Ventilation How can you create a healthy indoor environment?

In order for the indoor climate in your living spaces to be satisfactory, rooms must be able to breathe. Modern windows are very tightly sealed to ensure excellent thermal insulation of the rooms. In order for the indoor air quality to be good despite this, a proper ventilation concept is needed. Windows also need effective ventilation systems.

How does damp develop in living spaces?

Damp in living spaces arises due to different factors. Besides the damp in new buildings introduced by building materials such as screed, plaster or mortar, other sources arise through use of the dwelling:

  • Water vapour from cooking and hygiene
  • Moisture given off by residents
  • Water for cleaning and watering plants
  • Condensation on component surfaces

The German Federal Statistical Office classifies moisture loads in dwellings according to different household types:

Household type No children 1 child 2 children More than 2 children
Moisture load per day 8 litres 12 litres 14 litres 15 litres

The relative humidity in bedrooms goes up at night, with each person giving off between 1 and 3 litres of water vapour overnight!

Relationship between dew point and critical temperature for mould growth

What’s the correct way to ventilate?

Regular and effective ventilation is important for avoiding excessively high humidity levels and hence mould growth or damage to the building fabric indoors. Mould can cause health problems. Air infiltration through joints and cracks is largely eliminated by the very tight structural designs mostly employed today. Continuous ventilation can be achieved through various systems and aids on the window, but this brings with it a continuous heat loss. Thus, manual purge ventilation and ventilation systems have proven to be good energy-saving ventilation alternatives. For intermittent ventilation, three to five times a day the windows are opened completely for a brief period so air can rapidly pass through. Cross-ventilation in which windows across from each other are opened completely for five to ten minutes is particularly effective. The heating is shut off during this time to avoid unnecessary heat loss.

Tip: To enable precise determination of how long ventilation should take place, a hygrometer that indicates when the optimal humidity in the room has been reached is recommended.

How do WERU windows ensure a good indoor climate?

Regular ventilation isn’t always possible. Despite this, healthy indoor air and a comfortable humidity level are still possible through the optional fitting of WERU windows with effective ventilation aids that support the important exchange of air:

  • Gap vents (night vents) are integrated into the hardware to enable partial ventilation.
  • For intermittent ventilation, slam stops and turn limiters can be installed to prevent the windows being slammed shut by air currents.
  • Various versions of in-window ventilation systems ensure regular exchange of air. Acoustic insulation elements and pollen filters can be optionally installed. Continuous ventilation systems provide basic ventilation.
  • With the Safe & Go system, burglary protection is even provided when the window is open for ventilation, and just as well as if the window were closed.
  • The Aeromat midi HY ventilation system provides demand-controlled ventilation based on the relative humidity.

Which ventilation concept is right for your use characteristics and your windows can be determined in a detailed consultation with the WERU experts, who will also recommend the ideal ventilation elements for a good indoor climate!

What can I do to prevent fogged-up windows?

In the cold season, when the relatively humidity is high and inside window surfaces are cold, bedroom windows often get fogged up, particularly in the mornings. Especially when highly insulating windows are installed in the house, this can be disappointing for the builder. This phenomenon cannot be completely avoided, but the manufacturers take it into account and design modern windows to ensure that condensation cannot do any damage. According to Section 6.1 of DIN 4108-2:2013-02:

‘Condensation is permitted temporarily and in small quantities on windows and mullion-and-transom facades if the surface does not absorb moisture and appropriate precautions are taken to avoid contact with adjacent sensitive materials.’

For the residents of the house, condensation on the window is an important signal: Ventilation is now needed to lower the humidity to a healthy level.

Gap vents

This hardware component provides for partial ventilation. Arresting the sash with the preset gap of 5 mm stops the window from slamming shut.

  • Single Option
Regel-Air

The Regel-Air ventilation system is a self-regulating system that is installed in the upper section of the window and can be retro-fitted if required. Fresh air supplied from the outside flows laterally over the narrowing seal in the window rebate. In normal operation the preheated air then rises preheated between the sash and the frame through the ventilator below the ceiling into the room. In stormy weather or strong winds the system automatically stays closed, thereby preventing draughts. The Regel-Air has a flow rate of 2.1 m3/h at 4 Pa. Additional benefit of the window rebate ventilator: It shuts out noise, the device can achieve high acoustic insulation values up to acoustic protection class 4 (= 42 dB).

  • Single Option
Safe&Go ventilation

Windows used to be tilted or opened all the way to air out a room. With the innovative Safe&Go ventilation system the top of the sash can be positioned 10 mm from the window frame. What’s special about this is that the window is locked on all sides when in the ventilation position. A basic level of ventilation is provided, but with the burglary deterrence of a closed window. Thus you can safely air out the room and do your errands at the same time. 

Contained in:
  • Comfort++
  • Single Option
Aeromat midi HY
  • passive demand-controlled window ventilator for ventilation of closed rooms
  • functions by pressure equalisation between outside and inside air (pressure differential principle)
  • the regulation of air intake is based on the relative humidity
  • via a three-stage controller you can select between continuous ventilation, humidity control and minimal ventilation
Contained in:
  • Comfort+++
  • Single Option
Weru-Air Comfort

Provides for fresh air in any weather. Air supplied from the outside flows upwards via recessed seals in the rebate and enters the room pre-heated via the special seal. In strong winds the seal pushes against the opening gap to restrict the amount of air flowing in. So even in this situation, basic ventilation is guaranteed and draught effects are avoided. With a fully open seal the system achieves a volume flow of 2.9–3.2 m3/h at 4 Pa. Even when the window is open the ventilation system is not visible either from the outside or from the inside. Weru-Air Comfort achieves high acoustic insulation values up to acoustic protection class 4.

Contained in:
  • Comfort+
  • Single Option
Slam stop

Prevents window sash slamming shut from gusts of wind by securing the sash in place and enables variable window opening control.

Contained in:
  • Comfort+
  • Single Option