night and day ventilation Specification Validation Conclusion

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Dutch Press


Modern balanced ventilation systems use centrally controlled heat exchangers. These need extensive air ducts placed in lowered ceilings which can claim 15% building volume.
A new ventilation solution can dramatically reduce this building space and allows rooms to be ventilated more effectively.

Prof. ir. Jon Kristinsson, architect and retired professor at the Delft University of Technology has developed a smart decentralised ventilation system named BREATHING WINDOW (BW) which can be installed next to windows or in the skin of buildings. In contrast to traditional centrally controlled ventilation systems each room is individually monitored. CO2- and humidity sensors check the air and activate the device when concetration levels surpass 500 parts per million (ppm).

Two fans in the top part of the BW result in opposite air streams: polluted air is blown out and fresh air streams in. The separated air streams are guided down through a heat exchanger and discharged in bottom part. Air from inside the building of 20 degrees Celcius can thus heat incoming air from 0 to 19 degrees Celcius. Capacity of one BREATHING WINDOW is 50m3 per hour: enough for 2 people.

The fine wire heat exchanger has been developed in the Netherlands by dr. ir. Noor van Andel and consists of 28 layers of in total 15 kilometers 0.1 mm thin copper wire (see picture detail on the left).

The system can be used in all world climats. In cold regions it will heat cool air, in warm areas it will cool hot air. Huge advantage is that no air ducts are needed. BREATHIN WINDOWS can easily be combined with existing kitchen or bathroom ventilation systems.
Heat regain is very high (up to 95%) thanks to four temperature sensors and a smart microprocessor which balances the temperature by altering the speed and direction of the fans independently. The combination of the electronic control and the fine-wire heat exhanger makes it a lot more effective than traditional ventilation systems.

The BREATHING WINDOW is financed by Kristinsson-Reitsema BV (using the Royal/Shell Award 1998) and was sponsored by Senter (BSE program) of the Dutch Ministry of Economic Affairs.
The makers are currently negociating to get the BW installed in new buildings.

For more information


new healthy ventilation

  • no airshafts
  • fine-wire heat exchanger
  • balanced ventilation
  • 95% performance
  • compact size
  • intelligent multifunctional control
  • functions with open window
  • little or no icing sublimation
  • capacity output from 35 to 50 m3/hour
  • new building technology
  • building-cost reduction