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“Cost-wise, it’s expensive.”
February 28, 2014 2:34 PM   Subscribe

Indeed, heated sidewalks are an uncommon luxury. “So many things have been done — the playrooms, the gyms, the sky lounges, the media rooms. But very few developers have looked at the experience entering the property.”
posted by R. Mutt (37 comments total) 5 users marked this as a favorite

 
Not so expensive if you have geothermal heat you can tap into, like in Iceland.
posted by Kabanos at 2:50 PM on February 28 [4 favorites]


Might not even be so expensive to run if your setup is smart enough to heat up only to 1C.
posted by ocschwar at 2:54 PM on February 28


And there are homeless people dying of exposure in the winter. You know, with a little community outreach, I think this could be win-win!
posted by univac at 2:55 PM on February 28 [9 favorites]


I'm glad we're fighting Petro-wars every couple years if it means that wealthy people can keep their feet dry.
posted by Mayor Curley at 2:55 PM on February 28 [9 favorites]


It's a hotel? Pipe the still-warm grey-water draining from the hotel-room showers through it. All that heat energy is just being dumped right now.
posted by anonymisc at 2:55 PM on February 28 [14 favorites]


If you'll excuse me, I really must get back to eating the rich.
posted by tybeet at 2:57 PM on February 28 [1 favorite]


If you'll excuse me, I have to go melt a sidewalk.
posted by Kabanos at 2:58 PM on February 28


They've been doing this in Iceland for 10+ years now. Add that to whale sushi in the list of things Reykjavik has that New York doesn't.
posted by Nelson at 3:02 PM on February 28


Let's all see if we can brainstorm cooler places to live than the Upper East Side if we had $114,000,000 to spend on a house.

The top story of the Tour Montparnasse.
The entire island of Komodo.
A 400 square foot studio apartment, carved into main-belt asteroid 31 Euphrosyne.
posted by theodolite at 3:08 PM on February 28 [16 favorites]


It was universally 'known' (though possibly this was a myth) among the students and teachers at my (suburban, public) high school that the campus had been built with electric heating elements built into the sidewalks to heat them.

As the story went, the system shorted out terribly the very first time it was turned on, and never brought back into commission.
posted by kickingtheground at 3:33 PM on February 28


This is a public utility in Helsinki, with energy provided by, among other things, reused heat from office equipment..
posted by bird internet at 3:37 PM on February 28 [2 favorites]


My last place (a non-luxury townhouse) had a heated driveway that used glycol lines. The lines were disconnected the entire 6 years I lived there. I'm not sure if the system ever worked.

I've seen other, functional, heated driveways here, but not heated sidewalks. People responsible for large buildings here use power brushes and make sure to keep on top of new snow as it falls.
posted by Pruitt-Igoe at 3:39 PM on February 28


I remember that some of the sidewalks at University of Idaho were heated by the steam tunnels below them. It was really nice to walk around in the winder without slipping all the time.
posted by Dr. Twist at 3:56 PM on February 28 [1 favorite]


I grew up in Chicago and went to school adjacent to a pretty ritzy neighborhood. OK, an extremely ritzy neighborhood. I remember walking around in it and came across a section of sidewalk in front of one townhouse that was perfectly clear of snow—no way it could have been shoveled that clean. I realized the owner had torn up the sidewalk and laid heating elements, and was simultaneously awed at the brilliance and shocked at the prodigality of it. This was back in the early 1980s.
posted by adamrice at 3:59 PM on February 28 [1 favorite]


For the Hydronic system you can use a solar hot heater for the system. On cloudy days such systems can't really heat enough water for domestic use (it isn't hot enough) but it doesn't take hot water to heat sidewalks. It only has to be 33deg or hotter to work. Any solar system can manage that on cloudy, short winter days. And once installed has zero costs from maintenance. You are going to have maintenance either way so it really is a zero cost system. There is increased cost for installing the system upfront, but I bet you make that up long term in snow removal cost saving and much, much longer service life for the concrete you are keeping from going through a freeze/thaw cycle.

