Radiant Snowmelt Tubing Size and Placement- Under Eaves

davidm2232 · May 15

I am designing a snowmelt system for my garage. There are two sidewalks 4'x28' on each eave side and an apron that is 28x20 on the gable end. I also have 2 12' overhead doors and 2 3' man doors on the eave sides. I live in the Adirondacks of NY so it is not uncommon to get 3' of snow along with wind and zero degree temps.

For the apron, I am probably not ever going to heat it, I may on occasion but the pex will be in there for heating the slab if I ever add on the garage.

The sidewalks will probably just be heated occasionally after I plow off the main snow just to keep them ice free.

The big issue are the man doors. I want those to stay clear all/most times. But they are right under the eaves and the snow slides off the garage roof. What tubing size and spacing do I need to make sure all the snow gets melted quickly? I was thinking 5/8 tubing at 4" spacing. Is that overkill? Also, do I have to worry about cracking the sidewalks if I am only heating a 4x4 section and leaving the rest cold? I am doing my design in LoopCad and have an estimated 115K BTU load if I was to run the entire system but only 6k for the man doors which is totally doable off my current boiler (85K).

hot_rod · May 17

Here are the classifications of snowmelt design. Bottom line…how much snow and how quickly do you want to melt?

Of course the faster the desired melt, the more boiler power you need. I would guess 200 btu/ sq ft or more for a system like that.

What will it be powered by, it will not be a cheap date to run.

Big Ed_4 · May 17

Food for thought in your design .. Drainage

davidm2232 · May 19

I have drainage thought out. My dad who pours concrete for a living thinks I am going overboard on the drainage, but he has no experience with snowmelt systems

As far as the ASHRAE, that seems to not cover anything about snow falling off roofs. I will be running off an oil boiler to start. I may add a wood or coal boiler if I determine I like the way the system performs.

hot_rod · May 19

I don’t think it really matters where the snow comes from, just the amount of snow and the time required to melt to water.

Chicago O Hare has or had some hydronic melt pads or pits they dumped snow onto with loaders.

I see more of the metal dumpster looking devices being used now to melt snow as it is dumped in, at Chicago

Regardless, it takes a lot of energy to melt snow.
I would run a section of 3/4” pex in that area, get the tube spacing as tight as possible, if you want to try this. Insulate below with 2” foam

With large diameter tube you “light bulb” the loop ends. A 10 or 12” diameter loop, then back to 6” spacing for the straight runs

Jamie Hall · May 19

The snow that slides off the roof over the main doors… um, no. What you will get if that happens is a pile of snow — essentially the entire roof above where it hits — in a dense heap. Much denser than fallen snow. To look at it another way — the equivalent of perhaps 8 to 10 feet of snow in a nice dense pile two or three feet high.

Seen that.

There is a very good reason why barns in snow country are designed to keep snow from sliding off the roof over a door (a door in a side wall). Now there are several ways to do that. A covered area like a low dormer to deflect that roof snow off to the sides is sometimes the simplest. Assuming, of course, that the door has to be in a side wall for some reason (and there are good reasons). Alternatively, brakes of various types and styles (there are a lot — homemade and commercial) to keep the snow on the roof in the first place. They work pretty well — though of course the roof has to be designed and built to take the snow load…

But don't think you are going to melt that heap of snow with a snow melt system. Not in the Adirondacks. Not going to happen. At least not in any reasonable time frame.

hot_rod · May 20

if you are just heating a 4’ wide path at the man door, that is more workable than the entire overhead door area.

Plow or shovel first, then melt for ice protection, maybe?

Big Ed_4 · May 20

Just thinking you living up in Gods country and all , if it were me , I would have the system humming for those night storms that could hit up there :). I would guess you have a plow…

EBEBRATT-Ed · May 20

@Jamie Hall Idea would be a lot cheaper and may cut down on the amount of snow that needs melting

davidm2232 · May 20

After looking at PEX and foam costs, I am not going to heat the whole apron/sidewalks. Just the areas in front of the doors. This will cut down the BTU load significantly. I can then focus on putting the max amount of heat into where I really want it while still making the system somewhat economical to run.

