Theoretical and practical evaluation of an earth-tube (E-tube) ventilation system

The concept of using earth-tube ventilation system as an energy saving technology has been theoretically and practically evaluated. The results have shown that the system has the potential to become an effective energy saving technology in buildings. For instance in March and July 2010 the E-tube system was able to contribute 62% and 86% of the peak heating and cooling loads respectively and also achieved corresponding COPs of 3.2 and 3.53. The average relative humidity level in the heating period was reduced by 10% whereas in summer the average humidity level increased by 15% and was attributed to high level of latent heat exchanges within the earth-tube. Even though the overall performance of the system was found to be encouraging for a typical hot and humid location there are certain conditions of soil such as wet, freezing and dry soils which could affect its thermal effectiveness. Further investigation into the impact of these factors on E-tube ventilation systems is therefore recommended.