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Mechanical Venting, Pit Zips, and Layering

Breathable Fabrics and The Emperor's New Clothes
Breathable Fabrics and The Emperor’s New Clothes

Are you sick of the exaggerated breathability claims made by outdoor gear manufacturers? Can you really afford to spend another $400 – $600 dollars on a jacket with the latest breathable fabric? Do you realize you are being played by unscrupulous manufacturers in a never-ending game of bait and switch? Are breathable jackets only as good as the Emperor’s new clothes?

Introducing the Pit Zip!

If you want to stay dry in cold weather, get yourself a hard or softshell jacket with pit zips that can be opened to vent off excess heat during high levels of exertion. Pits-zips augment the breathable fabric in your existing jacket and prevent it from becoming overwhelmed when you really start to sweat. They also can eliminate the need to take off layers and help avoid added delays when you need to make tracks.

Pit Zip with Green Fleece Poking Out of It
Pit Zip with Green Fleece Poking Out of It

Called mechanical venting, pit zips typically run from underneath your elbow to the middle of your torso, where you sweat the most. Some manufacturers, like Outdoor Research, provide extended pit zips on their hard and softshell jackets that run from the back of your elbow all the way to your waist, enabling a poncho-like effect that further accelerates the evaporation of sweat when opened.

Outdoor Research Torso Flow Pit-to-Hem Venting System
Outdoor Research TorsoFlo Pit-to-Hem Venting System

I think we have to give Outdoor Research some credit: they include TorsoFlo vents on jackets made with breathable fabrics, obviously because they understand the limitations of breathable technology. They’re one of the few technical apparel companies I know of that put vents on jackets made out of Gore-tex Pro and Gore-tex Paclite.


Layering is even more effective than zippered vents because it enables you to release heat more quickly and prevent sweating.  It’s simple, dress like an onion in cold weather with multiple layers of clothing (click for KISS layering in Winter). As you start to sweat, stop and take off your outer layer in order to vent the moisture from the next layer down, and so on. It’s not unusual for me to strip all the way down to my base layer in 20-30 degree weather if I’m snowshoeing or hiking vigorously up a steep mountain.

Dress Like and Onion - Pinkam Lodge Ready Room
Dress Like and Onion – Mt Washington Ready Room

If you’re hiking with an experienced group of people, no one will object to you stopping to strip off a layer and stuff it into your backpack. All of the people in your group are probably heating up and cooling off at the same time you are and they’ll be relieved when you call for a “layer break.”

The Breathability Trap

So, the next time you feel like the urge to buy a jacket made with the latest breathable fabric technology, remember that low tech solutions like layering or pit/torso zips are more effective and cost far less. There’s a reason why jackets and rain pants with pits zips and side zippers like the Marmot Precip remain so popular after being on the market for so long: mechanical venting works and it’s far less expensive than the emperor’s new clothes.

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