How to tell dual pane/thermal pane windows on Arctic Fox?

My 2015 AF 1150 came with the 'thermal pane windows' option. They are not dual pane windows like you would find in a residential window installation. There is a removable glass window pane in the dinette slider, the cabover window, and the rear dining area window. I removed mine and haven't used them since I brought the TC home. If you were camping in very cold weather they would be nice to have in place. They are listed on the Northwood Manufacturing website under options as a thermal pane window.