High efficiency retrofit in historic buildings by demand-controlled ventilation

Effective conservation of historic buildings subject to monumental restrictions is realized through a re-use for modern functions. In fact an attended and therefore ventilated and climatized building can be maintained in thermo-hygrometric conditions suitable controlled in order to avoid the occurrence of mold. Often only the use can justify a timely and adequate maintenance. Although the sustainability of the requalification requires acceptable management costs and therefore a limitation of the energy consumptions which must be comparable with those today prescribed for new buildings. But the monumental restrictions normally prevent interventions on building envelope. Even more than in modern buildings, it is therefore necessary to focus the efforts on plant efficiency by introducing innovative solutions. 
For this goal, significant ventilation rates and high variability in the attendance suggest the realization of central plants necessary for a demand-controlled ventilation and efficient heat recovery even if their design in a monumental building can be very difficult and challenging. 
In this paper are described two plants, now under construction, realized in the mainframe of the retrofit of two historic buildings in Venice. For both cases a preliminary analysis by building-plant system simulation is illustrated which was carried on to optimize the design and to assess the energy performances. The results highlight the possibility to achieve strong energy savings without compromise the monumental conservation.