For naturally ventilated spaces, windows, doors and vents are often the means for providing outside air.
In colder weather, stronger winds and cooler outdoor temperatures increase airflow. Therefore, windows, doors and vents do not need to be opened as wide.
Opening vents can enable more mixing of the outside air with warmer air in the indoor space. This allows colder outside air to be introduced to the space without greatly reducing thermal comfort.
Practical steps to improve natural ventilation
To increase natural ventilation, you may wish to consider:
- opening windows, doors and vents that don’t need to remain closed for other purposes (for example, internal fire doors should be kept closed)
- where there are both high level and low level windows in a room then it is recommended to open the high level windows during cooler weather in the first instance, as incoming air will be warmed as it flows down into the room thereby reducing cold draughts. This also improves mixing of the outside air with air in the room before reaching the occupied zone
- to maximise airflow during warmer weather when draughts are not a concern, both high and low windows can be opened. This not only increases the opening area but creates a more efficient flow, thereby reducing the risk of transmission
- use indoor fans in combination with open doors and/or windows to further increase air circulation
- in addition to specialised window fans, box fans or tower fans can be placed in front of a window. Fans can face toward the window (blowing air out of the window) or away from the window (blowing air into the room) Note: if a single fan is used, it should be facing (and blowing air) in the same direction the air is naturally moving
- using multiple fans, for additional ventilation, to push air out of one window and draw it in from another
- don’t position fans so that they may blow aerosols from one person’s breath directly towards another person
- where practical, spaces where there is potential for long duration exposure over several hours within the same group (e.g. offices, schools) would benefit from allowing occupants to have regular breaks, ideally with time to air the room, to reduce the potential for viral exposure. This may mean alterations to the pattern of use of space
Any actions taken must also comply with broader health, safety and welfare regulations, including the legal requirement to maintain reasonable temperature in the workplace, which in most cases would take priority over the ventilation requirements.
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