Model Geothermal Installation Supports Habitat For Humanity Development

By Jeff Griffin, Senior Editor | June 2010 Vol. 65 No. 6
Vertical drilling to install the geothermal closed loop pipe. HDD and trenching are also sometimes used.

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.

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