Not all heat cable is created equal

This is a guest blog post by Steve Kuhl of Radiant Solutions Company. This is the second in a three-part series.

Over the past 30 years, I’ve been asked countless times if heat cables are a good solution or a bad solution for ice dams. My answer has always been, “Yes”. They are a great solution when you use the right cable and a bad solution if you don’t. Heat cables are a controversial topic in the field of ice dam prevention for good reason. They can be inefficient, short-lived, ineffective and even pose a fire hazard in some situations.

But to be clear, all of these issues relate to installations involving a low-quality class of cables known as ‘Constant-Wattage’, which are usually bought on Amazon or at big-box retailers and installed by less-than-professional hands. Constant-wattage cable gets its name from the fact that–unlike self-regulating cable–it does not automatically adjust its energy consumption with changes in outdoor temperatures. It is hot, hot, hot, 100% of the time when plugged in. There are many other dubious distinctions described below.

Sadly, constant-wattage heat cable is the most widely used roof deicing cable in the country, accounting for roughly 90% of all residential installations and nearly 100% of all complaints. Based on my many years of experience in ice dam prevention and residential construction, my opinion on constant-wattage cable is clear: It is better to not install anything than to use these products on your home. This explains why 60% of the heat tape installations we do in the Minneapolis area involve tearing out constant-wattage and replacing it with self-regulating cable, even on systems less than a year old. Bummer.

Quick facts about constant-wattage heat cable

Cost: A 100-foot constant-wattage cable will cost you around $75 whereas a self-regulating cable of the same length will be closer to $350. Ultimately, being cheap is the only short-term advantage constant-wattage cable has over self-regulating cable. Self-regulating cable is far cheaper over the long run when lifespans and energy consumption are factored in. If the cable feels very affordable, it is probably because it’s cheap.

Dimension & Brand Names: How does the average person tell the difference between self-regulating cable and constant-wattage cable? Here are a few quick tips. Identifying constant-wattage cable visually is easy. It’s normally black and round, measuring about ¼” in diameter and is usually sold under the brand names of Frost King, EasyHeat, Wrap-On or Heat-It.

Constant-wattage cables are typically the only option at local hardware stores both large and small. In contrast, self-regulating cables are normally ¼” x ½”, similar in shape to standard Romex® wire used in American homes. For all of our installations, we use Heat Tape Pro, a commercial-grade self-regulating heat cable that carries a five-year manufacturer’s warranty.

Performance & Limitations: A quick review of the manual and marketing materials will tell you quite a bit about constant wattage cable including these crucial limitations that few people are aware of:

Constant-wattage cable will operate effectively when it’s warmer than 15 degrees outside.
Constant-wattage cable can not be used on metal roofs, rubber roofs, wood roofs, flat roofs, slate roofs, tile roofs, synthetic roofs or roofs with gutter guards.
Constant-wattage cable can’t overlap or touch itself at any point on the installation. If it does, it can burn out, overheat and/or start on fire.
Combustibles such as leaves and pine needles to be cleared away from constant wattage cables to reduce the risk of fire.
Constant-wattage cables can not be repaired if damaged.
Constant-wattage cables only carry a one- to two-year warranty.
Constant-wattage cable is not effective at temps lower than 15 degrees and can make ice dams worse if used below that threshold.
Constant-wattage cable can’t touch any metal on your roof including valley flashings, gutters, plumbing flashings, and skylights unless that metal is electrically grounded by a licensed electrician.

Quick Facts About Self-Regulating Heat Cable

Self-regulating heat cables were originally developed over 50 years ago for use in arctic oil fields to prevent pipelines from freezing. It’s a robust technology with many years of proven effectiveness. It has a special conductive core that asks for more energy in response to cold and less when temperatures are warmer. In other words, it ‘self-regulates’. Here are some benefits to self-regulating heat cables:

Self-regulating cable can overlap itself without risk of shorting out and never overheat.
Self-regulating cable can be used on any roofing material or slope including asphalt, metal, rubber, wood, synthetics and flat roofs.
Self-regulating cable will not start leaves or pine needles on fire.
Self-regulating cable has an expected lifespan of ten years.
Self-regulating cable can touch metal objects such as gutters and gutter.
Self-regulating cable can be repaired in the field and modified with splices to accommodate any design.
Self-regulating cable adjusts its energy consumption in response to outdoor temperatures.
Can be installed quickly using Grip Clips which eliminates the need to put nail holes through the roof system.

Heat Tape and Ice Dam Prevention: Some Final Thoughts

After all of these years in the ice dam, roofing and remodeling industries I still find myself coming back to this natural law in home maintenance: The solution is always about the budget. If you have a lot to spend you will choose one path, if you have a tighter wallet you will choose another. In terms of ice dams, I’m afraid there aren’t always ‘cheap’ solutions. Homeowners must sometimes choose from the lesser of three evils: 1) Spend a lot on architectural enhancements, 2) Spend a lot on professional roof shoveling or risk a lot doing it themselves or, 3) Spend a fair amount on heat cables. The average self-regulating heat cable system we install in the Minneapolis area runs between $1,000 and $2,000.

My advice to anyone considering heat cable for ice dam prevention is to either install a high-quality, self-regulating heat cable or skip it altogether. Constant wattage heat cable is a total waste of money. Worse, it can create a false sense of security for people who have most likely already had a bad relationship with ice dams in the past.

Next week I will be writing a follow-up post that discusses how to install a long-lasting heat cable system, including design, materials, expected costs and installation tips.