Peter Holzer
Bibliographic info:
33rd AIVC Conference " Optimising Ventilative Cooling and Airtightness for [Nearly] Zero-Energy Buildings, IAQ and Comfort", Copenhagen, Denmark, 10-11 October 2012

The paper in hand investigates the potentials and limitations of ventilative cooling strategies in the moderate Central Europe climate region of Vienna, Austria, offering a a basic load break down of the thermodynamic night ventilation sub-processes plus an overview over frewuent practical limtations and finally a recent monitoring result from a single family model home.

Even in urban areas within the moderate continental climate of Austria, night flush ventilation may contribute a daily cooling potential of 70 Wh per square meter of thermally active wall-, ceiling and floor area, resulting realistically in possible cooling contributions up to 150 Wh per square meter of treated floor area, leading to mean cooling loads during exemplary five hours of the day up to 30 W per square meter of treated floor area, what clearly improves the summerly thermal building performance significantly.

Ventilative cooling has a number of very tempting strengths, being

  • highly efficient
  • immensively long lasting and robust
  • supportive of flexibility
  • supportive of climate sensitive archchitectural design
  • supportive of adaptive comfort concepts with rich and healthy thermal sensations

The bottleneck in the system of Night Flush Ventilation is the need for a high air change rate during the night hours, which has to be pushed up to 10 air changes per hour, if the physical potential is to be made full use of.

Besides, a number of constructive and operational limitations occur, which, if overseen to face, spoil the possible contributions of ventilative cooling. Those are burglary, wind and rain, intimacy, noise, insects, usability and finally, if automated, the energy demand for vents and controls. Facing these operational limitations there’s still a significant demand for technical development.