Blowing hot and cold is the answer

THE principles of geothermal heating are widely understood. Essentially you collect heat from the ground and use this free energy to provide or boost central heating.

At a depth of around two metres, the temperature of the earth is fairly stable at approximately 12-14C all year round, and certainly much warmer than the ambient temperature in winter.

Traditional geothermal systems boost this free heat to much higher temperatures so that it can be used for central heating: it’s the same principle as a fridge operating in reverse. However, geothermal systems are quite expensive to install and have a limited lifespan; they are, after all, motors and compressors with many working parts that can wear out over time.

That said, we can capture and use this free energy without incurring the significant expense of a full blown geothermal heating system by means of a Canadian or Provençal well.

Essentially these "wells" are simply pipes buried in the ground (to around two metres) through which air is drawn from the outside and blown into the house.

In winter, the soil at this depth is much warmer than the outside temperature and therefore the cold air is preheated as it passes through these pipes. This is the Canadian well; in summer, the relative coolness of the ground can be used to lower the temperature in the home, hence the Provençal well.

To make this work, a very small, lowpower ventilation pump, such as those used for extractor fans, is needed.

However, most new-build properties will have a VMC simple flux or double flux installed: these are simple ventilation units that pump fresh air around the property through pipework typically installed in the ceiling void.

In the case of the VMC double flux, this incorporates a heat exchanger, which captures any warm air before it leaves the building during winter. These VMC units already have a pump and pipework, so if we feed this VMC unit via our
Canadian /Provençal well, we have an all-round heating, cooling and ventilation system at a relatively low cost.

This system will not heat your house to comfort levels. However, you can give the central heating system a lot of help, cool your house and reduce your lifetime bills significantly, so for any new builds and many renovations, this really is a "must do".