Icicles along the eave look harmless until you understand what is behind them: a ridge of ice holding a pool of meltwater against the roof, working its way under the shingles toward the ceiling. Here is how ice dams form, who gets them, and when heat tape is the answer.
How An Ice Dam Forms
Heat escaping through the attic warms the upper roof and melts the snow on it. The meltwater runs down to the eave, which hangs past the heated house and stays cold, and refreezes there. Each cycle adds to the ridge. Eventually the next melt cannot get past the ridge, pools behind it, and backs up under the shingles. Water in the attic insulation, stains on the ceiling and peeling paint on the fascia follow.
Who Gets Them
- North- and east-facing eaves that sit in shade through the winter afternoon
- Bench homes in Cottonwood Heights, Sandy, Holladay, Millcreek, Bountiful, Kaysville, Provo and Ogden that catch lake-effect snow against the mountains
- Park City, Heber and the Wasatch Back, where nearly every roof dams during a cold snap after a storm
- Homes with warm attics: recessed lights, leaky attic hatches, thin insulation, bath fans vented into the attic
- Complex rooflines with valleys and dormers that concentrate melt
- Gutters that went into winter full of leaves, which freeze solid and start the dam
What Heat Tape Does
Self-regulating heat cable runs in a zigzag along the eave and down each downspout. It does not melt the whole roof; it keeps a channel open through the ice so meltwater can reach the downspout and get off the roof instead of backing up. On a sensor controller it only draws power when it is below freezing and wet, which on a typical home costs $25 to $80 a winter in electricity depending on the length of cable and how cold the site is.
What Heat Tape Does Not Do
It does not fix the cause. If the attic is leaking heat, the roof will keep melting snow from below and the cable will keep working all winter. Heat tape is the right fix for the eave; air sealing, insulation and ventilation are the right fix for the attic. On most bench homes you need the heat tape regardless, because shade and snow load will dam the eave even over a well-insulated attic, but we will tell you plainly when the attic is the bigger issue.
Self-Regulating Versus Constant-Wattage
Constant-wattage cable from the hardware store draws full power whenever it is plugged in and is a known fire risk when overlapped. Self-regulating cable adjusts its output to the temperature along its length, can be overlapped safely, and lasts ten to fifteen years. We only install self-regulating cable on a dedicated circuit with a sensor or thermostat controller.
What It Costs
Installed heat tape runs $12 to $25 per foot of cable plus $150 to $400 for the controller. A typical bench home with heat tape on the north and east eaves and downspouts lands between $800 and $2,000. Roof-edge ice melt panels for chronic problem areas run $40 to $70 per foot of eave.
When To Install
Before the first lasting snow. Fall fills up fast, especially in Park City and Heber, so book by early October. If you already have a dam, see ice dam removal for steam removal that does not damage the roof.
Full details are on our heat tape and ice melt page.
Ready for a number on your own house? SwiftHand Gutters gives free, itemized estimates across Salt Lake, Utah, Davis, Weber, Summit and Wasatch counties. Request a free estimate or call 801-784-6712.
