and should, become involved when it's time to embed the heating elements in the slab.
Snowmelting systems are generally grouped into three classifications based on the amount of snow actually melted. The systems can be designed to:
- not melt snow while it's falling, but afterward
- melt half of the snow during snowfall, the rest afterward
- melt all snow and ice while snow is falling
It takes a lot of energy to melt snow, roughly five to six times the load required to heat a building of similar size. For example, it may take only 30 to 40 BTU per hour per square foot to heat a structure with a floor-warming (radiant heat) system. But it can take up to 150 BTU per hour per square foot or more to melt snow and ice and ice from a surface.
When snowmelting first begins, energy is lost when the fluid is moved from the heated pipe to the surrounding ground; frequently, the ground is frozen hard. Because the warmed fluid gives off heat as it travels through the slab, contractors prefer to lay the tubes in a spiral or serpentine pattern to distribute the heat evenly.
Insulation substantially reduces operating cost. When added under the slab and at its perimeter, heat loss into the ground is reduced, and the slab heats faster. The preferred insulation material is usually 1- or 2-inch-thick rigid polystyrene foam.
Insulation also helps to channel the heat in the direction it's wanted. Contrary to popular belief, energy doesn't necessarily rise. It travels in any direction, from hot to cold, or from areas of high concentration to low concentration. This works great for interior spaces. But outdoors, four "thieves" work in tandem to steal the heat.
Ground: Heat is literally sucked into the surrounding ground. Heat loss to the ground is about 10 to 15 BTU per hour per square foot.
Atmosphere: The atmosphere works even harder than the ground to swipe the heat you'll be putting into the slab. That's why energy must be fed into the slab continuously. Loss to the atmosphere can be up to 90 BTU per hour per square foot.
Water: As the snow or ice turns into water, it runs off into drains, storm sewers, and surrounding areas. This water runoff carries precious energy away from the slab, too. Care must be taken to ensure the water runoff from the snowmelting system has a place to go. If not adequately designed for, water will run off the slab and "pool" in low spots around the system and freeze. It may be necessary to heat drain pipes and water runoff areas.
Evaporation: As melting snow and ice turn from liquid to gas, more energy is carried off. This energy also must be replaced by the heat source.
Typical snowmelting systems employ tubing buried in a concrete slab. The most popular tubing used is either cross-linked polyethylene (PEX), or synthetic rubber (EPDM). PEX is made of high-density polyethylene that has been "linked" into long, stronger chain molecules. EPDM rubber also is cross linked for strength and durability. Both varieties of tubing have a long history of performance and longevity.
According to Keith Whitworth, a regional manager and design engineer at Springfield, Mo.-based Watts Radiant, tubing comes in a variety of sizes, typically 1/2- to 3/4-inch inside diameter (ID). The flexible tubing ties into supply and return piping at distribution points, or manifolds, that come in pairs: a supply manifold where the tubing starts and a return manifold where the tubing stops. The layout usually is easiest if these manifold pairs are located together next to the zone or area to be snowmelted.
Tubing is spaced from 6 to 12 inches on center and circulates a solution that has been heated to 110° F to 140° F. Tube spacing is varied according to the degree of snowmelting required.
Tubing usually is strapped or tied to reinforcement, whether mesh or rebar. Even if reinforcement is not needed for other reasons, it may be needed to keep the tubing from floating to the concrete's surface during the pour. A minimum of 2 to 3 inches of concrete cover must be maintained over the top of the tubing. Tubing also can be hooked to a base material with turf hooks, stapled into rigid insulation, or otherwise connected to a compacted base.
At expansion joints, where slab movement could cause stress, it's necessary to take special precautions. "We recommend slipping the tubing through collars cut from plastic pipe or pipe insulation and placing it several inches below the expansion joint," says Whitworth.
"Another key precaution," he says, "is that the system must be pressure-tested before and during the concrete pour to ensure that no damage has been done to the heating elements during installation."
Helipads: With space becoming more precious, many hospitals are forced to install helipads on building roofs. These rooftop helipads can become extremely dangerous when coated with ice and snow.
Sidewalks: Convenient and more inviting to passersby, snowmelting systems can increase business and decrease liability. Customers are more likely to shop stores with clear sidewalks, free from ice, snow, and chemicals.
School entrances: Children are protected by maintaining clear walkways. Snowmelting systems keep accidents at a minimum and prevent chemicals from being tracked inside.
Stairs: It's all too common for stairs to become slippery and dangerous during the winter season.
Hospital entrances: "Because they are usually considered critical systems," says Whitworth, "these snowmelting systems are most frequently 'idled' during the winter months—continuously operated at a reduced output—to decrease system lag time." That minimizes the time required for the system to reach full operating temperature and start melting snow after sensors detect precipitation.
Parking garage ramps: Snowmelting systems ensure that cars driving in from the street can safely negotiate up and down parking garage ramps. System sensors are usually placed away from the ramp so that they can detect snowfall or precipitation, and temperature.
Loading docks and ramps: Here, moving the goods is the essence of business. Another good application for snowmelting systems.
On-off operation: Some snowmelting systems operate only when there is ice or snow. These on/off systems work in the presence of precipitation when the ambient temperature is below 35° F. While less costly to operate, these system take longer to start melting ice and snow because they must first increase the temperature of the slab.
Idled operation: In order to help systems respond faster, some systems are idled—or operated at reduced output—until precipitation is sensed with a temperature below 35° F to 38° F, when the system is operated at full output. These systems permit faster system response, and no snow or ice accumulation is permitted.
