There is a product called Reflectix that is sold at Lowes and Home Depot. It comes in different size rolls and can be cut to fit. I have to agree that the front of our trailer is cold too and also has the aluminum rock guard outside. We put a piece of the Reflectix between the matress and wall and the matress holds it in place. It helps out somewhat. Look at the product online and see if that may work for you.
You have to attack this problem from the inside. That's where the moisture is. I do not believe that there is anything that can be done on any practical level from the outside to make a difference.