A few feet beneath the surface, the earth's temperature remains fairly constant -ranging from 7º or so in Canada's northern latitudes to about 20ºC in the US deep south -year round. Geoexchange takes advantage of this constant temperature to provide extremely efficient heating and cooling.

In winter, a water solution circulating through pipes buried in the ground absorbs heat from the earth and carries it into the home. The Geoexchange system inside the home uses a heat pump to concentrate the earth's thermal energy and then to transfer it to air circulated through standard ductwork to fill the interior space with warmth.

In the summer, the process is reversed: heat is extracted from the air in the house and transferred through the heat pump to the ground loop piping. The water solution in the ground loop then carries the excess heat back to the earth. The only external energy needed for Geoexchange is the small amount of electricity needed to operate the ground loop pump and fan.  It is more efficient and environmentally superior to 'transfer' heat than to 'create' it through combustion.

In recent years, though, many improvements have been made in the materials used, the installation methods, and the efficiencies of the compressors, pumps and other equipment.

Since a geoexchange system burns no fossil fuel to produce heat, it generates far fewer greenhouse gas emissions than a conventional furnace, and completely eliminates a potential source of poisonous carbon monoxide within the home. Even factoring in its share of the emissions from the power plant that produces electricity to operate the geoexchange system, total emissions are far lower than for conventional systems.

That would be the equivalent of converting about 58,700 cars to zero-emission vehicles, or planting more than 120,000 acres of trees.

And the waste heat removed from the home's interior during the cooling season can be used to provide virtually free hot water-resulting in a additional savings in hot water costs of about 30% annually, and lowering emissions even further.

For example, worth particular note is the pioneering effort of Enwave District Energy Limited in bringing the geoexchange principle to the downtown Toronto core via a partnership with NRCan.  From Queen's park to the waterfront, the Toronto Hydro subsidiary will cool 50 million square feet of office space by using the deep water of Lake Ontario, starting in 2003.

Particular advantages come to building heating systems which can generate scale, such as district systems (like Toronto, a utility or a developer could respond to customer demand and install geoexchange for an entire suburban neighbourhood street or a large apartment building) or common institutions.  In the United States schools have been a particularly popular place for the use of this technology. Across the continent, schools using geoexchange right now are saving an estimated C$45,000,000 in energy costs-which can be used instead for better educational equipment and more teachers. These schools also save all of us half-billion pounds of CO2 emissions per year.

If we make the same comparison across all commercial and residential segments in Canada, the potential for environmental benefit is staggering.

Moreover, installation costs have declined substantially in recent years, and they're expected to continue to fall, as more builders and contractors offer geoexchange systems, and as the industry develops innovative ways to install the systems faster and more efficiently.

Altogether, geoexchange systems are a very sound investment. The amount they save the homeowner every month in energy costs is more than enough to offset their higher installation cost.

 Remembering that geoexchange also means extra savings on repair, maintenance, and hot water bills, the energy efficiency of geoexchange adds value to your building whether home, apartment building, condo, skyscraper, or sports stadium.