RE: water heater insulation
I replaced the old water heater in my motorhome with a new one. The old one was basically wrapped in fiberglass insulation and contained in a cardboard box. The new one was contained in a Styrofoam box with no fiberglass.
When you consider that under normal operation the tank doesn't exceed 120 degrees F, I would imagine that you could simply wrap the water heater in a single batting of fiberglass insulation.