There is also a real cost to the salt everyone uses to melt the snow also if the walks aren't heated, and a real carbon footprint to getting and transporting the salt as well. And all that salt damages concrete, drastically shortening its lifespan and it isn't real good on shoes or paws or skin either.

Slushy, frozen or icy sidewalks are also really, really hard for the disabled to navigate and this helps preserve mobility for those people as well.
posted by bartonlong at 4:07 PM on February 28 [9 favorites]


Most really rich people in Chicago in the Lincoln Park area don't bother to heat their sidewalks. They don't even clear them. They just leave for the entire winter.
posted by srboisvert at 4:17 PM on February 28 [2 favorites]


"Not having to worry about the salt or the snow, “that is absolutely a great thing,” he said, recalling how he had once tried to put booties on his late, beloved Shih Tzu, Ludlow. “He just kicked them off like one of those punching nuns."
posted by sciencegeek at 4:21 PM on February 28


"Sidewalks"? Is that one of those things that you people who don't live in suburbs use? Why don't you just take a car where you want to go?
posted by happyroach at 4:22 PM on February 28 [1 favorite]


Clear sidewalks in a city are more than a convenience; they're an awful lot safer. It's so odd to me that more waste heat isn't reclaimed and used for something like this. Lots of buildings in NYC have cooling towers to get rid of waste heat; I don't know if they use that waste heat in the winter. I'm visiting Colorado right now - lots of bright sunny days even in winter - and I'm amazed at how few solar panels I see, although Fort Carson has a couple solar fields.

When I lived in town(Portland, ME), I deeply despised people who didn't clear their sidewalks, or businesses who had a plow service that cleared the driveways and left the snow in a wall blocking the sidewalk.
posted by theora55 at 4:30 PM on February 28 [7 favorites]


... a section of sidewalk in front of one townhouse that was perfectly clear of snow—no way it could have been shoveled that clean.

FWIW, when I blow the snow from my driveway, I also clear the sidewalk next to the street to the property lines on both sides. If it doesn't snow more after I do that, it's bare until the town guy comes and does the rest of the sidewalk. I may be the only one in town to do it, but there's a state law saying I have to. Besides, I walk, too, and it bothers me when I have to go into the street because the homeowner's snowplow guy buried the sidewalk under three feet of compacted snow.


Around 1960, the suburb where I grew up expanded the town library, and the new stone front steps were heated. I wonder if they still are.
posted by Kirth Gerson at 4:36 PM on February 28


The college where I went to had "heated sidewalks" by virtue of making the sidewalks actually the top of cut-and-cover steam pipe tunnels. It seemed to work pretty well, but my understanding is that central heating systems like that aren't in vogue anymore. Easier just to pipe natural gas around to furnaces in each building than have a central steam plant I guess.
posted by Kadin2048 at 5:21 PM on February 28 [1 favorite]


114 million for a house? Fuck that.
posted by Benny Andajetz at 5:53 PM on February 28


114 million for a house? Fuck that.

Well it's probably not his first 114 million.
posted by R. Mutt at 6:02 PM on February 28 [1 favorite]


Of course when it gets cold enough the 'heated sidewalk' becomes 'frictionless skating rink'. That's a lot of fun, I can tell you.
posted by sweet mister at 6:10 PM on February 28 [1 favorite]


What a waste of...

...oh, I can't...I just want that SO MUCH, knowing we're supposed to get another foot of snow on Monday.
posted by xingcat at 6:11 PM on February 28 [1 favorite]


Our 100+ year old building renovated in the early 90s, and with that renovation came heated steps to the entry. It's very practical, as stairs are difficult to keep clean during constant snow, or ice-snow, and these stairs had already claimed enough broken hip-bones. The heat comes from geothermal energy.
posted by dabitch at 6:59 PM on February 28 [1 favorite]


I don't get the hate. The building residents are what, 1% of the foot traffic going past? A clear sidewalk is better for absolutely everyone, worse for exactly no-one and the multi-millionaire landlords are the ones paying for it? Heated sidewalks for all!
posted by Skorgu at 7:02 PM on February 28 [11 favorites]


FWIW, when I blow the snow from my driveway, I also clear the sidewalk next to the street to the property lines on both sides.

