How to Choose the Best Long Underwear for Women

Amber  the author  styles it up the Petit Groupon in Rocky Mountain National Park in the Capilene 3 1/4 zip  a variation of the crew neck that we review in this article. There are many options  styles  colors  and features to choose from when you consider your next base layer. Learn about what's out there!
Article By:
Amber King
Senior Review Editor
OutdoorGearLab

Last Updated:
Monday

A long underwear top, also known as a base layer, is a versatile piece of clothing that will keep you comfortable whether you're boating, climbing, running, biking, or just hanging out on a cool and colorful fall day. If you haven't already, we highly recommend trading in your old cotton long johns and investing in a long underwear top made of wool or synthetic materials. Not only will you be warm and cozy, but the breathability will result in a huge performance difference in cold, wet weather.

With a plethora of new fabric technologies it's no wonder you might be confused about what to buy. What fabric to choose? What weight to get? What style to sport? Have no fear - OutdoorGearLab is here! Whether you are in the market for an inexpensive base layer shirt or a top-of-the-line long underwear top, we will help you choose the best layer for you! Read on to learn more.

How Does Moisture Wicking Fabric Work?


There are a variety of fabrics used when manufacturing a base layer. Some of the most common include merino wool, silks, Capilene, and different forms of polyester. Cotton is not a common fabric in performance base layers because it does not wick moisture, instead holding it next to the skin. If you perspire while walking up that hill at the back of your house, and a chilly wind comes through, you will find yourself cold. Unfortunately, layering clothing on top won't do too much to help since the cold moisture is locked in right next to your skin. On the other hand, wicking fabrics take any type of moisture that comes in the form of perspiration or precipitation and transfers it from the inside of the fabric to the outside. As a result, you stay warmer longer and your body won't experience serious temperature swings. The wicking fabrics on these layers aren't waterproof by any means…so if you get caught in a downpour without a jacket, know that they won't keep you 100% warm…but it will still provide some insulation when wet.

As water molecules accumulate (in a gaseous from) between the fabric and perspiring skin and high humidity situation is created. Water molecules move through the fabric in synthetics and are absorbed in merino wool. After it travels through the fabric (to an area of low humidity)  the water evaporates effectively "wicking away".
As water molecules accumulate (in a gaseous from) between the fabric and perspiring skin and high humidity situation is created. Water molecules move through the fabric in synthetics and are absorbed in merino wool. After it travels through the fabric (to an area of low humidity), the water evaporates effectively "wicking away".

Why Wicking Is Important


Typically made of wool or synthetic materials, a wicking base layer can be pertinent to survival in cold conditions. By comparison, cotton long underwear that you might find in department stores are not the answer to staying comfortable and warm in cold weather situations. Cotton absorbs any moisture (like sweat) and keeps it against your skin. It does not dry out when it's underneath other layers and the water absorbed by the fabric will stay cold. As a result, cotton actually keeps you cold, even if it warms up. This is the reason the age old saying "cotton kills" is so true in cold weather situations. These cotton layers might be an OK option when it is warmer outside, but if you're caught in an extreme wind or cold spell, you might find yourself in a life threatening situation.

Instead of cotton, we recommend purchasing performance long underwear that will 1) wick moisture or perspiration from your skin; 2) dry quickly; 3) regulate body temperature; and 4) provide comfort for prolonged activity. If you're anticipating exposure to any cold or windy extremes, your body will be thankful and you'll be able to climb that mountain without freezing your buns off. Not only that, but you'll come back to tell all your friends about your mission.

When you go from warm to cold on any endeavor  you need a fabric that will wick moisture and regulate temperature. All the base layers in this review including the Smartwool NTS (our Top Pick for Comfort) do just that and more!
When you go from warm to cold on any endeavor, you need a fabric that will wick moisture and regulate temperature. All the base layers in this review including the Smartwool NTS (our Top Pick for Comfort) do just that and more!


The Pros and Cons of Base Layer Fabrics


Now that you know how these fabrics work and why their performance is important, let's take a look at the pros and cons of the different types of materials out there. We'll discuss warmth, breathability, temperature regulation, and odor control.

Synthetics


This refers to layers with polyester and polyester combinations. For example, our Editors' Choice Award winner, the Arc'teryx Rho LT Zip - Women's, is made up of 84% polyester and 16% elastane. Our Best Buy Award Winner, the Patagonia Capilene Midweight Crew - Women's is made of 100% polyester. Most blends will contain some percentage of spandex or elastane to increase stretch, while others might incorporate a more durable fabric like nylon. Synthetics come in a variety of weights and blends, making different models more or less suitable for different seasons. Other synthetic pieces that we tested include the Hot Chillys Micro-Elite Crew - Women and Under Armour Base 2.0 Crew - Women's.

