What is the best insulated underwear for keeping you warm? Well, first we must understand how Thermal underwear works, then we can look for those fabrics that have the best characteristics we are looking for in our base layer.
To begin, insulated underwear are not designed to keep you warm, but to keep you from getting cold. So you need to think in reverse, somewhat like a freezer. A freezer does freeze things by generating cold air, but instead removes the heat, making it colder.
So base layers will keep you warmer how? By removing sweat! So you want a fabric (base layer) that fits tight to the skin, making as much contact as possible. Next this fabric needs to be hydrophilic, absorbing sweat quickly and hydrophobic, dry as fast as possible.
Best Fabric:
Cotton – not what you want here, it absorbs sweat well, but dries why to slow.
Polypropylene – absorbs sweat well, but retains body odor and will smell within hours.
Polyester – absorbs sweat well, dries fast, great mobility, will develop odor over time.
Merino wool – hydrophilic, dries faster than Cotton, natural antibacterial properties, so no odors over time. This is definitely the best Fabric on the Market for Thermal Underwear (Base Layers).
*Recommendation, when you are enjoying the Outdoors do not cut corners by buying something cheaper that you will not be happy with. Spend a few more dollars and get the best. Below is the Best Thermal underwear for 2021!
2021’s Best Thermal Underwear for Men.
#1 WoolX Merino Wool Leggings & Turtleneck
Peyton Turtleneck & Avery Leggings – Ultimate in Warmth & Comfort
The WoolX Looks great and makes a perfect base-layer under your hunting & hiking outfits. The turtleneck can also be worn as an outer layer and looks great for any occasion. This fabric is soft, breathable, wicks moisture away from your skin, and will not hold odors.
Tailored to fit a woman’s body, the Peyton and Aver not only look great, but allow you to move freely and comfortably, keeping you warm all day long.
#2 Icebreaker 200
Icebreaker Women’s 200 Oasis
Icebreaker Oasis is made from 100% merino wool. These base layers are designed to keep you comfortable in even the most extreme weather conditions (hot & cold). Merino wool’s wicking properties and incredible breathability make these base layers an excellent choice for hunting, hiking, and many other outdoor adventures.
Merino is lightweight, soft, non-itchy, non-clammy, and naturally odor resistant.
#3 Smartwool IntraKnit Merino 250
Smartwool IntraKnit Merino top & bottom for Women
The MERINO 250 will keep you comfortable for a long day hunt. This fabric is soft 100% Merino wool made with an interlock knit for enhanced comfort, breathability, thermoregulation, and odor resistance.
#4 MERIWOOL 400g
100% Merino Wool Heavyweight 400g Thermal Pants Legging crewneck tops for Women
Women’s 400g/m² merino wool thermal pants and crewneck top are 100% all natural superfine 18.5-micron Merino wool, ensuring comfort and warmth for any hunting or hiking adventure.
These 400g base layers are not mid-weight, but heavy-weight and designed to give the outdoors activist temperature regulation all day long in extreme weather conditions.
#5 Alpine Onset
Outdoor Research Women’s Alpine Onset V-Neck & Bottoms
The Alpine Onset base layers are all you need to keep your temperature in check. With the ability to hold onto heat in cold temps, manage moisture, and dry quickly is why Merino Wool is the number one choice.
Each Alpine Onset piece features a trim fit and fits comfortably next to your skin. These base layers allow for easy layering and provide efficient temperature control during any hunting or hiking adventure.
