Day 1 of Geothermal: Why We’re Doing It

When I mentioned to my parents (among others) that we were installing a geothermal system in our new house, they had blank stares. “What does that mean?”

 My long and winding path through the selection of the best heating and cooling system began six months ago and culminated with the selection of a geothermal system, which is right for us for so many reasons.

The process I went through was extensive and included everything from a tour of the Viessmann US headquarters located here in RI to interviewing the top HVAC (heating venting and air conditioning) installers in the state. I analyzed the cost to own both for the short and long term, the carbon emissions, the fossil fuels and the overall equipment impact – even the landscaping needs of both systems. I have to say thanks to Hazard Stewart at Newport Geothermal of Newport, RI for his patience, education and incredible graciousness in standing with me in 50 mph winds and freezing temperatures as I questioned and questioned him on the system. I also owe an incredible thank you to the team of Jeanne and Dennis Reddy at Reddy Piping of Narragansett, RI who designed and installed the interior portion of the system including all of the ductwork, piping, tanks and EVRs for a HVAC system.  The system, on its blower test, scored an impressive > 2% leakage rate in zones 3 & 4 of the house! (Note: Zones 1 &2 had a wet glue issue and zone 5 is cooling only and wasn’t in yet.)

Today’s post is the first in a four-part series on why we chose geothermal and what it is. Tomorrow is a list of FAQs accompanied by the first round of photos to help readers understand what the equipment looks like and what it takes to install a geothermal heat pump. Part three will run on Thursday and, along with more photos, will cover the drilling of the well. Friday I am going to share my cost analysis graph including our upfront costs, comparison cost to gas and oil systems, payoff time and our tax rebates. I don’t have all the numbers yet but when I do I will share the impact of the system on our HERS rating, our ENERGY STAR score and ultimately how many LEED points it helped us get.

One of the top reasons we selected a geothermal system is that it will rely primarily on the Earth’s natural thermal energy, a renewable resource, to heat or cool our house. Geothermal exchange systems work on a different principle than an ordinary furnace/air conditioning system. Furnaces must create heat by burning a fuel–typically natural gas, propane, or fuel oil. With geothermal systems, there’s no need to create heat, hence no need for chemical combustion. Instead, the Earth’s natural heat is collected in winter through a series of pipes, called a loop, installed below the surface of the ground in a well expected to run 800 feet deep in our case. Water circulating in the loop carries this heat to the home. A geothermal system then uses electrically-driven compressors and heat exchangers in a vapor compression cycle–the same principle employed in a refrigerator–to concentrate the Earth’s energy and release it inside the home at a higher temperature. (A temperature, I might add, that is significantly cooler than the hot, dry air found in boiler systems that most people find too hot when blowing and incredibly drying.)   

In summer, the process is reversed in order to cool the home. Excess heat is drawn from the home, expelled to the loop, and absorbed by the Earth. Geothermal systems provide cooling in the same way that a refrigerator keeps its contents cool–by drawing heat from the interior, not by injecting cold air. A refrigerator transfers heat in only one direction. A geothermal heat pump can transfer heat in two directions, thereby heating or cooling the space. Most heat pumps heat or cool the air. Some heat pumps heat or chill water. An additional component, a reversing valve, is added to a heat pump, which allows the refrigerant to change direction, allowing the space that was being cooled to be heated.

5.22.09 HVAC (2)A geothermal heat pump has a compressor, a condenser, an expansion device and an evaporator like a refrigerator; but also includes a reversing valve to allow both heating and cooling. The big difference between a refrigerator (or traditional AC) and a geothermal heat pump is the way heat is transferred. A geothermal heat pump transfers heat between the refrigerant circuit and the ground instead of between the refrigerant circuit and the air. The ground is a much milder heat source, since temperature changes very little over the course of the year. The outside air temperature, however, varies significantly over the year, making a geothermal heat pump much more energy efficient that a traditional air conditioner. A geothermal heat pump compressor also operates at lower pressures because of the milder heat source/heat sink (the ground), helping provide longer life expectancies.

Our system has been set up with dual domestic hot water tanks, one of which is a holding tank that stores additional hot water for when we need it whether that is for heat or hot water. 5.22.09 Water tanks

All of our equipment is in for the interior part of the project (see pictures). You’ll see the dual Rheem Marathon hot water tanks, two of the air handlers for the house (the first and second floor) and the unit for the wine cellar. You’ll see all of our ductwork is sealed with cement and insulated to an R-6 for the greatest performance and efficiency of the system. The piping then runs our through a hole cored in the foundation and back to the ground source heat pump connected to our closed loop system and our well.

The well and exterior piping takes approximately four days to install so each day the rest of this week we have a new story and new photos posting on the project. Wish us luck, we start at 9 AM eastern time Tuesday with final location and the digging of the slurry pit.

Posted by KDL follow me on Twitter: newscaster


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