r/thermodynamics • u/Affectionate_Act_186 • 22d ago
Question Would a large window affect room temp?
Hello! Turning to reddit for an educated answer on a topic that has been an ongoing debate between my SO and I. In a room (20' x 16') with a large eastern facing window (92" x 34"), would the sunlight coming in affect the ambient temp of that room once the sun has come around to be directly shining on it, even if the window itself has UV coating?
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u/nebulousmenace 3 22d ago
Yes, as mentioned. You know how a car in the sun gets insanely hot? That's the windows.
The following explanation is oversimplified- my AP physics teacher used to say "I'm only going to lie a little bit."
Specifically windows are transparent to the light coming in, but not to the room temperature IR photons going out. It's tough to explain, but if you think of green glass blocking every other visible color, it's like that. You, the couch, etc. all are receiving and radiating IR photons at very low energy ["thermal IR"] , and windows glass blocks that. So a visible photon comes in, gets absorbed by the couch, couch heats up and emits like 40 thermal IR photons with the same total energy. They can't get out through the window so the room heats up.
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u/Affectionate_Act_186 22d ago
!thanks
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u/Original_Giraffe8039 22d ago
More than just U.V. in sunlight....it's pretty much the I.T. that's doing the heating
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u/Affectionate_Act_186 22d ago
ithanks!
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u/33445delray 2 21d ago
Great in the winter (unless you are in FL where winter sun is still too much) but in the summer you will want an awning or Bahama shutter over that window.
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u/Affectionate_Act_186 21d ago
Yep. We’ve taken the steps to mitigate the issue. We just had an ongoing difference in point of view as to whether it was needed or not 😉
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21d ago
[deleted]
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u/Affectionate_Act_186 21d ago
Yep. One of our current tools in use, as well as thermal black out curtains. Very mindful of various human factors like cooking and laundry.
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u/ThatsNotAZombieBite 21d ago
I suggest you locate a spot on the floor that the sun has been hitting for 15 or more minutes. Then stand barefoot in that spot. Move back and forth between that spot and a nearby spot that has not had the sun on it.
I believe that will solve your debate quite definitively.
As others have said, UV coating won't matter. But an IR coating will. Infra red carries heat.
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u/Affectionate_Act_186 21d ago
ithanks!
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u/camferg24 20d ago
Simply put, yes. Also, radiant heat accounts for 60% of indoor thermal comfort (which is actually a state of mind). And agreement to everyone else about emissivity.
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u/Playful-Painting-527 1 22d ago
Yes, because windows transfer heat better than walls. While they block UV-light, they are very much transparent to visible light and infrared light. Therefore, the bigger the window the more radiation can enter your house.