Geothermics: Right under your feet
Geothermics not only offers the advantage of using an inexhaustible source of energy – the sun – but it doesn't burn fossil fuel and therefore doesn't produce greenhouse gases. The results speak for themselves: On the one hand, users can expect to save 60 to 70 percent on heating costs; on the other, the average size household can cut its carbon dioxide emissions by 2.5 to 5 tonnes per year, according to Natural Resources Canada.
An intelligent technology
Did you know that almost half of the sun's geothermal energy is captured and stored in the ground and in water? At a depth of approximately two metres, ground temperature is constant during winter and summer, varying between 5°C and 12°C, depending on the geographic location of your home. A geothermal system makes it possible to extract and harness a part of this energy, and it produces a more uniform heat than oil or electricity. However, if your home is poorly insulated to begin with, a geothermal heating system will not necessarily make it more comfortable.
Geothermal systems can be installed in new and old homes alike. The process involves the installation of underground pipes outside the house and a geothermal heat pump inside the house.
Two types of geothermal systems are currently offered: open-loop and closed-loop. The open-loop system uses energy stored in a lake or wellbore, a method seldom used owing to tougher policies on the protection of waterways. The closed-loop system taps into the energy stored in the ground. In both cases, the heat pump circulates a liquid through a series of pipes buried beneath the ground or water. As its name suggests, the heat transfer fluid carries the heat to the heat pump, which compresses it before pushing it through the home-ventilation conduits. Thanks to its coils, the geothermal system can also be used in homes heated with hot water. It works the same way for air conditioning but in the reverse direction: Hot air drawn from the home is sent back into the ground, and cool air is pumped into the conduits.
While a geothermal system will meet almost all of your home-heating needs, it is still equipped with a backup electrical system in the event that the heat pump breaks down or for especially cold days. And it has the added advantage that it can be attached to a “desuperheater,” which uses a part of the heat recovered by the heat pump to preheat the water used in the home.
To install the piping system, consumers can choose between drilling vertically or horizontally into the ground around the house. In the first case, the borehole will reach 30 to 122 metres (100 to 400 feet) in depth, depending on the amount of energy the home requires. This method uses a minimum amount of space but is more expensive than drilling horizontally – which requires that the pipes be installed only two to three metres below the ground. The two methods are equally effective, and the final choice will depend on the size of the property (a minimum of 3,700 square metres – 40,000 square feet – is needed for horizontal drilling) and the type of soil (such as sandy or peaty).
Save money at what cost?
According to the experts, the installation cost is the only reason geothermal systems are not already widely used. For a home measuring 139 to 186 square metres (1,500 to 2,000 feet), this system (warm-air heating and air conditioning) costs between $18,000 and $25,000, or roughly $7,000 to $10,000 more than a traditional central-heating system.
That said, a geothermal system presents a huge advantage in that the investment can be recovered in five to 10 years. And you will continue to save several hundred dollars a year long after it has finished paying for itself. There are financial-assistance programs for homeowners intent on installing a geothermal system. Natural
Resources Canada offers a maximum grant of $3,500, provided that the installation is carried out by an accredited contractor.
Qualified contractor an absolute must
Up to now, mandatory training and certification have not been required to install geothermal systems. However, effective January 1, 2008, all installations must be certified by the Canadian GeoExchange Coalition – all the more reason to choose a certified contractor, particularly if you intend to apply for a grant. This way, you can be sure that the contractor – like the drill operator – holds a valid licence and has the proper liability insurance and the experience necessary. An experienced contractor must know, for example, how to precisely calculate the number of metres that must be drilled for home heating and air conditioning, while taking into account the quality of the home's insulation.
The Canadian GeoExchange Coalition offers training in geothermics; you can contact the coalition for the names of contractors who have taken the training course. Initially reserved for installers and drill operators, the course is now available to designers of residential and commercial systems.
Natural Resources Canada advises people to contact at least three certified contractors for a written estimate of the work to be done. Once you choose a contractor, the contract you sign with him should include: an analysis of the job; the work to be done at each stage; a list of the equipment required; the cost of materials and labour; and a payment schedule. And don't forget to read the contractor's warranty. In general, contractors offer a one-year warranty on parts and labour, while the manufacturer's warranty may vary between five and 10 years for labour and the heat pump, which has a lifespan of roughly 20 years. As for the pipes, they are often guaranteed for 25 years or more.
Canadian GeoExchange Coalition
Natural Resources Canada publishes Residential Earth Energy Systems: A Buyer's Guide. To order a free copy, call 1-800-387-2000