Smart use of mechanical ventilation for energy retrofit of residential dwellings

Residential buildings of Italy built during the last century usually show very poor energy performance. The only retrofit action widely implemented on their envelope is substitution of windows. These are very seldom coupled with mechanical ventilation, however, so their high air tightness induces serious problems of moisture condensation and mold formation-unless they are left open and their usefulness nullified. In this work, a smart combination is simulated of single flow mechanical ventilation, in itself essential to control indoor air quality and ventilation heat loss, with a relatively inexpensive sunspace built on an existing balcony, aimed to behave as a preheating chamber of the inlet cold air in winter. Moreover, mechanical ventilation is combined with an electric heat pump for hot water production, in which the outlet air flow of warm exhaust air is introduced to improve the coefficient of performance of the heat pump in the cold seasons. Energy savings allowed by such smart yet simple combination of existing technologies are discussed.