Numerical Evaluation of Earth to Air Heat Exchangers and Heat Recovery Ventilation Systems

In France there is an increasing demand for energy efficient and environmentally friendly buildings of high thermal comfort. Balanced ventilation systems with heat recovery on the exhaust air and earth to air heat exchangers (EAHEX) are interesting techniques which can reduce the heating and cooling demand of buildings, and improve internal thermal comfort. A numerical study was carried out to evaluate the impact of these two systems on the energy performance and internal thermal comfort of a dwelling, with respect to the French climate characteristics. The impact on CO2 emission was also analyzed. The results showed that a balanced ventilation system with heat recovery is a better preheating technique than the earth to air heat exchanger. The additional heating gain obtained from coupling an earth to air heat exchanger to a balanced ventilation system is rather marginal. However, earth to air heat exchangers present a significant potential for cooling. Regarded in this way, winter preheating becomes an additional free service, which can be coupled to other preheating techniques.