Sophisticated controls: Automatic controls that sense slab temperatures, outdoor temperatures, and precipitation can also be used. They're more costly, but allow greater system control.
Snowmelting systems themselves are not that expensive to operate, especially the on/off types because, typically, they operate only a few times a year. The biggest cost with a snowmelting system is the upfront price.
"Considering the cost of insulation, tubing, boiler, and pump system, and all installations, a snowmelting system will usually cost between $6 to $12 per square foot, with commercial systems at the higher end," says Whitworth.
On/off system: This is the cheapest system to operate. As an example, a Class II system in Buffalo, N.Y., may cost about $0.21 per square foot per year. The same system in Chicago may only cost $0.12 per square foot per year. Minneapolis or St. Paul may be in the range of $0.25 per square foot per year.
Idled system cost: Because it may operate any time the temperature is below 38° F, it will clearly cost more to operate these systems. Considering that it may operate for up to a third of the year (about 3000 hours), the total system energy would be 300,000 BTU per year. Hospitals may have waste heat from steam or condensation that may be readily available, greatly reducing or eliminating energy needs.
Icy surfaces are no longer a threat. Home or facility maintenance costs are reduced because snowplowing is eliminated or reduced, and ice-melting chemicals that kill landscaping and degrade concrete aren't required.
The cost of the system is more than returned with one avoided lawsuit. Even insurers recognize the value of these systems by rewarding commercial building owners with reduced insurance rates.
So, whether you're melting snow for a sidewalk in Columbia Falls, Mont., or warming an emergency room entrance in Gnome, Alaska, a properly installed snowmelting system will easily do the job.
-John Vastyan is president of Common Ground, Uncommon Communications, Manheim, Pa. He specializes in communications for the radiant heat, hydronics, plumbing and mechanical, and HVAC industries, serving regional, national, and international business-to-business manufacturers and trade associations. He can be reached at 717-664-0535.
What goes in the system makes a difference
If you find yourself at work on a snowmelting system without inhibited glycol in it, there are key steps to take to ensure that you aren't introducing good fluid into a bad system. Factors that cause excessive fluid degradation include operating temperature, the amount of air or dissolved oxygen exposed to the fluid, system age, the construction materials, and the quality of the heat transfer solution, including proper dilution and maintenance, to name a few.
Using a poor quality glycol fluid can lead to serious corrosion problems. Any glycol can provide freeze protection, but only a properly formulated glycol, at the right concentration level and with industrial strength corrosion inhibitors can keep corrosion in check. All glycols can introduce the potential to thermally degrade or oxidize even when left alone in their original sealed container. Degradation proceeds even more rapidly when glycols are operating in a system.
Many system owners learn the hard way that not all glycols are capable of providing long-term protection of system components from corrosion. The old adage "Do it right the first time" holds true because it always costs more to correct a serious corrosion problem than it is to prevent it from happening.
Plain glycol solutions, because they lack corrosion inhibitors, can increase the threat of corrosion in a hydronic snowmelting system. Moreover, putting them into your system cold will eventually cost you far more than the initial fluid price. Uninhibited glycols are less expensive, but become an ongoing threat to your system components.
Heat, oxygen, chlorides, sulfates, metallic impurities, and other contaminants can increase the rate of corrosion in the system. Combined, these are likely to create unscheduled system shutdowns, maintenance issues, and reduced system life. Glycols produce organic acids as they degrade, especially when heated. If left in solution, these acids lower the fluid's pH.
Specially formulated industrial inhibitor packages used in some glycol-based fluids help prevent corrosion in two ways. First, the corrosion inhibitors actively make the surface of the metal less susceptible to corrosion. Second, they buffer the organic acids formed as a result of glycol oxidation to keep the fluid from becoming acidic.
What's the ideal boiler for a snowmelting system?
A snowmelting system is the ultimate challenge for a boiler. Considering that a large volume of ice cold fluids will rush in on it at start—up, a boiler for this has to a be tough. New on the block is a condensing boiler.
The ultimate tool for low and super-low liquid temperatures at start-up. The boiler's secondary heat exchanger transfers exhaust heat to warm liquids before they reach the primary heat exchanger. At peak efficiency, water vapor produced in the combustion process condenses back into liquid form to release latent heat. Its sealed combustion, positive-pressure design assures that the boiler can be installed in many environments, even outdoors. Without the need of room air for combustion, the boiler is not affected by limited air from within the building, or by negative pressures created by other equipment. These units can also offer up to 96% efficiency.
Radiant heat in and outside a concrete home
If homeowners choose a concrete home, then radiant heat is the way to go. Slab on grade, combining massive concrete walls and large, glass-enclosed areas challenges the best of conventional forced air systems.
In this Springfield, Mo., home, abundant Frank Lloyd Wright-inspired concrete acts as an effective thermal storage system. Even the finished floors, concealing a half-mile of radiant heat tubing, are the actual scored and colored slab. It provides optimal comfort and an attractive, easy-to-maintain floor surface. Installer Bob Rohr says that, combined with a substantial under slab insulation to minimize heat loss, the high efficiency system will provide unsurpassed comfort and low operating cost for years to come.
Weather-responsive controls and multiple zones allow the home office and guest rooms to be controlled separately in this 2800-square-foot home that includes some walkway snowmelting, a radiantly-warmed, sunken concrete bath, and a cascade that spills from the back of the house where water accents the mature property's sloped features.