Geothermal Heating

Photo: N. Glenn Perrett
The pros and cons, costs and savings of tapping into geothermal energy for your home.

Last fall our family took the plunge. We had a ground-source heat pump (also known as geothermal heat pumps and earth energy systems) installed in our yard. Our main goal was to reduce our carbon footprint, but substantial rebates, long-term savings and a need to replace our oil furnace also influenced our decision. Although the initial cost was steep in comparison to purchasing a new gas or electric furnace, our big dig has been worth every penny. Here’s why—as well as a few things I learned along the way.

Sales of ground-source heat pumps have increased dramatically in recent years, but they have been around for decades. These systems use the earth as a direct source of energy, taking advantage of the fact that several feet below ground the earth has a fairly constant temperature. During the winter, ground temperature is warmer than the air, and during the summer it’s cooler than the air. As a result, heat can be transferred from the earth through “ground loops”—durable plastic pipes that contain a liquid—and channeled indoors. Once inside, the heat that has been captured by the ground loops is gathered in an air handler and distributed by an air delivery system (often the home’s existing duct system).

Not All Loop Systems Are Created Equal

There are several different systems that gather heat from the ground, and they vary in terms of efficiency, maintenance and their impact on the environment. Loop systems include open loops, pond/lake loops, vertical loops and horizontal loops. Vertical and horizontal loops are the most common. All of them feature a network of high-density polyethylene pipes filled with a water/anti-freeze solution (ours contained 75 percent water and 25 percent corn-based ethanol) that is connected to a heat pump air handler. Most heat pumps will both cool down and warm up a home.

•    Vertical loops are generally used when space is limited, such as in urban areas. Installation involves drilling deep holes into which geothermal pipes are then inserted. Since these loops are deep enough to enter groundwater, care must be taken to ensure that aquifers are not contaminated.

•    Carefully installed ground-source heat pumps that feature horizontal loops are very efficient, environmentally friendly heating and cooling systems.

•    Pond/lake loops, for which pipes are sunk to the bottom of a pond or lake, have the potential to damage fragile ecosystems including shorelines, shoreline buffers and the water body itself.

Environmental Benefits

Installing a ground-source heat pump, provided it is done correctly and in the appropriate situation, has many benefits. Obtaining energy from the earth and dispersing it using minimal electrical energy is an efficient use of a clean, renewable energy. It also significantly reduces energy consumption and cuts down on greenhouse gases and other pollutants created by the burning of fossil fuels—as well as with the processing and transporting of these fuels.

Those who don’t use, and store, fossil fuels eliminate the potentially devastating (and expensive) environmental problems created when oil (and propane) tanks leak.

Ground-source heat pumps also maintain a comfortable humidity level inside the home. And, because they don’t rely on outside air for combustion, they minimize the amount of outdoor pollutants and pollens circulating inside the home, which may benefit allergy-sufferers.

Economic Benefits

While the initial cost (often $25,000 or more) of installing a ground-source heat pump is substantial, you can recoup your costs fairly quickly. According to Mike Lawlor of Don’s Heating and Cooling in Orangeville, Ontario, who did our installation, ground-source heat pumps can save you 30 percent to 70 percent on utilities, and additional savings on domestic water heating costs—compared to conventional energy systems such as oil, gas and electricity.

In addition to saving on utilities, there are several rebates totaling thousands of dollars associated with installing a ground-source heat pump. Check with your installer. Qualified installers should be aware of whether there are national, provincial, local and manufacturer rebates available.