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Do I Need Jacket Pit Zips? What Are Pit Zips and Are They Worth It?

Rei Rainier Jacket Pit Zip

You can find pit zips in the armpits of many waterproof hard shell jackets. As the name implies, they’re usually located right inside the armpit (or close to it) to provide airflow, but do they actually work? Are pit zips worth it and when would I need them?

You should definitely consider a pit zip jacket to prevent condensation and sweat. They give waterproof jackets a vent to help remove excess body heat and reduce sweat without damaging the waterproofing properties. Your shoulder/arm blocks rain from entering the jacket while allowing air to get in and reduce sweat and condensation.

Jacket pit zips are one of the many steps you can take to avoid perspiration and condensation in waterproof jackets. Waterproof jackets are great for keeping water out, but they’re just as good at keeping in sweat and causing condensation.

The only way to reduce condensation/sweating is to increase airflow and pit zips are one of the many solutions to that problem. I’ll go over a few of the reasons why you may want to consider a pit zip jacket over some of the other ventilation options.

Why Use Jacket Pit Zips?

Rei Rainier Pit zip jacket armpit

Waterproof rain jackets and winter shell are designed to keep moisture out of the jacket, but that comes at a significant cost. Once you zip up the jacket, it’s going to insulate you by trapping your body heat. No moisture will get in from the outside, but that also means sweat won’t be able to escape from the inside. This leads to excessive sweating and condensation.

Excessive sweating is the primary problem, but you also run into condensation issues in waterproof jackets. Your body heat doesn’t have anywhere to go so the internal temperature can quickly lead to perspiration. You’ll start to sweat (to cool down) and the sweat gets trapped in the jacket. Without ventilation there’s no way for the sweat to evaporate so it can become a serious problem.

Condensation will also occur when the sweat tries to evaporate. Water vapor gets doesn’t have anywhere to go so it latches onto the fabric. The outside air is cooler than the inside of the jacket so condensation will soak through the fabric. It’s like the condensation that forms on the outside of a cold glass of water.

Sweat and condensation are two of the reasons why your waterproof jacket will feel wet inside. Poorly ventilated waterproof jackets can cause more harm than good in light rain. Putting on your rain gear is almost like a balancing act. Put it on too early and you’ll be sweatier/wetter than if you’d left the jacket off completely.

Most waterproof jacket manufacturers combat this problem by using covered mesh ventilation holes, pit zips or core vents to increase air circulation. All these options help, but pit zips are easily one of my favorites. Your arms and shoulders cover the exposed area so light rain won’t get in and you can zip them up when the weather picks up. It gives you a lightweight jacket that can be used in wider range of applications.

Before I get into the details lets compare the weights of a few of my favorite pit zip jackets. I’ll separate them by price so you have a better idea of what to expect in each price range. Prices are constantly changing so I can’t give an exact price but I’ll separate them into budget (less than $100), Mid-Price ($100-200) and High-Price ($200-300).

Marmot Precip Jacket10.9 ozBudget
REI Rainer Jacket11.4 ozBudget
Black Diamond Stormline Stretch9.9 ozMid-Price
Enlightened Equipment Vist5.3 ozMid-Price
Lightheart Gear Silpoly Rain Jacket 6.7 ozMid-Price
Outdoor Research Foray Jacket (Full Torso Length Zipper)16.3 ozHigh-Price
REI StormBolt (cold weather)14.6 ozHigh-Price
Montbell Storm Cruiser10 ozHigh-Price

Are Pit Zips Worth It?

Pit zips are definitely worth considering if you’re considering a long backpacking trip. There’s no way to completely plan around the weather so it’s always nice to have a rain jacket just in case the weather turns. They’re light enough to toss in your pack as an extra jacket and provide excellent ventilation to reduce sweating and condensation.

I carry a lightweight Marmot Precip Eco jacket (10.9 oz). It’s affordable compared to other options and it’s the perfect weight for spring/fall/summer use. You can even keep the pit zips open the entire time you hike, without getting wet. You might feel a little cool before the hike, but your body heat will bring you to the perfect temperature.

I recommend waiting to toss on your pit zip jacket until the rain picks up above a light drizzle. Just toss on the jacket as soon as the rain picks up and open up the zipper whenever you start to feel hot. Try to time it so your jackets zipped up when the heavy rain starts, but open it up in light rain.

The key is unzipping the jacket as soon as you start feeling warm. Don’t wait until you feel wet with sweat, because that will lead to condensation issues. It’s better to get a little wet under your arms from the falling rain than be completely soaked from sweat/condensation. Your shoulders and arms will block most of the rain so rain will only get in on windy gusts.

Why Don’t All Rain Jackets Have Pit Zips or Core Vents?

There was a time when you couldn’t buy a high quality hard shell waterproof jacket without a pit zip, but they’re becoming less common. Gear manufacturers are improving their gear and coming out with breathable membranes that don’t sacrifice waterproofing, but are they as good as pit zips and core vents?

