On Tuesday, April 21, 2015 at 2:35:46 PM UTC-4, Robert Green wrote:
"Ed Pawlowski" wrote in message

If you really want to do the job right, you'd put a couple of inches of
foam board under the concrete. Otherwise, yes, you are trying to heat
the entire earth. Foam is used on some highways in Europe and is
becoming popular in garages here. I don't know, nor am I inclined to
search for, the specifics of the construction.

Well, it interests me enough to look. At one of the northern universities I
recall them designing the steam tunnel piping to run under all the sidewalks
and it worked out very efficiently. Since the steam was being piped to all
campus buildings anyway, it made perfect sense to use some of that heat to
melt snow.

FWIW, I really doubt if foam is necessary because heat rises and even
heating the soil below will eventually cause the surface to become warmer..


Heat doesn't rise, heated *air* rises.



http://www.homeadvisor.com/article.s...way.11202.html

talks about home-based systems.

Heated Driveway Costs
Typically, the cost of a heated driveway system is between $12-$21 per
square foot. Looking at our data, the average cost of a radiant heating
system installation is $3,892, with a low of $1,300 and a high of $7,500 in
that range. However, this price does not include the removal of the old
driveway or the cost of the new one. Unfortunately, our data doesn't show
the cost to remove the old driveway, but we do show the average asphalt
paving cost ($4,457) and concrete driveway cost ($3,650). The range of
asphalt driveway projects is much greater at $2,000-$25,000 than concrete at
$650-$7,091.

http://www.angieslist.com/articles/a...worth-cost.htm

says:
Actual Experience
Permalink Submitted by Frugal Rich Guy on Thu, 2013-04-18 08:46
I've had one for 20 years. It cost about $5k, because I needed to replace
the driveway anyway. I still have to use the snowblower, because I still
have to dig out the big pile at the end of the driveway thrown up by the
plows. So I remove the bulk of the snow all over the driveway with the
snowblower and then use the heat to melt what's left down to bare pavement.