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Trying to decide if geothermal is a way to go for us

Posted by andry (My Page) on
Wed, Apr 25, 12 at 10:42

Hi there - we are about to embark on a new build. Our home is in the Chicago suburbs, on a 1/2 acre lot. There is a lot I like about the geothermal route but my husband has reservations.

First, one selling point is the fact you do not need an external compressor. But my husband believes you still do in our area - thoughts??

Second, my family had a heat pump in Michigan, and it was great, but on the really cold days, we needed supplemental heat. Now, that was a 100 year old farm house, with minimal if any insulation. The house we're building will be about 4000 sq. feet, with closed cell spray foam insulation. Do you think we would need supplemental heat?

Any other "cons" I'm not thinking of (I know up front cost is much higher)

Also, we have lots of allergies in our house - would a geothermal unit vs. another kind make any impact on that?

I'll look forward to your sage advice!


Follow-Up Postings:

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RE: Trying to decide if geothermal is a way to go for us

Does the new lot have natural gas available? Geothermal with very tight insulation will likely achieve reasonable bills and be comfortable. However build cost is more expensive. Currently natural gas is cheap and might save money short-term.
You will probably want supplemental heat just in case but you likely will rarely/never use it if your house is as insulated as you say and your system is working properly.


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RE: Trying to decide if geothermal is a way to go for us

Heating and hot water supply with natuaral gas is the way to go if it is available.

Below is a thread that was started 6 years ago and is still active. There is some interesting discussion if you have the patience to read it.

Chicago winters can be very cold. I would imagine you will need so type of supplemental back up heat.

Here is a link that might be useful: Up front costs of Geothermal heat pump vs. other heating methods


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RE: Trying to decide if geothermal is a way to go for us

Since this is new construction and you're well aware of the higher cost of geothermal I would say that the main difference in cost between a conventional system and geothermal would be the cost of drilling the boreholes or installing a horizontal ground loop. That's basically it unless you want to go for premium system that incorporates both in-floor radiant and forced air.

Geothermal only requires supplemental heat, which should always be installed, if the heat loss of the envelope is greater than the HP can provide and as a backup incase of compressor failure or lockout. Remember, the efficiency of geothermal never changes due to it getting colder outside and that unlike a conventional air source HP geothermal never has a defrost cycle. The backup only comes on in tandem with the geo to assist the geo not instead of it. The backup is only on for relatively short periods of time till the thermostat is satisfied, then everything shuts off and goes back to 'normal'.

Do you have access to natural gas and are you planning to install it for other uses such as a kitchen stove, gas fireplace, gas dryer, or instantaneous domestic hot water tank?

SR


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RE: Trying to decide if geothermal is a way to go for us

I hate to overgeneralize but usually geo is a feasible option when NG is unavailable. Also, generally more cost effective to improve the envelope (new construction) then to put money into geothermal. This is often true even when NG is unavailable. The compressor outside is an issue but if planned for well, it can be hidden nicely. I can't see or hear ours ever.

That being said, it is rarely cost effective to do spray foam insulation in new construction.

If you are looking for the most efficient house on the block, use rigid foam on top of your sheathing. You can do 1 inch or 2. Cheaper than spray foam and far more effective. 2 inches of rigid foam on top of 2x6 walls can give you an effective r-20 wall which spray foam can never give.


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