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How to Choose the Best Base Layer Top for Women

Alison and Amber summit Mt. Sneffels in the San Juan Mountains of Colorado while sporting bomber base layer tops. Worn either on their own or under another layer  these tops are integral in any outdoor woman's wardrobe.
By Amber King ⋅ Senior Review Editor
Wednesday November 14, 2018

While you're crushing in the backcountry, owning a solid base layer top is a top priority. But even when shoveling snow or waiting for your car to heat up in January, these are great tops to have on. Designed to sit next to the skin, the ideal top will regulate temperature by wicking moisture away from the skin, and providing warmth — even when wet. Its materials should be soft and cozy for all-day wear and will keep you comfortable while you tackle technical terrain. While most base layers are engineered to fit underneath other layers, many women wear them as a stand-alone piece on warmer days or while hitting the town. So what do you need to consider in this important piece of outdoor gear? In this article, we provide an overview of the different parts that make up these tops; specifically, different fabrics, weights, and features. In addition, we offer insight on style and fit. We hope these topics will guide you to find the best base layer top for you.

Baselayers are an integral piece of gear to keep you comfortable and dry in all kinds of conditions.
Baselayers are an integral piece of gear to keep you comfortable and dry in all kinds of conditions.

Learn more about layering by checking out our Introduction to Layered Clothing Systems article that explores what a fantabulous set-up looks like.

Fabric Types


To start our discussion, we will begin with the pros and cons of different types of fabrics that these tops are constructed from. On the market, there is a slew of options extending from cheap and scratchy cotton jumpers to expensive yet cozy Merino wool constructs. Below we outline the pros and cons of the different types of fabrics on the market. In this section, we discuss cotton, synthetics, merino wool, and blends.

When buying long johns, check the tags to see what the fabric make-up is. If shopping online, be sure to click on the "specs" tab to see what the materials are constructed from. Avoid cotton or cotton blends at all costs if you plan on going into the backcountry. They will not keep you warm in cold or wet weather and can actually be dangerous to choose in these conditions.

Cotton


Cotton is widely used because of its low cost. Those who aren't aware of the ramifications may buy these cotton garments from popular stores without realizing what happens when the material gets wet. In warm, dry weather, it can be amazingly comfortable as it breathes well. However, it's a highly absorbent material, doesn't wick and holds moisture in humid or wet conditions. If you sweat while wearing the material, the sweat will stay on your skin, condense, and keep you cold. You might find your base layers freezing, ultimately lowering your body temperature. If you get into severely cold and wet weather, the popular phrase "cotton kills" marches in…it can result in hypothermia and some extreme cases death. As a result, don't buy or depend on cotton for cold or wet weather.

Pros
  • Inexpensive
  • Very breathable
  • Feels nice on the skin when dry
  • Easy care
  • Fine around town

Cons
  • Absorbs water
  • Slow to dry
  • Cold in the slightest bit of humidity or cold weather

Best For…
  • Warm and dry weather
  • Non-active use

Synthetics


Garments constructed with synthetic fabrics are often either 100% polyester or a blend of synthetic materials. While these garments are typically less expensive and quick to dry, they are often not as warm as Merino wool options. Here is a quick list of the pros and cons of Synthetic competitors.

The REI Co-op Midweight is a perfect option for skinning uphill on warm winter days. This synthetic wicks well and dries quickly.
The REI Co-op Midweight is a perfect option for skinning uphill on warm winter days. This synthetic wicks well and dries quickly.

Pros
  • Quick to Dry
  • Absorbs less water
  • Durable fibers (doesn't stretch out)
  • Often less expensive
  • Easier to layer with smoother face fabrics
  • Wicks well

Cons
  • Sometimes stinky (even with odor control technology)
  • Petrol-based fibers
  • Smaller range of temperature regulation in comparison to Merino wool
  • Moisture can linger in the fabrics
  • Not as warm as Merino wool

Best For
  • Wet conditions
  • Friction-based sports like crack climbing, canyoneering, or bushwhacking
  • Where drying quickly is a necessity
  • Layering under sticky midweight layers
  • Outdoor aerobic activities as a wear-alone piece

Merino Wool


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. 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!

Alison enjoys the perks of her 100% Merino Wool zip neck top that offers a wide range of thermoregulation and comfort throughout the day...whether she's running or taking a break to take in the views in the towering San Juan mountains.
Alison enjoys the perks of her 100% Merino Wool zip neck top that offers a wide range of thermoregulation and comfort throughout the day...whether she's running or taking a break to take in the views in the towering San Juan mountains.

Pros
  • Fantastic temperature regulation
  • Natural fibers
  • Easy Care
  • The odor is not an issue
  • Warm when wet
  • Amazingly comfortable on the skin

Cons
  • Less durable (holes easily appear)
  • Longer time to dry
  • Absorbs more water
  • Typically heavier in weight
  • Typically more expensive than synthetics

Best For
  • Pretty much everything except friction-based activities that might tear the fabric

Merino Wool-Synthetic Blend


We haven't reviewed a whole lot of these blends, but the revolutionary new technology developed by Patagonia is a show stopper. This fabric blend features both Merino wool and polyester materials. This high performing material is excellent for a wide range of uses, offering the best of both worlds.

The Capilene Air by Patagonia is a Top Pick for its wide range of thermoregulation and amazing wicking power. A perfect option for a Fall hiker or while layering underneath a shell on a blasting cold day.
The Capilene Air by Patagonia is a Top Pick for its wide range of thermoregulation and amazing wicking power. A perfect option for a Fall hiker or while layering underneath a shell on a blasting cold day.

