Guide To Choosing The Best Thermals & Base Layers

Whether you're hitting the slopes, camping, hiking or travelling in chilly conditions, you'll need the right clothing to ensure you're warm and happy, not cold and miserable. Wearing layers is the key to staying warm and comfortable, and this buying guide outlines the importance of wearing a base layer. When you get dressed, you put your thermals on first. Their job is to help keep your body warm, drawing moisture away from your skin so sweating or standing still doesn't make you feel cold. This ensures your body temperature is comfortable in conditions ranging from mild to ultra-cold.

Quick Links

• What Are Thermals & Base Layers?
• How Do Thermals Work?
• Choosing Your Thermal Materials
• Thermal Sizing And Fit
• Seams & Cut For Thermals
• Best Thermal Clothing & Base Layers For Extreme Cold

What Are Thermals & Base Layers?

In the context of clothing, thermals refer to insulating garments designed to retain body heat and keep wearers warm in cold conditions. Made from materials like wool, polyester or specialised fabrics, thermals include base layers such as tops and leggings. They are essential for outdoor activities in winter, providing warmth without bulk by trapping air close to the body.

Base Layers Vs Thermals

Base layers and thermals are both designed to keep you warm in cold weather, but they serve different purposes. A base layer is typically the first layer of clothing worn next to your skin, and it's designed to wick moisture away and regulate body temperature, so you stay dry and comfortable. Thermals, on the other hand, are often thicker and designed more for insulation to retain body heat. While base layers are ideal for moisture management and can be worn in a range of conditions, thermals are best for extreme cold, providing added warmth when you need it most.

How Do Thermals Work?

A thermal base layer works by trapping body heat and minimising heat loss. Made from insulating materials like wool or synthetic fibres, these garments create a layer of warm air next to your skin and wick moisture away, keeping you dry and warm. Thermal clothing is typically worn as a base layer to maximise heat retention in cold weather.

Choosing Your Thermal Materials

The material the base layer is made from determines how warm, dry and comfortable you'll be. Materials can be natural, synthetic or a mixture of both, and each fabric has different benefits.

Best Material For Thermals

There are a number of materials you can choose from when selecting your thermals or base layers. These include:

Merino Wool Thermals

Base layers made from merino wool are natural, breathable, warm and lightweight, so they feel nice to wear. Because the outer surface is hydrophobic (water repelling) and the inner surface is hydrophilic (water attracting), merino wool base layers protect you from weather changes and ensure that you're always comfortable.

Merino wool is also hygroscopic, meaning it can absorb skin's moisture vapour and release it all at once. Merino wool thermals absorb up to 35% of their body weight before feeling damp, making them perfect for outdoor winter activities such as snowboarding, hiking, camping and skiing. It will keep you warm even when wet (but take longer to dry than polypro), and it's antimicrobial, meaning it will kill odour-causing bacteria. Plus, merino wool is an extra fine fabric so it feels lovely and soft against your skin while keeping you warm, and the higher the wool density, the warmer the fabric will make you feel.

Polypropylene Thermals

Polypropylene (often shortened to polypro) is an ultra-comfortable, extra-warm engineered polyester that's superior to conventional long johns. Polypro is hydrophobic so when sweat moves away from your body and into the fabric, it dries fast. It also wicks skin moisture away but only absorbs 1% of its weight before you feel damp and cold. Polypro is thin and lightweight (70% lighter than wool) so it's great for layering without adding bulk and is extremely hard-wearing. That means polypro thermals are long-lasting, and they're easy to wash and dry quickly.

Synthetic Materials

Thermals made from synthetic, man-made fabrics like polyester provide a lot of warmth and will dry fast, making them ideal for snow and winter activities. Synthetic materials can start to smell as your body odour seeps into the fabric, so some have an antibacterial treatment to help with odours.

Natural Materials

Thermals made from natural fabrics like merino wool are breathable, so they'll keep you at a comfortable body temperature in both cold and warm weather. It provides better all-round comfort than thermals made from synthetic materials. Merino wool thermals absorb more moisture than synthetic materials but take longer to dry. And lastly, they don't absorb odours so you can pack light for camping and hiking trips without washing.

Polypro Vs Merino Thermals

When it comes to warmth, both polypropylene and merino thermals have their strengths, but they work in slightly different ways. Polypro is excellent at trapping heat close to the body, making it a good option for high-intensity activities where you generate a lot of body heat. However, it doesn't insulate as well when you're not moving, and it can feel cold if it gets wet. Merino wool, on the other hand, provides more consistent warmth across a range of conditions. It's great at regulating body temperature, keeping you warm in cold weather and cool when it's warmer. Additionally, merino retains warmth even when damp, making it a better option for those looking for warmth in wet conditions.

Thermal Materials Based On Activity

The more active you'll be in your gear, the more important its breathability is. If the fabric doesn't breathe, the moisture leaving your body has nowhere to go so you'll feel hot and sweaty, and your clothes can become a bit stinky.

