Natural ventilation through building automation in retrofitted office buildings in Italy: a case study about implementation, optimization and thermal comfort assessment

Extended abstract 8-277-26

We present a case study on the implementation and evaluation of natural ventilation (NV) strategies, particularly nocturnal ventilative cooling, in the retrofit of an office building. The retrofit introduced several integrated interventions aimed at improving summer comfort and operational resilience. Existing windows were motorized and connected to the building management system (BMS), enabling automated NV operation. High-volume-low-speed ceiling fans were installed and integrated into the same control infrastructure to enhance indoor air movement and extend the comfort conditions range under the ASHRAE 55 adaptive comfort model. Additional measures included thermal insulation, temporary external solar shading, and the installation of a green wall to shade the highly glazed west-facing façade.

Initially, the operation relied heavily on an hour-by-hour operation by our research group with feedback from occupants. Subsequently, a control algorithm was developed incorporating indoor and outdoor temperature, wind conditions, and solar radiation, to coordinate windows opening and fans operation. The implementation phase addressed and resolved significant interoperability limitations between technologies integrated into current BMS environments, showing the need for broader adoption of universal communication standards. Acoustic concerns, security constraints, and occupant preference for conventional air conditioning also emerged as major barriers to NV adoption. However, occupant acceptance progressively shifted toward increased use of NV and ceiling fans over time.

The research further developed an advanced monitoring methodology including measurements of air temperature, surface temperature, heat flux, mean radiant temperature, globe temperature, air speed and 3D air velocity, and CO₂ concentration. We studied the interaction between ceiling fans and NV, as well as the role of nocturnal ventilative cooling. Results indicate that approximately 90% of the floor area remained within adaptive comfort limits for 98% of occupied hours, without the use of AC. In the remaining 10%, essentially the parts exposed to direct solar radiation due to lack of external shading, night ventilation was insufficient to remove the excess solar gains and those areas were frequently out of comfort. Findings also demonstrate that, within the relatively low-wind summer climate of Milan, buoyancy-driven ventilation can play a dominant role when supported by favorable building morphology and controlled air movement strategies.

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