Extreme weather conditions require extreme clothing, and nothing beats top quality thermal underwear when it comes to keeping warm. Modern thermal underwear can be composed of multiple thin layers of fabric to trap more body heat and still allow the skin to breathe. Polyester, Wool, and silk are all commonly available materials, but what is the best thermal underwear for extreme cold outdoor conditions? Here we have a head-to-head comparison of the three main fabric types.

Polyester is a man made fiber that is fairly inexpensive, and is becoming more and more commonly used in thermals. It does a pretty good job of imitating natural fibers like wool, but unfortunately it has a habit of trapping odors. The combination of ammonia and bacteria that live on your skin quickly results in smelly clothes. Poly-cotton and polyester-wool blends can be a reasonable compromise, being comfortable and fairly breathable. However, when the polyester ratio in thermals goes above 20 or 30% you will find it has a distinct plastic quality. My verdict: Good for a budget solution, and great for short term sports or running underwear for women or for guys, but not for the serious outdoor enthusiast. Although synthetic fibers are constantly advancing, these are not the best thermal underwear for extreme cold situations. Still, this might change in the next few years. We’ll see.

Silk is not usually associated with hard wearing underwear, but silk long johns for men and women are not a bad choice. Silk breathes well, and has a delightfully smooth and cool feeling when worn under heavier outer clothes. In a single layer silk is not terribly effective as insulating underwear, but thanks to its very fine fibers and resulting light fabric it can easily be fashioned into 2 or 3 layer composites. Quite often silk is combined with wool or a cotton layer to increase its weight and thermal properties. Although expensive, silk composite is often regarded as the best thermal underwear for extreme cold where you can stay fairly dry.

Fine wool, most often from Merino sheep farmed in Australia and New Zealand, is probably the ultimate material for thermal underwear. In my opinion pure wool is simply the best thermal underwear for extreme cold hands down. Superfine wool is very smooth and light weight (nothing at all like a scratchy woolen jumper!) and keeps you amazingly warm. For people like me who are into outdoor sports it is ideal because you don’t ever get soaked in sweat, and if you do get wet through you still don’t freeze. Wool doesn’t hold water like a sponge like cotton does, so you still end up with air pockets trapped in the fabric even when it is wet – the result is that it still insulates you. If you are into skiing, hiking, or any other adventure sport then woolens are the best thermal underwear for extreme cold no matter where you are. The only downside to pure wool thermals is that they cost a lot more than polyester or cotton, but once you have worn them you will appreciate it as money well spent. Be wary of really cheap wool-polyester blends that advertise “contains pure wool” or “real wool” and similar – have a look just how much wool they actually contain, since quite often the fine print reveals that they might only have 10% wool with the balance being a cheap and nasty polypropylene filler. A small percentage of synthetic fiber can make woolens more elastic, but above that 20-30% threshold you lose effectiveness.

Remember that you generally get what you pay for, and super cheap outdoor clothes are rarely worth it. Online store like Amazon are a great place to shop for the best long underwear for cold weather and other great camping gear, so keep an eye on the “featured products” list down below to snap up the bargains that come up from time to time.

Thermal underwear may not get a mention at the fashion parades, but warm long underwear is something that everyone should have in their wardrobe. Feeling cold may be uncomfortable in small doses, and extended exposure can lead to hypothermia or worse. So what is the best long underwear for cold weather, and why? Here is some basic info about the different types of fabrics, to help you decide what will work best for you.

Cotton thermal underwear is soft and comfortable, and as such is a good choice if you want a cheap solution. Cotton pyjamas and tracksuit pants are great for keeping warm in winter, but cotton is not perfect: it has a tendency to act like a sponge, and hold water – after all, cotton is the preferred material for towels and cleaning cloths. Cotton long johns may be the best long underwear for cold weather if you are going to stay dry at all times, but it is not recommended if you are venturing outdoors, say going skiing or camping. Once wet, cotton is hard to get dry, and until it is completely dry, it will actually draw heat away from your skin. So, it’s a great low cost choice for indoors or maybe the workplace, but a no-no for adventure sports. In winter long sleeve thermal shirts for men or women who work outdoors can discretely be worn under business shirts or uniforms.

