First hour — freezing. Second hour — overheating. You are still in the same building, walking the same hallways, yet somehow the temperature feels completely different. So why does it vary so dramatically from room to room?

Many students assume that teachers are responsible for these noticeable differences. While teachers do have limited control over their classroom settings, personal preference is only a small part of a much larger and more complex system. In some cases, classroom practices may even interfere with that system without anyone realizing it.

To better understand what is actually happening, we spoke with Mr. Litschauer, our head custodian, who oversees the school’s heating and cooling operations. From a computer in his office, he monitors and manages a highly coordinated system designed to regulate the climate of the entire building. As it turns out, the explanation for our temperature inconsistencies lies in both engineering and environmental factors.

During the winter months, the building is heated using a boiler-based hydronic system. Boilers heat water and send it circulating throughout the school along a continuous loop. As the hot water travels through the pipes, it passes through each classroom before eventually reaching areas farthest from the boiler room, including rooms on the north side of the building.

However, as the water circulates, it gradually loses heat. This means classrooms located farther from the boilers may warm more slowly or feel slightly cooler because the water reaching them is no longer at peak temperature. The same principle applies in warmer months, when chilled water is circulated to cool the building. The farther a room is from the source that is heating or cooling the water, the less efficient the system becomes in delivering consistent temperatures.

Inside each classroom is a unit containing a coil. Depending on the season, either hot or cold water flows through this coil. A fan then pushes air across the coil before distributing it into the room. If the coil contains hot water, the air is warmed as it passes over it. If the coil contains chilled water, the air is cooled. This fan-and-coil process is what ultimately controls the temperature you feel.

Airflow, however, is critical to this system’s performance. When books, storage bins, or other materials are stacked against the air grills along the walls, airflow becomes restricted. According to Mr. Litschauer, blocking these grills forces the fan to work harder and can even cause it to “fail” or shut down. Without proper airflow, the room cannot heat or cool efficiently, no matter what temperature is set.

Another major influence on indoor temperature is exterior weather. Classrooms with more exterior walls are more directly impacted by outside conditions. On extremely cold days, these rooms lose heat more quickly than interior classrooms surrounded by other heated spaces. Similarly, warmer days can cause exterior-facing rooms to gain heat more rapidly.

Mr. Litschauer referenced the extremely cold week we experienced towards the end of January as a clear example of how outdoor conditions affect building performance. The ventilation system uses dampers to regulate how much outside air is brought in to maintain air quality. However, during very cold or windy conditions, these dampers can sometimes become stuck open. When that happens, freezing air enters the system uncontrollably.

If extremely cold air continuously flows across coils containing water, the water inside can freeze. Since water expands when it freezes, this expansion can cause coils to crack or burst. Because the system operates under pressure, a ruptured coil can create significant damage and a major water leak. Wind can also interfere with dampers by forcing them open, further disrupting indoor temperatures.

All of this is controlled digitally. The entire heating and cooling system runs from a centralized computer in Mr. Litschauer’s office. Each day at 6:00 a.m., the building enters “occupied mode.” At that time, the system begins conditioning the air to prepare for students and staff. It continues operating throughout the school day and adjusts once the building becomes unoccupied in order to conserve energy.

One exception is the pool area, which operates on a 24/7 schedule. The air temperature in the pool space must remain consistent with the water temperature. If the air is cooler than the water, evaporation increases significantly, which can lead to excess humidity and potential moisture-related issues. For that reason, both the air and water temperatures are carefully maintained at all times.

So while teachers may have some input on classroom comfort, the reality is far more technical. Temperature differences are influenced by distance from the boiler or chiller, heat loss during water circulation, exterior weather conditions, airflow blockages, damper performance, and the building’s automated schedule.

The next time you transition from a freezing classroom to one that feels overly warm, remember that it is not random. It is the result of a complex mechanical system working continuously — and sometimes imperfectly — to manage the climate of an entire school building.

A special thank you to Mr. Litschauer for taking the time to explain the inner workings of our school’s heating and cooling system and for the work he does every day to keep our building running smoothly.

Photo taken by: Meredith Huettl

Caption: The school’s boiler and climate control system displayed on the central computer.