The thermals you wear need to suit the type of activity you're doing:

• A lightweight base layer: Best for stop-start activities like skiing or climbing.
• Heavier thermals: Best for just camping and walking around in cold weather.
• Merino wool: Best for low-moderate activities in the cold, it keeps you warm and won't get smelly.
• Polypropylene: Best for high-intensity activities like cross-country skiing and running.
• Long hiking trips: Merino base layers are the best, as they suit all temperatures and are odour-resistant.
• Bush hiking: Be aware that merino wool is super fine so may tear if it snags on trees etc.

Thermal Sizing & Fit

Your thermals need to be the right fit for your body, and the type needs to suit the conditions. Thermals should sit close to your skin to be able to wick moisture and trap heat for maximum dryness and warmth, so choose a snug-fitting size (but not too tight!). They should feel snugger than a t-shirt - any looser and they won't do their job.

Are Thermals Meant To Be Tight?

Thermals should fit snugly against the skin without being too tight. A close fit ensures optimal heat retention and moisture-wicking while allowing flexibility and comfort. They should not restrict movement or circulation. Properly fitted thermals trap body heat efficiently, enhancing warmth and comfort during cold weather activities.

Seams & Cut For Thermals

When choosing thermals, paying attention to the seams and cut is key for both comfort and performance. The right design can ensure a snug fit that doesn't chafe or restrict movement while also maximising insulation and breathability.

Seams On Thermals

Look for flatlock seams or seamless designs on thermals, as these reduce friction and prevent chafing, ensuring a comfortable fit for extended wear. Double-stitched seams offer durability and prevent the risk of splitting, while taped or bonded seams can improve breathability. Pay attention to the seam placement too, as strategic positioning can enhance freedom of movement and minimise discomfort during physical activities.

Base Layer Cut Options

Sleeveless Vest

A sleeveless vest gives your arms more freedom to move but is not as warm as a thermal top with sleeves. It offers core warmth without adding bulk to the arms, making it an excellent base layer. Its streamlined fit enhances mobility and layering efficiency, ideal for fluctuating temperatures, and it's this versatility that makes it a sophisticated and practical choice for outdoor adventures.

Short Sleeves

Short sleeves make an excellent base layer due to their balance of comfort and versatility. They provide coverage while allowing for breathability and freedom of movement. They also keep your core warm and dry but ensure you won't get too hot, so they're best for warmer weather. Short sleeves are ideal for layering as they minimise bulk and enable effortless pairing with outer garments. Their adaptability suits various climates and styles.

Long Sleeves

Long sleeve thermals are an outstanding base layer for their warmth and comfort. They will keep the full length of your arms and legs warm, so they are best for cold conditions. They provide full-arm coverage, which is essential for insulation in cooler temperatures. Their snug fit aids in moisture-wicking and layering without adding bulk. And lastly, they're ideal for diverse climates, ensuring a polished look and functional foundation for your next outdoor adventure.

Best Thermal Clothing & Base Layers For Extreme Cold

For extreme cold, look for thermal clothing and base layers made from high-quality merino wool or advanced synthetic fabrics like polyester and polypropylene. Merino wool is naturally breathable, moisture-wicking and offers excellent warmth without bulk, making it ideal for frigid conditions. For even more warmth, consider a two-layer system, with a moisture-wicking base layer to keep sweat away from your skin and an insulating layer on top for added heat retention. Look for designs with a snug fit to trap warmth, and ensure the fabric is durable enough to withstand the harsh conditions of winter adventures.

Best Thermals For Snow

When you're heading to the snow, choose thermals made from high-quality merino wool or advanced synthetic materials like polyester and nylon. Merino wool is perfect for cold environments, offering excellent insulation, moisture-wicking properties, and breathability to keep you warm and dry. For extra warmth, look for thermals with a thicker weave or double-layered construction. Synthetics, while not as warm as merino, dry quickly and can be a good option for layering. Ensure your thermals have a snug fit to trap body heat, and choose designs that allow for easy movement, especially if you're active in the snow.

Hiking Base Layer

For hiking base layers, the best thermals are those that balance warmth, breathability, and moisture-wicking performance. As always, merino wool is an excellent choice - it regulates body temperature and keeps you comfortable in varying conditions. It's lightweight, naturally antimicrobial, and helps manage sweat without leaving you feeling damp. Synthetic materials like polyester and nylon are also great for active use, as they dry quickly and offer flexibility for movement. Look for thermals with flat seams to reduce chafing and a snug fit to trap warmth while allowing sweat to escape so you stay comfortable and dry on the trail.

Play More & Pay Less With Our Quality Thermals & Base Layers At Anaconda Today

Comfort and warmth in the great outdoors starts at skin-level, and with the massive range of women's thermals, men's thermals and kids' thermals at Anaconda, it's never been easier to ensure you stay cosy when you're outside. Plus, check out our huge selection of gloves, hats and other accessories for cold days!

Also remember to check out our Adventure Centre for more exciting camping tips, hiking destinations and more, such as:

• Winter Clothing Accessories Buying Guide
• Winter Camping Tips: How To Stay Warm While Camping In Winter
• How To Choose Insulation & Outerwear Clothing

Explore our outdoor clothing at Anaconda today.