In a text about properties of aerogel I read some interesting facts - clothes with aerogel proved to be impractical, being far too warm to wear. If you isolated a house with aerogel and lit a candle in one of the rooms, after a few days the house would become too hot to live in, just accumulating the candle heat.
What properties (thermal mechanics?) of aerogel allow it to be this good a thermal isolator?
Would a sealed box made of aerogel work just as well maintaining the temperature of enclosed (solid) items in void - with no air inside the box?