Heated Driveway

[Coloshaver]

My house/shop are oriented so the driveways are on the north side hence snow and ice that doesn’t melt off. Being in Colorado, anywhere the sun hits melts off in a couple days even if the temperature stays below freezing but not in the shade on the north side. I am thinking about redoing the slabs and have thought about adding heat to reduce the buildup in the winter. Even before utility prices started to skyrocket, I was not interested in paying to heat the outdoors.

The other side of the house faces south so one thought I had was to use passive solar panels and a small pump to heat antifreeze and pump it through tubing buried under the slab. I wouldn't have any auxiliary heat. I’d control the pump with a thermostat. For example, when the fluid got to 40F, I’d start the pump. I don’t need to keep the area snow free, but if I could create enough heat to get some melting, it would be a bonus.

Have any of you done anything like this? Any thoughts?

 

[Shiftless]

I’m in for the details.
Even though I live in a very mild climate, I’ve always been interested in harnessing solar energy to do things like that. Back in the early ‘80s I put together a DIY rooftop solar water heater to warm the water for my young son’s wading pool.

Your idea will definitely work, but how well it will keep that driveway clear depends on lots of factors. Until an expert chimes in, I’m gonna guess that you’ll need quite a bit of area for your solar collector and maybe even insulation under the slab. How many square feet of concrete are you trying to keep clear of snow and ice? What are the hourly air temperatures during the days and nights for the months you will be using this setup?

One payoff will be the envy your friends and neighbors will no doubt have when they see your driveway cleared as if by magic.

 

[HoosierBuddy]

To even have a shot you'd have to insulate the lines bringing 40-degree fluid over. Even then I don't think you'd get enough heat to do much melting. A tractor with a blade on it or standard ice-melt would be way more effective.

I do agree with you that accomplishing this using natural gas or (CRINGE) electricity would be ruinously expensive.

 

[Perroflojo]

My friend did something like what you trying to do except he used a wood burning water heater.

Put some wood on it, let get get to temp and pump begins to work.

 

[andyvh1959]

Use geothermal along with solar panels to use the 50 degree heat from geothermal boosted by energy from solar panels?

 

[yeldogt]

You would have to do the math -- but, snow melt is all about getting the temp above as it's coming. It's very straightforward -- you do it like a garage slab with Pex and glycol. You need a huge BTU input per SF .... google around. There was a post not long ago where someone posted his driveway system.

I have only done a few small areas -- landings and steps. W/o natural gas it's expensive. My grandparents had a huge property with heated drive (buried cast pipe) -- huge oil fired boiler. It was crazy expensive.

In SA we have solar hot water and the gas filled collectors will work in cold temps and low winter sun angles .... but they still take a large collector to get the 40k BTU or so needed ..... snow melt needs lots more

 

[Grant F]

I like the idea. The concern that comes to my mind is - if u are relying on solar heated fluid, it is only warm during the day/when there is sun. Would you create a problem of melting enough but then refreezing at night and actually making an icy situation/worse situation?

 

[GrayFlattop]

A friend of mine has this for his driveway. After using it one winter month, his gas bill was almost $500 higher - for that month only and that was 4 or 5 years ago when natural gas was cheaper. Now he only uses it if we have ice (rare here - it's typically snow) or when he is out of town on business - with the family still at home.

Very sophisticated system - Huge high efficiency boiler, 6 parallel "zones", in-slap temp sensors, snowfall sensor, etc. Multiple zones / loops needed as the temperature drop for a single loop was too great.

If you have the money - sure, why not enrich the utility company? But a set-up like this is out of reach for most normal people.

 

[FMB4]

Following. Our driveway, and the others on our (N) side, maintain snow and ice for days and weeks while those on the opposite side melt free in what seems to be a day or two in the sun.

 

[ScaldedDog]

We did this in our last place, and it worked great. That's with a 175K BTU boiler running all out for hours on end during a storm, though. Pumping 40* water into a slab isn't going to do much.



