Winter Underwear - Arctic / Antarctic, Cold Weather, Thermal Clothing

The base or foundation layer is worn next to the skin, for cold climates this is "thermal" underwear.

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The layer of clothing next to the skin has two jobs to do, the obvious one of keeping you warm and then the equally important but less obvious one of removing perspiration from the skin so it doesn't cause chilling later on.

In cold temperatures perspiration can be more of an issue than in a warmer climate. The skin loses moisture at all times whether undergoing exertion or not. If there are overlying insulating layers keeping you warm, it is more difficult for this perspiration to escape, If it is not removed it will result in the wearer becoming uncomfortable with a feeling of clamminess as well as lowering the efficiency of the insulating layers.

Underwear that is able to wick this moisture away from the skin surface therefore becomes much more important. Modern "thermals" are made of natural merino wool or synthetic fibers such as polypropylene and "fleece" that have good insulating properties and are also able to efficiently wick moisture away from the skin. The golden rule is to avoid cotton except in some very specific situations.

Features of the foundation layer

Foundation layer - long thermal underwear

Which material for your
foundation layer?

Foundation layer - long thermal underwear

There are a number of materials commonly used for the foundation layer, each has its advantages and disadvantages:

Merino Wool - this has become the gold standard material for the foundation layer, as you may suspect from this, it is not the budget option but it does deliver on performance. It is simply the wool of the merino sheep, a particularly soft and fine natural product. Merino wool garments deliver significant warmth with light weight, they are very good at wicking sweat away from the skin surface and so are particularly effective in use during exertion. They are also odor resistant and so can be worn for extended periods without changing or washing while still making you someone that others still want to be near.
Buy: Men's | Women's

Synthetics - A range of materials, polyester and polypropylene are commonly found as are proprietary versions (brand names) of generic fabrics. If I made my own I could take a form of brushed polyester (say) and call it CoolAntarcticene for instance. Synthetics wick sweat away from the skin very effectively, insulate well and are available in different weights, they dry faster than any of the materials on this page, but are not so good at being odor resistant, but may be treated to make them more so.
Buy: Men's | Women's

Silk -  Another natural material, very thin and light weight delivering excellent insulation for minimal bulk. Not as effective as merino or synthetic, though silk really comes into its own in situations where looks matter, you can squeeze a silk layer under something else without it being noticed or where a matching or contrasting patch of colour enhances an outfit. It is also particularly delightful to the touch. A good choice for cold weather in the city under your office workwear.

Cotton - A traditional, natural material but outperformed in most circumstances by the alternatives. Cotton doesn't wick sweat well which can make it feel cold and clammy with retained sweat after exertion, it is also relatively heavy and has a tendency to go a bit baggy with use, especially at knees and elbows. It is more fire and electricity resistant than many thermal underwear materials which makes it recommended and in some cases the only permitted material where these are a real hazard.

Merino Wool Base Layers

Women's Merino Wool base layers
Women's merino wool foundation layers
Buy: Mountain Warehouse | Kathmandu

Women's Merino Wool base layers
Men's merino wool foundation layers
Buy: Mountain Warehouse | Kathmandu

Synthetic Base Layers

Women's Merino Wool base layers
Women's synthetic fiber foundation layers
Buy: Mountain Warehouse: tops  bottoms | Kathmandu

Women's Merino Wool base layers
Men's synthetic fiber foundation layers
Buy: Mountain Warehouse: tops bottoms | Kathmandu

Silk Base Layers

Women's Merino Wool base layers
Women's silk foundation layers

Women's Merino Wool base layers
Men's silk foundation layers

Cotton Base Layers

Women's Merino Wool base layers
Women's cotton foundation layers

Women's Merino Wool base layers
Men's cotton foundation layers


  • Lightweight - approx. 170 gm2
  • Midweight - approx. 250 gm2
  • Heavyweight - approx. 400 gm2

Foundation layers come in a range of weights usually described as light, mid and heavy. The one to go for depends on a number of factors, your anticipated activity level, the external temperature and how keenly you feel the cold. There is also the fact that heavier weight materials will be more bulky and so require more flexibility of fit of the over-layers.

Information Pages

Clothing in Antarctica
Cold Weather Boots
Shell Jackets
The Foundation Layer
3 in 1 Jackets
Sport in Cold Weather

Outdoors and Sports Wear


Men's Hiking Boots
Men's Court Shoes
Men's Cross Training Shoes
Men's Football Boots
Men's Running Shoes
Men's Tennis Shoes
Men's Track Field Shoes
Men's Trail Running Shoes
Men's Walking Shoes

Women's Hiking Boots
Women's Netball Shoes
Women's Running Shoes
Women's Track Field Shoes
Women's Trail Running Shoes
Women's Walking Shoes

Boys Cross Training Shoes
Boys Running Shoes
Boys Tennis Clothing

Girls Running Shoes
Girls Tennis Clothing

Kids Hiking Boots


Men's 3 in 1 Jackets
Men's Compression - Bottoms
Men's Compression - Tops
Men's Cycling Clothing
Men's Down Jackets
Men's Fleece Jackets
Men's Gloves
Men's Gore-Tex Jackets and Pants
Men's Gym & Training Clothing
Men's Hiking Pants/Trousers
Men's Hiking Shorts
Men's Long Sleeved Shirts
Men's Long Underwear - Bottoms
Men's Long Underwear - Tops
Men's Merino Clothing
Men's Pullovers
Men's Running Clothing
Men's Short Sleeved Shirts
Men's Softshell Jackets and Pants
Men's T-Shirts
Men's Tennis Clothing
Men's Travel Clothing
Men's Triathlon Clothing
Men's Waterproof Rain Jackets
Men's Waterproof/Rain, Pants/Trousers
Men's Winter Jackets

Football Clothing

Women's 3 in 1 Jackets
Women's Compression - Bottoms
Women's Compression - Tops
Women's Cross Training Shoes
Women's Cycling Clothing
Women's Down Jackets
Women's Fleece Jackets
Women's Gloves
Women's Gore-Tex Jackets and Pants
Women's Gym Training Clothing
Women's Hiking Pants/Trousers
Women's Hiking Shorts
Women's Long Sleeved Shirts
Women's Long Underwear Tops
Women's Merino Clothing
Women's Pullovers
Women's Running Clothing
Women's Softshell Jackets and Pants
Women's Sports Bras & Crop Tops
Women's T-Shirts
Women's Tennis Clothing
Women's Travel Clothing
Women's Triathlon Clothing
Women's Waterproof/Rain Jackets
Women's Winter Jackets

Kids 3 in 1 Jackets
Kids Hats
Kids Down Jackets
Kids Winter Jackets and Vests
Kids Fleece Jackets
Kids Gloves and Mittens
Kids Pants/Trousers
Kids Shorts
Kids Long Sleeved Shirt
Kids Long Underwear
Kids Merino Clothing
Kids Pullovers
Kids Short Sleeved Shirts
Kids Waterproof Rain Jackets

Boys Compression Clothing


Beanies, Adult
Caps, Adult
Neck Gaiters
Running Socks

Sports Equipment

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Squash Gear
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Camping Gear

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Eating Outdoors - Crockery & Cookware
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