VIDEO LINK: https://www.youtube.com/watch?v=qL04ibBNKr8
Hello, I’m David Harris with M&M Gutters & Exteriors. Today, we’re up in Park City, Utah, and if anyone knows anything about Utah, especially Park City, Utah, we are in snow country. Today, we want to talk a little bit about heat cable, particularly self-regulating heat cable.
Understanding the Formation and Risks of Ice Dams
But before we dive into the heat cable aspect of things, I want to talk about the purpose and the reasons why — most importantly, the ice dams, how they’re created, and the damage they can cause.
In order to understand how the ice forms, you have to understand the thermodynamics of your home. As much as we like to create perfectly 100% energy-efficient homes, it’s pretty impossible. You have your warm living space, and as you heat up that space, you lose some of that heat into your attic. Even on the coldest days, the attic temperature is warm enough that it’ll melt the snow off your roof.
Now, pan over and take a picture of that roof. Here, I think this particular home has a vaulted ceiling, but typically, you’d have a roof lining above and an attic space. When you lose the heat from your home, that fills the attic space, and everything above the warm walls is melting snow. And as that water drains down the roof, as you get past the warm wall, you have what’s called the warm roof or soffit area. From that area to the edge, where typically your gutters would be, the ice freezes.
How to Minimize Ice Dams
There are a couple of things you can do to minimize ice dams.
1. Add Insulation to Your Home: One is adding insulation to your home. If you add insulation to your home, it’s like a blanket in the wintertime. You put more blankets on; you stay warmer — it’s the same thing in the home. So, if you add more insulation in the attic, it prevents a lot of that heat from escaping. Not all of it — but more of it. It eliminates melting the snow on the cold days.
2. Ensure Proper Attic Ventilation: Another thing you can do is make sure you have proper attic ventilation. Make sure you have enough air intake and exit so that as the heat rises, it circulates the cold air through, therefore keeping the attic at a cooler temperature.
3. Install Roof Heat Tape: Even if you have the perfect system, all the insulation, and the proper attic ventilation, you’re still in Park City. You minimize the ice buildup, but you’re still going to have ice buildup. That brings us to the third option, which is heat cable. You can have some here on the roof — I have one because we’re going to be stringing another eave on the other edge. Particularly, it’s going to be the self-regulating heat cable. There are two types:
a. Constant Wattage Roof Heat Tape: There’s constant wattage, which you can buy at Home Depot. If any of you homeowners or contractors have seen it, it’s just thin wire with not a lot of insulation.
b. Self-Regulating Roof Heat Tape: Then you have a self-regulating heat cable. I get asked a lot if that means it turns itself on and off, and no, self-regulating heat cable does not turn itself on and off. You have a couple of insulated sections of the heat cable. That black one in the very center — I don’t know the exact science between it — that, when the temperature gets hotter, it expands, puts pressure on the wires, and actually causes the heat cable to not pull as much current. When it gets colder, it pulls more current. I don’t know the exact science; I just call it “heat cable magic.” If it’s 40 degrees out, you’re going to be pulling less electricity to run the heat cable than if it’s 25 degrees out.
When to Install Roof Heat Tape vs. Replacing the Roof
If the homeowner is looking for heat cable, they ask if it needs to be zigzagged on the roofline or just in the gutters. I always try to figure out what’s happening. In theory, if you have a new roof and the underlayment was underlaid properly — proper ice and water shield, all the proper flashing — then technically, you don’t need a heat cable on your roof system. The roof systems are designed so that you can have ice dams on the eaves without leaking into the home.
But that won’t prevent the gutters from freezing over, and then you get the ice on your driveway and your decks. In order to prevent the gutter from freezing, you do need a heat cable in the gutters. Roofline depends on whether you’re experiencing roof issues because of an improperly laid underlayment. That could lead to probably just doing a new roof. But if you’re trying to buy time because your budget doesn’t allow you to do a new roof at that time, then yes, you can put a heat cable up there to prevent the ice dams if you’re having roof issues. Otherwise, have it at a minimum in the gutters so you won’t have ice overflowing your gutters.