If I had it to do over again, I would not insulate the driveway. You lose the ability to leverage the heat of the earth, and thus must melt every flake that falls.

Mark

 

[rlitman]

I heated my north facing steps with a hydronic loop. It circulates glycol through a heat exchanger which is heated by my boiler. The amount of heat required to work on steps is extraordinary. I couldn't imagine running it on an entire driveway.

I have another exterior staircase that gets no sun that has HeatTrak electric snow melting mats. They're designed to output 50w/sq-ft for reference. The last snowstorm we got exceeded their capacity, so I still had to shovel them out, but at least there was no ice, and nothing stuck to them.

 

[PoorUB]

Figure 125-150 BTU per square foot, then figure out the size of your driveway. For me it would be around 1800 square feet so 225,000 BTU for a minimum up to about 275,000 BTU. With natural gas at 70 cents a therm it would cost me $1.50-$2.00 per hour of operation, not including electricity for controls and pumps.

As for doing it with solar panels, You would need to find panels that will match the BTU requirement. Plus you want the snow melt to run while it is snowing. Solar panels don't work very well covered in show.
Also how much sun do you normally get in the winter? Here in ND we get very little, generally overcast most days, and the days we get bright sun is usually very cold.

Not much is available for BTU's per square foot on solar panels, but some numbers I have seen suggest around 1,000 BTU per sqft. So in my case, lets just average out to 250,000 BTU so I would need a panel 10x25 feet. Not sure where I would put that!

Another question I have is how do you handle the don time? 250,000 BTU of solar sitting through the summer? I suppose you could heat domestic water, but that seems like a ton of heat available!

 

[FredWanaker]

The amount of btu needed would be quite a bit. Unless you have very deep pockets conventional heating would be too expensive. When you would need it most is when it is snowing and overcast, and the solar array is covered about that time. Going geothermal would be expensive especially if you are over an area with a lot of rock. Some homes have dug huge basements, and filled them with tanks full of river rock packed together. Solar collectors collect heat in summer and pushed thru the rocks to heat that mass, and then used to heat the glycol in winter which warms the house or in your case driveway. Still a very expensive solution compared to a snow blower, and you could probably cjust hire a local snow clearing service cheaper than building a permanent solution.

 

[HoosierBuddy]

1 BTU is the amount of heat it takes to raise one pound of water one degree Fahrenheit.

But that's to raise it from 60 to 61 degrees F. With Ice you have to cause it to melt (enthalpy of solidification) which takes 144 BTU's per pound. Snow can vary in density, but one cubic foot of ice weighs 57 pounds. Spread a cubic foot of ice over 24 square feet of drive way and it would be 1/2" thick and take 8208 BTU's to melt.

Getting there.

A 10 X 100 driveway is 1000 square feet so to get 1/2" of ice to melt (go from 32 degree ice to 32 degree water) takes 342,000 BTU's. Now...real world with heat loss from your loops to the ground and additional heat it takes to heat the ice up to 32 degrees and the loss of heat as melted water runs off the drive....I'm saying you're 1/3 efficient ballpark...so I'm going to round to 1,000,000 BTU's. That's like in a condition where it's not snowing anymore....the air and ground temp are near 32 degrees F.

That's as much heat as a standard electric water heater can generate flat out in 29.4 hours....so you need a solar water heater with more than twice the capacity of a standard electric water heater or you'll run out of daylight long before you can melt your drive. Not saying it won't work. I'm saying it would take cubic yards of cash to build a solar water heater of that size, and if you did have it....the dumbest thing you could use it for would be to keep ice off a driveway. If you have solar capability to heat that much water, you'd use it to heat your house and the neighbor's house all winter long and heat your swimming pool in the summer time.

Of everything discussed here the only thing I think makes sense is the wood fired idea. If you already had a big old outdoor boiler, it might have 300,000 or 400,000 BTU an hour you could valve over to the driveway only during snow events. You'd just have to keep feeding it until the snow was gone. Assuming here you are getting your wood for free.

