In the same 22 C room, why might someone who just climbed stairs feel warm while someone sitting in a T-shirt feels chilly?

Answer: Activity and clothing differ

The thermostat is broken — A bad thermostat can happen, but it is not the first explanation here. A thermostat mostly reports air temperature at one place, while comfort depends on the person as well as the room. Someone coming off stairs has a higher metabolic rate; someone lightly dressed has less insulation. The same 22 C can therefore be too warm for one heat balance and too cool for another.

Humidity decides alone — Humidity matters, especially when sweat must evaporate, but it does not decide comfort by itself. ASHRAE-style comfort methods combine humidity with air temperature, radiant temperature, air speed, clothing, and metabolic rate. In a cool office where little sweating occurs, clothing and activity can dominate the argument. This is why office thermostat fights are often biology plus wardrobe, not just weather.

Activity and clothing differ ✓ — Correct. Climbing stairs raises metabolic heat production, while a T-shirt reduces insulation compared with heavier clothing. Thermal comfort standards explicitly treat metabolic rate and clothing insulation as inputs, not afterthoughts. The useful takeaway is that one room temperature is serving multiple moving heat balances, so disagreement at 22 C is expected rather than irrational.