Earth Tube

Earth tube or a ground-coupled heat exchanger is a way of pre-heating or cooling air that is being brought into the house. Essentially, the idea is to place the air intake a fair distance from the furnace and instead of bringing the air directly into the furnace it is passed though metal or plastic pipes underground. By dragging the air over a longer distance prior to introducing it into the house, we can take advantage of the subterranean temperatures to pre-warm or cool the air.

• If it is winter and the outdoor air temperature is -40 degrees celsius, the ground temperature will be approximately 5-7 degrees celsius. Thus considerably pre-heating the air prior to it reaching the furnace, ultimately saving energy. This system can be used in conjunction with the more conventional air to air heat exchanges see more commonly today, it just adds to the efficiency of the overall system.
• If it is summer and the outdoor air temperature is 30 degrees celsius, the ground temperature will again be very close to 5-7 degrees celsius and will significantly cool the air prior to it being introduce into the house.

Since this system requires no compressors, chemicals, or burners and essentially maintenance free after installation, it it a pretty economical way of saving energy. The only real mechanical component is the fan that would be running to feed the furnace anyway, and this system just asks it to pull it’s intake air from a little further away. These systems while not widely used in North America have become more commonplace in Europe since the mid 1990’s.