Need to insulate large, deep casement windows

I am looking for low cost (as low as possible) acrylic sheets or Lexan to cut into size to put over the inside of my large 76" X 68" deep casement windows for less heat loss. Any steers on where to find this stuff or something else that would work? Must be as transparent as acrylic (.080").
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

low cost lexan? good luck
shrink film like this might be an inexpensive alternative for your application, at about $10 to $15 http://builders-hardware.aubuchonhardware.com/window_hardware_and_weather_stripping/plastic_sheeting/frost_king_shrink_film_window_kit-for_patio_door_or_picture_windows-282979.asp
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
We have some plexiglass sheets used that way. The windows are about 72 inches tall by 32 inches wide. The sheets have a tendency to bow. I think your installation will require structural support. TB
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Whip up some sort of simple frame, and use the hair dryer shrink to fit window film over the resulting window.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.