Leaving blackout blinds on window to heat room

[Derek Chevalier]

Early in the morning, the sun shines on our childrens' bedroom windows, and when I open their curtains I feel how warm the blackout blinds (bits of black plastic stuck to the windows with static) are. If I want to maximise the warming of the room, do I remove the blinds, or leave them in place?

[fredbrad]

Remove the blackouts. The short wave radiation from the sun penetrates the glass in the window, but the reflected long wave radiation in the room cannot escape through the glass, as in a greenhouse. This is the principle behind global warming, substituting glass for CO2.
The blackouts, being black, absorb all wavelenghts from the sun, which is why they are warm.

[crofty1984]

fredbrad said:

Remove the blackouts. The short wave radiation from the sun penetrates the glass in the window, but the reflected long wave radiation in the room cannot escape through the glass, as in a greenhouse. This is the principle behind global warming, substituting glass for CO2.
The blackouts, being black, absorb all wavelenghts from the sun, which is why they are warm.

Yup. The sunlight hiting the window caries a finite amount of energy. Some of it's being wasted heating up the blinds.

[Use Psychology]

but the black blinds absorb a broad spectrum of the sun's radiation and re-radiate as heat (lower wavelength radiation).

[Eggman]

Any energy that comes through the window will end up as heat*. It can't just disappear.

* In before the smart-ass: unless the room contains things that'll convert it into some other form of energy first, like plants, luminous paint or photovoltaic panels.

[Use Psychology]

that's not true, some light will reflect off things in the room and leave again via the window.

[Eggman]

That is true, unless the OP's children are mini-goths and their room is done out like a funeral parlour in black crepe.

(There's always one, eh? )