How to Wash Your Thermal Underwear

Author: Kate Amore, an alpine ski coach

As a ski instructor with years of experience teaching kids and adults how to ski, I know a thing or two about staying warm and how to wash all my gear. I've learned that base layers can make or break your day on the mountain - and washing your thermal gear correctly helps keep it free of dirt, sweat and in tip-top shape. 

Ask any seasoned skier or snowboarder, and they'll tell you that quality base layers are worth their weight in gold, but only if you take care of them properly. In fact, I've seen perfectly good thermals ruined by tossing them in the dryer or using the wrong wash settings. 

Keep reading as I show you exactly how to wash thermal underwear to keep it fresh, effective, and ready for your next outdoor excursion.

How to Wash Your Thermal Underwear

As the temperatures drop and the outdoor adventures ramp up, my thermal underlayers become my best friend. As a ski coach, synthetic layers are the key to staying warm all day on the mountain. However, like any clothing, they require proper care to maintain their effectiveness and longevity. Most of the time you’re wearing thermals, you’re probably doing something active, so they can get sweaty and need washing often. In this guide, we'll explore how to wash thermal underwear to keep them in top shape.

Why Proper Washing Matters for Thermal Materials

Thermal underlayers are designed to trap heat while wicking moisture away from your skin. Washing them incorrectly can degrade the fabric, leading to less insulation and moisture-wicking properties. Because they’re expensive, it’s important to wash them correctly and ensure they stay effective. Here’s how to properly wash your thermal underwear:

Check the Care Label

Before throwing your thermal underwear into the washing machine, always check the care label. Different materials have different care requirements. Most thermal underwear is made with merino wool, synthetic blends, and polyester. Understanding the specifics of how to wash each will help you choose the right washing method.

Washing Methods

Hand Washing

Best For: Delicate fabrics like merino wool.

1. Fill a Basin or Sink: Use cool or lukewarm water, and add half a HeySunday laundry sheet.
2. Submerge the Garment: Place the garment in the water, swirl and allow to soak for about 10-15 minutes.
3. Rinse Thoroughly: Drain the water and rinse the garment under cool running water until all detergent is gone. Avoid twisting or wringing, which can distort the fabric.
4. Dry Flat: Lay the garment flat on a clean towel to absorb excess water, then reshape it and let it air dry away from direct sunlight.

Machine Washing

Best For: Durable synthetic materials.

1. Set the Machine: Use a gentle cycle with cold water and ½ - 1 HeySunday sheet (depending on your load size). Avoid bleach and fabric softeners, as they can damage the thermal fabric fibers.
2. Turn Inside Out: Place your gear in the washer inside out. This protects the outer surface from friction and pilling.
3. Use a Mesh Bag: Place your thermal layers in a mesh laundry bag to help prevent snagging.
4. Drying: Air dry whenever possible. If you have to use a dryer, select a low heat setting to avoid shrinkage and damage.

Additional Tips for Care

1. Avoid Fabric Softeners: Fabric Softeners coat the fabric fibers and will reduce moisture-wicking properties of thermal fabrics.
2. Don’t Overwash: Frequent washing can wear out thermal layers. Unless they’re heavily soiled, a good airing out may suffice.
3. Store Properly: When not in use, fold your thermal layers and store them in a cool, dry place to prevent stretching and fading.
4. Repair Rather Than Replace: If you notice small holes or seams coming undone, repair them instead of tossing them out. This will extend the life of your layers.

Conclusion

With proper care, your thermal layers will keep you warm and dry season after season. Follow these washing guidelines to protect your thermal underwear and stay warm out there. Now it’s time to gear up, head out, and enjoy the great outdoors with confidence in your thermal layers!