Whether you’re an avid skier, an outdoorsy type, or simply cannot stand the winter months, chances are you’ve had to google thermal underwear at some stage in your life.
The world of thermal underwear – or long johns as they call them over in the states (after the 19th Century boxer John L. Sullivan) – can be slightly confusing. They come in all sorts of materials, sizes, lengths, and types that can become so muddled together that you forget what you were looking for in the first place.
Fear not, for we’re here to help you navigate the strange world of winter warmers.
Layering
It’s all about layering. A basic set of thermal underwear consists of a pair of leggings and either a long-sleeved top or camisole vest. If you’re set to attack some seriously cold temperatures – and we mean Baltic – you’ll want to stock up on a collection of thermal underwear that is interchangeable and buildable. This means that, if the weather is particularly brisk, you can add in a pair of thermal pants underneath your leggings, and layer up with a camisole and long-sleeved top together.
Material
The best material on the market for thermal underwear is Merino wool. It’s a spectacular insulator that combines ever-important breathability and comfort with the ability to keep in all that precious warmth. It’s also naturally moisture-wicking, allowing you keep dry while remaining active. However, Merino is the most expensive thermal material on the market.
As such, pure cotton, wool, and cotton/nylon blends are also fantastic alternatives for retaining heat, flexibility and breathability, which brings us nicely to...
Breathability
As we said above, the real trick to battling the cold is about layering, but it’s important that you don’t overdo it. Layering too much can be detrimental to your circulation, which will reduce your body temperature even more.
If you’ve gone for a lighter material for your thermal underwear such as cotton, it might be tempting to throw on two of the same long-sleeves, and two pairs of socks. However, it’s far more worthwhile to let the insulating material do its job, retain that body heat, and maintain good circulation. This is why we recommend building up a capsule collection of pieces that can layer while remaining breathable.
Keep scrolling for a round-up of our favourite thermal tops, leggings, shorts, and socks right now.
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John Lewis Heat Generating Lace Trim Thermal Vest, Campanula
This vest from John Lewis comes in an array of colours, and is made from 58 per cent acrylic, 38 per cent viscose and 4 per cent elastane. We can already hear you shouting – ‘but you just said wool and cotton!’ – but fret not. Acrylic still has fantastic insulation and heat trapping abilities, though isn’t very breathable on its own. An acrylic blend such as in this vest is excellent for breathable warmth during the winter.
Buy now £14.00, John Lewis
Black/Cream Next Elements Lightweight Thermal Camis 2 Pack
For a great value thermal camisole set, look no further than Next. Though they’ve traded in acrylic for a viscose and polyester blend, you can once again be sure that this cheaper alternative to wool thermals will keep you toasty throughout the colder months.
Buy now £32.00, Next
Dilling women's merino wool strap top
This merino wool vest from Dilling is sure to be a super soft and ultra-warm addition to your thermal underwear collection. Made from 100 per cent organic merino wool, the Danish brand guarantees itch-free and seamless wearability - whether you plan on using it as a base layer during the day, or to sleep in at night.
Buy now £25.99, Dilling
Dilling women's merino wool shorts
Why not make it a matching set? These stunning merino shorts paired with the above vest top from Dilling would make for a luxuriously soft night’s sleep, or an incredibly warm base layer to go under your daily outfits.
Buy now £21.99, Dilling
Icebreaker Women’s Merino 175 Everyday Cami Thermal Singlet
Icebreaker has absolutely won our hearts with this 100 per cent merino wool, ribbed vest with adjustable straps. Who knew thermal underwear could look so good? Guaranteed to keep you warm in the winter and cool in the heat, this thermoregulatory material is worth the extra spend.
Buy now £55.00, Icebreaker
M&S Flexifit™ High Rise Sleep Knicker Shorts
Though these shorts are designed to be worn for bed, we think the 89 per cent modal fabric would actually make a fantastic base layer underneath your favourite pair of leggings or jeans during the winter.
Modal is a bio-based fabric that is made from spinning beech tree cellulose. It’s a lightweight, extremely soft material that’s often marketed as ‘artificial silk’. It’s incredibly breathable, resistant to shrinkage and a great insulator.
Buy now £8.00, M&S
Skims Cotton Rib Boxer
Though you’ll often see folks sporting a pair of Skims for style purposes only, these ribbed boxers are made from 95 per cent cotton and 5 per cent spandex which makes them a great choice for a thermal base layer. They’ll keep you warm while allowing you to retain breathability on the move – plus, they just look so good.
Buy now £32.00, Selfridges
Icebreaker Women’s Merino 200 Oasis Thermal Boy Shorts
If it’s everyday comfort and warmth you want, look no further than Icebreaker’s 100 per cent merino wool boy shorts. Despite the price tag being a little steep, once you grab a pair of these for the winter, you’ll be saving up for a whole set.
Buy now £45.00, Icebreaker
Sweaty Betty Merino Fairisle Base Layer Legging
Whether you’re on the slopes, or prefer relaxing by a warm fire, these merino blend leggings from Sweaty Betty will be your saviour, They’re lightweight, sweat-wicking, temperature-regulating and simply great to look at – what more could you possibly ask for?
Buy now £95.00, Sweaty Betty
Uniqlo Heattech Thermal Leggings
Uniqlo’s Heattech clothing items are a cult favourite for a reason. They’re made from a combination of all of the above synthetic fabrics that we just made so much noise about: polyester, acrylic and viscose – plus some elastane for some extra stretch where it matters. We’re not sure how Uniqlo did it, but it has resulted in some truly magical warmth.
Buy now £14.90, Uniqlo
Women's Merino 200 Oasis Thermal Leggings
Like the above boy shorts, but longer. As we said, you can’t really go wrong with a pair of 100 per cent merino wool in your base layer. Grab these while they’re still about and stock up for next year.
Buy now £85.00, Icebreaker
TOG24 Pine Womens Merino Ski Socks
We know, we’re starting to sound like a broken record. But these ski socks are constructed from a wonderfully soft and warm merino-blend yarn that’ll keep your feet fresh, dry, and warm all day long. They’ve also got some heavy cushioning at the heel and an elasticated arch for that extra bit of support.
Buy now £12.00, TOG24
Falke Womens SK2 Knee-high Skiing Socks
Though these socks are technically made for skiing, we think the knee-high style and virgin wool blend make for a fantastic winter investment – whether you’re a snow bunny or not.
Buy now £36.00, Falke
Heat Holders Ladies Original Socks
Moving into less ski-ready territory, these original socks from Heat Holders are a sure-fire investment in warmth this winter. With a tog rating of 2.34, these socks are made from a specially developed heavy yarn with unbeatable thermal qualities. They’re also designed to relieve those with circulation problems from unbearably cold feet.
Shop all thermal socks at Heat Holders
Buy now £9.99, Heat Holders
Explorer Womens Merino Thermal Mid-Calf Socks
Perfect for those of us who love a winter walk, these mid-length socks from Mountain Warehouse are made from a super-soft merino, acrylic, nylon and polyester blend for a comfortable, wonderfully warm and secure fit.
Buy now £12.99, Mountain Warehouse
