Better alternative to heat tape for downspouts
I’ve been trying to deal with a frozen downspout for a couple of years now. The downspout is run between two building so it doesn’t see much sun, it also handles about 50% of the water from the roof. Usually after a longer cold spell and lots of snow it will freeze up solid.
The icemelt in the sock works great, but I’m hesitant to use it often with a metal roof (plus climbing on long ladder in the middle of winter is not pleasant).
This year I fished two runs of roof melt heat tape through the downspout. This works when the weather is not very cold, stops working bellow -10 deg C (14 F), which is where I need it to work. It doesn’t put out enough heat to melt the ice, just enough to allow it to drain. It is also a huge energy waste (~10 kWh/day).
I’m just wondering if people have found better ways of dealing with this.
Thanks,
Akos
P.S. If you are building with dark metal roofing in a cold climate, I would recommend locating downspouts where they get a lot of sun.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Metal roof, well there's part of your problem. Snow and ice will slip down the roof and where does it end up? In the gutter. I'm not a big fan of gutters. I like diverters instead to direct water off a roof though it may be a little more difficult on a metal roof. No clogging, cheaper, easily replaced if damaged from ice and snow build up etc. Use other techniques on the ground to divert rain water away from your foundation.
This is a tricky problem. Depending on the situation, it is possible to replace the downspout with a thick length of chain -- the water will adhere to the chain and flow down it, at least in most conditions. In the winter, the water will freeze on the chain, turning it into a giant icicle, but it will give you a lot more leeway before the flow of water is blocked. Note that I have not seen this done for more than one story though.
I had this problem at one of the commercial buildings I oversee. The gutters were all on the north side of the building, and in cold conditions they would freeze and ice up so badly there would be big upside down cones of ice as tall as me at the bottoms. Needless to say, water would find its way inside the building when this happened and set off moisture alarms (the building is a datacenter facility).
I specced the raychem self-regulating heating cables. These are far and away better than the usual heating cables you find in hardware stores. They cost a lot more too. The self-regulating cables don’t have thermostats, instead they’re made of a material that makes more heat (and uses more power) the colder it gets. They’re larger than the usual 1/4” or so cables too, the raychem cables are maybe 5/16” x 5/8”, an oval shape. They work awesome though, totally solved the problem. They also have bulk kits so you can make “T” taps to drop down downspouts from a main run in a gutter.
I wouldn’t use the “salt in a sock” method. The salt will cause the metal to deteriorate much faster, especially any aluminum components.
Bill
Deleted
Hi Akos -
I bet more GBAers could weigh in on this one if you sent some photos of your situation. How much melt you get is a function in part of heat loss from your roof and particularly at the eaves. While it is true that some roofs and some climates mean that gutters don't work or are an annual installation cost, I think we need more intel...
Peter
Bill, I'm hoping to avoid throwing more power at this problem, it just feels wrong. That Raychem part sound great, but it is also very pricey. Out of curiosity, is the cable capable of completely melting the ice or it provides enough heat to keep some of the cross section open.
I've tried to take some pictures, but is quite hard as it is in a tight location. My problem is that the gutters are about 30' in the air and the houses here have stone rubble foundation without any waterproofing, so the no downspout solutions won't work.
One idea I might try is wrapping the bottom section of the downspouts with insulation tape. There is a large horizontal run to bring the water away from the house, which is not helping.
That is a tight space! Wow. On the plus side, it’s so tight you probably couldn’t fall backwards off the ladder since you could just push against the opposite wall.
Anyway, yes, the raychem cables can keep the ice away completely unless it’s gets really cold. They are much more capable than the regular cheap cables you see. I also think they’ll last a long time too, not just a few years.
I don't think the insulation will help unless you put a heat cable in to provide a heat source. Presumably a self regulating heat cable would use less power if you insulate the downspout since the cable would stay warmer in that case. I don’t know how much difference that would make in overall power consumption though.
