Ski pants come in many different levels of insulation and protection. With so much tech built into our pants, it is easy to overlook the layers you wear underneath. Do ski pants take care of all of the insulation I need for different temperatures? Is it important to add extra layers underneath when skiing in cold weather? Can I just wear a regular pair of shorts or underwear under my ski pants regardless of the winter weather? Read on to find out.

Types of Ski Pants

Different types of ski pants require different underlayers. It is important to first determine the type of pants you own and then plan accordingly. Some pants are just a “shell.” That is, they are just designed to be the outermost layer that protects you from the elements and do not have any built-in insulation. These types of pants typically require more layers because they are naturally not as warm. Other pants contain insulation—either synthetic or down—that adds some bulk and helps keep you warm. These types of pants typically require less layering.

For shell pants, a baselayer plus a midlayer and/or an insulation layer is best. For insulated pants, a baselayer is fine on warmer days, and a baselayer and a midlayer are best for winter months. When skiing in freezing temperatures, a bonus layer is always a great choice!

Types of Layers

Baselayer

At a minimum, it is best to wear a baselayer that fully covers your exposed skin under your pants. Not only does this layer keep you warm and dry, but it also prevents the transfer of oils on your skin from reaching the membrane of your ski pants. Without this layer, your pants would quickly lose effectiveness at waterproofing and breathability. For this reason, I highly suggest a true baselayer instead of a pair of shorts. At a minimum, the baselayer should be a three-fourths length that reaches your ski socks. Often called thermals, long johns, long underwear, or tights, this layer is typically lightweight and thin, and it is made to wick sweat off of your skin. I will cover more info on the common materials used in just a bit.

Midlayer

Some skiers chose to add a thicker midlayer on top of their baselayer for added warmth. Midlayers differ from true insulating layers in that they are made of a single material, not a baffled material with an insulating filler. Often made of fleece, wool, or other thicker materials, these are thicker than their baselayer counterparts and are often a bit looser-fitting.

Insulation Layer

Finally, some skiers choose to wear an insulation layer under their ski pants. Insulative layers differ from midlayers in that they use a baffle design with an insulative filler to provide added warmth. Typically filled with down or down-like synthetic alternatives, these layers are best for the coldest environments or for skiers who like added comfort and warmth. Unlike an insulation layer under a jacket, removing an insulation layer under your pants midday is a challenge because it typically requires fully removing your boots and pants. For this reason, this layer is less common.

Baselayer Materials

Synthetics

Many baselayer options are made out of synthetic materials that are moisture-wicking or quick to dry. Synthetics are a great option because they are typically highly durable and great at moisture management. The trade-off with synthetic materials is that they often carry odors much more than their organic counterparts.

Some of the most common materials found in baselayers are polyester, polypropylene, rayon, or nylon. Many baselayers also feature a blend of these materials. Polyester is known for its ability to wick moisture, but it isn’t as quick to dry. Polypropylene dries quickly yet is less absorbent. Rayon is semi-synthetic, more antibacterial than other synthetics, and less prone to odor. Nylon is used infrequently because it is a thicker and less breathable material, but it is often mixed into fabrics for its durability.

It is common to see synthetic materials weaved into a waffle knit pattern. This design adds a raised triangle texture to the fabric, and the main reason it is used is to absorb water while also increasing the breathability of the garment to speed up the drying time. Synthetic thermal leggings are often the most inexpensive baselayers and are common for outdoor activities in winter weather.

Organics

Organic materials are a great choice for baselayers because of their natural odor resistance and ability to regulate temperature. Wool is a common organic baselayer choice since it is renowned for its antimicrobial and temperature-regulating abilities. Similarly, merino wool (wool with smaller fibers) is also commonly found in thermal pants due to it being softer and offering even better temperature-regulating properties. Despite its added cost, merino wool makes for a great baselayer and is often the material used in the best thermal underwear.

Silk thermals are also common because of their smooth and comfortable feel, but they are more expensive than other options and are occasionally less durable. However, this depends on the quality of the silk.

Many of the clothes we already own in our wardrobe are cotton. Cotton is cheap, comfortable, and accessible. But in the mountains, cotton has an infamous adage: “Cotton kills.” Because of its tendency to hold moisture, cotton baselayers are considered unsafe and unwelcome on the ski hill. To best enjoy your day on the mountain, ensure that you leave your cotton layers at home.

Midlayer Materials

Fleece

Fleece is a napped insulating fabric that comes in lightweight, medium-weight, or heavy-weight options. Despite the reference in its name, fleece is actually a synthetic material. It offers great added warmth, water resistance, and breathability. Fleece is not a good outer layer due to its wind permeability, but it works great under your pants.

Wool

Some brands also make thicker wool midlayers. Although this is more common in tops than bottoms, there are some wool midlayers on the market that have heavyweight wool and are more toasty than a standard baselayer.

Insulation Layer Materials

Organic Insulation

Down is an insulating material that is sourced from feathered animals. It is known for its water resistance and warmth, but some users avoid it for ethical reasons. It is more common to see insulating layers with alternate materials. One of the materials that is appearing more often in baffled insulating layers is wool. Wool can be sourced more ethically, and when used in a baffled design, it provides plenty of warmth and water resistance.

Synthetic Insulation

Synthetic insulation differs from down in that it is not sourced from animals. Often sold under different brand names, this insulation provides ample warmth and is often cheaper than down. These down alternatives may not be quite as warm as down and are also a little more prone to capturing moisture compared to down. But the hydrophobic polyester that they are made out of typically resists moisture relatively well, and they are known for drying even faster than down-filled alternatives. Most users are best off with synthetic insulation options for under their pants.

What to Wear Under Your Ski Pants

So, what should you wear under your ski pants? Depending on the conditions, you will want to use a combination of the layers listed above. In cold conditions, this means the warmest baselayer, a thicker midlayer, and a baffled insulating layer if your ski pants don’t have built-in insulation. On warmer days, simply wearing a pair of thermal long johns under your pants will likely suffice! Because layering depends greatly on location, I highly suggest messaging a Winter Sports Expert here at Curated and explaining your current gear and common ski conditions to help you find the best underlayers for you personally.