The plan is to run just a 4' section in front of each of the man doors pretty much all the time. I don't plow the driveway unless we get over 6" or so. I just need to keep it clear in front of the doors so I can walk to my car in the morning without getting snow on my boots. If we get a 2' storm, I can plow away the majority then let the snowmelt run in front of the doors for the smaller piles the plow can't get to. The overhead doors on the gable ends will just need to keep it warm enough so that when I plow, the snow right next to the doors will melt so that they will close all the way.

I like the idea of 3/4 pex closely spaced in front of the doors to give maximum heating.

Jamie Hall · May 20

Good luck. Your two foot snowfall will put eight to ten feet of snow dense packed into a three foot mound in front of those doors when it slides off the roof. I've watched it happen to folks. Then came over with the front end loader on the tractor and shoveled them out…

Kaos · May 21

https://forum.heatinghelp.com/discussion/comment/1855799#Comment_1855799

This!

There are a number of snow melts around me that do an excellent job of turning some easy to shovel snow into an iceberg at the end of the driveway where the heat stops that needs to be chipped away.

hot_rod · May 21

define the space. .4x20’ work for you?

A grate at the end running yo a pit or gravity drain in some cases we would run a pex loop along the drain. Until it could drain away without re-freezing

Actually wet heavy snow melts best. Light powder snow would “bridge”. The light fluffy snow would not push down against the warm slab. An air space would form between the snow and slab.

So you have that going in your favor, with dense snow.

As you know, the more snow you can move manually the less work the slab has to do

At the ski areas were I worked, lodges with metal roofs always had snow hooks to keep snow on the roof, and off the tourists

Obviously those roofs were designed for heavy loads.

davidm2232 · December 15

I figured I'd follow up with my install. It works pretty well. All the concrete has a 2% slope with broom finish

I have a 4x28 area in front of the overhead doors with a trench drain at the end of the heated area

A 4x10 area in front of the front door with 42" of trench drain at the edge of the sidewalk with heat just on the one side, no pex between the drain and the edge of the sidewalk. This leaves snow on the other side of the drain but I was worried about water/ice running into the rest of the driveway

A 4x6 are in front of the side door with 42" of trench drain at the edge of the sidewalk with heat on both sides of the drain. This keeps the whole sidewalk area clear and I have not seen an issues with ice thus far

These three loops go into a 3 zone bluefin manifold. I am running a Taco 008 circulator, air scoop, 2 gal expansion tank, and Cryotek antifreeze at 100% concentration. It is heated with a 60k FPHE. I am seeing 110-140 inlet into the slab and around 60-70 return after the system has been running for an hour or so.

FPHE is on a dedicated 'heat exchange' loop which currently has the snowmelt fphe and I also plumbed in just the boiler side of a stainless hot tub heater that I will hook to the spa eventually. I am going to add a sidearm exchanger for the domestic water heater in the future. This loop/zone is done with a Taco 007

Overall, I am very happy with the system. It comes up to temp from ambient (10-25 F) and begins melting within an hour or so. If I keep it on, it will keep the slab pretty much totally snow free even during heavy snows. I am getting a lot more heating at the beginning of the loop and a lot less near the end. I am thinking of either a stronger circulator or a 4 way reversing valve. I'm open to recommendations. I do still need to plow when heavy snow comes off the roof. But it does solve the main problem, snow building up in front of the overhead doors preventing them from closing. That area which is on the gable end is kept totally snow free when the system is in operation.

Weil McLain oil boiler I got for free from the scrapyard hasn't missed a beat. I'd say it's late 90's vintage with a .75 nozzle in it. Boiler has no issue staying 170-180 with the snowmelt, radiant floor in the living room, garage fan coil, and bedroom fan coil all running at once. If I add in the dhw, spa, and fan coil for the living area, I could see boiler temps dropping if all were calling for heat at once. I plan to add temp sensors for boiler outlet, dhw tank, snowmelt supply/return, and a temp sensor in an empty pipe I put in the slab. This will give me all the info I need to let HomeAssistant set priority for each zone and keep boiler temps up. I hope to add a coal boiler and wood boiler in the future to reduce fuel costs.

I'm happy to go into any more details that anyone would like to see. I certainly want to get pictures of the whole thing a do a writeup. Seems not too many people have a start to end writeup on how these systems work.

Radiant Snowmelt Tubing Size and Placement- Under Eaves

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