To the OP
If your sound dampening insulation also provides thermal insulation, all you will be doing is slowing the rate of change of the temperature in the tanks. Insulation doesn't create heat on one side and cold on the other, all it does is mitigate the transfer of heat from the heated side to the cold side. If you have moist air above the fuel in your tanks, then when the outside temperature is lower than the temp inside the tank, there will be some condensate form on the inside of the walls in the top, air filled portion of your tanks that are exposed to the outside cold. Just like the outside surface of a glass of any ice cold beverage in summer heat. That process will occur. If insulation is present, it will occur over a longer period of time. If the outside temp is warmer than that inside the tank, no condensation will occur on the inside. If there is warm, moist air in the ER and ice cold fuel in the tank, condensate will form on the outside of the tank. This would be as hard to detect as the condensate on the outside of a beverage glass in an insulated cup. Present, but not detectable under normal conditions.
