One of the most exciting and unexpected opportunities related to our house project is the installation of a geothermal heating and cooling system. Like many great opportunities, this one was borne out of necessity. As the design of our addition was getting into the final stages two things were clear: 1) We were going to need two air conditioning zones which would mean two outdoor compressor units; and 2) we had no room for either of them.
|Nothing quite ruins a quiet summer evening like the sound of an AC compressor.|
Then, like a knight in shining armor, our new contractor said "geothermal". I didn't know that to make of it. The only thing geothermal meant to me was a vague recollection that Iceland uses naturally occurring subterranean hot spots to heat buildings. What could that have to do with air conditioning? It doesn't. Let me try and sum it up as simply as possible:
- An anti-freeze like fluid is pumped in a closed tube loop into the earth.
- In the summer the fluid takes heat from the house and disperses it into the 55 degree Fahrenheit (13 Celsius) ground and returns chilled fluid to the house.
- In the winter the same fluid takes cold from the house and collects heat from the 55 degree ground. That is then compressed to hotter temps.
- The cooling process requires NO outdoor compressors whatsoever.
- Both heating and cooling makes domestic hot water as a by product so that, except for shoulder seasons when we don't use either, we don't pay anything for hot water.
- The systems typically reduce heating and cooling bills by 47%.
- Until 2017 there is a 30% tax credit with cap. That means that when spread over the cost of the whole HVAC system related to the geothermal we will get a tax benefit equal to the additional cost for installing the geotherm system (which isn't cheap).
We jumped on the idea.
If you have lots of land you can have loops of tubes installed about 10 feet down in the ground across a broad area. If you have a city lot like we do the tubes need to be put straight down into the ground to provide enough energy transfer area.
In our case two wells had to go down 400 (yes, 400) feet.
Thankfully, both wells were drilled without encountering any groundwater. If that had happened the water would have been pumped into this tank that was waiting in the street.
Our neighbors had to put up with two days of drilling and our yard looked like hell.
|The tubing waiting to be threaded into the 400-foot wells.|
|When the excavation and back filling is completed, the black tubes coming out of the white conduit will be buried horizontally about four feet down and go into the heating/cooling system in the basement.|
|Geothermal can feed AC, forced hot air, and radiant heat. Our heat will be a combo of radiators and in-floor radiant heat. Here you see the forms for the installation of in-floor heating tubes.|