I don't understand the heat-transfer part of your answer, Q_Goest. Are you saying that in reality, it would take very little energy to create the vacuum?
I've been wondering a couple things:
1. How much energy would it take to evacuate* a 1 cubic meter volume at sea level and some convenient temperature?
2. If the structure containing the vacuum weighed, say, 1kg, how high up would it go?
*arbitrarily close to a vacuum to avoid getting into...