Page 62 - North American Clean Energy November December 2015

geothermal energy

Award-Winning Net Zero Energy Home

Heating and cooling with a geothermal system

by Tim Litton

WHEN CARL BENKER AND HIS WIFE, Elizabeth Wegner, designed their irst home, the couple air-conditioning (HVAC) systems, ofering savings as high as 70% for heating, cooling, and
never intended to win contests or awards. As the parents of two young children, they just hot water.
wanted to build something that was right for the world today and the world they’ll leave

behind for their children and grandchildren. Together, they selected a builder with a simi- Eficiency, cleanliness, and comfort sell geothermal
lar philosophy, whose sustainability message reads, “Each home relects our desire to substan- Geothermal has three main advantages;
tially reduce our impact on the world which will afect our children, grandchildren and all future • Eiciency. Nothing can touch geothermal as far as eiciency goes.
generations.”
• Cleanliness. he carbon footprint of a house using a geothermal system is extremely

hat’s why the 2,755-square-foot home has won three prestigious awards. Early this year small, because the system doesn’t burn any fossil fuels.
the Benker home was named the winner of the 2014 Connecticut Zero Energy Challenge,
• Comfort. A geothermal system provides much more comfort than a conventional heating
a statewide design/build competition for single- and multi-family homes that challenges and cooling system.
builders and homeowners to create homes which consume as little energy as possible. Resi-

dential Energy Services Network (RESNET) rating standards determine each home’s Home he geothermal system for the Benker/Wegner residence uses two, 300-foot vertical
Energy Rating System (HERS) Index, a nationally recognized scoring system that measures wells for the geothermal loop and a residential variable capacity geothermal heat pump
energy performance. he lower the number, the more energy eicient the home. A score of which surpasses an Energy Eiciency Ratio (EER) of 41 in cooling and a 5.3 Coeicient of
zero represents a net zero energy home.
Performance (COP) in heating. hat’s more than twice as eicient as today’s most eicient

With a HERS Index of -23, the Benker/Wegner residence also won the RESNET 2015 air conditioners or heat pumps and a third more eicient than standard geothermal units.
Cross Border Challenge, sponsored by RESNET and its Canadian counterpart, CRESNET. his variable capacity geothermal heat pump scales compressor output and airlow to ex-
he challenge recognized the residence as the home built in North America in 2014 report- actly the level needed for any heating or cooling situation. he unit can ramp down to 20%

ing the lowest HERS Index with photovoltaics (PV). Steven Winter Associates, Inc. (SWA), of normal operation for the ultimate eiciency and comfort or scale up to 130% output for
in their role as an ENERGY STAR rater, LEED for Homes provider, and rater and National those brief periods when extra conditioning is required. And due to its large range of capac-
Green Building Standard veriier, nominated the home for this award and guided the team ities, it provides unmatched humidity control and can even eliminate the need for auxiliary
through the Connecticut Zero Energy Challenge. Most recently, the home was named a heat in cold-weather climates.

2015 Housing Innovation Award winner by the U.S. Department of Energy.
Free hot water
Solar array and geothermal make a good match
he unit is also equipped with a desuperheater, which provides all of the domestic hot wa-
he Benker/Wegner home produces more energy than it needs, thanks to a PV array on
ter during the summer. In the winter, it will pre-heat water and a hybrid hot water heater

a steel pole that rotates and follows the sun throughout the day. he PV array generates will inish heating it to the required temperature. he hot water system also uses insulated
enough electricity to power everything in the home, including all appliances, lights, hot tubing to reduce heat loss and an on-demand hot water recirculation system that stops
water heater, and the home’s heating and cooling system — that makes it net zero. he ex- warm water from being wasted when waiting for hot water to arrive at the faucet.
tra energy it produces will be used to power an electric car for approximately 12,000 miles Benker and his wife are happy with their decision to use a geothermal system to provide

per year.
heating and cooling to their four-bedroom home. hey appreciate the eiciency, humid-
Deciding to install a geothermal heating and cooling system was a big decision. Carl’s ity control, and that it responds very quickly to the thermostat, gradually ramping up and
family has been in the fuel oil business since 1923, so he briely considered installing a fuel down, enabling the temperature to remain uniform and comfortable. he 30% federal tax
oil system, but he really wanted to build a home with as small a fossil-fuel base as possible. credit also makes it afordable.

With only so many ways to heat a house without using fuel oil, natural gas, or propane,
they could have selected an electric resistance heating system, but from an eiciency, per- Sustainability deines house
formance, and comfort standpoint, geothermal was a much better choice.
he house is illed with a variety of other sustainable features, including:
A geothermal system takes advantage of free energy stored just below the surface of
• ENERGY STAR appliances, including a heat pump clothes dryer and induction cooktop;

the earth. Using a series of pipes (an earth loop) buried in the ground and a geothermal • LED lighting ixtures;
(sometimes referred to as a ground source) heat pump, the geothermal heating and cooling • Low VOC, GREENGUARD-certiied components, including insulation, drywall, joint com-
system extracts heat from the earth and carries it to a building in the winter. An indoor pound, and wood inishes;
unit compresses the heat to a higher temperature and distributes it throughout the struc- • hermomass centrally insulated foundation with an R20 total insulating value;

ture. In the summer, the process reverses, and the system extracts heat from the build-
• Naturally cooled root/wine cellar maintained at 56°F year-round without using any power;
ing and rejects it to the earth. In both cases, the geothermal system delivers consistent • Aluminum rooing shingles with a 70-plus-year life span;
temperatures and eiciencies that exceed those of conventional heating, ventilation, and
• Fire sprinkler system which uses the existing cold water supply lines;

62 nacleanenergy.com
NOVEMBER/DECEMBER 2015