A question about Geothermal (Knoxville: house, approval, contractor)

[Tek_Freek]

We have a lot in Fairfield Tennessee and are starting to look at what we will be able to do. We figure about 3-5 years and we'll be heading down to begin building and now is a great time to start getting serious.

One of the options I want to explore is geothermal for heating and cooling, but I'm concerned about the ability to put the system in. From what I've read it requires either a couple of 200 foot wells or 400 feet of tubing buried 6 feet down. We have room to do the trenching.

So if I understand the lay of the land in that area it's basically rock. One of the most interesting things I saw the year we were down there was a huge jackhammer being used to dig the holes for power poles. I gotta tell ya, for a kid from Iowa that was really weird to see.

How much of a pain is it to dig those wells or 6 foot deep trenches if the underlying base is rock? Is it possible the expense will be so great that using geothermal is out of the question?

And as a hoped for benefit, if they're digging two wells would it be smart to have them dig three if they hit water and have a water well?

If anyone knows I 'd sure appreciate any ideas.

Thanks,

Tek

[yarddawg]

I haven't seen any geothermal installed on the Plateau but I have witnessed a few go in on some of the lowlands surrounding it. Strictly as a voyeur, not my field except in the tangential matter of enforcing setbacks from things that are my field. Typical usage here seems to be as a loop in front of a standard heat pump. You're going to have a couple of hurdles I can think of offhand.

First is lot size, which you don't mention. A developer's first instinct seems to be to cut the lots just large enough to get septic approval. Which means that the mandatory buffer zones between the septic system and the geothermal wells or trenches which are needed to prevent groundwater contamination just aren't there in many cases. If the lot is less than 3/4 of an acre for vertical wells or an acre for trenches that could be a deal killer.

The rock is a problem, no getting around it. Most of the Plateau is less than 4' to solid bedrock. Some of it quite a bit less. 6' deep trenches over an area of any appreciable size would require either explosives or a trencher with a rock saw unless you're really, really lucky. Difficult to guess what that would cost, I doubt a sub would even bid it without sinking a few test holes to estimate the depth and extent of the rock. Vertical wells are even more expensive. A typical waterwell on my part of the Plateau is comparable at about 200' deep and used to cost about $7,000 to drill, including casing and cap but not pump, plumbing or wiring. Before the price of fuel went insane. It's a moving target at the moment.

Not trying to be a wet blanket, I actually think geothermal is a great supplemental system. But it's a lot easier and more cost effective to install in the deep clay loams that surround the Plateau than in the thin bony stuff on top.

[Tinman313]

Ground Loop Geothermal Ground Source Heating Air Conditioning

[Pam& Bill]

Yarddawg made some great points. I think your questions could best be answered by a company that installs geothermal systems.After all they are the professionals that know what depths, widths are needed for their systems.
All the best,
Pam

[Mike in TN]

I could be wrong on this, but I think a developer in Mt. Juliet is putting geothermal into a new subdivision being built there. IIRC, there was an article in The Tennessean about it, maybe 6-12 months ago.

[Tek_Freek]

Lot size should be sufficient - 120 x 180 and sewer lines are in place so no need of septic tank. Groundwater contamination should not be a concern since the well is only for a "U" tube of water that is completely encased. The water in the pipes is there strictly to gather heat for a heat pump.

I'll go snooping for a company that might be active in the area. Thanks.

[Tek_Freek]

Originally Posted by Tinman313

Ground Loop Geothermal Ground Source Heating Air Conditioning

I appreciate the link, but this is a company in Maryland. I doubt they are well versed in the Tennessee arena.

Edit: I see now. There are some good cost estimating tools available. Thank you.

Edit edit: Okay, so I'm slow. There are dealers for the WaterFurnace stystem in Knoxville.

[Tinman313]

........ It was the only link that had some meat. I would really get a person that knows how to calculate heat gain. And sit down with what your going to build, when you do the calculations you have to have the square foot. Which way the house will face - materials that will be used on the home - and number of people in the home to give you a true calculation. Then compare a standard electric heat A/C with the geothermal unit and see what you have gained - vs cost. I have seen a similar system where they dig a trench x feet deep by x feet long and accomplish the same as a well.....

The trench can be serpentine........

[knoxgarden]

TVA has some info available for homeowners. They seem to provide more help for big installations, like factories.
energy right: Geothermal Heat Pumps
At least they've got links to resources and approved contractors.
Check with the power company there. They might provide some free planning help.

[Tinman313]

Some more information to ponder....

EERE Consumer's Guide: Types of Geothermal Heat Pump Systems