Objectives and challenges

Manual window ventilation and comfortable indoor ventilation compared

For the case study, the four flats were equipped with a sophisticated sensor system and continuously monitored. A comparison of numerous measurement data on indoor air quality and energy consumption clearly shows the advantages of comfortable indoor ventilation.

Building units

  • A total of 4 flats
  • including 2 with balanced ventilation,
  • 2 with window ventilation,
  • 2 with 80 m2 
  • and 2 with 110 m2 

Building type

Timber construction apartment blocks

Research project (participating companies)

  • Zehnder Group Switzerland AG
  • az Holz AG, a provider of integrated planning and timber construction services,
  • Swiss timber construction specialist Lignotrend GmbH
  •  Bern University of Applied Sciences for Timber Construction
Zehnder products
  • Two Zehnder ComfoAir Q350 ERV
  • One Zehnder ComfoHeat 25 kW brine-to-water heat pump
  • One Zehnder hot water storage tank

Heat pump and comfortable indoor ventilation for the optimal indoor climate

The ventilation units were installed in the plant room in the basement, together with the Zehnder ComfoHeat 25 kW geothermal probe heat pump and the Zehnder hot water storage tank. The heat output in the flats is provided by underfloor heating. In summer, the underfloor system can also be used for cooling.

Zehnder ComfoAir Q Lüftungsgeräten
Plant room in the basement with two Zehnder ComfoAir Q ventilation units
Modern apartment
Modern apartment block with Zehnder comfortable indoor ventilation

Odours and pollutants are also removed much more effectively than with manual window ventilation. Even if residents were disciplined in the way they ventilate through their windows, it would not be possible to achieve the same air quality as with comfortable indoor ventilation.

Kitchen with comfort ventilation
The comfortable indoor ventilation removes odours and pollutants

Research project: manual window ventilation and comfortable indoor ventilation compared

The measurements in the 4 flats provide a wealth of data on indoor air quality, outdoor conditions, and energy consumption for heating and cooling. To summarise, it can be concluded that professionally designed comfortable indoor ventilation makes a significant contribution to pollutant-free indoor air and a healthy indoor climate in living spaces. CO2 limit values are not exceeded or are significantly reduced when operating comfortable indoor ventilation.

Zehnder ComfoAir Q Lüftungsgeräte
Zehnder ComfoAir Q ventilation units in the plant room
Healthy indoor air in the living area, even with closed windows
Healthy indoor air in the living area, even with closed windows