I guess I need more of an explanation as to how it actually works. I was assuming that you'd be moving heat up from below ground (which was really what I was asking - how far down do you have to go around here to find a source of geothermal energy?). But can you do the cooling too? Does the system work like a heat pump? I'm intrigued.

The system IS a heat pump. Traditional heat pumps move heat between the inside and outside air. They aren't efficient when it is hot outside and you try to move heat from the inside to the out; or when it is cold out and you try to move heat from the outside to the inside.

Geothermal in this context uses the steady temp of the earth (55?) to move heat to/from. The coils burried in the ground are used to either radiate heat or absorb heat.

For electricity generation, geothermal 'wells' are drilled to take advantage of relatively high differences in the temp of the heat of the well vs the air temp. That difference in temp can be used to produce steam which drives turbines. This is a lot more rare and is found in places like iceland.

That sounds about right. The other component that can be tied in is a special hot-water heater that gets pre-heated by the geothermal system in the winter and basically produces free hot-water in the summer whenever the air-conditioner is on. I'm not sure if we are going to use this manufacturer, but here is a decent video that explains the basics of geothermal (see "A Convenient Truth" at the top): http://www.waterfurnace.com/webcasts_videos.aspx

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Out of curiousity, how much is this system and dig going to run you approximately, and what is the annual maintenance cost? What happens if it needs service? Are there qualified servicers in the area?

I was actually thinking of looking into this for my place in Roxborough but I saw the loop requirements and said forget it. But if you can do it as a straight channel down, then it might not be so bad.

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In terms of cost, one of the biggest items is going to be the drilling. In fact, depending on where you are in Roxborough, there may be too much rock to make it worth a driller's time. If you want, PM me and I'll send you the names of some drillers/geothermal people I am talking to. As for service, the people who install them can also service them if they need it.

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The loop requirement is just the length of the loop that is in the ground - it is just a big radiator. Veritical or horizontal doesn't matter, except for installation costs. Backhoe for a horizontal dig is cheaper than a drilling rig.

i guess the jumpoff to understanding is the answer to your question - ''how deep?''

it is amazing to consider that - only 5 or 6 feet anywhere outside the house, under the ground, the temperature of the earth is 50-60 degrees, year round. depending on the region of the country. in the dead of winter? 50-60 degrees. thats a lot of energy.

heat travels to the area of least resistance.

the loop in a geothermal system is essentially a simple heat exchanger. water is circulated in a loop, picking up btu's (heat energy) as it passes through the warmer earth. the captured energy is 'forced' out of the loop in the area of your home via a more complex system of vapor compression -the heat pump.

interestingly - 50-60 is pretty ideal for a seasonal area. it can be used to sink heat in the summer (allow the earth to absorb it) or pick up heat (absorb it from the earth) in the winter.

the system requires some electricity to operate, nothing to sneeze at, but ultimately it costs less to run give proper design and installation. if not designed right, its going to fall back on its supplemental source of energy - dreaded electric heat.

But can 50-60 temps beneath the earth in winter time translate to warming a house to, say, 70 degrees?

Im not expert.
But Ive been researching radiant floor heating.
Becuase of the way that the heat works - the typical setting is 65 deg for the floor. It "feels" warmer than that becase it heats the FLOOR to 65 - where you are.
When you have forced air you heat the AIR to 7o - which promptly rises to the ceilings - where you arent.

Ive seen temp differntial of like 70 at the thermostat on the 2nd floor, higher at the 3rd floor and 40 1" off the slab kitchen floor..

I am a huge fan of radiant floor heating. in asia, homes are built with raised floors around a sunken fire pit. the heat from the pit warms the air under the floor, making the floorboards warm to the feet. it's an amazing feeling waking up, dropping your feet down and feeling warm stone.

if it weren't prohibitively expensive, I'd redo my entire house with radiant floor heating and stone tiles.

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