How To Buy Midlayers

Because of the ver­sa­til­i­ty of out­er­wear, many peo­ple use all sorts of jack­ets, vests, sweaters and turtle­necks as mid lay­ers. Many work just fine but with a lit­tle plan­ning you can accen­tu­ate the engi­neer­ing of your base and shell lay­ers, expand the tem­per­a­ture range of your out­fit and min­i­mize the bulk around your body.

For the pur­pose of this arti­cle, mid lay­ers are those between a base lay­er (one or two gar­ments worn next the skin) and the shell (which direct­ly faces the elements).

This mid lay­er could be made up of a sin­gle or mul­ti­ple items of cloth­ing, such as a thin fleece com­bined with a down vest, or just a sin­gle insu­la­tor like a heavy fleece jack­et worn under a shell.

Insu­la­tion – The pri­ma­ry pur­pose of a mid lay­er is to hold warmth close to the body while mov­ing mois­ture away. This cre­ates dry, warm micro-cli­mate near the skin.

The con­cept of micro-cli­mate means it’s com­fort­able near your body regard­less of what­ev­er nas­ti­ness may be going on out­side your clothing.

By reg­u­lat­ing the flow of mois­ture and air near your skin while block­ing wind, rain, snow and oth­er crud far away, you cre­ate a hap­py place for your body to exist regard­less of the elements.

Mate­r­i­al – The most sought-after mid lay­ers are con­struct­ed from mate­ri­als that are light, insu­lat­ing, and breath­able. The most com­mon fab­rics for this lay­er are wool, fleece, and down.

Wool – A time-test­ed mate­r­i­al with excel­lent insu­lat­ing prop­er­ties, wool is water resis­tant, very breath­able and insu­lates when wet. Wool gar­ments of many thick­ness­es pro­vide great ver­sa­til­i­ty. The draw­backs of wool are bulk and weight, espe­cial­ly once wet. Wool does not com­press very well, so a heavy sweater will take up quite a bit of space in a pack.

Fleece – the term fleece orig­i­nal­ly meant wool, but in mod­ern times it is used to iden­ti­fy syn­thet­ic mate­ri­als with prop­er­ties sim­i­lar to wool. Fleece is usu­al­ly made of poly­ester fiber.

Fleece, espe­cial­ly thin gar­ments worn direct­ly over base lay­ers, makes excel­lent insu­la­tion. Fleece main­tains warmth when wet and is breath­able. Some fleece is designed with lay­ers of GORE Wind­stop­per or oth­er wind-block­ing material.

Like wool, fleece tends to be a lit­tle bulki­er and heav­ier than down insulation.

Syn­thet­ic Down – Sev­er­al types of insu­la­tion, such as Polartec Alpha, Pri­maLoft and Cli­mashield, have sim­i­lar insu­lat­ing prop­er­ties as down. They are very breath­able and work well even when wet.

Syn­thet­ic down does not com­press as well as real goose or duck down so it will take up more room in a pack although they are clos­ing the gap on nat­ur­al down.

Mod­ern syn­thet­ics are ver­sa­tile and accept­ed by high-end man­u­fac­tur­ers for their mois­ture man­age­ment and durability.

Down: Still con­sid­ered by many to be the best insu­lat­ing mate­r­i­al avail­able, high-end down is warm, light and extreme­ly com­press­ible. Some well-designed down mid lay­ers will com­press to the size of a cof­fee cup or small­er for stow­ing in a jack­et or pack.

For many years, the only neg­a­tive asso­ci­at­ed with down was that it lost most of its insu­lat­ing prop­er­ties when wet. This is still the case with stan­dard down, which must be kept dry to work properly.

With the advent of Dri­D­own, this mate­r­i­al became much more ver­sa­tile and resis­tant to mois­ture. Hydropho­bic treat­ments have cre­at­ed a type of down that dries quick­ly and main­tains loft even when damp. These treat­ments are not a cure-all and down should still be kept dry if possible.

Down is rat­ed by fill pow­er. An entire arti­cle can be devot­ed to the types and qual­i­ties of down, but the short ver­sion is this: the high­er the num­ber, the lighter, more effi­cient, more com­press­ible, warmer per ounce, and more expen­sive a down jack­et will be.

Frank Kvi­etok, the Direc­tor of Advanced Devel­op­ment at Amer­i­can Rec (mak­ers of Sier­ra Designs Dri­D­own) explained the advances in hydropho­bic down technology.

“Basi­cal­ly think of Dri­D­own as a down with a Durable Water Repel­lant on it. You have not made the fab­ric water­proof, but the fibers are water­proof. It doesn’t turn a down jack­et into a rain­coat. It makes the down itself high­ly water repellent.”

Types – Mid lay­ers are designed in many dif­fer­ent jack­et con­fig­u­ra­tions. Hood­ed coats, vests and pullover type sweaters are all com­mon­ly used as insu­la­tion under a shell layer.

When choos­ing a mid lay­er style, con­sid­er things like inte­ri­or pock­ets to keep phones or cam­eras warm and func­tion­al, hoods to insu­late around your head under a shell and if the lay­er has a zip­per or but­ton down the front to open if you need to cool your body after exertion.

Weight – some jack­ets – espe­cial­ly wool and fleece – weigh more than oth­ers. Keep this in mind when choos­ing a mul­ti­ple lay­er sys­tem. The com­bined weight of four or five lay­ers can become cumbersome.

For lay­ers that will be stowed in packs, nat­ur­al down is usu­al­ly much more com­press­ible for the amount of warmth. Thin down sweaters also make for pop­u­lar belay parkas, pulled on for extra heat dur­ing body chill­ing breaks dur­ing climb­ing, because of their light weight and compressibility.

Use these tips to help guide your choice of mid lay­er gar­ments. Be sure to read reviews of items that catch your inter­est and find the most fit­ting cloth­ing for your next adventure.