Geothermal Heat Exchange Ventilation

What is Geothermal Heat Exchange?

A Geothermal heat exchanger or Ground - Air Heat Exchange (GAHE) uses a network of pipes that are laid underground, typically at a depth of 1.5m to 2m and are designed to enhance the efficiency of a heat recovery ventilation system.

How it Works


The fresh air is drawn in through stainless steel tower (located in the garden) whilst the other end connects to the air intake of a heat recovery ventilation system.


The Rehau geothermal ducts use the energy stored in the ground. At a depth of 1.5 - 2 metres, the ground temperature varies between 5 and 12 ºC depending on the season and on the soil type.

By using the relatively stable temperature at this depth, the efficiency of the ventilation system is greatly improved and by drawing in air through an underground network of pipes, it provides a source of heating or cooling for a building.


As an example, if in the winter months the outside temperature is -5ºc, the ground temperature is +8ºC, the incoming air to the house from the earth ducts could be around +4ºC.


Conversely, in the summer where the outside temperature is 28ºc, whilst the ground temperature is +12ºC, the air into the house could be a more comfortable ±18 - 20ºC.

The benefits of a Rehau system


• Reduced heating costs by pre-warming the air in the winter.

• Pleasant cooling effect in the summer, reducing the need for air-conditioning.

• Improvement of the air quality in the building through duct and pollen filters.



• No build up of microbes inside the pipe system due to silver compound in pipe lining.

• Polypropylene material with improved heat conductivity for optimal heat transfer.

• Robustly manufactured earth ducts prevent sagging for reliable condensation removal.

The Importance of advance planning.

Rehau Geothermal Ducting is so much easier to accomodate if it is planned from the beginning of a building project. This means deciding on the position of the MVHR unit and arranging for access for the geothermal ducting. This may mean that a small section of the duct is cast into the foundations of a building to which the main run of ducting can be connected later.