Heat Recovery Ventilation - Earth-to-air Heat Exchanger

Earth-to-air Heat Exchanger

This can be done by an earth warming pipe ("ground-coupled heat exchanger"), usually about 30 m to 40 m long and 20 cm in diameter, typically buried about 1.5 m below ground level. In Germany and Austria this is a common configuration for earth to air heat exchangers.

In high humidity areas where internal condensation could lead to fungal / mould growth in the tube leading to contamination of the air, several measures exist to prevent this.

• Ensuring the tube drains of water.
• Regular cleaning
• Tubes with an imbedded bactericide coating such as silver ions (non-toxic for humans)
• Air filters F7 / EU7 (>0,4 micrometres) to traps mould (of a size between 2 & 20 micrometres).
• UV air purification
• Use a earth to "water" heat exchanger, see below.

The pipes may be either corrugated/slotted to enhance heat transfer and provide condensate drainage or smooth/solid to prevent gas/liquid transfer.