Jewberrywilcum.

"Jim Mc Namara" wrote in message
news
Makes sense - thanks Art.

Jim

"Wood Butcher" wrote in message
news:FbDPa.36743$H17.10746@sccrnsc02...
It's the latter. A vacuum would be the ideal insulator but
nobody has managed to engineer a window that is strong
enough to keep the panes from flexing inward and touching
and/or breaking.

Art