Snow-melting systems provide access to your residence or commercial facility during all winter weather conditions.
By Monica Irgens
Snow-melting systems provide access to your residence or commercial facility during all winter weather conditions without the use of manual labor or chemicals and abrasives. They also help to alleviate such conditions as:
- Walkways with irregular surfaces such as natural stone that can be challenging to shovel completely, ultimately creating a slip and fall hazard.
- Garages at the end of a steep driveway that can become inaccessible, causing you to park your vehicle on the street and in harm’s way.
- Icing, from the re-freezing of melt runoff from adjacent areas, which can happen for days after a snow event, requiring repeated application of chemicals or traction abrasives.
- Interior floors become dirty and damaged from tracked-in chemicals and abrasives.
When deciding on a snowmelt system, it is essential to determine its purpose and how effective the system should be. Should the ground be dry, or is it acceptable with some snow slush shortly after a snowfall? The American Society of Heating, Refrigerating and Air-Conditioning Engineers classifications split snowmelt systems into three groups:
- Snow free ratio 0: Designed not to melt snow while falling, but afterward.
- Snow free ratio 0.5: 50% of snow is melted while falling, the rest afterward.
- Snow free ratio 1: All snow and ice is melted while falling.
“When designing a snowmelt system, it is essential to know the area conditions: snowfall days, temperature, surface type, heat loss to the ground, atmospheric loss, and perimeter insulations. These are some of the parameters needed to create snowmelt solutions according to expectations.”
The traditional snowmelt system is based upon an on/off concept. The system is energized before or at the start of the snow/ice event and requires significant energy (30-50 W/sq. ft.) to heat the surrounding mass to a temperature above freezing. This system is then left on for the time needed to evaporate any free moisture and prevent any freezing of melt runoff. This time duration could be hours or even days. Once the system is no longer needed, the system is de-energized and goes idle.
These systems are either hydronic or electric. A hydronic system uses a boiler to generate hot glycol-treated water pumped through tubing embedded in the surface to be heated. The tubing is installed in a serpentine pattern to distribute the heat throughout the slab. An electric system typically consists of a heat-generating cable supplied in bulk, on spools, or as a mat. The bulk cable is a thick, high-wattage cable installed in a serpentine pattern, just like the hydronic tubing. Also, some electric systems feature smaller, lower-wattage heating cables pre-installed in a serpentine pattern in a fabric mesh. These pre-sized mats are then rolled out and embedded in the slab.
Another option available is the STEP Snowmelt™ system which takes an entirely different approach, offering a much lower wattage product while providing significant energy efficiency compared to most on/off high energy systems. This heating method involves using a thermal reservoir to give the bulk heat required during a snow event. For large areas, such as a driveway or parking area, the geothermal energy that naturally comes up from the depths of the earth creates a thermal reservoir of heat.
Vertical insulation is installed along the edges of the heated surface as a thermal barrier. This thermal and heat barrier prevents the ingress of cold into the ground under the heated surface, using the earth’s natural heat to maintain the heated surface above freezing.
The key behind creating the thermal reservoir is to energize the electric heaters before the ground begins to freeze. The ground freezes from the top-down, and the heat barrier will prevent the ingress of cold from the top and prevents the cold from creeping in from the sides. The open bottom then freely lets the earth’s geothermal energy rise and keeps the reservoir at a minimum of 55°F. Once energized, the system must remain energized during the snow/ice season to maintain the thermal reservoir. Your typical weather-related outage is short enough not to cause the loss of the thermal reservoir.
Monica Irgens is the President of STEP HEAT.