In a message dated 8/21/01 5:50:55 PM Eastern Daylight Time,
[log in to unmask] writes:
> or if plastic will work as well --
Plastic can sag so provide some support.
Thats what "thermoplastics" do with heat.
I use storm windows (glass) that you can get free from anybody upgrading
their old house to insulating glass.
Usenet newsgroup has a group called "alt.solar.thermal" those guys have
all the answers.