A close up of the synthetic fiber of the Micro-Elite Crew. The fabric is tightly woven and the fibers are made of plastics. These fabrics will wick well  dry quickly  and regulate temperature.
A close up of the synthetic fiber of the Micro-Elite Crew. The fabric is tightly woven and the fibers are made of plastics. These fabrics will wick well, dry quickly, and regulate temperature.

Pros:
Dries more quickly than others
Retains its structure (i.e. it doesn't stretch out)
Better for wet conditions
Often less expensive

Cons:
Not odor resistant unless treated, and even after that they tend to have long-term stink
Petrol-based fibers
Temperature regulation isn't as effective as merino wool.

Wools


The outdoor industry has come a long way since the age of thick, heavy, and utterly itchy union suits that soldiers would wear on the front lines in the early 1900s. This is a great example of no temperature regulation. Thanks to technology, and merino's "ultra-fine" fibers, wool has evolved. It's not itchy, too hot, or heavy, and it is one the best temperature regulating fabrics out there, making it great for all seasons. Not only that - but it doesn't develop a long-term stink! Merino wool layers that we tested included the SmartWool Merino 250 Base Layer Crew - Women's, Minus33 Ossipee, and Icebreaker Oasis - Women's.

A look at one of the more solid merino fabrics. This will regulate temperature REALLY well  stay soft on the skin  and won't get smelly as easily as synthetics. We did notice a tiny bit of pilling on the seams  but that's about it.
A look at one of the more solid merino fabrics. This will regulate temperature REALLY well, stay soft on the skin, and won't get smelly as easily as synthetics. We did notice a tiny bit of pilling on the seams, but that's about it.

Pros:
Great temperature regulation
Natural fibers
Easy Care
Resistant to long-term odor
Warm when wet
Feel amazing on the skin

Cons:
Stretch out after ample use
Some wool blends can irritate skin - test before buying
Take a longer time to dry

Silks


Even though we didn't review any silk blend long underwear, we figured it would be worth the mention. As the popular Seinfeld episode brought up in issue, it may reduce sperm count (due to a lack of breathability)…but that's a non issue for us ladies (thankfully!). Silk is a comfortable, smooth, and luxurious fabric that is best for cold weather use since it doesn't breathe as well as other fabrics. Save these for cold days sitting in the shade instead of the sunny spring days skinning the mountain.

Pros:
Feels amazingly smooth and luxurious against the skin
Ample warmth
Natural fibers
Very thin and easy to layer

Cons:
Not very durable
Not very breathable
Needs special laundering care (i.e. hand washing)

Cotton


Cotton is widely used and folks who don't know any better will show up to the trailhead wearing cotton long underwear without realizing the risks in cold weather. In warm, dry weather, they can be amazing if you're not moving around too much to generate any sweat. But in general, cotton does not wick- instead, it absorbs and holds water. So for really hot weather it's a good option. It's also nice and cozy when dry. So if you do buy a pair of these, reserve them for your dry endeavors in warm weather. Do not wear them in cold weather or if there is a chance you might get wet…worst case it could be quite dangerous to your own livelihood.

Pros:
Inexpensive
Feels nice on the skin when dry
Light and breezy
Easy Care
Breathable

Cons:
Absorbs water
Slow to dry
Will stay cold
Not good for a cold and windy weather layering system

These are the most common performance base layer fabrics you'll find in the stores today. Take some time to consider what you are looking for in your long underwear.
If warmth, versatility, and odor control are most important to you, opt for a merino wool layer like the Icebreaker Oasis Crew or the Minus33 Ossipee. If you like a layer that dries incredibly fast and doesn't stretch out over time, you might want to consider buying a synthetic layer with 100% polyester like the Patagonia Capilene 3 or a synthetic blend like the Hot Chillys Micro-Elite Crew.

Fabric Weights


Opening the door to the REI, you are greeted by smiling faces and a gargantuan maze of aisles and gear. You set out on a quest to find the base layer section. As you snake your way through the store and past climbing ropes, helmets, bikes, and paddles, you take a left and find yourself in women's clothing. Looking over the racks of cute clothing by popular manufacturers like Prana and Mountain Hardware, you locate the long underwear. Zeroed in, you move towards them. As you get closer you notice that the selection is huge and a bunch of the layers are in funny cans and boxes - not the most welcoming for trying on. Not only that, but they have different numbers of numbers and weights for each type. What does this all mean?

