How to Prevent Condensation in Tents

Waking up in a tent with drops of condensation on the walls is unpleasant, but a frequent occurrence, especially when camping in the mountains. However, once you understand why it occurs, it can be minimised with a few simple steps. This article explains the tips to avoid condensation in your tent.

Ventilation and space, a remedy for condensation. Photo: Sea to Summit

Imagine spending a beautiful day trekking in the mountains, you were caught in a short rainstorm but only your outer clothes and pack are wet. You find an idyllic spot to pitch your tent, next to a mountain lake. Before going to bed, you decide to cook inside the tent as it’s a bit chilly. The next morning, in spite of a dry night, you find the walls of the flysheet are covered in drops of water.

What happened? The tent is waterproof and it hasn’t rained all night. Where did so much water come from? The answer is the accumulation of condensation . This is uncomfortable, but normal and does not mean your tent is faulty.

What Produces Condensation?

Condensation is the conversion of a vapour or gas into liquid and this depends on two factors: relative humidity and temperature (also pressure, but we can leave this out for now). When air becomes saturated with water vapour and it cannot hold any more, it reaches what is known as the dew point and turns into clouds and frost. But if this water vapour comes into contact with a cold surface, it does not have to be totally saturated to produce condensation.

In small spaces, such as in a room, car or tent, the air humidity is high when the conditions are right and condensation occurs if a surface is significantly colder. This explains condensation on a kitchen window when something next to it is boiling, or the bathroom window after taking a shower or in a vehicle full of passengers. Condensation inevitably occurs in winter when the windows are much colder than the air inside

The Particular Case of Tents

Before we continue, we invite you to take a look at ourarticle about how to choose a tent which compares the different types, structures and designs. If you also want to know about the lightest tents available for multi-day treks, check out our article on lightweight camping equipment. But here, we are going to focus on the latest geodesic or igloo tents, as well as tunnel tents, as both structures cover the whole range of one-room tents available today.

The fly sheet of a tent is usually made of polyester and the groundsheet of nylon or polyester. Although polyester is quite water repellent, it is unable to withstand heavy rain unless it has some kind of coating. Tents are usually coated with an internal layer of induced polyurethane (PU) which is waterproof, lightweight and excellent value for money.

Millet
Fabrics that are waterproof but not breathable produce condensation. Photo: Millet

Polyurethane makes fabric waterproof and windproof, but not breathable. This means the fabric is unable to wick moisture in either direction and the water vapour inside the tent ends up condensing onto the cold fabric surface as temperatures drop at night. The same happens with the cold metal tent poles, although in this case the water droplets run off to the ground. In tents made of other materials such as canvas or cotton fibres, condensation is less noticeable because moisture is absorbed by the fabric.

A 2-person igloo tent usually has a maximum volume of 6 m³. The volume is even smaller in tunnel tents, which are lower and more aerodynamic. This means the volume of air per person is very small and it quickly becomes saturated with moisture, so condensation can only be avoided if there is some sort of ventilation.

It is usually quite cold at night in the mountains and the difference in temperature between the warm, humid interior and cold outer almost inevitably leads to condensation.

Which Tents Minimise Condensation

The shape of the tent is important, as well as features that increase the air volume and improve ventilation. The more air flow and air volume per person , the less condensation.

Igloos and tents with more vertical walls have a greater volume and the drops slide off the walls more easily, compared to tunnel tents.

In general, single-wall tents should be avoided because they are designed for the extreme cold where condensation is less of an issue as the low temperatures turn it into a layer of frost. Air circulation is also not an issue in these conditions, but if used in milder climates, condensation would be unavoidable. For this reason, single-wall tents are exclusively designed for expeditions and high mountain use as they are fast to pitch, lightweight and take up little space in your pack.

Barrabes
The North Face Stormbreak2 inner tent. Highly ventilated to minimise condensation.

Tents with snow skirts are not recommended, unless the snow skirt can be folded out of the way. Snow skirts are an essential feature in 4-season tents, but they restrict air-flow and increase condensation.

