Condensation

Condensation is moisture from breathing and body heat that collects on cold interior surfaces, especially windows, when warm humid air inside a sealed vehicle meets a much colder surface overnight. It is one of the most common complaints from first-time car campers, since a completely closed-up vehicle traps far more moisture than most people expect.

The amount of condensation depends heavily on outside temperature, how many people are sleeping inside, and how sealed the vehicle is, with cold, still nights producing the worst buildup. Wiping windows in the morning treats the symptom but not the cause, and damp bedding from repeated condensation can make a vehicle feel persistently humid over a multi-night trip.

Cracking two windows slightly on opposite sides of the vehicle for cross-ventilation reduces condensation far more effectively than wiping, since it lets moist air escape instead of recirculating. A common mistake is sealing every window and vent to stay warm, which traps moisture and often makes the vehicle feel colder and damper by morning than a slightly ventilated setup would.