Green painted walls making the room hotter?

Netherspark

For the last few years my room has been unbearably hot in spring and summer, and it doesn't make any sense because every other room in the house is noticeably cooler, even rooms that are right next to or below it.  And it wasn't always this bad, I only remember it being like this since about 3 years ago.

It's been wracking my brain for ages and today I had a thought - about 3 years ago I painted this room green.  Green is one of the most energetic wavelengths of light (why plants are green) and it will absorb more heat from light than most other colours.  But would it be enough to noticeably raise the temperature of the room?

grumbler

I don't think so. From outside windows look equally dark regardless of how rooms inside are painted. This means that most of the light that gets inside through the window gets absorbed there thus heating the room.

Mutton_Geoff

Netherspark said:

It's been wracking my brain for ages and today I had a thought - about 3 years ago I painted this room green.  Green is one of the most energetic wavelengths of light (why plants are green) and it will absorb more heat from light than most other colours.  But would it be enough to noticeably raise the temperature of the room?

You've wracked your brains so much you're imagining things or just making them up.

Green is not the "most energetic of light". Far ultraviolet is with >598 kJ mol−1 compared to green which has 226.

Plants are green as they contain chlorophyll which appears green.

Something appears a colour because the object is absorbing all other colours except the one you see, so something green isn't absorbing green, it's reflecting it. For something to absorb heat and light, it has to reflect the least amount of colours. That "colour" is black.

Heat doesn't get absorbed from light, heat is part of the electromagnetic spectrum that you can't see (it's below red, ie infrared and beyond). You can have loads of light with little or no heat (eg LED lighting) or very little light with loads of heat (those infrared heaters).

The temperature of your room is nothing to do with the colour green, it's either a perception or the outside walls are south facing or similar.

https://en.wikipedia.org/wiki/Color

https://en.wikipedia.org/wiki/Infrared

grumbler

Mutton_Geoff said:

Heat doesn't get absorbed from light, heat is part of the electromagnetic spectrum that you can't see (it's below red, ie infrared and beyond).

I disagree. All light absorbed by things converts into either heat or chemical energy (plants).

You can have loads of light with little or no heat (eg LED lighting) or very little light with loads of heat (those infrared heaters).

This is correct, but itfraread is just invisible. Just imagine few kW of visible light produced by LED.