Hank,
Depends on what you are trying to do. In my part of the country (south Atlantic seaboard) cold isn't the issue. I use
Reflectix in the windows, to bounce the heat away, but you can't see out when it is in there. For cold weather I just draw the drapes and turn the heat up. FWIW Airstreams are not particularly thermally efficient. AFAIK the ribs have little to no thermal breaks on them, other than a thin strip of sealant. They will and do transmit heat and cold.
Aaron
