Ice Melt SystemsConcrete driveways offer many advantages over asphalt, including greater durability, longer service life, and less maintenance. But in the winter, when temperatures plummet and the snow flies, concrete and asphalt surfaces have equal maintenance needs: Both require frequent shoveling and de-icing.
Or do they? Some homeowners and businesses are keeping their concrete driveways and other exterior flatwork surfaces maintenance-free and safe year-round by installing ice and snow melting systems. Not only do these in-slab snow melt systems eliminate plowing, backbreaking shoveling, and icy spills, they prevent potential damage to the concrete caused by snow-removal equipment and corrosive de-icers.
Though contractors usually install these systems in new slabs before placing the concrete, the heating elements also can be retrofitted into existing slabs.
The heating element in a hydronic system is a closed-loop tubing made of a flexible polymer (typically a cross-linked polyethylene) or a synthetic rubber that circulates a mixture of hot water and propylene glycol (antifreeze),much like the mixture used in a car radiator. The fluid is warmed to temperatures of 140 to 180 F to provide sufficient heat for snow melting. The tubing ranges in diameter from 1/2 to 3/4 inch and is flexible enough to bend into various layout patterns. Its also designed to have a long service life. The tubing resists chemicals and corrosion and does not become soft at high operating temperatures or brittle at low outdoor temperatures.
The heat source--typically a water heater or boiler--can be powered by any energy source that satisfies the systems Btu requirements, including natural gas, electricity, oil, wood, or even solar collectors. For residential and light commercial snow melting, Bailey recommends providing about 100 to 150 Btu per square foot of slab surface. A circulating pump and supply and return manifolds, installed in an easily accessible location, transfer the water between the heat source and tubing.
Successful operation of a hydronic heating system depends on proper tube spacing and layout. Because the hot water gives off heat as it travels through the slab, manufacturers usually recommend laying the tubes in a spiral or serpentine pattern to help distribute the heat evenly. Tube spacing depends on several factors including the snow melting rate desired, the amount of insulation used under the slab, and the anticipated rate of heat loss. A typical spacing for an exterior slab on grade is 6 inches on center, which conveniently corresponds with the 6-inch grid pattern of welded wire reinforcing. But closer spacings may be needed in some applications. Snow melting systems can be controlled manually or automatically. Automatic controllers use sensors to trigger the start of the heating element and to determine when its time to shut the system off; the user doesn't have to be around to activate the controls. The sensors measure the airs temperature and moisture content. When they detect the presence of moisture at near-freezing air temperatures, the system will kick on automatically and raise the concrete surface temperature to about 45 F. When the precipitation stops or the air temperature rises, the system will shut off. An override switch allows the user to control the system manually if necessary. In a heavy snowfall, when snow accumulates at a faster rate, extra heating time may be required for complete removal. Sensors can be mounted in the pavement being heated, on a nearby post, or in any spot not sheltered from the weather, such as on a garage overhang or roof. More sophisticated systems can have multiple sensors that control different zones of a pavement independently.
Some system owners, particularly businesses that don't operate round-the-clock, prefer manual controls that don't rely on sensors. These controllers generally are less expensive to install and can be turned on only when snow removal is required.
Once activated, hydronic systems usually have a slower response time than electric systems because the fluid that circulates through the tubing must first be heated. If fast response is critical, hydronic systems can be operated during the winter at a reduced idling rate to keep fluid in the pipes warm enough to react quickly to impending snowfall.