Why The Office Is Always Too Cold Or Too Hot

Half the floor is in coats and the other half has the fan on. The air conditioning is working correctly, and the disagreement is built into how the system is designed.

One thermostat controls a large zone

Air handling is divided into zones, and a zone typically covers a substantial area served by the same supply of conditioned air at the same temperature.

The controller reads one sensor in one location and adjusts for that reading, which means everyone in the zone receives whatever suits the position of that sensor.

Subdividing further means more ductwork, more dampers and more controls, all of which cost money at construction and are rarely retrofitted afterwards.

The building was modelled on an average occupant

Comfort standards are built from models combining air temperature, humidity, air movement, clothing and how much heat a person is producing.

Those models assume typical values for clothing and activity, and the result is a target that satisfies most people while leaving a predictable minority uncomfortable.

Dress codes, seasonal clothing habits and the fact that some people are walking about while others sit still all push individuals well away from the assumed values.

The perimeter and the core are different buildings

Desks beside glazing gain heat from sunlight and lose it to cold glass, swinging widely through the day and the seasons. Interior desks do neither.

A single zone spanning both is being asked to solve two opposite problems with one setting, and it will always be wrong at one end.

Solar gain also moves. A side of the building that was pleasant in the morning becomes the problem after lunch, while the control setting stays where it was.

Cooling is mostly about equipment

Offices generate substantial heat from equipment, lighting and people, and much of the cooling load exists to remove that rather than to make anybody comfortable.

Server cupboards, printers and dense desk areas create local hot spots that pull the whole zone toward more cooling than the rest of the floor needs.

Occupancy changes this constantly. A floor designed for a full complement behaves differently when half the desks are empty, and the system is rarely rebalanced.

The complaint is often about draught

Air velocity affects comfort strongly, and a person sitting under a diffuser feels cold at a temperature that is entirely comfortable three metres away.

Because the sensation is caused by moving air rather than by the reading, lowering or raising the set point does not help and usually makes the argument worse.

Facilities teams know this, which is why the practical fix is often a deflector on a vent rather than any change to the thermostat everyone is arguing about.