[RGordon]

Air may flow freely through our units, but they brag on the 3-1.4" walls with the high R Insulation values. They would really be efficient if you had no slide outs, but unfortunately the more you have the more cold air that flows. I do have a double slider rubber seal under the kitchen slide. I would think any ole country boy with some common sense could engineer a slideout seal that would stop most of the airflow. If fulltiming in colder climates, you really need a large external propane tank.