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My project team is looking into geothermal heating and cooling. What are its benefits and drawbacks and is it applicable to both residential and commercial buildings?

Geothermal is a renewable energy source that the EPA calls the most energy-efficient, environmentally clean, and cost-effective space conditioning system available.

Penny Bonda -- Interior Design, 9/17/2007 12:00:00 AM

This is a big topic for a short column but I'll do my best to explain the basics. Geothermal is a renewable energy source that the EPA calls the most energy-efficient, environmentally clean, and cost-effective space conditioning system available. It works by collecting the earth's natural heat through a series of pipes buried in vertical wells or horizontal trenches and releasing it, during the winter, inside the building. In summer, the process is reversed. Excess heat is drawn from the building to the pipes and absorbed by the earth. This technology is sometimes called ground-source heat pumps (GSHP), as opposed to air-source heat pumps, because it relies on the constant temperature of the earth just a few feet below the surface. It also relies on a water-based refrigerant fluid circulating through the pipes to deliver or extract heat.

Geothermal can be used in any type of building and is becoming more common and popular because of its many advantages. GSHPs replace both the furnace and the air conditioner, are compact, quiet, efficient, durable and low-maintenance. Since no fossil fuels are combusted, emissions are greatly reduced. However, there are some downsides. GSHPs are not recommended for very cold climates and installing the system can cause site disturbance, especially the horizontal trenches. Initial costs are higher than conventional systems but the payback from lower utility bills begins immediately and continues forever.

There is so much more to know about this technology including the difference between open and closed loop systems and applicability to new construction, renovation and retrofits. The Geothermal Heat Pump Consortium is a great resource and includes specific market sector information, case studies and videos.