I think a heating cable is probably going to be your only real option here.
Bill
I don't think any gutter solution will work in that situation. You'll have to find a solution to the "alley" way between the buildings to melt and move the water. Perhaps a small solar or other type of hot water/electric radiant system in the alley way might work.
In order to minimize ice buildup, you want keep the water moving and minimize the contact it has with the metal of the gutter. You have a substantial bend in that gutter at the very start (edit: and a long horizontal run at the very end) which is detrimental to both. While you might not be able to get rid of the bend entirely, making it gentler will help a little bit.
It looks like aesthetics are not important in this situation, given the secluded nature of the alley. Perhaps you can replace the downspout with a simple PVC pipe and increase the diameter. The PVC is less conductive than metal, so it will not freeze the water as quickly. Since it is a little more insulating, it will retain the heat of the water better as well (after all, the water is above freezing when it enters the downspout -- the metal downspout serves as a giant heat sink and rapidly cools it). Adding further insulation to the outside of the pipe will boost this effect, and make your heat tape more effective. And using a larger diameter will make it harder for the gutter to freeze completely through, extending the number of days your system can go before needing to clear the ice.
Thanks for the ideas folks. For now I've added a timer to only run the heat tape during the day, this has made a huge difference in power use. With the weather warmer, the heating is keeping the ice at bay, I'm going to look at insulating the outside next. For now I want to avoid replacing the downspouts (plus round pipes crack if they ever freeze up).
You might also be interested to know that there are both thermostats that you can use, and also snow sensors. The snow sensors are just moisture sensors so the cables only run when there is something that needs melting. For a roof, you really need the cables on before it snows so I’m not a big fan of snow sensors for heating cables that are supposed to prevent ice damns. In a gutter though, you only really need the cables to run when it’s below freezing AND there is snow that needs melting to keep the gutter clear.
Bill
May I ask if this relates to the installation? For the cables below they run it both on the roof and in the gutters. Is that what you did or just inside the gutters?
https://www.nvent.com/en-ca/raychem/products/icestop-self-regulating-heating-cable-0
Came to ask the same question. While one of the gutters is not in quite a narrow space as on Akos's photos, it is the same problem - no sun, narrow space.
Is Raythem self regulating heating cable still the best solution? and if so - which one (there are different (seemingly) kinds:
https://www.nvent.com/en-ca/raychem/products/self-regulating
The gutters and downspouts are being installed, so can add anything while convenient. Same climate as Akos (Zone 5/6)
Bump
There is the specific icemelt version, I would use that.
I've had no isssues with two runs of the box store heat tape in my downspouts. It doesn't melt the icebuildup but melts enough of a channel to allow the water to drain down. This keeps it from freezing solid so it is good enough.
I have it on a timer I can enable when needed, no need to keep it on all the time. I only need to run it during the day after about 11am till 3pm on very cold but sunny days after a snowstorm.
Thank you! This one?
https://www.nvent.com/en-ca/raychem/products/icestop-self-regulating-heating-cable-0
Could you tell me more about the timer? It sounds perfect.
Consider moving the gutter on that side to the ground and allowing the water to fall and land on rock or concrete be collected and directed away from the building.
Walta
That is a cool idea but unfortunately too late for that.
Late? Time is not a factor.
Yes, you may have to decide it is better to remove and discard stuff you paid for but that is not impossable.
If something is a problem and not a solution it no longer adds any value in its current location what is the point of keeping it.
It is a sunk cost just because it was expensive when you bought it does not mean it will be as valuable when you sell it.
Very few things are truly permanent in this world.
Walta
Walta,
I like the way James Tuer did that on this house using an open-ended gutter and concrete basin.
Actually it is not that. It is the roof design that simply makes it impossible. See image.
I was pondering if the downspout in the OP was too small. Lot of roof to drain through one downspout. overload pipe, velocity goes to zero, water freezes. Doesn't' thaw until over 32 for 'x' period of time