We just finished a 2000 mile cool weather trip(vermont). We lined all the back of the cabinets and under bed with reflectix - to make it look nice we covered inside with stick on wall paper after done you wouldn't know it was there and really helped. We also cut 2 inch foam pieces for all the vents carried a small electic space heater we like spending nights in casino parking lots (better half might have a gambling problem lol) We did notice a draft from wall slides so that is next item on list. I think these modifications will help in hot weather too.
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