Clothing has always been an important aspect of our lives since time immemorial. Basically, we wear clothes to cover our nakedness and protect the outer layers of our bodies. Aside from these two reasons, we also dress up depending on the weather condition. If the weather is hot, we tend to dress in light, brief, and breathable clothes; if it is cold, we tend to wear thicker and more covering clothes.
Usually, wearing layers of clothes during winter can help you cut out very bulky clothing without sacrificing your wellbeing to the weather. On that note, it is important to have a few best thermal underwear pieces in your closet to help keep your body warm, free, and comfortable, even in very harsh conditions.
This clothing item, also known as long johns or long underwear, is two-piece innerwear with long legs and long sleeves worn as a base clothing mostly during cold weather to keep you warm and comfortable. With so many products in the market, how can you tell which one is functional?
You don’t want a base layer that will trap all the moisture in and make you toasty on the inside, do you? The aim is to go for something that will keep you warm and not sweaty. We looked into that and came up with a few products that have the best thermal underwear quality. We made our selections based on the following considerations.
- Perfect fitting, almost like a second skin.
- Function – warmth, bacteria resistance, stretch, moisture-wicking, and loft.
- Cleaning and maintenance.
- Style and design – one or two-piece.
- Fabric – the weight and the material used.
These points would guide you to pick a base layer of inner wear that is most suitable for you. Sweat-wicking, flexibility, comfort, and energysaving are some of the advantages you’d get from making the right choice.
Top 5 Best Thermal Underwear
5. Smartwool Merino 250
- Flatlock seams and base layer tops
- Slightly duck tailed back for tucking in
- Odor resistance
- Well secured stitches in strategic areas
- Made of merino wool
This is a very good product that has gathered some reputation as the best thermal underwear womens choice. It has a feminine undertone to it, and it is cut in a very fitting manner that would stay on your skin all day long providing warmth and coziness. A flatlock that prevents chaffing, amazing wicking properties, and a super soft comfortable material. The manufacturers are experienced as well, setting the pace for many others in the market.
- It is super comfortable and reliably stretchy
- Designed to resist odors and keep you fresh all day long
- The flatlock seams prevent chaffing
- Stays in place and works perfectly well under layers
- Suitable for most weather conditions
This best thermal underwear womens choice is recommended for skiing, diving, snowboarding, backpacking, hiking, and other such activities. It also comes with a 2 years warranty and a lot of great reviews.
4. Smartwool Men’s Merino 150 Base Layer Long Sleeve
- Available in different shapes and sizes
- Made of 87% merino and 13% nylon core micro weight fabric
- Warm insulation
- Made with an interlock knit
- Weighs 8 ounces
A lot of these inner wears come as a one-piece or two-piece suit. If your choice is to buy a one-piece top only, then the Smartwool Men’s Merino is the one for you. After this brand was compared to a lot of other top brands, it was tagged the best thermal underwear mens choice for a number of reasons. From the tests, it was discovered that it is nothing less than a workhorse base layer that wicks, stays in place, and fits perfectly.
- Designed for enhanced comfort and durability
- Very light fabric but great insulation in every temperature
- Easy to clean and maintain, dries quickly
- Breathable and keeps you dry
- UPF 30 protection
- Cost is a bit on the high side
- Insulation is not good enough for extremely cold weather conditions
This is a good product for you if you are conscious of weight. It is very light, easy to wash and maintain, and it wicks away sweat very fast leaving you dry for as long as you’re wearing it. The problem, however, is that it may not work so well in extreme weather conditions if not paired with other layers.
3. Cuddl Duds Climatesport Long Sleeve Suit
- Formfitting on all body shapes and sizes
- Reliably stretchy
The higher the quality of the product, the more it would cost, right? Well, as true as that may be, every now and then, we’re surprised by a few products that meet all the specifications of the high-end ones, but is still pocket-friendly. The Cuddl Duds Climatesport suit is one of such products. It is a close second to the best thermal underwear mens choice, and it is pocket-friendly too.
- Comfortably made and fits perfectly well
- Very affordable and high quality
- Stays in place through high levels of movements
- It is not suitable for very cold climate
- Not odor resistant
Going for this product for the first time was somewhat skeptical for a lot of customers. Imagine their surprise when they came back with great reviews. It is not a good option for non-overnight activities like day climbing and hikes.
2. Trew Men’s Lightweight Nuyarn Merino
- Made from NuYarn material – merino and nylon
- Extra stretchy
- Overly long sleeves
- Stays in place through rigorous activities
This is another product from the merino line that has been tagged the best thermal underwear for extreme cold. It was originally designed for snowboarding, but you can wear it on other similar occasions like skiing, climbing, or anytime you need more warmth. It is made out of NuYarn, which is a combination of merino wool and nylon, with the wool drawn around a thin core of nylon. Special care was put into making this product; it’s more durable and feels very soft to the touch.
- Durable and cost-effective
- Functional in extremely cold situations
- Wicks away sweat very fast and dries quickly
- Extra-long sleeves for extra covering
- Doubles as a pyjamas
- Mostly suitable for performance
From some of the reviews, this product may be scratchy for some people and does not work well for house wear. As the best thermal underwear for extreme cold, it needs to be worn in environments that are a little bit colder than usual.
1. Minus33 Men’s Katmai Expedition Bottom
- 100% merino wool and weighs 14.4 ounces
- Heavyweight and machine washable – 400g/m2
- Flatlock seam
- Ribbed cuffs
- Inbuild UPF 50
The very top of our list is the Minus33 Men’s Katmai underwear. It has gathered a lot of great reviews online and offline as one of the best out there. The price is a little bit on the high side, but it is worth it at the end of the day. It is made from pure wool – merino, it dies a good job as the best mens thermal underwear for all weather, and it has a versatile fit.
- Suitable in extremely cold weather situation
- The flatlock seam prevents harsh chaffing while on the move
- UPF 50 protection in case of sun exposure
- Wicks away moisture very easily
- Can be worn as a base, mid, or outer layer
Here is one of the reviews about this underwear – “This product has kept me warm at -10 degrees, and I would push them even lower. I wear these under a waterproof shell when hiking where the temps are near zero. Otherwise, for hiking at 20 degrees, the lightweight Minus22 product, sheltered with my waterproof shell pants, keeps me nice and warm while in motion. So, in that case, I carry the Expedition weight to change into for sleeping, and of course it always feels good to get into nice dry and warm bottoms for bed”.
What makes the best thermal underwear for men and women? The material plays a very crucial role. Something wooly and comfortable is what you should be on the look out for. It may cost money, but it usually gets the job done keeping you warm all day long.
Thermals are great base layers, a good one would let you layer other clothing over it without limiting your movement or making you feel uncomfortable in any way. This is a good place to start the day from – layers of clothing – but as the day goes by and it gets less cold, you can take them off as required.
The best thermal underwear for men and women should have all the basic properties (as already mentioned), but sometimes, they come with a little more extra, which makes a whole lot of difference.
Some materials come with a thumbhole in the sleeve which helps to keep them in place. Some also come with small pockets on the sides or waist for your phones and other tiny accessories. Some come with a hood, flattering neck designs (high neck, v-neck, etc.), UV protection, and fleece lining.
All of these extra features contribute to making them the best women’s and best mens thermal underwear. They make the underwear a little more comfortable and functional compared to the more conventional types.