How To Buy Baselayers

One of the most impor­tant pieces of any wilder­ness adven­ture and out­door ath­let­ic kit, base­lay­ers dry quick­ly, trans­port mois­ture away from the skin, resist odors, feel great, and last for many years. This all-impor­tant lay­er that is often not changed for days on end and acts like a sec­ond skin is no place to skimp. Our guide will help you learn how to choose the best base­lay­er for your needs.


Mate­rial: The choice of base­lay­er mate­ri­als real­ly boils down to two options: syn­thet­ic and wool. Both have advan­tages, var­i­ous styles, and legions of fans. The dis­ad­van­tages of both are few among top man­u­fac­tur­ers.

Wool: Used for cen­turies in tex­tile man­u­fac­tur­ing, wool is proven as a base­lay­er. Most qual­i­ty wool base­lay­ers use some blend of meri­no wool as the main fab­ric com­po­nent. This wool is some­times blend­ed with small amounts of poly­ester, span­dex or oth­er syn­thet­ic mate­ri­als to enhance the prop­er­ties of the shirt.

Meri­no Wool is trea­sured for its abil­i­ty to dry quick­ly and resist odors.

Some meri­no base lay­ers also use acti­vat­ed car­bon addi­tives such as Cocona to enhance the wool’s hydropho­bic, quick-dry­ing prop­er­ties. An added bonus of acti­vat­ed car­bon treat­ments is they tend to resist odors even bet­ter than meri­no wool alone.

Syn­thet­ic: Syn­thet­ic base­lay­er mate­ri­als often rely on poly­ester as the main ingre­di­ent.

Many com­pa­nies have pro­pri­etary poly­ester-based fab­rics such as the pop­u­lar Patag­o­nia Cap­pe­line. Oth­er fab­rics used by many com­pa­nies are made by name-brand fab­ric sup­pli­ers such as Polartec and Scholler.

These fab­rics are often sim­i­lar across brands, so oth­er fea­tures in the gar­ment set one brand apart from anoth­er. Expe­ri­enced users trust name-brand fab­rics to work well under tough con­di­tions.

Many poly­ester-based gar­ments blend span­dex or oth­er syn­thet­ics into the cloth to add stretch.

Some syn­thet­ics include antimi­cro­bial treat­ments to com­bat body odor.

Nicole Rock, Direc­tor of Design and Devel­op­ment at cloth­ing man­u­fac­tur­er Isis, said a few fac­tors help cus­tomers make the deci­sion between wool and syn­thet­ic.

“Deci­sions can be made on price point. Meri­no can be a pret­ty big invest­ment,” Rock says. “A lot of times depend­ing on knit, con­struc­tion and weight, syn­thet­ics may dry a lit­tle faster. If you have wool that gets wet, it still has good insu­lat­ing prop­er­ties.”

Eric Larsen, an Arc­tic Explor­er who has been to the sum­mit of Mount Ever­est and the North and South Poles in the same year, said he dress­es in mul­ti­ple base­lay­ers in extreme cold

“I start with a very light lay­er of syn­thet­ic, then wool because it’s nice and does­n’t smell,” Larsen says. “On top, I will wear a fleece as well. For long, extend­ed trips in extreme cold, I want all syn­thet­ic.”

Rock says many peo­ple choose wool for less demand­ing out­door adven­tures for its soft­ness and nat­ur­al feel.


Weight: Base­lay­ers are used in all weath­er con­di­tions, from frigid ice climb­ing to blaz­ing hot sum­mer runs. Accord­ing­ly, they come in a wide range of weights.

Light­weight: Many peo­ple choose a light­weight base­lay­er, either a tee or long sleeve shirt, as the first lay­er against the skin regard­less of the tem­per­a­ture. Light­weight base­lay­ers wick mois­ture away from the skin and offer the bonus of ver­sa­til­i­ty. Both syn­thet­ic and wool light­weight base­lay­ers can be used in hot tem­per­a­tures as a tee or under many oth­er lay­ers in the cold heart of win­ter.

Mid weight: A mid weight base lay­er can be worn against the skin or over a light­weight base as added insu­la­tion. Most mid weight bases are heavy enough to pro­vide some warmth on their own, espe­cial­ly in con­junc­tion with a light shell. These lay­ers are pop­u­lar as sum­mer moun­taineer­ing shirts, around the camp at night, or as part of a win­ter lay­er­ing scheme.