Polyester is a synthetic fibre that is produced in many variants that come under different names like Polartec, Polypropylene and Capilene, many of which are actually the same stuff but under different trade marks. Polyester is fairly inexpensive (about the same price as cotton) and provides significantly better all weather performance. Wring it out when wet and put it back on, and although it won’t feel great, it can keep you from freezing. Some people swear that it is the best long underwear for cold weather, but it has a slight drawback – it smells after a while! Unlike natural fiber, synthetic fibers are not advanced to the point of being able to “breathe” as well as say wool or silk, and the combination of ammonia from sweat, constant moisture, and naturally occurring bacteria on skin can result in a strong BO smell that is hard to get rid of even with washing. Nevertheless, synthetic long underwear has a lot going for it, being hard wearing and nicely elastic, hence it being used in modern sports and running underwear for women and for men.

Sometimes the oldest things are the best, and wool is a case in point. Wool seemed to go out of fashion in the western world in the later part of the 20th century, as everyone embraced modern new synthetic materials. But ask any serious adventurer and they will tell you that super fine wool simply makes the best long underwear for cold weather hands down. Why? Natural oils and the structure of the fibres means that wool doesn’t hold water, and is resistant to bacteria and therefore bad odours. It doesn’t burn, and high quality fine wool is every bit as soft as cotton. The downside is the price – good long underwear made of merino wool (merino is a breed of sheep prized for their very fine wool) can easily cost twice as much as cotton or poly-cotton blends.

So, the choice really comes down to cost.

If you can afford it, buy wool. It is comfortable, versatile, and hygienic and makes great insulated underwear for men or women on the go. Equally good indoor and outdoor, from lounging in front of the television to canoeing in Alaska, wool is a tried and true solution.

For a cost effective indoor or fair-weather solution go with inexpensive cotton. For its reasonable price tag it is the best long underwear for cold weather to wear under your business attire or casual clothing when going out in winter.

If you need a low cost outdoor solution, a synthetic blend can tick all the boxes for you – just wash it often, and hand it out to air well to prevent it from starting to smell. You might be able to find a wool/polyester blend, and these can make a good compromise, although you will find that as the amount of wool in the garment increases so does the price tag.

Thinking of getting some thermals?  Good move.  Whether it’s for cold-weather sports, keeping warm during exam time, pajamas for lounging in the winter holidays, or just to keep you warm in those in-between months where it’s a bit on the cool side…

The big question is, of course, which is better – natural or synthetic thermals?  Some people automatically choose one or the other – “crunchy” people (known for their habits of a big bowl of crunchy granola for breakfast!) will probably grab the natural thermals without any hesitation, whereas people who have lots of faith in the abilities of modern science to improve our culture will no doubt be choosing the synthetic thermal underwear every time.

However, it might pay for both parties to take a look a the benefits of each type of thermal underwear.  The boundaries between natural vs synthetic thermal materials are now so often blurred that to say one is better over the other is to argue over which is better, apples or oranges.  Before the natural crowd holler that thermals made with natural fibres are better because anything natural is better than anything synthetic, let’s remember that a lot of new textiles considered to be “natural” are actually processed so far as to render them no longer purely “natural”.

Bamboo, for example, is a textile which began its life as unfertilized and unsprayed bamboo canes, but once processed into today’s bamboo fabric, is now considered to be a rayon.  Rayon is a name for a type of man-made fibre which may or may not originally have been sourced from a natural plant.  You may find thermals and other clothes which are labelled “rayon from natural fibre”, which means that the fibres used once came from a plant.  It’s fairly safe to assume that fabric labelled simply “rayon” came from synthetic fibres in the first place – one example is recycled plastic bottles, an increasingly popular choice for textile producers, making a very soft fibre and recycled too thus saving on the environmental impact of the garments made.

However, for all this talk of bamboo and rayon and other fancy man-made things which it can’t be denied, are pretty clever – there is still a whole lot to be said for natural fibres and natural cotton or wool thermals. Caring for thermal underwear made of natural materials is not hard – just remember to put them through on a gentle (wool) wash cycle.

