THSCC Forums

So we're in the planning stages of building a new house at the BMW Farm. We've got the basic house plans down pretty well, but we're looking at some different options for HVAC. We have access to electricity but no natural gas, only Propane. I'm seriously looking into a Geothermal heat pump system- it looks like once you get past the initial cost, these systems have the potential to pay for themselves in a couple of years.


Anyone have any knowledge/experience with this sort of thing?? Any do's/don'ts/gotcha's???




Thanks!

Bret.

I'm told closed loop is the way to go, though open loop systems can be cheaper up front (but are only an option if you have well water and a really high output well).

My mountain house has a geothermal system. It's closed loop. It was built about 11 years ago now, but we bought it six years ago (and thus weren't the builders). It's never given us any trouble and works great. That said, I don't have any cost comparisons to make or anything as I never owned anything else in that area.

But from what I know, if you have the land to do it and the money and plan to own the house for a long time, it's the way to go. One thing to consider, though, is that your geothermal "field" renders that land unusable for any further building, so keep that in mind. Seems like ours is something like 1500 feet of pipe buried 6' down that snakes down the mountain in front of our house.


--Donnie

When we switched to a heat pump a few years ago we asked about geothermal. The fellow we used (out of Allen Kelly & Co of Raleigh) said that they usually send the "geothermal loop" down rather than out, so they bring in a well drilling machine and bore a couple holes and drop loops down into them. Of course Bret has a lot more land so going "wide and shallow" is an option we didn't have, and the cost may have been less. I don't remember what the payback period would've been in our case, but in any event we decided it wasn't worth it.

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Carl Fisher

Be Cool to the Pizza Dude:
http://www.npr.org/templates/story/stor ... Id=4651531

Both Donnie and Carl are right. When Donnie's system was built the normal way to do a closed loop was bury a loop much like in slab heat. The problem with that system was that the heating and cooling of the ground could cause the heat transfer to fall off from the ground heaving. And also the wasted space. Now they do it like Carl mentioned by dropping loops into a well or wells and letting the well water act as a transfer medium to the ground.

When I was in college they did the 2 well system. You pumped water out of a supply well through a heat exchanger and dumped it into a dry well. The problems with those was getting enough supply and grit in the water tended to clog the flow control valves.

As far as payback I think you are looking at a longer period than a couple of years. That is unless you are only looking at the difference in price between the geothermal system and a conventional heat pump. You might also want to consider having a dual fuel system. A heat pump with propane heat as a backup instead of resistive heat.


We can help you spend your money faster than "This Old House"

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George Bright Member # 141
One of the youngest of the old farts.
Yes I voted against you joining the club.

Last week's episode of Dirty Jobs had Mike Rowe installing a Geothermal system. That was the first I had heard of it. Very intriging. they were installing it down like Carl described as opposed to sideways like Donnie's. It really was a dirty job, mud flying everywhere!!!!

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Todd Breakey
STS 42 - 1992 Sunburst Miata
Dammit!
"You souldn't play leap frog with a porcupine. You might get hurt." - Eliza

George, when building new the only cost that is worth considering *is* the difference between conventional and geo, right? That's what you have to worry about recouping. You'd only be concerned with the entire geo system if you were thinking about "upgrading" a perfectly good system.

Anyway, good info on the well system. Makes a lot of sense. Sounds like if anything were to fail in my loop it might make sense to just "upgrade" the loop portion to the well type.

The previous owner of our mountain house did electric as the backup. There is no natural gas available there and they didn't go propane for anything else, unfortunately. I'd rather have propane backup. In fact, when we remodeled our house here we went with buried propane tanks and a 500 gallon boiler that is both our hot water and the backup heat source to our traditional heat pump. Wish I had known about the well based geo system then (this was only five years ago) as I would have definitely done that. I only knew about the longer loop system, and that wasn't practical here, really.


--Donnie

A friend of mine has one in his house. The biggest problem is when anything goes wrong with the well, there is no water and no heat. (It happened last week to him)

That sounds like it must be an open loop system, which would suck for many reasons, IMHO. Plus, well, if there's no water from the well, you've got bigger problems than *just* having no heat.

A closed loop system wouldn't affect whether you have well water or not and would still work even if your well *was* experiencing issues.


--Donnie

Thanks for all the info. We'd definitely go with the closed loop system, probably the horizontal tubing as well. I don't think there's much difference in efficiency/ground temp around here between the horizontal and the vertical (well-type) systems. Considering that I'd be able to do the horizontal tubing installation myself- at least a large portion of it, and you definitely need to hire a well drilling crew for the vertical type- horizontal is the way to go for us. We should have enough land available for the horizontal system.

From what I've seen/read, the general rule of thumb is that this type of "Water source heat pump" costs about 2x as much as the normal HVAC system up front, but the annual costs are anywhere from 30-60% less since they are so much more efficient. Most seem to agree that they pay for themselves within 5-10 years depending on climate, etc.


So, I think this is one area in which we are going to "splurge" and spend the extra $$$ up front in hopes of future savings. I think the payoff could come even more quickly if electricity and LP gas prices rise- as I'm sure they will.



Bret.