I do that as well. And usually I make it a point of pride to clear it wider than the town does. Also, I know my neighbor doesn't bother to clear his sidewalk to the property line, so after heavy snowfalls I make an extra cut out to the street so my cleared path actually goes somewhere.
posted by RonButNotStupid at 7:08 PM on February 28 [1 favorite]


Where I live, if you don't do your duty clearing your sidewalk, someone can call the city. If they deem your walk uncleared per ordinance, they put a hanger on your door and you have 24 hours to finish the job, or a city crew will come and do it for you. The charge, typically $400 for the small lots close to downtown but much much higher for the ranch house subs (and heaven forfend you have a corner lot), can be added to your property tax if unpaid.

For various reasons, including my own health and availability problems this year, I haven't been that prick who tattles, but next year I should be in good form again. It's ridiculous when pedestrians have to walk in a fast one-way street to get past your uncleared walk.

Anyway, one of my rental lots is north-facing, and it's also the busiest for pedestrians. If I don't hit it first (which usually happens), the snow gets compacted by foot traffic. It gets no sun whatsoever and the whole thing is a headache year after year, so I have seriously considered installing a glycol system that's solar heated -- the only problem is that it's perfectly good sidewalk so I'd have to do a retrofit. The sidewalks on my other three properties are west and south facing and it's really amazing how well they clear on a good sunny day.

Of course I've also considered how I could pull a Frank Gehry or something and create a lens that would focus the sun along that sidewalk. If I position and curve it right it would go from one end to the other over the course of a day ....
posted by dhartung at 9:42 PM on February 28 [2 favorites]


I make an extra cut out to the street so my cleared path actually goes somewhere.

That's a good idea; I'm going to start doing it.
posted by Kirth Gerson at 5:05 AM on March 1


-41C at my house today. I'd like to see the power bill that would be required to maintain a slab of concrete a couple of degrees above freezing in those conditions, all without cracking the slab.
posted by blue_beetle at 8:14 AM on March 1


I live on a fairly short avenue between two streets. When I had a snow thrower, I'd just go from one end to the other while I had it out and take care of the whole ( admittedly, not all that long... ) block. Property Lines are a TOOL OF THE MAN, man! ALWAYS GO OUTSIDE THE LINES, man!
posted by mikelieman at 11:29 AM on March 1 [1 favorite]


Where I live, if you don't do your duty clearing your sidewalk, someone can call the city.

In the system I'm familiar with, mail delivery persons end up policing this. They usually let it slide for 24h but if you neglect it for too long they write you a ticket and start skipping your house (you can pick up your undelivered mail at the post office) until a safe path has been cleared.
posted by ceribus peribus at 6:12 PM on March 1


Where I'm at, we have no sidewalks; it's the residents' job to clear the street itself: [part way along], [done].
posted by woodblock100 at 9:51 PM on March 1


bartonlong: "On cloudy days such systems can't really heat enough water for domestic use (it isn't hot enough) but it doesn't take hot water to heat sidewalks. It only has to be 33deg or hotter to work. Any solar system can manage that on cloudy, short winter days."

It's got to be a lot warmer than that if you want a reasonable flow rate. Figure at least 55F and realistically 80-120F.

blue_beetle: "I'd like to see the power bill that would be required to maintain a slab of concrete a couple of degrees above freezing in those conditions, all without cracking the slab."

It differential contraction hat causes cracking a heated slab is going to have less differentiation and therefor less cracking.
posted by Mitheral at 6:13 AM on March 2



bartonlong: "On cloudy days such systems can't really heat enough water for domestic use (it isn't hot enough) but it doesn't take hot water to heat sidewalks. It only has to be 33deg or hotter to work. Any solar system can manage that on cloudy, short winter days."

