I know this title sounds crazy but I don’t know how to phrase my question better
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Bodies and physics are wonderful and weird. I will answer from the perspective of someone who is interested in making people feel comfortable in buildings (I can’t speak to the biological side).
Heat is just energy. Energy moves around in different ways. Energy is also measured with different tools, depending on the form it takes.
One way is radiation. When you stand next a hot oven with the door open, you are feeling radiation heat from the oven. If you stand next to a cold window, and one side of you feels cold its because you are radiating away to the window. The cold surface sucks away your energy.
Another way is conduction. You’ve probably heard of this in electricity and maybe heat too. Every material will “carry” heat from one place to other. materials that do this badly are called insulators. Air is a very good insulator which is why most of the “insulation” in our buildings actually work by trapping air.
When you put your hand on a warm surface, you are conducting heat away from whatever you are touching. When you put your hand on a cold surface (like a cold steering wheel), the surface is conducting heat away from you.
Then there is convection. When a gas or liquid gets warm, it expands: it gets lighter than cold gas. The warm gas or liquid starts to float. Heat doesn’t rise, but hot air does, which is one reason why it is often warmer near the ceiling than near the ground.
The last bit is about humidity. It takes energy (heat) for phase changes – think melting ice or water drying away. Did you ever do that experiment where you measure the temperature of a pot of water while its boiling? It stays at a consistent 100C (not sure what that is in F) until all the water boils away – the water stays consistent but the steam temperature increases.
So when we wet a surface and let it dry, the water uses the energy from the surface to transform into vapour (drying off). If the water is on our hand, we feel our skin loosing energy in the form of feeling cooler.
If the air is moving, the speed water evaporates is quicker, so we feel colder (more energy is lost more quickly). If the air is already pretty moist, the water doesn’t evaporate and we don’t feel cooler. Funny example of this, I rode a motorcycle in the rain with gloves that weren’t waterproof. My hands weren’t cold while it was raining. Water couldn’t evaporate from my gloves. As soon as the rain stopped, my hands went numb really quickly because the air was drying out my gloves so fast.
Most thermometers measure heat through conduction; air molecules touching the sensor. Thermographic cameras measure radiation and estimate temperature based on radiation and the type of material being photographed (its a wild set of equations). We can measure air humidity and air velocity directly and estimate how the temperature will be perceived by humans.
When we design buildings for comfort, we have to take into account the temperature of surfaces (e.g. the cold window or floor), the speed at which the air is moving, the humidity of the air, as well as the direct temperature of the air. Mechanical engineers and architects can play with all of these variables to make a comfortable space. Or do it badly and make hell in a box.
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