User blog comment:Godisme/Eternal Flame/@comment-7418318-20130912192734

Well... in a window it makes sense to have a vaccum between two glas panes for heat isolation, but I really don't the same concept will help ice to not be molten by fire, so I'm right there with you.

It's like Kubo heard of the concept somewhere and immediately incorporated it into his story without thinking it through first.