It's got to be a lot warmer than that if you want a reasonable flow rate. Figure at least 55F and realistically 80-120F.


I would think you only need the temperature differential if you are relying on it for circulation. If you hook up an electrical pump and use the glycol directly as the fluid through the solar collectors you only need to heat it up barely above freezing to keep the concrete/pavement above freezing.
posted by bartonlong at 11:53 AM on March 2


I can't remember the physics basis of this to explain it specifically. Practically speaking though heat transfer in a slab is governed by many factors but ultimately the rate at which heat is transferred from your circulating fluid to the concrete surface is determined by the ΔT between the fluid and the desired surface temperature (in this case above freezing). The higher the ΔT the greater the required rate of transfer. In order for ice and snow melting to be successful in keeping a surface clear the system needs to transfer more heat to the slab than environmental factors are taking it away. The surface is constantly being cooled by radiation, convection and the heat required to melt ice/snow.

So what are some of the major factors that determine our transfer rates?
  • Ambient temperature: The colder it is the faster heat is pulled from the slab
  • Wind speed: more air movement increases convective losses. Every 10 mph increase in wind speed can increase the BTUH/sq ft heat requirement by almost 50% over the 0 mph wind requirement.
  • Accumulation rates: two inches per hour takes more heat to melt than one inch per hour
  • Minimum temperatures system needs to be protected at. Colder minimums mean higher concentrations of antifreeze and higher concentrations of antifreeze lower heat transfer capacity of the system.
  • How the tubes are connected to the slab (embedded in concrete is better than bedded in sand) and how much insulation is installed. Side walks are particularly hard to insulate because there isn't any way to insulate the curb edge.
And remember your coolant tubes aren't at the surface, they'll be at least an inch or two down for protection, so you have a temperature gradient across the concrete between tube location and the surface (IE: your tubes have to be warmer than your surface).

This is a pretty good introductory design document[PDF] on determining input temperatures. Here's an example from it:
You are to provide a snowmelt system for a 100’ x 100’ pedestrian plaza with brick pavers over a sand bed with 2” insulation under the area and on the vertical edge. Only light maintenance vehicles will be permitted in this area and it is not critical to keep the area completely clear under any conditions. Some snow accumulation will be permitted during heavy snowfalls, but it is expected that the area will be generally free of snow and ice during “normal” conditions. It rarely snows in this location if the temperature is below 20°F and the temperature never drops below -5°F. The system will have a separate heating plant and is expected to operate without supervision. The mechanical room will be at the center of one of the boundaries of the melt area with all equipment and manifolds located in the room.
And the required input temperature:
Equipment Size: When you check the chart for Heat Output and Fluid Temperature for tubing in a sand bed under brick pavers you can see that at +10°F with a 10 mph wind you need approximately 100 btuh/ft². Total system output required for this system will be a minimum of 1,000,000 btu/hr. Remember that this is NET OUTPUT of the heating plant. The heating fluid will be a solution of 40% propylene-glycol and water, providing freeze protection to a temperature of approximately -10°F. Total system flow rate at a 25°F drop across the system will be about 1,000,000 (btuh req’d) / 12,500 (system flow at 25°F ΔT) x 1.10 (flow correction for 40% P-G) = 88 gpm total flow. From the same chart we can see that the average fluid temperature should be 99°F. The supply temperature is now 99°F (average fluid temp) + 12.5°F (½ of the ΔT) = 112°F
Temperatures lower than the 112°F design temperature require higher flow rates but there are limits to how much fluid we can pump through any given diameter of pipe. As input temperature decreases we'll be forced to increase the size of and decrease the space of the pipes. At a certain point the pipes are massive and touching each other and no more compensation is available to us.

TL;DR: minimum practical coolant temperatures start at ~55°F and go up rapidly from there for places you actually want to install this.
posted by Mitheral at 2:06 PM on March 2 [2 favorites]


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