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Why Is the AC on in the Morning? 

Lots of TherMOOstat voters leave comments asking why their air conditioning is running in the mornings. Isn't this a sign of  the campus wasting energy by blasting the AC when it's cold outside? 

The truth is that the air you're feeling may not in fact be air conditioning! Read on to discover what's really going on in your rooms. 


TherMOOstat Comments Asking Us to Turn off the AC:

“The AC seems to be constantly running even at 8am in the winter.”


What's Really Going On? 

If you are sitting in class when it's cooler outside and you feel cold air blowing into the space, don’t assume we are wasting energy cooling the air – we may be bringing outside air into the building to do the cooling.

Building heating, ventilation and air conditioning (HVAC) systems on campus have the ability to bring in outside air to ventilate spaces and maintain indoor air quality.

When the system is in cooling mode, we can also use this outside air to cool spaces when outside air temperatures are cooler than indoor air temperatures.

The three scenarios below illustrate what can happen in a building that is in cooling mode in the morning. 

Recirculating Air In Hot Weather

scenario 1.png
Energy Saving

This is a scenario where it's hot outside but we don't want to waste energy by bringing this hot air inside. In this case, we only bring in the minimum amount of outside air and recirculate air throughout the building using the air handler. Recirculating the air requires less cooling, and is one way to save energy in non-laboratory spaces.

What is an economizer?

Economizers are often the unsung heroes of HVAC systems, allowing units to use outdoor air for cooling inside buildings.

Your TherMOOstat Feedback

In the summer, some buildings will also pre-cool classrooms using outside air so less mechanical cooling is needed during the day. But if temperatures don’t seem right in your room, it's possible your space is being over-cooled or over-heated and we want to hear from you! This isn’t always easy to fix, but we can’t fix it if we don’t know about it, and with so many spaces on campus we often rely on your TherMOOstat feedback to tune HVAC systems to make them as comfortable and energy efficient as possible!

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