The place where natural gas fired snow melting is sometimes used is in commercial settings. It's horrendously expensive, but might be cheaper than having a customer slip on your sidewalk and sue you for damages. But you look at, say, Walmarts. They don't have it. They pay people to plow and shovel snow....so if it made sense economically....Walmart would be doing it already. I guarantee they've looked at it and decided it doesn't make sense.

So best solution, hang onto your cubic yards of cash and dole it out in small bills to a neighborhood kid to shovel your drive. It'll save you $$$ and teach the kid a valuable lesson. Two birds. One stone.

 

[engineer2]

A waste oil boiler would be a good way to heat a driveway provided you can get enough free or low-cost used oil. Around 200,000 BTU per gallon or so?

 

[rburke65]

Sounds like a train load of BTUs will be needed…..good luck

 

[Jackfre]

You don’t give the dimensions of the drive. I have done snow melt on my own home and a couple jobs about 40 yrs ago. You will need storage. I think we used to figure storage at 1.48 gal/sq ft of collector. I would suggest a two step process. Do the apron leading to the face of the garage, say 20 or 25’ and see how it goes. Do you have a boiler in the house? I added snow melt on my MA home in the sidewalks and steps down to the drive. I insulated it, piped it and ran it off the grossly oversized Buderus boiler and a HX I welded up . Pricey to run but very gratifying when you get up in the morning after 2’ of snow and have a dry sidewalk.

 

[LS6 Tommy]

1 BTU is the amount of heat it takes to raise one pound of water one degree Fahrenheit.

But that's to raise it from 60 to 61 degrees F. With Ice you have to cause it to melt (enthalpy of solidification) which takes 144 BTU's per pound. Snow can vary in density, but one cubic foot of ice weighs 57 pounds. Spread a cubic foot of ice over 24 square feet of drive way and it would be 1/2" thick and take 8208 BTU's to melt.

Getting there.

A 10 X 100 driveway is 1000 square feet so to get 1/2" of ice to melt (go from 32 degree ice to 32 degree water) takes 342,000 BTU's. Now...real world with heat loss from your loops to the ground and additional heat it takes to heat the ice up to 32 degrees and the loss of heat as melted water runs off the drive....I'm saying you're 1/3 efficient ballpark...so I'm going to round to 1,000,000 BTU's. That's like in a condition where it's not snowing anymore....the air and ground temp are near 32 degrees F.

That's as much heat as a standard electric water heater can generate flat out in 29.4 hours....so you need a solar water heater with more than twice the capacity of a standard electric water heater or you'll run out of daylight long before you can melt your drive. Not saying it won't work. I'm saying it would take cubic yards of cash to build a solar water heater of that size, and if you did have it....the dumbest thing you could use it for would be to keep ice off a driveway. If you have solar capability to heat that much water, you'd use it to heat your house and the neighbor's house all winter long and heat your swimming pool in the summer time.

Of everything discussed here the only thing I think makes sense is the wood fired idea. If you already had a big old outdoor boiler, it might have 300,000 or 400,000 BTU an hour you could valve over to the driveway only during snow events. You'd just have to keep feeding it until the snow was gone. Assuming here you are getting your wood for free.

The place where natural gas fired snow melting is sometimes used is in commercial settings. It's horrendously expensive, but might be cheaper than having a customer slip on your sidewalk and sue you for damages. But you look at, say, Walmarts. They don't have it. They pay people to plow and shovel snow....so if it made sense economically....Walmart would be doing it already. I guarantee they've looked at it and decided it doesn't make sense.

So best solution, hang onto your cubic yards of cash and dole it out in small bills to a neighborhood kid to shovel your drive. It'll save you $$$ and teach the kid a valuable lesson. Two birds. One stone.

I'm glad I don't have to do those calculations anymore... They're not that hard, just a little time consuming, especially if you're figuring for more than one change of state.

Tommy

 

[PoorUB]

That 125-150 BTU per sqft came from a buddy that helps contractors design floor heat systems. It is the number they use when sizing tubing, tubing layout and boiler.

