Feeling the Heat

This season’s soaring fuel costs have many homeowners cringing when they open their utility bills. Owners of homes with new geothermal systems, however, are seeing the payoff for their investment in drastically reduced heating and cooling bills. “I had a client come back to me after a year and show me his utility bills that averaged about $50 per month,” says Patrick McDonell, owner of McDonell Construction in Hudson, Wisconsin. This owner would be paying closer to $450–$500 per month in a less energy-efficient, similar-sized home with a standard heating and cooling system. While McDonell is certainly not claiming that the entire savings is the result of a geothermal heating and cooling system, he does say that a fair share of it is due to the new technology. Typical utility savings for a 4,000-square-foot home range between 35 percent and 70 percent with a geothermal system.

Combined with other built-in, energy-saving options, the new geothermal systems are becoming a major player in green building in the metro area. “I think geothermal systems are becoming a definite trend,” says Jim McNulty, owner of McNulty Homes in Minneapolis. “Once customers become aware of the technology, they want us to pursue it for them.”

Geothermal heating and cooling systems use the constant temperature of the earth below the frost line, or about five feet down, to remove the excess heat in homes during summer and to heat homes in winter. Between five feet and about 1,000 feet, the ground temperature is at a constant year-round temperature of 50°F.

Horizontal Loops
There are two types of geothermal systems, horizontal loop and vertical loop.  “The piping that carries the water in a horizontal loop system is a coil that looks a bit like a slinky when you stretch it out,” says Larry Sharpe, project manager for McNulty Homes. The coil is buried at a depth of about eight feet. As water runs through this closed loop system, it is warmed to the temperature of the ground.

An electric heat pump then concentrates the water temperature to heat the house. The pump also has a reverse switch on it, which allows it to remove excess heat from the home in summer. The water in the geothermal piping, which has been warmed by the excess heat from the house, transfers the heat back to the earth.

The horizontal geothermal systems used by both McNulty Homes and Brandl Anderson Homes of Eagan require a fairly large geothermal field, or lot. For instance, Sharpe says a 3,000–4,000-square-foot home would require a lot space of seventy feet by seventy feet dedicated to the geothermal field.

Chris Brandl, part owner of Brandl Anderson Homes, says that while he is not installing many geothermal systems yet, he anticipates the number to increase as fuel costs rise and as the technology becomes more widely recognized. “The costs are pretty great up front. I’m trying to figure out a way to incorporate geothermal systems into affordable homes,” says Brandl, whose company builds homes in the $180,000 to $2 million price range. “I’m trying to figure out if we can make it work in a move-up home, say a $400,000 home,” he says.

Brandl has used the technology to heat an outdoor swimming pool of an upper-end home, and the cost savings have been phenomenal. “You pump water from the swimming pool through a plate heat exchanger that has been warmed by a horizontal geothermal loop system,” he explains. “You can heat a swimming pool for basically nothing,” when traditionally it costs about $600–$800 per month.

McNulty, who builds in the $850,000 range and up, says half of his clients choose geothermal systems and he believes that the systems will soon begin showing up in middle-range homes as well.