Canadian wells, also called Provençal wells, are a passive technique for heating or cooling a dwelling.
How Canadian wells work
The principle is to circulate the outside air in pipes buried at a depth where the ground temperature is almost stable (at a depth of about 1.5 to 3 meters the temperature varies very little throughout the year – between 12 and 14ºC).
The outside air then cools or warms up on contact with the ground and enters the dwelling via ventilation. The pipes must be inclined at an angle of 1 to 3% from the horizontal over 30-50 meters.
Canadian wells are even more effective when the temperature differences between inside and outside are high.
Canadian wells and bidirectional controlled mechanical ventilation ?
There are different opinions on the combination of a Canadian well and a dual flow CMV. On the one hand, this combination can provide double protection against the cold, and is particularly effective in regions with large temperature variations. Indeed, the preheated air of the well will be heated again after its passage in the double flow ventilation. However, this system is complex to set up, can be expensive and is not interesting in hot regions. The Canadian well can cause malfunctions.
The air can be replaced by a mixture of water and glycol. It is cheaper than an air well, requires no maintenance and does not present any risk of condensate. On the other hand, glycol can pollute the soil in the event of a leak.
ADEME warns that a poorly designed installation can degrade the quality of the air entering the dwelling and cause the development of moulds linked to the phenomenon of condensation. It is also important to pay attention to the quality of the soil and whether or not radon is present.
The sizing and installation of a provençal well and the choice of ventilation are quite complex and therefore require the intervention of qualified experts.