CONDENSATION AND VENTING IN POLYESTER AND NYLON TENTS
Through perspiration and breathing, an adult gives off about a 1,5 litres of water overnight. If it cannot escape, the water vapour condenses to liquid. Most often, water found in the tent is a result of this condensation rather than from the tent leaking.
As you probably know, there are many causes for condensation. Besides moisture in the breath of the inhabitants of the tent, condensation can appear due to cooking in the tent, the proximity to bodies of water (lakes, rivers), dampness in the ground of the vestibule or damp clothing in the tent or vestibule.
When warmer air on the inside of the outer tent comes in contact with the somewhat cooler surface of the outer tent fabric, it condensates: the fine water molecules, because of the ever so slightly cooler surface contract and combine themselves to droplets.
Particularly when it rains and the rain cools down the surface of the outer tent, condensation can develop, even when there are no people inside the tent. The air inside a tent quickly gets warmer than the air outside it and then it does not take long for this moisture to develop. On a thin matter like our fabrics, condensation is only the visualisation of physical laws that we have, materializing on the side of warmer air.
Especially with our family-models where the extended vestibule covers a larger area of potentially damp ground condensation may occur. We naturally have tried to eliminate the occurrence by incorporating vents of various construction, but for vents to work you need certain circumstances, and these are not always given.
For the same reason one can get damp areas under a foam pad. Here, body warmth rises the temperature of the pad, which in turn passes this on to the groundsheet of the tent. This is naturally much cooler from the ground and dark moisture stains or even wet patches show up. This is absolutely not always a case of leakage but rather one for a small cloth to wipe off the moisture and get on with your daily routine.
Given the importance of proper ventilation to reduce condensation, We use High/Low venting in most of our tents. This allows cooler air in through the low vents and warmer, moist air up and out through the high vents. High/Low venting is accomplished within the inner tent via roof vents, doors and windows. It is important to vent the vestibule. Unvented, it can inhibit airflow into the tent.
Our tent vestibules profit from the ability to “short sheet” by means of zippers & toggles and staked vestibule pull outs create a bellowing effect. Most of our tents are equipped with a High/Low venting door. This design allows increased airflow into the tent from the bottom. Open the low vent/window to admit cool air, forcing the warmer air out through the high roof vents. When rain and wind prevent the low vents from being opened, the high door vents can still be used. Fly overhangs or vestibules protect it.