People can feel cool when their skin feel air movement which enhances moisture (sweat) evaporation ( Evaporative Cooling Effect). The more exposed skin feels air movement the more cool one feels.
A breeze that comes and goes at a certain slow rate is felt more cooling than a constant breeze of same velocity.
An exhaust system (passive cooling) that sucks air out can give a lot of air changes but if it is not able to create air movement felt by people, they will not feel cooled. Also the exhaust system’s air will find short routes to the fan bypassing people.
For an exhaust system to provide air movement to people in this way it has to be very powerful and energy hungry since the “inlet” is so large.
A Spacefan, on the other hand, proves “active cooling” by directing airflow to people who can feel the air movement.
Hot air rises to the ceiling. Insulated ceiling helps to reduce heat conduction.
Let’s say initially the fan is not running. Hot air stays up. When the fan runs initial hot/warm air is brought down and will be felt by people. However with all windows and side doors open to encourage natural cross ventilation, the built-up warm air will soon be dissipated and people will feel cooled as fresh incoming cooler air is being circulated. If the space is enclosed and warm air is trapped with no escape, fans will not work. In the same way aircon is ineffective in open spaces.
Fans can provide 4 deg C below ambient temperatures.
Fans are generally not design to run effectively in both directions.
From the evaporation cooling for human comfort, breeze speed below 3m/s is most efficient. Breeze exceeding this velocity will not be comfortable and power consumption increases exponentially.
Spacefans’s design in minimum energy, max cooling and max coverage.