Gear Shed

Q:

How can I prevent condensation inside my tent?

Every time I wake up in my new Marmot Swallow tent the condensation is so bad that my sleeping bag and clothes get wet, so much so that I'm considering taking the tent back and exchanging it for a Mountain Hardwear Skyview or MSR Fusion. I have searched the Internet and read many positive reviews about the Swallow, so is this just a common problem in three- to four-season tents, or did I just get the one defective tent in the batch?

    Photo: Jens Ottoson via Shutterstock

A:Marmot's Swallow ($359; www.marmot.com) is a big, roomy two-person tent. As you know, it's designed for three-season use, meaning it has quite a bit of mesh in the tent canopy mesh doors, a mesh panel at the back of the tent, two mesh panels in the ceiling. I've not used this tent, but I've slept in tents that have similar designs (if you look closely at tents, you realize that all the big makers Marmot, Sierra Designs, Mountain Hardwear, The North Face, and the like share about six basic designs).

In my experience, this kind of design does a reasonably good job at keeping condensation to a minimum. So whether you have a real problem depends to some extent on where the condensation is appearing. Keep in mind that double-wall tents such as the Swallow are designed on this principle: Warm, moist air given off by the tent occupants passes through the mesh and permeable ripstop nylon of the canopy. When it hits the (presumably cooler) fly, which is waterproof, it will likely condense out. It's then supposed to drip down the fly to the ground.

At least, that's the idea. In certain conditions, the design of any tent will be overwhelmed by moisture. That's especially true on cool, still nights. When there's no wind, there's no air circulation between the canopy and fly, so the warm air from inside the tent isn't mixed with cooler outside air. And when the temperatures are relatively low (below 40, for instance), it's easier for liquid moisture to form on the underside of the fly.

So, in conditions such the above, I wouldn't be surprised that there's extensive condensation. It's just a fact of life. If you're getting a lot of moisture on the canopy the surface nearest you when you're inside the tent then that's a potential issue. Still, even at that, I'm not sure I can say the Swallow is better or worse than any other tent designed for similar weather conditions.

The question then becomes, how to minimize condensation? Ventilation is the key. If the weather isn't crummy, then do all you can to open up the tent. Leave a door open, for instance. And when pitching the tent, try to orient it so that any breezes can blow in under the fly. In the morning, if time allows, I find it helpful to remove the fly and lay it out upside-down so it can dry out some.

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