Pros
-A range of temperature regulation comparable to merino wools
-Super cozy and comfortable
-More durable than 100% merino wool
-Amazing wicking power
-Very quick to dry

-Very warm

Cons
-Less durable than most synthetics

-Absorbent

Best For

-A wide range of activities including those that are highly aerobic and for those requiring just a sit-down moment.

So what do you need? Consider where you live and the performance that you require from your piece. If you're in wet conditions, a merino wool contender will keep you dry and warm throughout the day. However, if you're seeking a top that will dry quickly and won't absorb a whole lot of moisture if wet, a synthetic option may be the best choice. Or, if you want a combination of performance features, consider a blend.

Choose your Fabric Weight


What are different fabric weights? There are four different fabric weights to consider when making your long underwear purchase.

Micro Lightweight


The lightest of them, this super fabric is meant for providing sun protection during the warmest seasons of the years. It is constructed of ultra-thin materials that are perfect for running in the warmer weather of the spring, summer, and fall.

Here in on Burch Mountain in Washington  Amber wears a micro lightweight running shirt. These layers (also long sleeve) are super light and meant for aerobic excercise in warm weather.
Here in on Burch Mountain in Washington, Amber wears a micro lightweight running shirt. These layers (also long sleeve) are super light and meant for aerobic excercise in warm weather.

Lightweight


Perfect for warm weather that has a little nip in the air. This lightweight option is a tad warmer than the micro lightweight fabric and ideal for year-round use when temperatures are warm. It's also an excellent option for warmer winter days where you might find yourself hiking uphill for a few hours, or for colder nights where you have a few additional layers. If you run warm, it's a great option. But if you run cold, you might want to graduate to the next weight category.

Midweight


A versatile weight that is perfect for a plethora of uses. It will keep you warm with a proper layering system in winter storms down to double negative digits. On warmer days, it can be worn on its own as a long-sleeve top. Great for year-round use.

The midweight WoolX Hannah is a great example of a 100% merino wool midweight base layer.
The midweight WoolX Hannah is a great example of a 100% merino wool midweight base layer.

Heavyweight


If you plan on hitting the coldest temperature on Earth, a heavy (or expeditionary) weight layer is best. Suited for frigid temperatures and frigid conditions, this layer is very thick and can be worn as an insulating shirt in cooler conditions. As a super warm base layer, it's not really functional for anything less than the coldest temperature out there, unless you want to wear it on its own as a warm insulating top.

Fit & Style


You know that saying "fits like a glove?" Well, that applies here. Base layers are meant to fit close to the skin and shouldn't be too fit nor too baggy. This enables effective wicking and warmth over time. Also, you want to make sure the arms and torso are long enough to cover all your skin. It shouldn't ride up while moving and ideally it's easy to layer underneath other layers. The takeaway? If the fit doesn't feel right, don't buy it.

If you're unsure about ordering online, make sure you purchase from a dealer with an easy return policy. This way you can try things on and send them back if you don't like them.

The Smartwool 250 Crew is comfortable for wear-all-day (and all-night).
The Smartwool 250 Crew is comfortable for wear-all-day (and all-night).

In addition to fit, choose a style that you prefer. Typically long underwear tops will come in different cuts. The most popular is crew cut, zip neck (with varying lengths of zipper), and hooded options. Crewcuts are a nice option as they don't have a collar on the shirt, and are fairly low profile, hiding underneath another layer. These are great for situations where you may not require additional neck coverage or if you have a variety of other layers already. A zip neck offers a collar and a little more warmth (and ventilation) and protection from the elements by providing insulation to the neck. These are quite versatile, as they can be zipped down in colder weather. Different zipper lengths (½ zipper v.s ¼ zipper) offer access to layers you might stack underneath the base layer top. A hooded option is the warmest and by far the most protective. These are awesome tops if you plan on wearing it on its own or you don't already have a layer with a hood. These aren't the greatest tops if you're layering and you already have a jacket with a hood and an insulating layer with a hood. This might add a little too much bulk. In our review, we outline the types of cuts available. Based on your needs, you decide what you need.

Features


What features should you consider? Long underwear tops come with a diversity of different features. Some are super simple while others come loaded with thumb loops, hidden pockets, hoods, and more. Here we explore a plethora of features that you should consider in your purchase.

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 an excellent addition that makes 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. The only shirt in this review with thumb loops is the Patagonia Midweight Capilene.

The thumb loops are a feature only found with the Patagonia Capilene Midweight Crew. A great extra for pulling on layers and keeping the layer in place.
The thumb loops are a feature only found with the Patagonia Capilene Midweight Crew. A great extra for pulling on layers and keeping the layer in place.

Pockets are super sweet. A little stash place for car key, credit card, or Kleenex is quite convenient while out on a jog around town. Our testers liked them for long trail runs and skinning adventures in the mountains. Sometimes they are located in a hidden pocket on the hem while other times they might be found on the arm or breast. The only layer that incorporated one in this review is the Arc'teryx RHO LT Zip.

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. If you plan on being in a super sunny spot like a glacier or the desert, UPF might serve you well. 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 Smartwool 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. The Patagonia Capilene Air offers a hooded option.

Conclusion


When considering the purchase of your next base layer top, consider what you demand in the performance of your top. What fabric type, weight, and features are right for you? Make sure the fit and style are exactly what you are looking for. To learn more about the best long underwear tops out there, take a gander at our comparative review of The Best Base Layer Tops for Women. It will serve you well in your search.

Base layers are great to wear either on their own or under several layers. Pictured here is a bachelorette hut trip on Red Mountain Pass in Colorado and a classic way OGL gets out to test base layers side-by-side!
Base layers are great to wear either on their own or under several layers. Pictured here is a bachelorette hut trip on Red Mountain Pass in Colorado and a classic way OGL gets out to test base layers side-by-side!


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