Geothermal system helps home achieve net-zero energy usage

Dec. 2, 2010
BAY CITY, MICH. — Vision Zero, Michigan’s first net-zero energy home, is utilizing a geothermal heating and cooling system, solar thermal system, photovoltaics, and an energy recovery ventilation system.

BAY CITY, MICH. — Vision Zero, Michigan’s first net-zero energy home, is utilizing a geothermal heating and cooling system, solar thermal system for domestic hot water, photovoltaics to collect energy, and an energy recovery ventilation system to ensure clean, healthy air. Being net-zero, the house will produce as much energy as it consumes, and any extra energy not used by the house will be sold back to the power company via net metering.

The home is a project designed and built by The Dow Chemical Co., Midland, Mich., and Cobblestone Homes, Saginaw, Mich.

“Pat O'Malley from Building Knowledge assisted in modeling the house based on the mechanical systems and the performance we wanted to see out of the house,” said Melissa Wahl, co-owner of Cobblestone Homes. “Dow Chemical scientists and building specialists were involved in establishing what products would best be suited for insulation and solar generation, and the entire Cobblestone Team worked to select the products and systems that would be incorporated.”

Incorporating innovative and energy-efficient technologies, the house will serve as an educational resource until spring of 2011. Tours and seminars are being offered, so people can learn more about the technologies used in the house.

Geothermal system

According to Wahl, a geothermal system was chosen to heat and cool the house because in addition to consumer interest and energy efficiency, there are incentives for installing a geothermal system, such as the 30% tax credit homeowners can receive on the installation of such a system.

WaterFurnace International Inc., Fort Wayne, Ind., a manufacturer of residential, commercial, industrial and institutional geothermal and water source heat pumps, provided the geothermal heating and cooling system for the house, and Walton Geothermal Heating & Cooling, Mount Pleasant, Mich., installed it.

Walton also installed the geothermal loop to support the system — a six pipe, horizontal loop application where the pipes are buried in horizontal trenches rather than vertically drilled holes.

“We had the land available, even on a subdivision lot, to do a horizontal loop,” said Wahl. “We opted for the horizontal to help keep our costs down.”

With the WaterFurnace geothermal system, the home is designed for heating and cooling cost savings — less than $250 a year to heat the home and $14 a year for cooling. The house is expected to save $3,507 in energy costs and prevent 44,855-lbs of CO2 emissions per year.

According to Tim Litton of WaterFurnace, the Envision’s two-speed compressor units are roughly five times more efficient than any fossil-fuel furnace in heating and more than twice as efficient as an air conditioner in cooling, saving homeowners up to 70% on their utility bills.

“There are a lot of people who really don’t understand geothermal,” said Mike Walton, president and applications engineer of Walton Geothermal Heating & Cooling. “What’s nice about this house is that it’s there for you to see in person. You’re hearing about it, you’re feeling it, and you’re seeing it.”

“In most cases people learn about geothermal through literature, video or on television,” said Wahl. “But many people don’t have the opportunity to go look at how it’s done and talk to someone face-to-face. This project lends itself to hands-on education.”

Solar systems

The solar thermal system by Enerworks, headquartered in Dorchester, Ontario, was selected to show that solar can work in a cold climate such as Michigan. Solar panels are on the south side of the house’s roof, and the Envision unit works with the solar thermal tank and electric hot water tank. With a desuperheater, the Envision captures the unwanted heat from the home, using it to preheat water in a storage tank. The electric hot water tank serves as the primary holding tank, so the geothermal and solar tanks are not competing with one another, which helps conserve energy.

“Besides having a dashboard on it which can be read to see the temperature of the water produced and many other facts of the system, there is actually one pipe in which I encourage people to touch that is very warm,” said Wahl regarding the solar thermal system. “Feeling this pipe gives visitors a tactical way to show that solar does in fact work even in a cool climate.”

Besides solar thermal, there are four photovoltaic arrays on the house. One array is showcasing the new Dow Powerhouse Solar Shingle by Dow Chemical. This thin film technology is a two-in-one product, which serves as the weather shielding shingle and produces electricity. Dow Corning has three other arrays on the home. One array is showcasing commercially available technology made by BP Solar, and the other two arrays are comprised of test panels for Dow Corning.

“The home is somewhat of a solar show piece,” said Wahl.

ERV, plumbing systems

The house also utilizes an efficient ERV system by Venmar and water conserving plumbing fixtures.

“All of our homes, as should all ultra-efficient homes, have mechanical air exchangers,” said Wahl. “This model was selected for its performance and the wattage it would take to run the unit.”

Plumbing fixtures consist of Moen faucets that meet or exceed the EPA’s Watersense requirements and dual-flush toilets by Sterling, a Kohler company.

According to Wahl, the house also features a graywater heat recovery system in which the heat from waste water (graywater) is being extracted and used to preheat water going into the hot water tank.

"The most unique thing about building the home is all of the learning the entire team did,” said Wahl. “One idea lead to another and looking at the house as an entire system and incorporating new technologies was intellectually stimulating.

“The project is about information, inspiration, innovation, and education and learning,” continued Wahl. “Our goal is that every visitor who tours takes at least one bit of information with him or her that can be applied to his or her current residence — that may involve looking at the addition of a renewable energy resource on his/her home or it might be as simple as air sealing around the windows. There is something for everyone — if we all worked to conserve the benefits are multifaceted.”

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About the Author

Candace Roulo

Candace Roulo, senior editor of CONTRACTOR and graduate of Michigan State University’s College of Communication Arts & Sciences, has 15 years of industry experience in the media and construction industries. She covers a variety of mechanical contracting topics, from sustainable construction practices and policy issues affecting contractors to continuing education for industry professionals and the best business practices that contractors can implement to run successful businesses.      

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