Do You Need Roof Heat Tape in Dead Valleys?
We all know that architects don’t design as well as they should for areas where ice is, so you’ll have a lot of what we call dead valleys or crickets. In those locations, even if you have a perfectly laid underlayment and roof, I would suggest heat cable in those areas because if you get five inches of ice buildup there, it could possibly go behind the siding and go over the step flashing that’s laid against the side.
If you have any questions, reach out to our company. We can come and assess the issue. I’m also a big believer that if you start small, put it in the gutters, and go a winter to see what happens with the commercial-grade or self-regulating heat cable, you can always add more on zigzag rooflines. That way, you don’t go crazy with the heat cable, which can get pricey. You can start small and add on based on your needs.
How to Install Heat Cables to Prevent Ice Dams
I’ve strung my heat cable. We’re actually powering up over here, but the eave we’re doing it on is over the ridgeline, so we’ll have to do some attaching here to get it back over here. But before we do that, there was something I wanted to tell you in regard to the soffits and the warm walls.
If you look here, you’ve got the pitch of the line, then the exterior of the home, and you have that last two and a half/three feet. If you’re going to be zigzagging the eaves of your home, it’s important to understand that for the heat cable to build that trough and keep the ice from building up, that zigzag has to go high enough to where it’s at least six inches on the interior of that wall.
Here, we have a slight roof. Your zigzag would here, out of two and a half feet — then you’ve got six-inch framing — would probably be three, three and a half feet to get inside that warm wall to where you get into the attic space. Otherwise, you could possibly get some ice buildup above the heat cable, which defeats the whole purpose of heat cables, which is to get rid of an ice dam.
Roof Heat Tape Installation Patterns
Also important to know that your standard pattern is two feet wide by however high you need. You will still get snow buildup in between those zigzags because the heat cable is amazing, but it’s not a solar shield. You’ll still get a little bit of snow scuff, but it keeps all of the ice from building up because that triangle pattern gives it easy access to run to the gutters. Water follows a path of least resistance.
Understanding Snow Rails on Metal Roofs
I mentioned before in regards to getting the zigzags within the warm wall. As you can see, in this case, I’m not going to do that. It’s a metal roof; they’re designed to have ice buildup. Because the snow rail is two feet off the edge, it wants to melt the edge so it doesn’t fall down. If I decided we have to get it up higher than the warm wall up to this point where it’s in the warm wall, then I’m melting all the snow that’s against the snow rail.
Eventually, all the snow above it will slide down. That snow that slides down, because I have now eliminated the snow rail because I melted all the snow that was helping keep it up, is now going to crash down on our heat cable and potentially rip it off.
Where to Place Heat Cable on a Metal Roof With Snow Rails
If you have a metal roof, and you’re doing a snow rail on it to prevent the snow slide, you can do heat cable on the metal roof, but you do not want to bring it past that snow rail — unless you’re doing multiple levels of snow rail. If this had another snow rail above it, then I would bring the zigzag up higher to get it inside the warm wall. But because I have nothing above it protecting this expensive electrical heat cable, I’m keeping it below the snow rail so the snow rail will protect it from getting ripped off the roof if the snow wants to slide.
How to Install Roof Heat Tape in Relation to Snow Rails
Here’s your snow rail. We got a good six-inch radius around the heat cable that’ll melt in the wintertime. Like I said, we’re at 29 inches a little over 2 feet. We’ll do these zigzags at 18 inches… you actually want the snow and ice to form around the snow rail because that helps keep the other snow loaded up above from sliding down. So I’ll mark all my brackets at 18 inches on the bottom, and that will melt the snow that otherwise would slide off onto the deck.
Heat Cable Installation Tips
When it comes to stringing the heat cable, make sure you’re not twisting the heat cable, so you’re not bending it and have a twist in it. Make sure it lays the same way all the way through. That’s the only thing. Also make sure the loops don’t go past the front of the heat cable so you don’t have a lot of slack in it so that it’s more of a zigzag.
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