I am refurbishing a 92 16ft Scamp and have the cabinets out to put in a new floor in the dinette area and under the vents.  Big job.  I have used pressure treated plywood to replace the rotten floor.  It is getting cold here and a lot of cold air comes in through the vents.  Has anyone put together a cover, inside or out, to restrict the cold air entering the trailer when no appliances are being used?  For me,  that would be about 99 % of the time.