I say cotton or wool because these are the most common fibres that natural thermals are made from, but within these categories there are many variations.  Let’s start with cotton, since that’s pretty simple.  The cotton plant has been used for at least 7000 years, maybe more, for the production of textiles.  It’s easy for textile producers to get hold of, so it’s inexpensive, and it breathes well and doesn’t require extra special processing so it’s widely available. Cotton makes for comfortable and soft, and is generally used to line thermal gloves as well.

Thermals made from cotton are soft and comfortable, cheap and widely available.  However, they do have one major drawback.  They hold moisture against the skin, which makes them completely useless for outdoors sports and endeavours such as hiking, camping or hunting.  Anything which will cause you to sweat requires you to wear underclothes that wick the moisture off your skin, otherwise you are going to be a candidate for chafing, clamminess, and maybe even frostbite if are wet and in cold conditions.  You don’t want to get sick in the wilderness, so please, for outdoors endeavours, avoid cotton thermal underwear, not matter how inexpensive and tempting they may seem.

Thermals made from wool are considered among the best you can buy.  Wool thermals are very good at keeping the warmth in and wicking the moisture out.   That’s because wool has natural wicking properties and is also designed to keep a sheep toasty warm – so wearing wool will also keep you toasty warm!

Some new advancements have been made in the breeding of fleece animals in recent years, and some of the most highly prized wools are Merino wool (a breed of sheep), possum (they’re not bred, but New Zealand is getting into possum wool processing since possums are a pest there – beautiful warm wool!), cashmere (from goats) and alpaca.  Alpaca thermals are a luxury indeed, lending warmth and wicking and a touch of class as well.

Then there’s man-made or synthetic thermals.  Don’t forget that many synthetic thermals are actually a blend of synthetic man-made and natural fibres. bringing the two together to truly get the best of both worlds.  Although these may be the most expensive option, due to clever processing and smaller runs of the garments, you will undoubtedly be impressed by the qualities of these garments.

On the whole, thermal underwear is fairly tough stuff. It stands up to years of abuse, and you can generally expect many years of service life from good quality garments. However, there are some basic tips that can easily help you increase the life expectancy, and the comfort of the wear that you get from your thermals.

Basically, there are three main factors that will destroy your thermal underwear.

1. Shrinkage. It’s a big problem especially with polyester and other synthetic underwear, especially because so many people use clothes dryers these days. Yes, you might lose a few pounds and fit back into it, but generally once the fabric has shrunk it won’t be a stretchy and comfortable any more.

2. Staining: Mainly this is an aesthetic issue, since nobody likes to wear tops with yellow armpits, can also be accompanied by persistent bad smells … potentially cutting short the life of a garment.

3. Pilling. This is when the fabric develops little rolls, or little pills of fluff, fibres and other bits and pieces usually picked up in the wash cycle. Not only is pilling unsightly, it also makes the underwear very uncomfortable to wear when these little rolls are on the inside.

Thermal underwear is best dried outside in direct sunlight. This is environmentally friendly, and naturally removes stains and bad odors.

So let’s go through some basic care instructions for different types of thermal underwear.

WOOLEN THERMALS: Merino wool is by far the best material available for robust and effective insulating underclothes. It is naturally antibacterial, and maintains good insulating properties even when it gets wet, and therefore makes the best long underwear for cold weather. It is very important to only ever wash woolen thermal underwear in a cold, or at most lukewarm wash cycle. Warm water causes wool to pull together and tends to permanently damage the garments. Additionally, you should not use normal washing powder or disinfectant to wash wool garments as this will cause the fibers to mat together like felt. Always wash wool garments on a gentle cycle, as excessive agitation will cause the fibres in the thermals to mat together, causing shrinkage and distortion. It will feel rough and uncomfortable, and won’t keep you as warm anymore.

If wool stains, hang it in the sun for a few hours, don’t use bleach or similar substances on it.