Heavy weight: Heavy base­lay­er gar­ments are usu­al­ly reserved for win­ter use. While they can func­tion well in spring and fall as stand-alone shirts, they gen­er­al­ly pro­vide too much insu­la­tion for warm weath­er activ­i­ties. Wear­ing heavy-weight base­lay­ers close to the skin pro­vides a wick­ing lay­er that dries quick­ly and also insu­lates against the cold.

Com­pres­sion: Some base lay­ers should be worn tight. These lay­ers, called com­pres­sion lay­ers, work by reduc­ing vibra­tions and lat­er­al move­ments in work­ing mus­cles to help reduce fatigue. Com­pres­sion gar­ments are pop­u­lar among run­ners, cross-fit par­tic­i­pants, and oth­ers who see a ben­e­fit from this type of mus­cle sta­bi­liza­tion. Most com­pres­sion lay­ers are not suit­able to be worn as win­ter base lay­ers for sports like moun­taineer­ing, hik­ing, and down­hill ski­ing where they will be worn for many hours or days on end.


Shirts: From tech tees worn year-round to heavy win­ter-wear, base­lay­ers are pop­u­lar shirts for all sorts of activ­i­ties. They can be worn in a broad range of con­di­tions and often are designed with fash­ion in mind.

Shirt fea­tures to con­sid­er are long zip­pers or but­tons under the col­lar that can be opened to dump heat dur­ing aer­o­bic exer­tion, thumb loops on long sleeve mod­els and hoods, which can sig­nif­i­cant­ly add to the warmth of the lay­er.

Bot­toms: Also called long under­wear or long johns, mod­ern base lay­er bot­toms are a crit­i­cal piece of gear dur­ing the win­ter months. A heavy weight bot­tom worn under a shell is often suf­fi­cient insu­la­tion for down­hill ski­ing even on mod­er­ate­ly cold days.

When choos­ing bot­toms, also con­sid­er the weight of your oth­er lay­ers. Will you wear only a shell over the bot­toms or do you wear an insu­lat­ed shell pant? Insu­lat­ed shell pants require much less addi­tion­al warmth and a light­weight base will like­ly work in all but the cold­est days.

A final thing to keep in mind when pur­chas­ing base­lay­er bot­toms is style. Remem­ber, there’s a pret­ty fair chance that they will be worn sit­ting around a fire­place with friends after a long day of ski­ing or rid­ing.

One-piece: No, onezies aren’t just for babies! While not the most pop­u­lar option, many com­pa­nies do offer one-piece base­lay­ers that cov­er the body from ankle to neck. The advan­tage of one-piece base­lay­ers it there are no seams at the waist to bunch or bind. There is also no chance of a shirt slip­ping up and expos­ing a large area of skin to the ele­ments dur­ing a fall or oth­er unplanned tum­ble.

Antimi­cro­bial prop­er­ties: Most base­lay­ers address body odor in some way or anoth­er. Most com­mon­ly, some type of antimi­cro­bial treat­ment or addi­tive pre­cludes the growth of stink-caus­ing bac­te­ria.

While most com­pa­nies treat their base­lay­ers in some way, not all are cre­at­ed equal. It’s worth inves­ti­gat­ing the way the treat­ment is applied and how long it’s guar­an­teed to work. Some old­er treat­ments were known to wash out of gar­ments over time. Most mod­ern tex­tiles are test­ed for antimi­cro­bial prop­er­ties through about 50 wash­es.

Exam­ples of pop­u­lar antimi­cro­bial treat­ments are Glad­iodor from Patag­o­nia, Poly­giene Active from Out­door Research made from sil­ver salts, and acti­vat­ed car­bon like that made by Cocona and used by var­i­ous man­u­fac­tur­ers.

SPF and UPF: If you’ve worn sun­screen you know about SPF. How­ev­er UPF is a slight­ly less seen rat­ing used for gar­ments. It stands for Ultra­vi­o­let Pro­tec­tion Fac­tor. Many base­lay­ers apply an addi­tive to increase resis­tance to ultra­vi­o­let radi­a­tion. They will fre­quent­ly list the SPF rat­ing of base­lay­er shirts in the tech­ni­cal infor­ma­tion of the prod­uct overview.

For ref­er­ence, a thin white cot­ton tee will have a UPF about 4, while a dark blue cot­ton tee could be as high as 18. Look­ing for a UPF or SPF rat­ing on out­door ori­ent­ed cloth­ing guar­an­tees a quan­tifi­able lev­el of pro­tec­tion.

Seams: Some tight fit­ting base­lay­ers, and par­tic­u­lar­ly com­pres­sion lay­ers, take seems into account dur­ing the pro­duc­tion process to elim­i­nate chaf­ing.