I mentioned up to $2 per hour of operation, that is $48 per 24 hour period in case nobody caught it. Also on natural gas. Electric, LPG or oil you can multiply that number four
times!

 

[thammel]

I actually installed delta-therm heating cable under my last house driveway. I ran 4 circuits - there were basically 2 tire tracks heated in series with 2 other tire tracks, so 4 circuits. As I recall each was 240v/40 amp. This was done because the house was at the bottom of a hill and the driveway was aimed directly at the house. Laid on top of existing asphalt with new asphalt on top of it. There was a moisture sensor on the top of the driveway surface and a temperature sensor embedded. I did all the electrical work and this was tiring work - laying out all the wire. Sold and moved to a house with a nice flat driveway!! The plan with a heated driveway is that it's only used a few times a year. If you're in really snowy cold climates, you don't want to do this....would be too expensive.

 

[ScaldedDog]

Just for the record, since so many are throwing shade at the idea, I'd absolutely heat the driveway again if I were in the OP's shoes. People with north facing garages in Colorado live an entirely different life here in the winter than their neighbors across the street. One just has to realize that there is no operationally cheap way to do it. An appropriately sized gas boiler is the only way to go, and it costs what it costs to run. In the case of our prior home, pictured above, the 2C garage faces north, and we blocked any western sun - the best sun for melting snow here - by building the shop on the right. Heating that section worked great.

If the OP is tearing out his slabs, anyway, running the tube for a system is fairly cheap, and I'd do that, even if he doesn't plan to run it immediately. As I mentioned earlier, I wouldn't insulate the slab, at least not with 2" foam.

Mark

 

[ripperd]

If you shovel/snowblow it manually, and then just run the heat for a few hours after each storm to get it clear the rest of the way, your operational costs wouldn't be terrible.

But yes, running it to continuously melt the snow as it falls is going to cut into beer/fun money.

 

[Copymutt]

KISS has worked for me. Not only are those complicated systems with exposure to issues, they will drain your wallet twice. Once for the initial cost and again for monthly energy bills.
Think I would mess around w/ a couple big mirrors focused on the most critical part of the driveway. You've already confirmed that where the sun hits the snow/ice is non existant. Even if you had to add a tracking motor you’re still in for a fraction of the cost and free after install cost.

 

[rlitman]

KISS has worked for me. Not only are those complicated systems with exposure to issues, they will drain your wallet twice. Once for the initial cost and again for monthly energy bills.
Think I would mess around w/ a couple big mirrors focused on the most critical part of the driveway. You've already confirmed that where the sun hits the snow/ice is non existant. Even if you had to add a tracking motor you’re still in for a fraction of the cost and free after install cost.

Oooooh, giant mirrors. Great for immolating attacking triremes too, for when your neighbors decide to come and plunder.

 

[PoorUB]

If you shovel/snowblow it manually, and then just run the heat for a few hours after each storm to get it clear the rest of the way, your operational costs wouldn't be terrible.

But yes, running it to continuously melt the snow as it falls is going to cut into beer/fun money.

That is correct! nobody in there right mind runs it all the time!

But one thing to consider, you are warming concrete out side to above freezing. Depending on where you live and the temperature out side it might take several hours to get that warm. The cost to operate will still be high, after all you are trying to heat the outdoors!

We did a huge home remodel and the owner was running a new sidewalk out to the garage and wanted snow melt in the side walk. We put it in and tested, all was good. First snow fall he calls up and asked to talk to the owner and he was pissed off about the snow melt because he had turned it on that morning and it wasn't doing anything an hour later. My boss told him to check it at lunch time and cal back. The walk was melting, but it wasn't good enough! Apparently the guy wanted instant gratification. My boss did tell him if the weather report calls for snow over night, then turn it on before he went to bed. The sidewalk did have a thermostat and slab sensor, but no automatic controls to turn on with the weather.

