On Mar 17, 12:49*pm, TimR wrote:
This isn't sounding good. *The first two replies fail to report any
decent results. *If this keeps up maybe I won't waste the effort.

Maybe I need to build something more substantial with real panes.

....or replace the windows.

Even if you build "something more substantial with real panes" you'll
need a way to seal them to the windows. If you don't create a dead-air
space, you won't gain anything.