[DarMar]

David: First of all Welcome to the MOC family, you will glean a wealth of knowledge and friendship during your time here.

The subject of dual pane windows is discussed here quite often and as I recall the actual weight DIFFERENCE between dual pane and single pane windows is actually less than 600lbs. This is our 2nd Montana with the dual pane windows and compared to the previous SOB that we had we will never own another unit without them. Your info is correct that they actually only add a very small R factor to the unit as a whole but the dual pane windows reduce the outside noise substantially. We also use our rig early in the season (end of April and early May) and late in the season (end of September and early October) and that is when we find them to be a real advantage. With the singles we would find copious amounts of moisture forming on the windows over night with the blinds drawn and as well during the day in the cooler temps sitting next to them one could feel a lot of cold radiating from them. Now of course the dual panes don't totally eliminate the moisture and coolness but the difference between the two is extreme. For those reason I would recommend to you for our climate you should strongly consider the dual pane.