 

[02camaro86]

maybe im missing something but isnt the entire point of the heated driveway is to heat it prior to the storm so any snow that falls melts when it hits the surface invalidating all those calculations of how many btu etc etc it costs to melt snow by the ton once its already accumulated several inches/feet?

 

[ScaldedDog]

The sidewalk did have a thermostat and slab sensor, but no automatic controls to turn on with the weather.

This is key, even though the auto-start functions aren't perfect. They either need to start with the first flake or, in some condtions like a fast falling snow, before the first flake. In addition to an auto-start function, we had ours on a manual time I could start ahead of time, without having to remember to turn it off.

maybe im missing something but isnt the entire point of the heated driveway is to heat it prior to the storm so any snow that falls melts when it hits the surface invalidating all those calculations of how many btu etc etc it costs to melt snow by the ton once its already accumulated several inches/feet?

Your first point is spot on. These systems melt falling snowflakes, not inches of fallen snow. They still need to be sized correctly, so I don't know that the heat calculations are invalid, but the calculations need to model the actual use case. Melting falling snow outside is a lot different than heating a building with radiant heat, for example.

Mark

 

[rlitman]

maybe im missing something but isnt the entire point of the heated driveway is to heat it prior to the storm so any snow that falls melts when it hits the surface invalidating all those calculations of how many btu etc etc it costs to melt snow by the ton once its already accumulated several inches/feet?

Energy is a measurement of work performed. Power is work performed over a time period.

The power output defines how quickly the driveway can melt a ton of snow, but the overall energy to melt that ton is going to be the same whether you melt it one flake at a time, or a foot at a time.

 

[HoosierBuddy]

maybe im missing something but isnt the entire point of the heated driveway is to heat it prior to the storm so any snow that falls melts when it hits the surface invalidating all those calculations of how many btu etc etc it costs to melt snow by the ton once its already accumulated several inches/feet?

yes you are missing the point. Mother Nature freezes water to snow sleet or ice in most instances where accumulation occurs before it lands on the driveway. It always happens during heavy cloud cover when the OP’s planned solar collector will be severely compromised or completely non functional (like during the 10 to 12 hours in the winter when it’s dark).

If you’re suggesting a fuel fired boiler be used to heat the drive 24x7 all winter it will still have to be sized to melt snow and ice AND your fuel bill could hit 5 figures.

 

[fitter30]

Solar can lower operating cost but with radiate there is alot of mass. Trying to heat a slab just by solar won't heat the slab warm enough to carry it over night with out having water storage to carry it over.

 

[rlitman]

yes you are missing the point. Mother Nature freezes water to snow sleet or ice in most instances where accumulation occurs before it lands on the driveway. It always happens during heavy cloud cover when the OP’s planned solar collector will be severely compromised or completely non functional (like during the 10 to 12 hours in the winter when it’s dark)...

Not to mention the fact that the same source of frozen water that coats the driveway will coat the solar collector.

 

[Steve in UT]

This is why my #1 first priority when buying a home has always been, "It has to face south!" Period. Also, I see many east and west facing homes that shade the walkway with the garage. Drives me a little nuts. Don't they know, all you had to do is flip the house plan to have the garage wall reflect the sun onto the sidewalk and keep it melted. I know this doesn't address the OP's original concern, but like the mirror idea, in some circumstances maybe a wall could be built on the north side of driveway or walkway to reflect and melt the snow.

 

[86turbodsl]

There's a reason snowmelt is also known as "rich man's toy" In most cases it's so expensive to run, only a rich man can afford it. There are exceptions, but they are rare.

 

[readhead]

I live in a resort area and there are lots of snow melt systems in driveways and walks. According to the plumbers I work with most systems get used the first winter and never get turned on again. It is cheaper to pay someone to shovel or plow than to run the melt system.
I have a driveway that is shaded most of winter and if I get 1/2" I'm shoveling it off or it is ice the next morning.
Another issue is the water has to go somewhere. I have seen elaborate drywells and other drain systems with mixed results.

 

[RoscoTom]

I used to kid my Dad about shoveling extra snow.