COTTON THERMAL UNDERWEAR: Cotton is generally a very forgiving fibre, and you can wash using normal detergent on a normal wash cycle, even in hot water if need be. Be aware that if you wash cotton in hot water it will shrink somewhat, but this is nowhere near as severe as for wool. Generally the biggest issue with cotton thermals staining, and Pilling. To avoid staining, the first thing you can do is wash your clothes on a regular basis. This might sound like common sense, but it really is the best way to avoid stainless. This includes not allowing a clothes to sit around for a week after you wear them before they go in the wash. Stains result from components in your natural perspiration which react with the air and other materials which are found already in the fibres. If you come home really sweaty, take your thermal underwear straight off and if nothing else drop them in a bucket of cold water to soak. This will immediately help draw the ammonia and other components of perspiration from the fibres, making them easier to clean later. The same goes for other stains from soil and dirt, on thermal clothing or otherwise. There are plenty of proprietary anti-staining products out there, or you can even use a mild bleach solution to get the garments white again. Alternatively, if you like a natural approach, you can simply wait for a sunny day and give the thermals a full day in the sun. The UV rays in natural sunlight are incredibly good at bleaching clothes to a bright white, and they are also able to kill any bacteria which may be lurking in the fibres.

In order to prevent Cotton thermal underwear from pilling, the best thing you can do is avoid washing them with any other clothes that are likely to shed a lot of fibres. Are the worst offenders tend to be bath towels and fluffy socks, both of which lose a lot of very fine fibres. Also, make sure you regularly clean the leaf filters on your washing machine. It’s amazing how to stuff accumulates in there, and once it overflows, it simply washes back and gets stuck on your clothes. While it is possible to shave the fine pills or fluff back off, it takes forever. Sometimes you can use strips of packaging tape to clean it off, and some people use electric shavers too. The to the inside out. Although washing things inside out is often recommended, this is to preserve the outer appearance. In the case of thermals, we are usually more worried about the inside since this will sit closer to the skin. So leave them the right way out when they go in the machine.

POLYESTER THERMALS: Caring for thermals made of polyester and other similar synthetic fibres is easy, because they are generally very hard wearing. They do not suffer from pilling or staining as badly as natural fibres do, but they certainly make up for it in their tendency to shrink very badly the greatest cause of shrinkage is excessive feet. It shouldn’t come as a surprise, since everybody has at some stage thrown a plastic bag or a plastic bottle in the fire. The first thing that happens? The item shrivels down into practically nothing, into a tiny ball of molten plastic. The same thing basically happens with fine synthetic fibres when they are heated, even to a low temperature of about 60°C. Never, never never put polyester thermal underwear in the dryer on a hot cycle!!! It will come out looking like dolls clothing, and you will never be able to wear it again. The best way to care for polyester thermal underwear is to wash them normally (they can handle warm water for normal detergent) and either air dry them, since they drive very quickly, or put them on a very low dry cycle. Acrylic and polyester thermal underwear and does not kill too badly, but you should observe the same rules as for cotton. Clean your lint filters regularly, and wash them the right way out.

What if your thermals smell bad? Don’t be embarrassed, it doesn’t mean you are a dirty person. Fabric worn close to the skin can easily develop BO smell even when well washed. As already mentioned, air drying especially in direct sunlight can be one of the best ways to overcome smells and stains in all clothes. You can also add a small amount of disinfectant (preferably a natural one like sphagnum moss) to the wash, and if you really want to nuke bacteria AND mold use some anti fungal product such as grapefruit seed extract. Personally I go for sunlight – Its still free, and leaves everything with a fresh fragrance and soft feel that you just cant duplicate.

This diagram shows the many different layers utilized in a Gore-tex thermal glove

Alongside thermal underwear, a good pair of thermal gloves is absolutely essential if you enjoy skiing, bush walking, or engaging in any outdoor activity that puts you out in the cold during winter. As anybody who spends time outdoors knows, there is nothing worse than being unable to get warm – and besides comfort, you need to seriously consider your personal safety. In winter time, hypothermia is a reality that is quite dangerous.

