The main mechanical room, which houses a 400-gallon buffer tank, is located on the ground level near the garage. (Photos courtesy of Watts Radiant and John Herr Photography.)
There is the argument that a sequel is never as good as the original.
That certainly isn’t the case with a custom-built, 10,000-square-foot home in the Mid-Atlantic region.
The house, which was a frontrunner in the use of a geothermal system when originally built in the mid-1980s, suffered severe damage several years ago from a fire started when fireplace ashes ignited in a garage garbage can. The blaze gutted the second floor, and fire and smoke damage greatly affected the first floor.
The owners of the home were so impressed with the design of the original house that they wanted it rebuilt nearly identical to how it stood before the blaze with the existing geothermal system kept intact. A few modifications included the creation of a tighter building envelope and an update to the HVAC system with the installation of radiant floor heating.
Ahead Of The Curve
To get the process started, the owners called New Jersey-based Jersey Devil, the original design-build group on the home (and known for its energy-conscious designs).“They kind of flattered me to do it again,” saysJohn Ringel, a Jersey Devil partner who helped build the original home. Ringel’s partners includeSteve BadanesandJim Adamsonand includedGreg Torchiowhen the house was originally constructed. Torchio was the architect of record on the rebuild.
“After 20 years of living there, we thought they wanted to make some changes, but they have children coming home with their families now,” Ringel explains. “They wanted it pretty much exactly the same.”
Ringel’s group has been doing solar installations since the 1970s and geothermal work dating back to the 1980s. When the homeowners expressed the desire for air-conditioning in the original home, the group, of course, had the solution.
“We felt we had to come up with a more efficient system than just air-to-air,” Ringel states. “We had experience with water systems. I had done one other house like it in New Jersey. We expressed to the homeowner there would be better comfort (with a geothermal system) because you’re dealing with a more temperate water source.”
The home’s original geothermal install in the 1980s may have been a first in that part of the country. “Nobody had heard of it when we got down there,” Ringel says.
While most of the home was ruined, the geothermal field survived the fire.
“Before the home burned down, water-to-air geothermal heat pumps took care of the home’s heating and cooling demands,” saysEric Jones, vice president of Jones-Rogers, the mechanical contractor chosen to complete the extensive system on the rebuild. “The geothermal exchange field was unharmed during the fire, so the melted lines coming into the mechanical room were cut and re-fused.”
The geo-exchange field consists of eight boreholes at an average depth of 320 feet. Each hole in the unique system has two loops running down through the bentonite grout. “The new engineering included all the existing loops in the system,” Jones notes.
The two-loop configuration is not commonplace, but Ringel did not want to take any chances on the original design.
“I specified two loops in each well. One would be redundant in case of a leak,” he explains. “We had one loop of pipe in each well that had never been used. They were effectively brand-new wells. (With the rebuild), it didn’t seem like we should abandon them. We had one of the most expensive components already installed. It seemed foolish to not use it.”
The home contains 10,800 lineal feet of radiant tubing. Radiant floor heating was the key addition to the home's rebuild and, coupled with the existing geothermal system, gives the homeowners reliable and energy-efficient heating and cooling methods.
The Big Change
When originally built, the home’s heating system was 100 percent dependent on geothermal. However, the homeowners were not completely satisfied with the heating component of the first system.“Despite the fact the geothermal system is a better system than air-to-air, they really didn’t like the heating capabilities,” Ringel says. “It was not necessarily a hot feeling.”
The large project team, which also includedTomaso Sargent(Sargent & Associates) andTom Virant(Virant Design) - who were in charge of project management and coordination of all site work - andDave Chandler(senior mechanical designer/project manager at Allen and Shariff Engineering and the designer of the home’s mechanical system), had the answer to eliminate that concern.
“A perfect fit with the geothermal is radiant heat,” Ringel says. “The slightly lower temperatures work well in a radiant floor. We went with radiant flooring using the geothermal as the primary heat source.”
Four 42,000-Btu ground-source water-to-water heat pumps supply heated water to 10,800 lineal feet of Watts Radiant Onix EPDM radiant tubing.
“The tubing is more like a rubber hose,” Chandler notes. “It helped with installation because there are a lot of curved walls and really obscure layouts in the house.”
The home has 11 hydronic zones with a Watts Radiant Hydronex control panel serving each one.“The prefabricated panels were a huge timesaver on a radiant job this size,” Jones says. “You pretty much plug them in and go.”
With the implementation of the geothermal/radiant combination, the homeowners are saving money on utility bills vs. a typical HVAC system.
More Mechanical
The water-to-water geothermal heat pumps draw from the geo-exchange field to heat and cool the house. The new units provide cool water to fan coil units (by IEC) throughout the house for air conditioning. One of the units has a WaterFurnace desuperheater for domestic hot water, which is assisted by three Takagi gas-fired tankless water heaters located throughout the home.The home’s heating and cooling system has four operating modes, roughly corresponding to the four seasons. In winter, it heats with radiant floors supplied by the geothermal heat pumps and no cooling is available. In spring and fall, it cools using chilled water supplied to the fan coil units. In swing seasons, a Lochinvar Knight high-efficiency, gas-fired 259 MBH modulating-condensing boiler provides hot water for the fan coil units. In the summer, the boiler is disabled and the heat pumps cool with chilled water to the fan coil units.
An onsite gas generator is a necessity due to frequent power outages and is capable of running a portion of the geothermal system. The main mechanical room, complete with a 400-gallon Cemline buffer tank, is located near the garage on the ground level.
A DDC control system from Johnson Controls allows for central programming of all temperature set points, as well as sequencing and scheduling of the mechanical systems. Variable-speed drives (by Eaton), installed on the condenser water pumps as well as the chilled water pumps, reduce energy usage during part-load conditions.
“Space was the biggest issue we ran into,” Jones says. “Not in the main mechanical room, but elsewhere within the home.”
Scattered throughout the home are 12 small mechanical areas. Hiding panels, circulators, numerous fan coil units, and a Greenheck energy recovery ventilator in and amongst ductwork was the key challenge.
“The homeowners didn’t care for the compressors out in the space in the original house,” Chandler says. “They could hear them, and servicing them was difficult out in the space. Now there are no compressors, just fan coil units. There is no noise associated with the fan coil units, which made the owners happy.”
A Little Touch Of Solar
There is a solar component to the home thanks to the use of direct-gain passive solar energy. The house is oriented on an east-west axis with the long side facing south. All window glass on the south side gains heat in the cooler months when the sun is low in the sky. The skylight system on the roof is designed to provide daylighting and direct-gain heat.“In the late spring and early fall, the boiler never comes on,” Ringel notes. “You put in your vertical south-facing glass and sunlight comes directly into the space and warms it. There is no need for equipment.”
A Tough But Successful Job
Chandler’s group has designed other geothermal systems, mainly in commercial settings. He rates this job an “8” out of 10 on the complexity and toughness scale.“It was a challenge to design because of the general construction layout of the house with the curved walls and the skylight that went down the center of the house,” he says. “The house has an obscure shape. They called it the ‘Hoagie House’ because of the large rectangular-shaped skylight down the center.”
Chandler emphasizes that while the project was challenging, it turned out to be a great accomplishment and a big success.
“From the feedback I’ve received, the owners are happy with the design and the installation,” he says. “They are saving money on electrical bills with the geothermal system vs. a typical HVAC system. For a house of that size, I couldn’t imagine what the electrical bills would be with air-cooled heat pumps.”
Ultimately, the tipping factor on the project was the introduction of the radiant floor heating.
“The radiant rounded out everything,” Ringel says. “Everybody was happy.”
