When living in an extreme environment, most RVs have inadequate insulation which means it must be added. Aside from poorly insulated slides, the windows are a major source of energy loss. One of the best products we have found to add insulation is bubble wrap with a layer of foil on either side, also known as Reflectix. For our first couple of winters in the Midwest, we covered our windows on the inside of our rig.
While spending a summer in Las Vegas, we were informed that placing the Reflectix on the inside, when it’s scorching hot outside, could heat the window up to a point of cracking it. The best thing to prevent the window from heating up, they said, was to place the insulation on the outside. We figured the same principle would hold true in the cold. So far this year, putting the insulation on the outside has proven more beneficial than having the insulation on the inside.
Placing it on the inside creates condensation.
A major problem in cold climates for RVers is condensation. This occurs when microscopic moisture in warm air collects on a cold surface causing water droplet, similar to a soda can on a summer day. There are two ways to combat this issue. The first is to decrease the humidity in your rig and the second is to increase the airflow.
When a window is covered with Reflectix, the air space between the window and the insulation doesn’t move much. This stagnant air creates a perfect environment for condensation. We had so much water in our large front window last year that it had to be soaked up with a towel. We had a dehumidifier, but the insulation prevented it from getting to that area. Since we've placed the the Reflectix on the outside and directed a small fan toward that window, we have seen little to no condensation in that area; that area appears warmer as well.
It’s better if you have pets.
We have cats that like to play with crinkly things. The foil on the outside of the Reflectix insulation is wonderfully crinkly. Consequently, keeping the insulation up all season was a battle when it was on the inside. Our dog likes to look out the front window as well, so we believe she would assist in the removal process when we were not around. Placing the insulation on the outside allows us to keep it away from the cats, and we are able to cut a couple of viewing holes for them.
Conclusion
Had we known then what we know now we would have never tried to place the insulation on the inside in the first place. If you are wondering how well the insulation works, I used an infrared thermometer to take the temperature of an uninsulated window versus an insulated one. The window covered in Reflectix was about the same temperature as the inside of my RV, while the uninsulated one was only a few degrees warmer than outside.