A vestibule is not only great for organizing your gear, but it also increases the volume of air inside, so it takes longer for water vapour saturation to occur. As it is more ventilated, the vestibule is also a good place for drying out wet gear and boots.

The mosquito net is another essential element for ventilation as it is specifically designed to remove moisture from the environment. Two layers tent doors allow you to leave the outer layer open and the inner mosquito net closed to keep out the bugs. In warm weather, you can just pitch the inner mesh tent to prevent condensation and over-heating.

Air vents are also an essential feature and are included in most tent designs to improve air-flow.

Barrabes
Air vents in the Robens Arch2 tent

But the most effective way to air a tent is with double doors. A door on each side of the tent not only facilitates getting in and out, but also allows maximum air-flow when both doors are open.

Why Don’t Tents Usually Have Waterproof Membranes?

You may have wondered why most tents are not made with waterproof and breathable membranes to minimize condensation.

Barrabes
The North Face Assault 2 with waterproof and breathable Futurelight technology.

There are several reasons. The first is that a tent is not in close contact with your body, like a jacket or pant. Condensation in tents usually sticks to the flysheet and rolls down to the ground in the space between the fly and inner tent, without coming into contact with the inner sleeping space. In the morning, it dries out very quickly so that the tent can be packed up quickly and easily.

Another reason is the high cost of a tent with a waterproof and breathable membrane. Although this sort of tent does exist, it is usually only intended for expeditions or high mountaineering to achieve a combination of insulation in freezing conditions with breathability to avoid condensation.

Where to Camp to Avoid Condensation?

Having a tent with good ventilation is not always enough to prevent condensation. Something as simple as choosing the right location to pitch the tent can save a lot of problems.

The soft rippling sound of a stream or lake may seem idyllic as well as practical for collecting water for cooking, washing or cleaning, but try to avoid camping too close to a water source. It is not only dangerous in case of heavy rain, but the air is more saturated with water vapour and this accumulates in lower terrain and hollows.

Vaude
High mountain camping. There are not always many options on where to pitch. Photo: Vaude.

Pitching your tent under a tree should also be avoided. It may seem a good idea; shade during the day reduces the temperature inside the tent, leaves on the tree attract humidity and also help to cool it down, but the disadvantages are greater. Dew drops, resin, fruits and bird droppings can all fall onto the tent and make a mess of the fly sheet. And of course, if there is any possibility of a thunderstorm, it should also be avoided.

Going to sleep in a damp tent will never lead to waking up in a dry interior. Good ventilation before sleeping is usually the most effective solution, as this sets the condensation counter to zero and dries out the humidity generated from ground evaporating and the heat accumulated during the day.

Avoid adding components that add moisture to the interior of the tent such as damp clothing, towels or shoes. Try to leave any wet items outside the tent and, if this is not possible, place them in the vestibule and as close to an opening as possible.

Cooking inside the tent should always be the last option when weather conditions prevent outdoor dining. This is not only due to the obvious danger of a having a powerful flame in a small, closed, unventilated room, but the water vapour from cooking will create greater humidity that will stay inside all night long. Don’t cook inside the tent unless there is no other option.

Robens
Camping next to a lake is not recommended, but the other measures are correct for preventing condensation. Photo: Robens.

One of the most simple and efficient tips is to pack a small microfibre cloth. It is useful for removing moisture while in the tent and it speeds up drying it out once it is disassembled. A microfibre cloth does not add weight or space and dries out surprisingly quickly.

An a finally, although camping with your partner in an idyllic location unequivocally leads to romance, remember that physical exercise inside a tent generates sweat and heavy breathing and with that comes condensation.

We hope you have these tips on how to avoid condensation in tents will help enhance enjoyment on your next camping adventures. You can check out which tent best suits what you are looking for on our website and we will be happy to assist with any queries.

On-line store: www.barrabes.com/en-gb/

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