notmyspacetom

They typically use a getter to maintain the vacuum over the lifetime of the window, similar to other sealed vacuum systems like CRT's or vacuum tubes.

There is a company called LuxWall that is producing vacuum insulated windows that act basically like a thermos. There is a tiny space between the two panes that is pulled down to a high vacuum that results in a window that only transfers heat via radiation. Conductive and convective heat transfer are essentially eliminated. This results in a window with a R value similar to a fully insulated wall. Because the full unit is so thin, they are able to replace single pane windows in old buildings and drastically cut buildings energy consumption.