What causes tent condensation?
Condensation is caused when the warm moisture vapor from a tent’s sleepers’ breathing and perspiration comes into contact with the cooler tent body or rainfly fabric, at which point it transforms and condenses into liquid form.
Condensation worsens in relation to the coolness of outside air temperatures compared to temps inside your tent. That means that if outside temps are significantly lower than inside your tent, then the potential for condensation—and the amount of it you can expect to build up in your tent—increases exponentially. This is most evident, therefore, when the variation between daytime temps and nighttime temps is large.
The likelihood of condensation also usually increases in wet weather because any rainwater that lands on your tent cools the fabric, thereby broadening the temperature variance between the rainfly and the air inside your tent.
How to minimize condensation in your tent
One person can produce up to one pint of condensation per night and other factors—wet clothes, humidity in the air, wet or damp boots—can add to that already sizeable total.
There are, however, several ways in which you can mitigate the problem. These are as follows:
1. Store all wet or damp items of clothing in your tent’s vestibule or in a stuff sack until morning.
2. Boil water and do your cooking outside the tent—vapor from boiling water or food can greatly increase the moisture content of the air inside your tent.
3. Pitch your tent on higher ground—cool air concentrates in low-lying areas or depressions in the terrain, making them primed for condensation.
4. Don’t pitch your tent near water sources like streams, rivers, lakes, ponds, or creeks as these increase the level of humidity in the ambient air.
5. Maximize ventilation in your tent by using all of the vents, opening the vestibule door at night, and/or rolling back or removing the tent’s rainfly if conditions permit.
6. If using your rainfly is necessary, you can optimize airflow by ensuring there is a gap between the rainfly and tent body when pitching. To do so, make sure the rainfly is pegged out tightly and use your guy lines to further distance the fly from the inner.
7. Carry a small rag or towel to wipe down any condensation on your tent walls before it can accumulate and soak your gear.
8. Consider suspending a tarp over your tent body instead of using a rainfly—this will provide both protection from rainfall and let your tent “breathe” more easily.