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Video tour of the homeowners’ geothermal system:

Here, as told by homeowner Jackie Fary-Moeller, is a step-by-step description of the installation process:

We own a two story, 2000 square foot Levittown colonial style home, built in 1969 in Maryland. We chose geothermal because of environmental concerns and significant energy savings.

How we chose the contractor

We used what is now called homeadvisor.com to have contractors come out and give bids. There are other similar websites that can help you compare different contractors. The prices ranged from $24,000 - $30,000. We went with the lowest bidder, Supreme Air in Baltimore, Maryland for their significantly lower price, great references, and knowledge of the project. We installed a four ton Water Furnace series with hot water generation to be piped to the hot water heater (that means that the heat given off will go to our hot water heater, for further energy savings).

This cost did not include landscaping the yard afterwards. The drilling rig and trenching made a huge mess and took out the walkway and our French drain pipe system. In our case the 30% federal tax credit applies to the cost of re-landscaping as well. We were responsible for the excess materials creating by the drilling. We took care of the dirt and rocks by using them to fill some holes around our yard and put it in the trenches for the pipes.

In addition, we added a two zone damper system for $2,400. This extra ductwork and control system allowed us to finally heat and cool the upstairs and downstairs of our house separately, which saved us even more. The computer card that controls the zoning actually allows us to heat/cool four separate areas, so in the future we can add more ductwork to control the temperature in our back and future workshop.

The Drilling

The entire first hole and some of the second hole were drilled on the first day. It was very noisy and the drilling rig is very large (smaller rigs are now available). For our four ton unit, we needed two 300 foot holes for the piping. These are vertical holes, which makes geothermal considerably easier for a retrofit installation such as ours. We simply don’t have room for all the ground loops/piping to be placed horizontally.

Due to the drought that occurred that year, the drilling rig did not hit much water, which was lucky for us. We didn’t need to use a siltbag ($450 each) to capture the silt and prevent it from running into the storm drain (and therefore into our local stream) with the excess water. All the material (dirt and rock dust) that comes up from the drilling was deposited next to the hole.

The drilling rig works just like a drill bit going into wood. As the drill bit goes in, sawdust comes out. As the well drilling bit goes into the ground, up comes the dirt and rock. The largest piece of rock is about the size of a pea and much of it is dust, creating gray slurry.

Grouting

Grouting is a small but important step of the process. When the well holes are drilled into the ground, they are only about 8” wide. The PVC pipe, called casing, is used to support the dirt/clay walls of the hole. Once they start drilling through bedrock (usually around 30’), the walls are not going to collapse and PVC casing is no longer needed. Our contract included a set amount of PVC pipe: we would have been charged for any additional pipe needed.

Special black piping (polyethanol pipe) is put into the holes and connected to form a continuous pipe. Then the grout (a type of cement) is poured around the pipe, which ensures good thermal transfer. Air is not a good conductor but the grout certainly is! The black pipe is then later filled with methanol (a lot like antifreeze) to bring either warm or cool temperatures to our house.

Trenching

Now, the black piping has to get from the holes and into our house. When it is in the ground, it is best if it stays four feet deep in order to insure the best thermal transfer. In this geographic region, four feet underground is below the freeze line and the temperature is always the same (about 55 degrees F). Remember, the geothermal process takes advantage of that constant temperature to heat and cool our house.

Practically speaking, that means a four-foot deep trench has to be dug from the well holes to the spot where the black pipes enter the house. This also entails a big dirty mess. For us, that means the front walkway to the house was in the way. We decided to let the excavator remove the portion of our walkway that was in the way. Otherwise, the installer would have needed to hand dig under the walkway. They hand dug around the sewage pipe that leaves our house and around our drainage pipes.

The Geothermal Pipes Go From Well to House

The black piping comes out of the hole and has to get connected to the other pipes that will go to the house. They used a tool that heats up both ends of the pipe and then fused the two ends together. Then the top of the PVC pipe is cut away so that everything is under the ground by four feet. At the end of the same day, the excavator pushes the dirt back into the trench, covering all the piping.

At least that is what is supposed to happen if things go perfectly. There was a small but not uncommon problem with the grouting. Sometimes there are pockets and crevices deep underground and the grout travels into them. It takes a while for the grout to settle down. But our holes were short on grout so the drilling company had to come back and top off the holes with more grout.

