Icicles: FAQs to Protect Your Home

FAQs about icicles on roof

Icicles: FAQs to Protect Your Home

Explore the commonly asked questions about icicles and ice-damming.

snow melt causes icicles
What causes icicles on your roof?

Icicles form on the edge of your roof in the winter time. They form when the snow sitting on your roof melts. The resulting water runs down the edge of your roof and refreezes, forming icicles.

Although, icicles appear at the edge of the roof, they form from melting snow. From the bottom edge to the peak of the roof, snow melts everywhere. Multiple factors cause the snow on your roof to melt:
  • inadequate insulation.
  • house air leakage into the attic through thermal bypasses.
  • improper ventilation. 
However, the structure of your house, weather conditions and even the color of your roof influence icicle formation. Finally, your lifestyle impacts icicle formation.

But there is good news. Some of the biggest factors that cause roof ice can be corrected or reduced substantially by the insulation, air sealing and ventilation work. However, ice cannot be eliminated. Although many factors are correctable, not everything is preventable.

What is the best solution to reduce ice on my roof?

In most cases, a combination of proper air-sealing, high levels of insulation, and adequate ventilation are the best solutions to reduce icicles.

Does raking off the snow help?

removing snow from roof helps prevent icicles

If you don’t have snow on your roof, it can’t melt and form ice. Although, shoveling snow off your roof is a short-term fix. Addressing heat loss remains the best long-term solution. 

In some heavy snow conditions, snow acts as an effective insulator on top of your roof. The snow warms the roof deck and increases melting. However, shoveling the snow off the first two or three feet of the roof won’t prevent the problem.

Snow further up the roof eventually melts down and creates ice dams. If you do rake the snow off—do not climb on the roof and be careful on the ground—the weight of snow falling off the roof is dangerous.

Does heat tape help?

Heat tape can help. However, it not only costs as much as $600 to buy, it must be installed, which adds penetrations to your roof. Plus, heat tape can be very expensive to run.

Essentially, you are paying to heat your roof. This should not be considered as an alternative to reducing heat loss into the attic. Generally, heat tape makes sense in rare cases with certain poorly thought out architectural details, such as roof valleys over an entryway.

Should I remove big icicles and ice dams from my roof?

Do not climb up on your roof and hack or chip away at ice. This is very dangerous. And there’s substantial risk of roof damage. Generally, you do not want to hack away at ice unless there is the risk of injury from falling ice. Frequently, trying to remove ice damages your roof and other parts of your home.

Is there anything I can do about an ice dam on the roof right now?

In the short-term, you can buy a special “melt sock” or fill a nylon stocking with calcium chloride. Place this over the ice dam, running it up the roof right where ice forms. This creates a channel allowing melt water to run off rather than back up into your house.

My attic is insulated. Why do I still have ice?

In most homes, proper attention has not been paid to air sealing. This allows warm air to escape into the attic and decreases the effectiveness of existing insulation. We often see homes that have a lot of attic insulation, but no air-sealing. Even if your attic is well sealed and insulated, there are additional factors that can contribute to warming your roof and melting snow.
  • Attic Ventilation.

    Improving attic ventilation helps control ice formation and reduces the risk of moisture damage from condensation in the winter. Attic ventilation without proper air sealing and insulation, however, rarely fixes the problem. In fact, increasing ventilation in these cases may cause your heating bills to skyrocket.
  • Chimneys and Flues.

    A chimney traveling through an attic crawlspace will radiate heat into the attic. Even if the attic is properly ventilated, some of this heat will reach the roof and melt snow.
  • Kitchen and Bath Fans.

    A kitchen or bath fan that is vented through the roof generates heat and melts snow around the fan. Icicles often form on the edge of the roof below the roof vents of these fans. Fans exhausting into the attic can warm the entire attic creating a problem (and leading to moisture and mold issues). Fans should be vented directly outside.
  • Roof Color.

    Darker roofs absorb more heat from the sun, and in certain conditions can accelerate snow melting.
  • Heavy Snow Fall.

    Snow acts as an insulator. Deep snow on your roof can warm up the roof deck and melt snow in contact with the roof—which then refreezes at the eaves. In very heavy snow fall, even well-insulated homes may experience ice as a result. The more insulation you have, the less likely this is to occur. With deep snow cover, roof raking may be helpful.
  • Outdoor Temperature.

    The outdoor temperature impacts ice formation. Each home responds differently to different temperatures, but temperatures in the low 20s seem to generate the most ice for most homes. At this temperature, it is warm enough so the roof can melt some snow, but cold enough so that it refreezes quickly at the eaves.
  • Indoor Temperature.

    The higher you set your thermostat, the more heat loss you will have, regardless of insulation levels.
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