In an effort to help Northern Michigan Spring along, he used to shovel snow out of the shade and into the sun.

Then, a couple of years ago, I caught myself doing the same thing.

 

[Rc_Guy]

I have watched youtube Outdoors with the morgans, they live in Pennsylvania and he drives down the road to plow his moms or someone's driveway, anyway, he drives by a neighbor that has a heated driveway, he said he was going to find out what heats it, it is a long driveway also

 

[ripperd]

This is why my #1 first priority when buying a home has always been, "It has to face south!" Period. Also, I see many east and west facing homes that shade the walkway with the garage. Drives me a little nuts. Don't they know, all you had to do is flip the house plan to have the garage wall reflect the sun onto the sidewalk and keep it melted. I know this doesn't address the OP's original concern, but like the mirror idea, in some circumstances maybe a wall could be built on the north side of driveway or walkway to reflect and melt the snow.

Yeah, the sun in the driveway is nice in the winter...

However, the sun coming in all the back windows, on the deck, and backyard during spring, summer, and fall outweigh that to me. We are really happy with the back of our house to the south. The neighbors on the other side of the street complain how their decks are cold and shaded for everything but the hottest days and times.

 

[dcg9381]

The other side of the house faces south so one thought I had was to use passive solar panels and a small pump to heat antifreeze and pump it through tubing buried under the slab. I wouldn't have any auxiliary heat. I’d control the pump with a thermostat. For example, when the fluid got to 40F, I’d start the pump. I don’t need to keep the area snow free, but if I could create enough heat to get some melting, it would be a bonus.

Have any of you done anything like this? Any thoughts?

I've owned a passive solar water heating system, but it had a tank with an "aux" heat element. It worked great unless we got more than 3 days of cloud (then we were on aux heat). Hot water "rises" (thermocycle) and had a large tank mounted on the roof above the panels that ciculated antifreeze internally to heat the water.. I think the way you're suggesting doing it you're just putting heat in the ground and likely won't have enough solar capacity versus the cooling you're going to get on the ground. IE - if you're gonna do this, I think you need a tank.

 

[Nosferatu]

There are companies that make electric pads to do this, no complicated water system needed.

One example:

https://www.warmup.com/snow-melting/heated-driveway

 

[u3b3rg33k]

My house/shop are oriented so the driveways are on the north side hence snow and ice that doesn’t melt off. Being in Colorado, anywhere the sun hits melts off in a couple days even if the temperature stays below freezing but not in the shade on the north side. I am thinking about redoing the slabs and have thought about adding heat to reduce the buildup in the winter. Even before utility prices started to skyrocket, I was not interested in paying to heat the outdoors.

The other side of the house faces south so one thought I had was to use passive solar panels and a small pump to heat antifreeze and pump it through tubing buried under the slab. I wouldn't have any auxiliary heat. I’d control the pump with a thermostat. For example, when the fluid got to 40F, I’d start the pump. I don’t need to keep the area snow free, but if I could create enough heat to get some melting, it would be a bonus.

Have any of you done anything like this? Any thoughts?

IF I was going to do this with with fuel, I'd use hydronic and a pool heat pump (or some other air to water heat pump). You can get a 13 ton pool heat pump for $5k or so, and they'll run a COP of 4:1 with a 20 degree temp differential. you'd have to verify low temp operation, but you don't need to make "hot" working fluid, just 33-40F. I doubt you can beat pool heat pumps on BTU/$ of capacity. they're cheaper to run than non-condensing pool heaters in many cases, even for pools.

if I wanted to do it and be able to afford to run it, I'd look into a geothermal style borehole filled with anti-freeze and a circulating pump. use the stored heat of the ground and just circulate it - maybe add in your solar collector to boost it/store heat in the ground when you don't need it.

since you're in CO, check this report out:

https://www.codot.gov/programs/research/pdfs/archive/passivedeicing.pdf

and another one:

https://onlinepubs.trb.org/Onlinepubs/trr/1984/962/962-008.pdf