Passive Air-Conditioning

In most cases the artificial ventilation system of low energy houses is used for cooling during the night. In some cases this will not be sufficient to reduce overheating of the day during the night.

Soil heat exchanging devices can provide a solution. The tubes in the ground under or nearby the building help to cool the fresh air in summer and to pre-heat the room air in the winter.

For houses with high thermal resistance, a ventilation strategy with regard to future weather conditions helps to save energy. This strategy can be applied in cases of artificial or manual ventilation systems. Today it is possible to forecast weather conditions for 7 to 10 days. An adapted reduced or increased supply of fresh air during the following days would prevent overheating. By this the retention of inside thermal comfort can be prolonged during the next days or one week. The thermal resistance period is extended and heat waves of more than 2 or 3 weeks can be managed without artificial cooling and the connected energy effort.

This principle can be used in cases of some days with low temperature in the summer too. So the effort for heating in a short period can be avoided.

Using the data of weather forecasts automatically still has to be developed. By this the power of heating and cooling systems can be reduced. Using the higher thermal resistance of "Passive Houses" and synergetic advantages of an adequate ventilation system and a foreseeing controlling system also offers economic advantages.

Tubes in the ground for passive air-conditioning (City of Dresden)