When it comes to “kicking natural gas” and reducing a home’s carbon footprint, geothermal heating & cooling is the “gold standard.” But it’s extremely expensive to implement as a retrofit and still quite expensive on new construction.
My friend, Martin Voelker, a leader with the Colorado Renewable Energy Society, recently replaced his gas forced air heating system with geothermal, and the cost for drilling the 300-foot-deep wells in his backyard was $18,000, which included running the pipes into his house but didn’t include the heat pump itself. Even though such a project would garner a 30% rebate under the Inflation Reduction Act, that’s still a heavy lift for any homeowner.
I know of another home which installed geothermal pipes horizontally in their large backyard at far less cost.
New construction is more affordable, because you can have the wells drilled within the footprint of the future home while it’s still open ground. And if it’s an entire subdivision, such as the Geos Community in Arvada, the cost is reduced because all the wells can be drilled one after the other.
In that scenario, each home still has its own geothermal well, but what if you could drill a geothermal well that was extensive enough to feed multiple heat pumps in multiple buildings?
That was the concept proposed by a group of Harvard students in Ivory Innovation’s annual Hack-A-House competition, for which they won first place in the “Environmental Solutions and Construction Technology” category.
Those Harvard students may have known something the judges didn’t — that Eversource Gas, a Massachusetts utility, had already begun a “networked geothermal” demonstration project 17 miles west in Framingham. That project is featured at www.HEET.org, short for Home Energy Efficiency Team, which in 2017 started promoting the concept of gas utilities delivering 55º water instead of gas to multiple buildings from a grid of geothermal wells. (The above graphic is from their website.) Think of it as a 21st Century version of what Con Edison still does in NYC, which is to deliver steam from its central boilers to local buildings through pipes under Manhattan’s streets. But steam, unlike water, can’t be used in the summer for air conditioning.
A local vendor that I recommend for both geothermal and air source heat pumps is Sensible Heating and Cooling, (720) 876-7166.
How Does Geothermal Work?
Geothermal heating does not require the presence of a thermal feature such as a hot spring. In fact, if you dig down about 10 feet anywhere at our latitude, you’ll find that the soil temperature is about 55ºF year-round. Circulating a fluid through underground piping heats that liquid to 55º so a heat pump can then raise its temperature to 100º or so for heating purposes utilizing either radiant floor heating, baseboards or forced air.
Geothermal is far more efficient than an air-source heat pump system which takes in outdoor air as cold at 10 degrees below zero and works much harder to achieve the desired temperature for heating.
In the summer the 55º fluid from geothermal requires far less energy to be cooled further for air conditioning your home.