Army Homes Test Zero Energy Design
It’s all about saving green —funds that are now sensibly invested in projects and technology that use energy frugally. Government buyers are guided by ever-more stringent mandates to invest responsibly.
A large military housing project at Fort Campbell, Ky., is a good example of tax dollar stewardship.
After two years in design and construction, two zero energy homes are occupied by Army families. LEED Platinum is being pursued for the homes in the military housing development and now serve as part of a test project for future military building projects.
“The zero energy homes are being compared to two adjacent baseline homes, all equipped with identical monitoring systems,” explained Patrick Tahaney, Campbell Crossing development manager. “Over the next four seasons, we’ll be gathering data from these homes, information we’ll use when we enter phase two of the project.”
Partnered with the U.S. Department of Defense, Actus Lend Lease — a community development organization, specializing in large, complex housing projects — is using these two homes as a prototype for future military housing neighborhoods. Campbell Crossing LLC is a 50-year partnership created between the Department of the Army and Actus Lend Lease through the Military Housing Privatization Initiative (MHPI). Since December 2003, Campbell Crossing has developed more than 1,000 new homes and renovated more than 2,000 homes, and will continue to finance, develop, build, renovate, and operate the site for 50 years.
“Together, we hope to build a model for zero energy to be used broadly by the construction industry, and for Department of Defense housing projects,” continued Tahaney. Through the use of photovoltaic solar arrays, each house produces as much energy as it consumes over an annual period.
Geothermal and low-impact have become synonymous, and the two homes at Fort Campbell Woodlands are no exception. Each house is equipped with a ClimateMaster Tranquility 27 water-to-air geothermal heat pump. Due to the area’s unstable limestone bedrock, no small amount of research and consideration went into designing the geoexchange field.
“With southern Kentucky and northern Tennessee’s propensity for sinkholes and cave-ins, we generally don’t do many vertical loop installations,” said Daryl Pater, owner of Mainstream Heating and Cooling, in Clarksville, Tenn. “We drilled seven test wells ranging from 200 to 300 feet at Campbell’s Crossing. We wanted to assess both stability of the earth, and conductivity values.” The tests were done by Jackson & Sons Geothermal. Miller Drilling Co. in Lawrenceburg, Tenn., drilled the final wells before installation.
The tests began two years before ground was broken for the green homes. The seven test wells successfully muted all concerns about ground stability and temperature. The last two wells were piped and filled with bentonite grout to run conductivity tests. The results, combined with an estimated heat load, showed that a 375-foot-long, 6-inch diameter bore hole would serve each home optimally.
One of the grouted test wells was close enough to the construction site of the homes that it was used as part of the exchange field. “We drilled an additional 100-foot well near the 300 footer,” explained Pater. “System fluid runs from the home, through the deep well, then through the shallow well, and back to the heat pump. We just drilled the shorter well so we weren’t wasting the test well.” For the second home, one 375-foot well was drilled.
Mainstream Heating and Cooling specializes in green HVAC. From pond loops to direct exchange systems, the company tackles a variety of different projects involving geothermal equipment. “We do a good volume of geothermal work, but in this area, the demand just isn’t high enough to make it
our sole activity,” said Pater. “For all our water-sourced projects, we prefer ClimateMaster.”
The New Army Green
A 12-panel, 7.4-kW photovoltaic solar array rests on the south-facing roof of each home. During the day, the panels produce enough energy to power the geothermal unit and appliances. With coordination from the Tennessee Valley Authority (TVA) all solar power generated goes directly to the grid. This allows the homes to be TVA Green Power Providers. A separate, three-panel solar array provides domestic hot water to the home.
The high-performance thermal envelope of the buildings consists of 2x6 stud walls, filled with open-cell spray foam insulation, ½-inch particle board, and 1-inch rigid Styrofoam board. The rigid insulation board was installed from the roofline to 3 feet below the first floor slab. The outside was then Typar house-wrapped, and covered in vinyl siding.
“This project is the first known zero energy duplex in the country,” said Jeff Morrow, senior project engineer for Actus Lend Lease. “It presented a lot of unique challenges to design and build a zero energy home to match our regular homes in terms of appearance and function. These homes have the same lot size and floor plan as our typical four-bedroom, 2 1/2-bath home.”
“We had to modify the roof framing to increase the amount of rear south-facing roof for the solar panels,” explained Morrow. “The roofing materials changed from shingle to standing seam metal panels. By mounting the solar panels to the standing seams of the metal roof, the number of roof penetrations dropped from 300 to four. From the street, it blends right in with the rest of the neighborhood. The systems on the roof, the materials behind the walls, and in the ground are what make the difference.”
Change on the Front Lines
“These houses are the Army’s first zero energy homes; they represent the Army’s and Actus Lend Lease’s commitment to sustainability, energy efficiency, and good stewardship of our natural resources,” said Col. Perry Clark, garrison commander. “The Army can no longer be casual about energy consumption. We’re in the middle of a shift from a culture of mission-focused consumption to one that includes sustainability as a means to increase our defense capability.”
The annual energy savings per home is expected to be more than $1,000 a year. If these savings were projected for all of the 4,457 homes at Campbell Crossing, long-term benefits would include an annual savings of up to $4.6 million.
Actus Lend Lease screened the housing list at Fort Campbell to find four families with normal, consistent energy consumption habits. Two of these families moved into the zero energy homes, and two more families moved into nearby standard homes outfitted with extensive energy monitoring equipment. To determine the true efficiency of the zero energy homes, the power consumption of households are being monitored and compared.
In addition, a 27 percent cut in total water consumption, and an estimated 7,300 gallons of hot water is also expected to be saved annually by each zero energy home. All the bathrooms in the home are centralized to allow for shorter piping runs, reducing the heat loss in the hot-water piping. The master and upstairs bathrooms are positioned back to back, with the downstairs powder room located directly underneath.
“Actus Lend Lease is committed to providing soldiers and their families with quality homes that are not only comfortable, but are environmentally sustainable. This innovative initiative once again demonstrates our commitment to do just that,” said Marc Sierra, Actus Lend Lease managing director. “As we monitor the success of the zero energy homes at Campbell Crossing, we’ll continue to work closely with the Department of Defense to identify future opportunities for homes like these.”
Publication date: 01/23/2012