Most clothing manufacturers don't just make one long underwear weight because each weight has a different function and place in the outdoor world. Some manufacturers call these different weights just that, while others use numbers to designate the different weights.
Generally speaking, there are four designations of weights to consider when you are making your way through those cans and packages:
microlight, lightweight, midweight, and heavyweight.


In this review  we cover mostly midweight and lightweight fabric options even though there are more out there for any adventure.
In this review, we cover mostly midweight and lightweight fabric options even though there are more out there for any adventure.

For example, Patagonia numbers its Capilene and merino wool products lines from 1 - 4. Number 1 is the lightest (aka ultralight weight) while the 4 is the heaviest (expedition or heavy weight). In general, microlight weight is intended for summer use or conditions where the weather is slightly cool and mild - a perfect addition for those warm summer nights. Lightweight pieces are intended for mild fall or spring days, perfect for a warm hike in October. Midweight pieces have a place for cooler to cold days. For example when you plan on head to the resort for a ski adventure on a cold day. Heavyweight pieces are intended for the coldest days of winter, or expeditions where cold weather is to be endured long term - perhaps an expedition to Antarctica or Northern Minnesota in the brunt of winter.

The longer length of the Arc'teryx Rho is perfect for any pursuit. From multi pitch climbing to skiing  this layer won't leave your skin exposed.
The longer length of the Arc'teryx Rho is perfect for any pursuit. From multi pitch climbing to skiing, this layer won't leave your skin exposed.

The long and short here is to anticipate what weather you will be experiencing and buy a weight according to what activities you anticipate doing. If you're just looking for an all-around piece, the midweight layer is a good route to go. If you know you run cold, get a heavier piece. If you run warm, get a lighter weight garment. If you plan on doing aerobic activities consider an ultralight weight running shirt.

Fit & Features


The fit and features of a base layer are also two important considerations. Different garments have different sizing, so trying a few models and sizes on will help you make sure that everything fits well. And ladies - let's face it - some of us have large boobies. Don't settle for a shirt that doesn't fit properly - take the time to find something that will accommodate your size. A layer with longer length and stretch like the Arc'teryx Rho LT proved to do well in this area. Rigid tops like the Under Armour 2.0 probably won't work for some women because of its lack of stretch. For features, you can choose from a simple layer, or a complex layer riddled with hidden pockets, built-in mittens, and/or hoods to accommodate for any and all types of weather.

The Space Dye that Sophia sports has a great zip up collar and thumb loops for more versatility!
The Space Dye that Sophia sports has a great zip up collar and thumb loops for more versatility!

Fit


One of THE most important things to consider is the fit of the garment. You know that saying "fits like a glove?" Well, that totally applies here. Base layers are meant to cover you and stay close to your skin. You don't want something skin tight or a bag-like fit. You want to be able to layer clothes on top and maybe below (so that you can strip down to your tank when the mercury rises). Not only that, but buying a base layer that is long will serve you well on active days. On of the pet peeves of our reviewers were tops that were simply too short. Having a layer ride up and expose your skin is no bueno and defeats the purpose of owning and using a base layer in first place. So we can't stress enough that your new long underwear should have a length that sits between your hips and bum and most importantly - make sure it fits like a glove.

Snug like a glove! This polyester blend long underwear feels good and has the right lengths wherever you need it. We especially loved its zip collar that lended additional versatility.
Snug like a glove! This polyester blend long underwear feels good and has the right lengths wherever you need it. We especially loved its zip collar that lended additional versatility.

Features


Long underwear also range from super featured to no features at all. The Patagonia All Weather Top is a new release that the main author just purchased and it has features like built-in gloves, a hood, venting in the back with a super secret pocket in the hem. None of the long underwear tops we tested were that fancy, but some, like the Arc'teryx Rho and Patagonia Capilene, did sport stash pockets and thumb loops. Some, like the Under Armour Base 2.0 had a crew neck, while others had a zip neck. Depending on what you need your layer for, consider these different cuts and features.

Thumb Loops are nice to have because they create an anchor point for your sleeves. Some people love them while other people hate them. Regardless, they are a nice addition that make the layer more versatile. When layering over other tops you can slip your thumb into the loop to help pull down the fabric of the arms. On some pieces you can use the thumb loops to help secure an iPhone in the sleeve of the garment. One of our testers found that the Under Armour Base 2.0 had large and thick enough cuffs and thumb loops to tuck her iPhone into the inside of the arm without it flopping around - a new stash spot! Not only that, but the thumb loop allows you to pull the fabric over your hand if the weather turns and you find yourself without gloves. The Under Armour and Patagonia Capilene tops were the only two tested with thumb loops - we thought they should be present on all shirts!

