Comfort from below (Spring 2007)

In heat mode, heat from the ground is absorbed by fluid in a buried pipe and pumped into the house. In the summer the system works in reverse. This time the colder ground temperature is used to cool the house. Some of the excess heat this produces can be used to heat a hot water tank and the rest radiates back into the surrounding earth.

While the whole thing sounds a little like magic, it’s based on the same principal that’s used in a refrigerator. The only major difference is where they get rid of the excess heat. A refrigerator dissipates heat into the air through a series of heat-exchange tubes mounted at the back; in a geothermal system the tubes are buried underground.

There are three basic types of geothermal systems on the market. In the first, the closed loop system, coils of plastic pipes filled with glycol are buried either horizontally or vertically below the frost line. The second, direct expansion, is similar to the closed loop but uses copper lines filled with refrigerant gases instead of plastic filled with glycol. Since there is no liquid to pump, there is no pump to wear out. The third, the open loop, works a little differently. Instead of heat from the earth, it uses water pumped from a nearby well, pond, or lake, for its energy source.

“A water-based system wasn’t an option here and a glycol system wouldn’t work either,” Donovan says. “For those you need to be able to bury a lot of tubing on your property below the frost line. We have rock 6 inches below our grass, so we weren’t going to bury much of anything. Then we heard about the direct expansion system; it only required one 100-foot hole to be drilled for every ton of heating or cooling we required. It looked promising.”

Donovan decided to do a business-case analysis to see if the higher capital cost of installing a system would be worth it. He started by having a heat-loss analysis done from the blueprints of his new home. Based on the size of his house, its insulation factor, the number of windows, the direction it faced, and how much sun it would get, the analysis determined it would cost the Donovans between $2,800 and $3,200 dollars to heat their house with propane. It would cost an additional $400 to $600 to cool the home in the summer months.

Donovan compared this to the cost of putting in geothermal and found that it would cost $8,000 to $10,000 more to install a geothermal system. However, with geothermal, it would only cost $1,300 to $1,400 a year to heat and cool their home. It was going to save them at least $2,000 a year on their energy bill. Once they saw those numbers, they were sold.

Geothermal systems are considered very environmentally friendly because they heat buildings without burning any fossil fuels. They are far more efficient than standard air conditioners, using only a fraction of the electricity on even the hottest summer days. According to statistics from the Geothermal Heat Pump Consortium in Washington, D.C., every 100,000 residential geothermal installations reduce U.S. reliance on foreign oil by 2.15 million barrels. This translates into 2.18 million tons less carbon dioxide being released into the atmosphere. They also reduce electricity consumption by 799 million kilowatt hours annually. Current U.S. installations have the same positive environmental benefit as taking 1.295 million cars off the road.

While homeowners like to be environmentally friendly, few are willing to install a geothermal system for that reason alone, says Mike Parlato, president of Earth Energy Solutions, an Ontario company that specializes in geothermal installations. “People are economically minded first and environmentally minded second. They want to know the total cost of the system and what their payback period will be. We need to prove to them that when we drill, they will strike it rich.”