In Innsbruck, at the Neue Mittelschule Hötting - a historic building and 3ENCULT pilot project - a new minimally invasive ventilation system for school buildings is being tested. The dual aim of this system is to preserve the architectural value of the building while guaranteeing scholars´ comfort.

When ventilation systems are integrated into historic buildings this requires minimal invasiveness (structurally) with maximum reversibility. For this purpose the principle of "active overflow", which is already used in refurbished dwellings, is an optimal energy efficient solution that can also be applied to school buildings. The idea is simple: fresh air is vented into the corridor and stair case, with fans actively pushing the air from the corridor into the classrooms. Typically to optimize this approach, the ventilation system is linked to heat recovery and therefore needs ducts for air inlet and - exhaust to and from the rooms. Silencers are also needed to prevent noise.

Two 3ENCULT partners, the University of Innsbruck together with the company ATREA, are testing the first prototypes of active overflow elements with vans and silencers in one class room of the Hötting school. The prototypes aim for the obvious advantage - to avoid the need for ducts in the corridor or for the installation of a vertical shaft to provide fresh air.

The heat recovery system is instead placed on the roof and the fresh air is distributed via the open staircase and corridors through vertical ducts. Driven by a fan through a silencer the air is then distributed through textile ducts. The flow rate of the central unit is controlled by CO2-sensor in the corridor and the fans in the classrooms are switched on according to a schedule one hour before the start of lessons. Motion control sensors switch off the fans after a delay of 15 minutes.

With a special focus on cultural heritage, this minimally invasive strategy is a big advantage to combine together preservation aspects and user comfort at the same time.