Thumb loops make layers more versatile and we wish there were more among the tops we tested. The cuff and thumb loop combo on the Under Armour 2.0 were rigid and thick enough to allow an iPod to fit in the sleeve. Talk about a secret stash spot! Sawwwweeeettttt!
Thumb loops make layers more versatile and we wish there were more among the tops we tested. The cuff and thumb loop combo on the Under Armour 2.0 were rigid and thick enough to allow an iPod to fit in the sleeve. Talk about a secret stash spot! Sawwwweeeettttt!

Crew Necklines are great for layer combinations where you have neck protection like a neck gaiter incorporated. They are also great for days when it's not too cold outside since they allow a little more breathability. Most of the layers we tested incorporated a crew neckline. We find that these necklines are not as versatile as the zip-up neck options.

Brittany and Amber sport the Under Armour 2.0 base and Patagonia Capilene 3 (our Best Buy Award). Both are crew necks  and are available in zip up options if you prefer.
Brittany and Amber sport the Under Armour 2.0 base and Patagonia Capilene 3 (our Best Buy Award). Both are crew necks, and are available in zip up options if you prefer.

Zip Necklines are a little more versatile since you can choose to stay unzipped for normal days out or to zip-up when the wind kicks up. Zip neck options tend to be a tad more expensive and add a little more bulk.

Sophia and Amber giggle over taking too many selfies on Red Mountain pass. They both wear zip neck options that allow more venting options than conventional crew neck tops.
Sophia and Amber giggle over taking too many selfies on Red Mountain pass. They both wear zip neck options that allow more venting options than conventional crew neck tops.

Pockets are nice to have on a base layer. A little stash place for a small iPod or a kleenex can be vital when you're using your layer as a stand-alone piece for more aerobic activities like skinning, running, or hiking. Sometimes they are located as a hidden pocket on the hem, other times they are on the shoulder or the breast. The only layer that incorporated one on the arm was the Arc'teryx Rho LT.

Stash pockets are sweet! The Arc'teryx Rho was the only top that had an extra stash pocket. Super handy for keys  cash  or whatever little extras you might need on the trail.
Stash pockets are sweet! The Arc'teryx Rho was the only top that had an extra stash pocket. Super handy for keys, cash, or whatever little extras you might need on the trail.

UPF (Ultraviolet Protection Factor) might be another factor to consider when purchasing a base layer, especially if you intend to use it while cruising across a glacier on a sunny day or while running through the desert. Ultraviolet light can penetrate through most thin fabrics and can still cause some sun damage. So if you're interested in protecting your skin or you are sensitive to the sun, find a layer with a UPF factor of at least 40+ like the Hot Chillys Micro-Elite or the Smartwool NTS 250 Crew.

Hoods are another feature to consider when looking at a base layer. Most don't come with a hood as they are intended to go beneath all your clothes and might add extra bulk; however, a hood also adds versatility. None of the pieces we tested incorporated a hood, but there are many out there!

The Patagonia All-Weather top is a good example of a fully featured base layer. It is synthetic with a hood  thump-loops  and cuffs that turn into mittens! Not only that but it has a zip up collar that goes over your chin for full coverage!
The Patagonia All-Weather top is a good example of a fully featured base layer. It is synthetic with a hood, thump-loops, and cuffs that turn into mittens! Not only that but it has a zip up collar that goes over your chin for full coverage!

So now that you have the 411 on the basics of buying base layers, remember the things you need to determine: start by choosing your fabric and weight based on the activities and climate you are preparing to tackle; then choose your features and fit; after that, choose the colors and styles you gravitate to the most and get ready to experience all sides of mother nature with confidence and comfort.

Amber King
About the Author
After finishing up her B.Sc and B.Ed in 2009, Amber moved to the U.S.A from Canada to spend time in the mountains of the West. Drawn in by dreams of climbing perfect cracks, and exploring new areas, she found herself in a few different places - Utah to Colorado to Arizona to Washington and back to Colorado. Along her journey she discovered trail running as a new found love and is learning to be an endurance athlete. When she's not playing in the wilderness, you can find her planning experiential based school trips as a high school science teacher or frollicking in the mountains of the San Juans.

 
 

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