Installation

The pipes from the wells come into the right front corner of the garage. From there they go up the interior all and along the ceiling to the mechanical closet (our “furnace closet” at the back of the garage). Usually the pipes would enter the house through a basement wall underground but since we don’t have a basement this alternative entry point was used.

The entire install took 5 days. That was 2 days for drilling, which can be done separately and without unhooking the existing heating/cooling system. Then 3 days from trenching to the new system up and running. That’s 3 days without the ability to heat or cool your home. This should be considered when scheduling your install.

In-depth - How the Geothermal Heat Pump Works at our House

The rectangular unit on the left is the Water Furnace geothermal/water source heat pump, which replaces both the furnace and air conditioner most of the time. However, every few years in our region there is deep cold spell in which the air temps never get above freezing for a week or so. The theory is that we will take so much heat out of the ground that the area immediately next to the piping will be “robbed” of heat and not able to recover. When that happens, the Water Furnace unit uses electric heaters to supplement the geothermal heat pump (usually labeled as auxiliary heat on the thermostat).

A backup heat source such as a wood-burning stove can be used to minimize the expense of electric heat. Some people who have room keep their gas furnaces as their backup heat since it is more efficient than the electric heaters. Interestingly enough, one of the contractors who gave us a bid said the backup heat wasn’t necessary, and another contractor insisted that it was. Supreme Air pointed out that it comes standard with the Water Furnace unit and that it probably depends on the geographic region.

It is our experience that the electric heat is used intermittently during nights with below freezing outdoor temperatures. Our bedrooms are upstairs. With our new zone heating, we can drop the temperature upstairs to 60 degrees during the day and vice versa for the downstairs at night.

We also have a transfer tank to save extra money. When we are using the air conditioning in the summer, the heat has to go somewhere, and it might as well go into water. The water in the transfer tank is pre-warmed and goes to the hot water heater, saving us money on heating our hot water.

How long did it take?

System installation began September 16, 2010, when the drilling rig arrived. We received a check from the State of Maryland in November 2010, about a month after we sent in the final paperwork. This is grant money, not a rebate, so we paid taxes on it as income. For such a grant you may need an acceptance letter BEFORE you begin installation, so give yourself a couple of months to get that done. Our county offered an additional rebate. However, it took five years to show up on our property tax bill.

How much money are we saving on energy bills?

We saw a significant savings after we installed our ground heat pump. We average about half the electricity usage during the summer, and virtually no natural gas. However, this doesn’t reduce the total bill in half since a set part of most utility bills are fixed fees. During the winter, our electric bills doubled and our gas bills are one third of their previous levels. Winter is the highest electricity use (which is the opposite of a conventional system), but insulating with a goal of reducing heat loss will help a great deal.

Cleaning up the mess and landscaping the yard

After installation, we had a mess to clean up in our front yard. From our point of view, this was acceptable since the driveway and front walk were in bad shape and needed to be replaced anyway. The driveway was already in a weakened condition and the heavy drilling rig driving over it accelerated the cracks in it. We did a cheap fix and had the top inch of asphalt resurfaced. The walkway was cheaply redone, simply by cementing the existing brick in place.

As you can see by the photos, there was a large amount of soil left over from the trenching and rock debris (ground up bedrock) created by what the drilling rig removed. The rock debris was very heavy and could be very densely packed when dry. We filled some holes around the yard but it could also be spread on a gravel driveway. The landscaper hauled away a portion of it.

The soil itself was incorporated into the landscaping by creating raised berms (the dirt could also be used to backfill a wall or terrace). Berms can create more interesting landscaping, especially in suburban yards that are usually very flat and monotonous.

How well has it been working?

We are very pleased. In the winter the heating feels great and keeps all parts of the house warm and comfortable. There is more humidity and there seems to be less dust, as the air is nowhere near as drying as the combustion of the old gas furnace. We skipped both humidifier and air cleaner with no regrets.

In the summer the air-conditioning has been working wonderfully. All areas of the house are cool and comfortable and the unit is very quiet. The zoning also works great: it gives us the unusual feeling of the air getting cooler when we go upstairs at night.