No a pit zip will almost always reduce sweating and condensation compared to breathable cores. So why don’t all manufacturers use pit zips in their jackets? They get to a point where the jackets are providing “enough ventilation” for most applications and they don’t want to increase production costs. Plus pit zips complicate production and it’s a weak point in their design that can potentially breaks. Here are a few other reasons why manufacturers decide to avoid pit zips.

  • It increases the manufacturing cost of the jacket. People work on set price points, so you can only increase a jackets price so much without affecting the consumer demand of the jacket. This cuts into profitability margins and limits their production of more profitable items.
  • Pit zips add extra weight to the jacket and diminishes the effectiveness of the breathable membrane. Waterproof jacket membranes are designed with ventilation issues in mind. They try to trap moisture away from your body, which adds insulation, but membranes can only hold so much without feeling wet.
  • Gore-Tex and some other waterproof jackets aren’t flexible enough to handle the movement of pit zips. They need clean straight lines and pit zips will rip straight through the fabric. Most of these jackets have mesh vents to increase airflow, but those don’t give you as much ventilation.
  • People will still buy jackets that don’t have pit zips without realizing how uncomfortable they can be. Most consumers have a set price point for their gear and don’t want to waste money on features they deem unnecessary. Think about how often you wear a rain jacket in your daily life. Backpackers, bikers, motorcycle riders and people that work outside are the only people that I can think of that have to deal with rain on a regular basis. Most people can get by without pit zips on their 3 minute walk from their car to a store/work.
  • There’s more potential for the jacket to get damaged. Pit zips increase the potential for damage on an expensive jacket. Zippers can break and loose flaps can get caught on branches and gear ripping the fabric. It’s just one more thing that can get damaged on the trail.
  • They prefer a sleek less complicated design with breathable membranes. Removing extra features on a jacket will significantly reduce overall production costs. Removing two zippers from a jacket might not seem like a lot, but it saves $3-5 per jacket. Plus there’s less of a risk of manufacturer defects and potential warranty claims.

When Should I Use A Pit Zip Jacket?

Pit zips are the most effective when there’s a big difference between your internal body heat and the outside air. This usually occurs in the spring/fall/winter when the outside air is cool. Your skin is about 91 °F so the internal jacket temperature can be significantly warmer than the outside air. This is a recipe for condensation without proper ventilation.

Pit zips will help keep out rain in the summer, but they won’t provide much relief. You might get a slight breeze to help reduce armpit sweat, but the temperature inside your jacket will be close to the outside air so there won’t be condensation.

Adding Pit Zips Is Easy!

You can always add pit zips to any waterproof rain jacket. It’s really easy to do an expands the versatility of the jacket. I decided to add pit zipps to my cheap Frogg Togg Ultralight jacket so I could get more use out of it. It can get kind of clammy without pit zips, but you really can’t beat the price at less than $30 for a jacket and rain pants.

Spend $5 on a zipper and sew it in to the jacket using a sewing machine or needle/thread. I got a quote from my tailor and she quoted me $15 to add pit zips to my jacket so that’s another option. Just make sure you use a coil zipper, because traditional zippers can’t withstand the constant movement under your arms. I recommend a #3 coil zipper, which can be found on Amazon or at any craft store.

Just flip the jacket inside out and use a sharpie to mark a straight line where you want the pit zip to go. Use a box cutter to cut a straight slit in the jacket. Take the coil zipper tape and sew it into the slit you cut into the jacket. Install the zipper slider and you’re good to go.

Pit Zip Limitations

Pit zips have lots of benefits, but they can only help so much in hot/humid weather. It’s impossible to remove body heat without a cool outside breeze. Any type of rain jacket will lead to excess sweating which will soak you just like the rain. Without the risk of hypothermia in the summer, it’s probably better to use an umbrella to keep your torso dry.

They make ultralight umbrellas for backpacking, but nobody likes carrying an umbrella. Check the weather and you might want to consider toughing it out if there’s sunny weather forecasted later in the day. Trekking umbrellas like the Euroschirm Liteflex Umbrella (7.3oz) are lightweight and have grooves to strap the umbrella to your pack.

Just use cord locks and a few inches of stretchy elastic cord to attach it to your backpack’s straps. You can buy elastic cord by the spool or cut up an old bungee cord to use with the cord locks. Just make sure you wrap the ends of the shockcord with tape and burn the ends to prevent fraying.

When there’s a significant difference between the inside jacket warmth and exterior temperature a pit zip or core vent jacket makes perfect sense. Look for a jacket with the biggest pit zips you can find. The zippers on the Outdoor Research Foray Jacket are particularly affective, but it’s expensive. It has zippers that run the entire length of the jacket from the bicep pits to the bottom hem.