Pit Zips: What They Are and Why They're Still Around

Are Zippers in the Armpits of Jackets the Key to Staying Sweat-Free?

Orange zip on a blue jacket
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Pit zips are the ventilation zippers offered on many hard-shell jackets. They are usually located right at the armpit or close to it, from which they get their alliterative name. Should you look for jackets that have this feature?

Why Active Outdoor Jackets Have Pit Zips

When you are hiking, climbing, running, or working outdoors, you can produce sweat, even in cold weather. Jackets for active outdoor use are designed with ventilation to let perspiration out as well as to let air in to help dry the skin. Some jackets have vents across the back to allow air in, and some also have zippers in the armpits to allow you to adjust the air flow.

If your perspiration can't escape from the jacket, you could end up drenched and shiver in your own sweat. If you're wearing a jacket that has a hard shell and isn't breathable, there is no airflow to carry away some of that moisture. Even if the jacket does an otherwise excellent job of keeping rain, snow and other bad weather at bay, you are the one producing the moisture inside your own jacket. You get wet from the inside out instead of the outside in.

Using Pit Zips for Jacket Ventilation

If you're working hard enough to sweat but the weather keeps you from shedding or opening your jacket, you just open the pit zips instead. You might want to open them a bit as soon as you are warmed up, to keep your body just slightly cool with the ventilation.

If it is raining, you might need to keep the pit zips closed to keep out the weather, especially if it is windy. Another consideration is that you should always close the pit zips before raising your arms overhead when it's raining. Otherwise, the rain can funnel right down the sleeves of the jacket and into the open pit zips. That's a cold surprise you'll want to avoid.

Another oddball problem of having pit zips is that you might mistake them for pockets, especially if your jacket has vertical zippered pockets on the chest. You might think you're stashing an important item in the pocket, but instead, you are dropping it right down the inside of your jacket. Often, that means it is going to drop onto the trail unnoticed and you'll lose it.

Where Have All the Pit Zips Gone?

Although they were once ubiquitous on good quality hard-shell jackets, pit zips are becoming less common. Gear manufacturers are zeroing in on how to build more breathable shells without sacrificing on weatherproofing. When they think they are providing enough airflow for ventilation, they don't include the complication of pit zips in the design. After all, this is a weak point and one more thing that could break. They prefer a sleek and less complicated design if they can make it work.

You'll still find pit zips on quite a few jackets because they give you more flexibility in terms of venting. Look for designs with pit zips if you have problems with sweating more than the breathable shell can handle.