The use of air handling units in residential near zero-energy buildings

The present work focuses on the advantages of using air-handling units in residential buildings characterized by high thermal insulation level. This type of buildings is the so-called "nearly zero energy buildings" because of low energy consumption for heating and cooling. Differently to what usually happened in the past, where the main costs of the air conditioning were related the heating purpose, today the main problem in mild climate condition is the cooling of the building, due to the high thermal resistance of the structures which does not allow the exchange of heat with the external ambient in summer especially during the night. The nowadays mechanical ventilation systems, however are equipped with a bypass of the heat recovery unit; this solution anyway does not seem adequate to be used for free-cooling operation. On the other hand, the use of radiant panels emission systems, very diffused in the last years, make difficult to follow the thermal load mainly due to solar and internal gains, especially when they are extremely variable during the day. The results of the work show the possibility of reducing the energy demand of the building, and consequently the CO2 emissions, by the use of air handling units as air conditioning systems in residential buildings.