What is the temperature of a vacuum? Could this be used as an insulator in windows/homes?
Thermodynamically, temperature for a vacuum does not exist (there is nothing that can have a temperature).
In windows/homes it isn't practical to maintain a vacuum just for its insulating properties: withstanding the forces from the atmospherical presssure would require a massive construction.
Real vacuum flasks aren't really vacuum, they just lower the pressure between the bottles
Depending on context, a space with only black body radiation is often interpreted as a vacuum with a certain temperature T.
It already is. Some window double glazing (2 sheets of glass vacuum or air between) methods already do this
Air is a poor conductor of heat
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