By Marc Simonpietri
You probably have more midlayers in your closet than you realize. That still-fitting fleece jacket from summer camp? It could work. A light, puffy jacket that never seems warm enough for actual cold weather? That could work too.
Truth be told, midlayers are a very adaptable layer that can come in many forms. But, that doesn’t mean you want to bring just anything along for your next summit. Below are some considerations on what kind of items can work as midlayers, and different features you may look for either in your closet, or at the store.
How it’s Used in the Layering System
First, let’s go through how a midlayer will be used in the layering system. As the name suggests, a midlayer will be used in the middle of your layering system. Above your baselayer, but underneath any other upper-body layer such as the softshell, hardshell, or insulated parka.
The midlayer should be a generally form-fitting layer, large enough to fit over a baselayer top (discussed here), but not so loose that it creates bulk under a shell layer. It should be relatively compact, as you don’t want it to take up a ton of space in your pack when not in use. And you don’t want a midlayer to be too warm. It should provide some warmth on a cold day, but still be light enough to vent extra heat while you’re working hard.
Fleece, Grid-Fleece, and Insulation
As with other gear in the outdoor industry, midlayers have plenty of different options to choose from. Let’s go through a few of them below.
This is your standard midlayer insulation material. Think back to that summer camp fleece you wore every day, similar to this one in our shop. While generally warm, these jackets tend to be a bit bulky and don’t retain heat very well compared to other midlayers.
A similar type of material to your classic fleece, but the grid-fleece pattern incorporates some new technology to improve its performance substantially. By using a grid or waffle-like pattern, products like the Patagonia R1 are able to trap more warm air while still remaining breathable enough to keep you from sweating. These newer pieces also typically pack into your pack smaller, and include useful features like thumb holes, chest pockets, and a longer hem to stay tucked in under your harness.
For those cold, cold trips a fleece might not be warm enough. You might consider using a very lightly insulated piece as your midlayer. Items such as the Arc’teryx Atom LT incorporate synthetic insulation in the body of the jacket, with fleece panels along the sides to prevent overheating and reduce weight. These types of jackets provide significantly more warmth than a classic midlayer, but if you’re on Mt. Rainier in the winter, or somewhere perennially cold like Vinson Massif, you’ll be happy to have it.
Lastly, when looking for midlayers, do yourself a favor and get one with a hood. Hoods can instantly make a jacket go from being just a little too cold, to just right – keeping you from stopping and digging into your pack for yet another layer. Midlayer hoods should also fit underneath your helmet, thereby creating much more warmth for that cold pre-dawn climb.
While many items in your closet may be able to serve as a midlayer, it is still worth taking the time to find the right one that incorporates good features, usability, and the right level of warmth for your climb.