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Geothermal is Key to Zero Net Energy Home in Sustainable Community Outside of Atlanta

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In the Chattahoochee Hills region outside of Atlanta, Georgia, the Serenbe sustainable community offers connections between nature, culture, and the art of living.

The 1,000-acre mixed-use community is anchored by a 25-acre farm that provides produce for residents and restaurants throughout the Atlanta area. Reminiscent of
old English villages, the community of hamlets connected by looping country roads and well-worn footpaths, links residents to each other, schools, shops, restaurants, cultural and recreational events as well as the natural environment.

The community of Serenbe requires all homes built there to be EarthCraft certified as part of its commitment to sustainability. The EarthCraft program was established in 1999 by the Greater Atlanta Home Builders Association and Southface Energy Institute, EarthCraft is a green building certification program that serves six Southeast states. EarthCraft certified homes demonstrate energy costs that are, on average, 30 percent below those of a typical new home.

A new home in Serenbe takes energy efficiency to the next level: net zero energy use. Net zero homes produce as much energy as they consume, through renewable energy sources.

One of the keys to producing enough energy through solar panels is to reduce the overall demand for energy in the home.

One of the best ways to do that is to make geothermal heating and cooling a part of the home. Geothermal does not use fossil fuels. Instead, geothermal heating and cooling works because the earth absorbs about 48 percent of the sun's energy, leaving a fairly constant underground temperature between 45° F (7° C) to 75° F (21° C). Geothermal technology uses this stable temperature to transfer heat to and from the earth, instead of using the air in the more common air-source heat pump systems.

A home geothermal system includes a geothermal or ground source heat pump and a ground loop system made up of pipes buried in the ground. A water/antifreeze solution flows through the pipes, absorbing heat from the earth in the winter and moving it to the geothermal system inside the house. Once there, the heat is condensed and transferred to the air that is circulated throughout the home, providing warmth when needed.

In the summer, the process is reversed as the system absorbs heat from the air inside the home, similar to how a refrigerator extracts heat from food to make it cool, and transfers that heat into the ground through the same ground loop.

Planning for Net Zero

With his retirement approaching, Richard Soper and his wife decided to build a two-family 2200 sq ft townhome in the community to provide a comfortable environment for their family, as well as rental income from a separate apartment unit.

As the former president of Bosch Thermotechnology Corp., Richard wanted to use technology to reduce the carbon footprint in the new home. The home is equipped with Bosch energy-saving appliances, high-efficiency geothermal heating and cooling system with Bosch gas tankless and mini-tank electric water heaters, and supplemented by solar photovoltaic roof panels. With all that technology, the townhome has a zero net energy footprint, generating as much energy as is consumed by the home.

Building for Green

Mac McKinney, president of McKinney and Sons of Palmetto, Georgia, was the builder of the townhome and integrated the systems to achieve the net-zero energy goal.

"The Bosch geothermal system is a logical choice to provide comfort conditioning all year. When coupled with a solar PV system, the home's energy use is virtually zero," McKinney said.
Three Bosch Greensource SM024 two-ton units were installed by Premier Indoor Comfort Systems of Canton, Georgia. They provide six tons of heating and cooling to the family's living space, plus a separate apartment.

Domestic Hot Water is supplied by Two Bosch Greentherm C950 gas condensing tankless water heaters with a Bosch Tronic 3000 mini-tank to provide whole-house hot water with recirculation. The Domestic Hot Water System units were installed by KLS Plumbing Inc., of Douglasville, Georgia.

Resource-efficient Bosch kitchen appliances include a convection wall oven and chimney hood, refrigerator and dishwasher, and the laundry is equipped with Bosch washer and dryer.

Living with Free Energy

When connected to a solar PV system to provide electrical energy, the home's energy bill is virtually zero, except for the basic monthly utility connection fee.

The federal government offers a 30-percent tax rebate through 2016 toward installation of a geothermal system, so first-cost is further reduced.

As explained by homeowner Richard Soper, "With a geothermal system there is no burning of fossil fuel, therefore no direct greenhouse gas emissions, better humidity control, and because the loop is underground and the heat pump equipment is located inside the house, the system is not susceptible to corrosion, weather or storm damage. Plus, geothermal systems are exceptionally quiet in operation so adjoining neighbors are undisturbed."

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