It happens. Sometimes condensation is unavoidable, however, there are ways you can mitigate it. Understanding how and why condensation forms will help you to make informed decisions when pitching your tent. Jump to the bottom for some pointers.

Below, we'll go over:

Terminology
Condensation

The transition of water vapor into liquid water.

On solid surfaces, condensation is experienced as water droplets forming on the surface (dew). In the air, water will condense onto tiny particles of dirt in the air (fog).

Humidity

A measure of the amount of water vapor in the air.

Relative Humidity

The amount of water vapor in the air compared to what the the air can hold at a given temperature.

  • At 100% relative humidity, the air cannot hold any more moisture at the given temperature.
Causes of Condensation
Drop in Air Temperature

Air temperature often falls at night. When it drops to the dew point, condensation will begin forming on tiny dirt particles suspended in the air.

Drop in Surface Temperature

Surface temperatures drop due to convective and radiative heat loss. When surface temperatures fall below the dew point, condensation will occur on the surface.

  • Convective heat loss occurs as cooler air travels over a warmer surface, carrying some of the warmth away with it.
  • Radiative heat loss occurs when an object loses heat in the form of electromagnetic radiation to cooler surroundings. This means surfaces (like your tent walls) radiate heat to the colder overall temperature of the cosmos (a clear sky). Cloud and tree cover can act as a blanket, reducing radiative losses. When you wake up with condensation on the exterior and interior of your tent, it is likely due, primarily, to radiative heat loss.
Increase in Humidity

If the amount of water vapor in the air increases while the temperature remains the same, the relative humidity will increase. If it reaches 100%, condensation will occur.

  • As a person breathes and perspires, water is lost from the body to the surrounding environment. In a semi-closed environment, like a tent, this increases the humidity. Body heat will help to raise the air temperature inside the tent, however surface temperatures do not change significantly. If the humidity increases enough relative to the temperature of the tent wall, condensation will form on the interior of the tent.
Mitigating Condensation
Increase ventilation

Pitch your tent with ventilation in mind.

  • For our Cirriform, orient your shelter with the head wall into the wind for maximum airflow.
  • If it's not raining, keep the beak/vestibule open and tied back.
  • If it is raining lightly, you can keep the beak/vestibule partially open and tied back.
  • On our shelters with secondary zipper pulls at the top of the outer door, unzip the top and use the prop to spread the zipper and increase venting.
Site Selection

Remember the 3 S's

  • Surface: Avoid pitching your tent on grass or ground surfaces containing moisture. Doing so will increase the humidity under the fly.
  • Sky: On clear nights, avoid pitching under open sky. Opt for tree cover.
  • Surroundings: Avoid camping near water (increases humidity) and in locations where cold air may sink and collect at night.