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Stuck in "Perpetual Fan Mode"

We get a lot of comments from TherMOOstat users who feel air blowing all the time, and think something is broken or it's a waste of energy. These users are right that fans do circulate air in occupied buildings, but this is not a mistake.


There are several reasons why the fans keep circulating air when people are in the buildings. The main purpose of 'perpetual fan mode' is to meet ventilation requirements and reduce stuffiness (thereby keeping you comfy)!

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"It's like the air is circulating but not cold. So like a perpetual fan mode."



Ventilation Is Required

We hear your comments. However, ventilation is required. Buildings need to be ventilated when they are occupied (aka “perpetual fan mode”) so they get fresh air and don’t feel stuffy. It’s actually required by the California Mechanical Code to circulate air through occupied spaces; for our energy nerds out there, see chapter 4 in the Code.

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People Generate Body Heat

This brings us to our secondary point: body heat. A lot of students in one classroom will generate a lot of heat. The heat produced by all the people in a room means that the space needs circulated air just to compensate for all of the body heat and keep it from getting stuffy.

Poor air distribution or lack of air mixing can be an issue

The cold air coming from the vents may not be mixing well with the warmer air in the rest of the room. This means that cold air is getting dumped on people before it mixes with the rest of the air already in the room. 


One reason for this is the vents aren’t adjusted properly. The good news is that we can work together to fix this. Let us know in your comments if you feel pockets of hot and cold air in a room. 

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