can I add a caveat that you should be very cautious of the asbestos siding and anything you do around it. Does the term mesothelioma sound familiar? If you do anything to that wall, wear protective clothing, a respirator or better yet get a professional to do it. As for the rest of it. good luck. Could you rig a door or slab of plywood to at least cut off the air flow between this room and the house. It wouldn't be pernanently sealed off but it might help with the temperature differential.
marni
Katy, Texas
Trek Madone 6.5- "Red"
Trek Pilot 5.2- " Bebe"
"easily outrun by a chihuahua."