Energy saving opportunities by suitable HVAC management: the Procuratie case in Venice

The thermo-hygrometric treatment related to the air change in buildings requires a relevant quota of the total energy demand for heating and air conditioning, especially when the ventilation exigency is significant. For this reason a correct energy saving strategy should always focus on the use of suitable techniques in order to reduce this consumption. For example, as the modern comfort science teaches, more flexible values can be accepted for the internal humidity set point without compromising indoor comfort conditions. But demand-controlled ventilation is the fundamental opportunity to reduce energy requirements in presence of high ventilation flow rates. An evaluation of the possible amount of the energy savings following this more flexible control strategy is here presented in a real application case. This refers to two historic buildings in Venice, the Procuratie 5 and 6 near S. Basilio harbour just transformed in modern university facilities and characterized by considerable design occupancy. As frequent in university buildings, the effective crowding has high peaks, but also an appreciable variability during the activity period. In addition to a smart humidity control, in these buildings it is therefore foreseen the presence of a variable ventilation rate on the basis of the real exigency measured by CO2 sensors installed in the return air ducts in the classrooms and a central system based on fans equipped with inverter. In this way the strong ventilation flow rate can be controlled in each air treatment unit (from one to four units in each classroom). The central supervision system is able to perform an independent control of the air change and of the thermo-hygrometric conditions for each internal unit. An user friendly interface permits an easy intervention of the building manager on the set point values of each unit. Starting from the data of monitoring enabled by the existing supervisory system an investigation about the contribution of demand-controlled ventilation to the energy requalification of one of these two buildings is here presented. The analysis of the performance of ventilation system has pointed out the possibility of remarkable energy savings.