Hope Crossing, a suburban housing development in northeast Oklahoma City, may not look much different than other housing additions of attractive, moderately-priced homes, but it is unique. Hope Crossing is the largest “green” Habitat for Humanity housing development in the United States, and it is believed to be the only Habitat multi-dwelling project in which all homes are served by geothermal heating and cooling systems.
More than half of the development’s 217 homes are complete and occupied with construction of the remaining houses scheduled to be complete by 2013.
The Central Oklahoma Habitat for Humanity (COHFH) development occupies a 59-acre tract in northeast Oklahoma City. Three-and four-bedroom, two-bath brick homes average 1,250 square feet of living space. Each home is equipped with a geothermal system using the earth’s relatively constant underground temperature to heat the home in the winter and cool it during hot weather.
Rather than conventional forced air heating and cooling systems, every home will have a ground source heat pump with integrated pumping and purging valves connected to a 400-foot-deep HDPE pipe loop. Water circulates through the system, drawing heat from the earth in cold weather and reversing the process in summer to extract heat from the house and dissipate it in the ground.
Greatly reduced heating and cooling costs are the primary benefit to home owners, said Ann Felton, COHFH chief executive officer. Hope Crossing residents say they are paying about half the amount of their past bills for heating and cooling a comparably-sized dwelling. Some report savings of even more.
The Habitat for Humanity program is well known for efforts of volunteer individuals and partner organizations who donate time for labor and materials and products to construct and outfit homes.
ClimateMaster, Oklahoma City, the world’s largest ground source heat pump (GSHP) manufacturer, donated Tranquility 20 Series GSHPs for every house in the Hope Crossing project. Drilling ground loops and installation of the GSHP system is done by Comfortworks, an Oklahoma City-based ClimateMaster dealer and contractor.
The first step in installing the system is drilling the 400-foot vertical loop. A truck- mounted vertical drill does the job before construction on a home begins.
Drillers generally place loops on 10 to 12 sites each time they come to the site, said Dan Ellis, ClimateMaster president. The goal is to always have the loop in the ground before a slab is poured. Soil conditions in the area provide “good” drilling, Ellis said. Most lots contain shale and sandstone with some clay. All drilling is with air; no downhole hammers have been needed. Each loop requires about two hours to complete. Pipe extends from the ground and is capped until the GSHP unit is in place and the loop can be connected.
ClimateMaster developed an innovative design for systems being installed to lower installation costs.
Typically, Ellis said, a system for homes comparable to those in the addition would use two, 200-foot loops installed in the yard. Excavation would be required to connect the loops and to bring piping to connect them to the system.
“By installing one 400-foot loop at the location of the GSHP and incorporating the loop pumping and purging valves in the GSHP, we have eliminated excavation and reduced labor costs,” said Ellis.
When all 217 homes in Hope Crossing are occupied, Ellis estimates they will collectively save 1,100 metric tons of CO2 emissions per year: 22,000 metric tons over 20 years, compared to standard gas-heated homes of comparable floor space located in the same climate conditions.
In addition to energy savings realized from the geothermal systems, OG&E, provider of electricity for development, is contributing $2,000 per home to underwrite the cost of adding other energy-saving improvements such as a low-e element windows that help keep the home warm in winter and cool in the summer, expandable foam insulation applied to the underside of the roof that gives the entire house a tighter seal, and compact fluorescent lighting to reduce energy usage. All of these approaches will significantly reduce energy bills for Habitat families.
OG&E also assisted COHFH in obtaining a $4,000 Oklahoma State Energy Efficiency tax credit on each home after completion.
Time is right
Geothermal heating and cooling technology has been available for years, but the higher initial cost of an installed geothermal system compared to conventional air conditioning and heating systems and the relatively low cost of natural gas and electricity have been primary factors that have discouraged widespread use of geothermal systems.
However, in recent years that has changed. Rapidly rising energy costs make geothermal systems a serious option for property owners, and proponents of geothermal technology believe its time has arrived in North America. A 30 percent tax credit and incentives offered by many states encourage consideration of installing geothermal systems.
“Interest in geothermal heating and cooling is growing rapidly — everything we hear is upbeat,” says Jim Bose, Ph.D., P.E, executive director of the International Ground Source Heat Pump Association (IGSHPA). “Ground source heat pump systems finally are mainstream and are capturing a growing share of the market.”
ClimateMaster’s Dan Ellis believes Hope Crossing demonstrates the viability of using geothermal systems in the affordable housing market on a large-scale basis.
“It provides an example of how to transform the residential building sector,” he said. “We already see a shift in business models and construction projects in this area. We now have local builders emulating the exact energy-savings components that we deployed in the Habitat for Humanity project.”
Central Oklahoma Habitat’s Felton said the Hope Crossing development team was comprised of mostly private sector partners. Land was donated by Edmond real estate investor Stephen Hurst and his partners in TexOk Properties LP. Others helping develop roads and utility infrastructure included 7 Eleven stores of Oklahoma, Chesapeake Energy Corp., the Oklahoma Housing Trust Fund and the Samuel Roberts Noble Foundation, joined by the city of Oklahoma City (HUD/Home) and several private contributors.
Felton said Hope Crossing homes are built to standards of the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) program which provides strategies aimed at improving performance to build across all metrics that affect energy savings, including water efficiency, CO2 emission reduction, improved indoor environmental quality and stewardship of resources.