Thermal gloves consist of several layers: at the very least there will be an outer layer and an inner layer. The outer layer (or layers as it may be) are there to prevent cold air from moving through the fabric of the gloves, to carry away precious warmth. Some thermal gloves may also have a waterproof layer, while others still may have a hybrid layer such as Gore-Tex which will repel water but still allow your skin to breathe. The inner layer(s) of the glove serve to keep your fingers comfortable and trap as much heat as possible in the fabric. In some cases, this fabric maybe acrylic, although top-quality thermal gloves still consist of superfine wool or even silk. Caring for thermal gloves is no different to any other thermals – wash them in mild detergent, and air dry.

There are many different types of thermal gloves, ranging from very thin light ones (you would never know that they are anything more than thin cotton gloves) to massive, the clubs like the sort you see worn by polar explorers. There is a thermal club for every situation-a lightweight glove that you can wear when you’re walking to work in the winter time, thermal gloves with removable fingertips which you can wear when you are hunting, and thermal gloves especially designed for motorbike or pushbike riding.

Thin and comfortable thermal gloves like these are essential if you are working in a cold environment

How much should you pay for a good set of thermal gloves? This is a fairly open question, because you can usually pay as much or as little as you want to. Generally speaking, you can get a good basic pair for about $20 from most camping or army surplus stores, and gloves like this will be fine for bush walking or similar activities. However, if for example you are going skiing or will be spending time in extremely low-temperature environments, you’re best off buying purpose specific thermal gloves which may then cost a bit more.

Who uses thermal gloves? Thermal gloves are very common these days, and are often issued to military personnel and law enforcement officers as standard equipment. They are also essential gear for explorers or adventurers, and you will even find highly specialized thermal gloves being worn by astronauts! usually they are worn alongside long thermal underwear as well, for all round comfort in cold conditions.

Buying a good pair of thermal gloves is an excellent investment, and you will not regret your choice the first time you are outside and the temperature drops. As we move towards Christmas time in winter, don’t forget that a pair of thermal gloves and thermal underwear also make an excellent present for somebody in your family!

We all know the signs of the changing seasons. We begin to dig out the thermal underwear, sweaters and winter coats from the depths of the closet. We start to put away our flip flops and shorts, some of us a little more begrudgingly than others.  If you are someone that likes the cold weather then this is a happy time for you but if you are someone who would prefer to be on sunny sandy beaches at all times then this is not a happy time at all. Either way we must be sure we can stay comfortable in the colder weather and thermal underwear makes it easier to do this.

Thermal underwear is a great weapon in your cold weather armory. It is a little more complicated than we give it credit for. The thermals work by performing two main functions to keep you warm. First thermal underwear traps and retains more body heat than regular cotton based clothing. This keeps the heat closer to your skin and in essence, keeps your body warmer. It is works very hard by keeping sweat and moisture away from your skin. This keeps you dry and allows you body to stay warmer. Many thermal undergarments are made up of a two-ply polypropylene fabric that breathes easier than regular clothing and is able to perform the essential functions mentioned above.

A plush cashmere coat can be worn over cashmere blend thermal underwear for true winter luxury

Another fabric that can keep you warm in the colder months is cashmere. This fabric comes from the soft hair of goats raised in the Gobi desert. We usually consider the desert to be a hot place but in the night time the temperatures can drop below freezing.  The goat hair (so soft) takes four years to grow to a useable length and is then hand sheared and hand processed. It is then made into luxury items such a women’s cashmere coat or men’s cashmere sweaters. These articles of clothing are very soft and plush. Since they are made from cashmere which is designed to keep the goats warm, it works very well to keep people warm in colder temperatures.  Thermal underwear is sometimes made of cashmere fibre, often as a blend mixed in with modern manmade fibres with thermal properties, or perhaps with merino wool fibre, which is considered the top of the range when it comes to thermal underwear warmth.

It is also very important to remember to keep your hands and head covered in cold weather. These are the areas of your body that lose the most body heat. A good winter hat and a pair of thermal gloves are essential, preferably thermal gloves. Remember to wear your thermal underwear, spoil yourself with some thermal cashmere clothing and gloves, and then get out there and enjoy the wonderful winter!