Investigating on electric consumptions for residential buildings ventilation in different Italian climates

Design strategies, policies and energy certification protocols often suggest (or prescribe), in an undifferentiated way, to provide mechanical ventilation with heat recovery systems in order to improve energy performance in residential buildings. However, the electric fans mounted on these systems consume energy and the benefits due to heat recovery, under some boundary conditions, may not be so effective to make this strategy convenient, resulting in a waste of electric energy. In this paper, a small sample housing unit provided with an autonomous ventilation system with heat recovery was simulated in different Italian climates. Then, for different airflow rates, the power absorbed by the fans and the actual heat recovery efficiency were properly evaluated, taking into account temperature differences occurring on an hourly-based simulation. Finally, overall yearly energy balances for the mechanical ventilation system under different boundary conditions were calculated and compared to the one resulting by assuming natural ventilation, while assessing energy and environmental performances.