Living in the humid south we have a prevalent problem with nest building insects; in particular mud daubers and wasps. They love to find crevices to build their nests and a RV is no exception.
I have been successful through lessons learned keeping them out of our former RVs with manufactured screens for the exterior vents for furnace, water heater and refrigerator, however, with our new View equipped with a Truma water heater - I not found anything that is custom fit for the Truma vent panel.
The solution part 1:
So, I got creative and bought screen panel that I cut to form over the Truma flue. It worked great, so I thought.
One day I was out checking around the RV and I noticed mud drops at the base of the Truma vent. I figured there was no way the mud dauber was getting in the Truma compartment.
Opening the vent door, sure enough, I neglected to see the intake vent facing down at the bottom of the access door and the mud daubers already built a large mud nest behind the burner (I was able to easily remove the nest by pulling the burner assembly).
The solution part 2:
For the intake vent I took the same screen and found it fit nearly perfectly if I put a 90 degree bend in the screen and tucked it in the louver. A dab of silicone adhesive to keep it from bouncing around. The rest of the summer was nest free.
I purchased the screen pack from Aleko