There’s no arguing with the effectiveness of thermal layers in cold weather. Fitting close to your skin, they trap body heat to keep to warm, and wick moisture from the skin when you sweat.
However, there are many products out there, as well as materials used in their manufacturing. In this article we take a look at the key factors you should consider when choosing thermals, along with some of our recommended products on the market.
Quick Answer: The Best Thermals
- 1ICEBREAKER EVERYDAY LONG SLEEVE CREWE
- 2XTM MERINO CREW
- 3Kathmandu Thermals - KMDCore Polypro
How to choose the best thermals
The key choice you need to make with thermals is between synthetic and natural fibres. Common synthetic materials are polypropylene, or “polypro”, while the most popular natural material is merino wool.
Generally, synthetic materials will be lighter weight, more durable, quicker to dry, and cheaper. Merino will usually be warmer, more breathable and feel nicer against the skin.
Below we take a closer look at some of the key features you should keep an eye out for on your hunt for the perfect set of of thermal underwear.
The warmth rating of thermals will usually come in the form of the manufacturers rating e.g. heavyweight/winter weight. They will also usually include a reference to the weight of the fabric, measured in grams per square metre e.g. a winter weight merino thermal is likely to be between 200-300gsm.
Your personal preferences and requirements will determine which weight is best for you. For skiing and snowboarding, you may be tempted to choose the heaviest weight, but do keep in mind you will be physically active while on the slopes, so a mid-weight option may be suitable.
Keep in mind that warmth generally translates to more weight, so if you’re going to be carrying your base layer in your pack, it’s worth thinking about this trade-off.
Breathability is a fundamental feature of your base layer for two main reasons.
Firstly, while thermals are designed to trap your body heat in colder temperatures, they also need to allow excess heat to escape during physical activity or in warmer conditions.
Breathability is also essential for wicking moisture away from the skin, in order to retain warmth even when you sweat.
Natural fibres like Merino tends to perform better in breathability than any synthetic alternatives.
Thermal underwear is meant to fit snug, with enough stretch to allow a wide range of movements. In terms of skin feel, merino is likely to be the most comfortable, especially over longer periods, making it a popular choice for hikers.
Some products come with features such as thumb loops, zip pockets, chin guards, hoods, or are longer in the body making them easier to tuck in. Think about the activities you intend to use your thermals for and what features are most important to you.
thermal underwear Reviews
#1 Icebreaker Everyday Long Sleeve Crewe Top
BUY AT amazon
Icebreaker are well known for their high-quality garments made 100% from New Zealand merino wool.
The Everyday Long Sleeve Crewe is a very versatile base layer, constructed for mobility, and with a soft and comfortable feel on the skin. It is also suitable for wearing for multiple days between washes, due to the odor resistant nature of merino.
At 200gsm, you probably want something more heavy duty for extreme cold, however this will be a perfect first layer for skiing, hiking, hunting, fishing, and many other outdoor pursuits.
- Designed for mobility and comfort
- More expensive than synthetic
#2 XTM MERINO CREW NECK BASE THERMAL TOP
BUY AT wild earth
A great option for those who really feel the cold, the XTM is a high quality, 230gsm, winter weight thermal from one of Australia’s favourite snow sport brands.
Made with 100% Australian Merino wool, this top will work well as a base layer or on its own, with the natural fibres properties regulating body temperature and providing warmth and breathability when you need it most.
- Very warm
- Thumb holes
- More expensive than synthetic
- Wider neck may not suit some people
#3 Kathmandu Thermals - KMDCore Polypro
BUY AT KATHMANDU
Warm, lightweight, and affordable, the Kathmandu KMDCore provides a great option for casual adventurers.
Perfectly suitable for skiing and hiking, the polypropylene fabric is super quick drying and is designed to wick moisture away from the body.
- Breathability inferior to merino
At the end of the day your budget and personal preference are going to determine which thermal is best for you. We are big fans of Icebreaker and from this list would opt for the Everyday Long Sleeve Crewe Top for general use, due to its superior warmth and temperature regulation, while still being light and comfortable.
While in this article we focused on thermal tops, don’t overlook the importance of thermal bottoms (or long johns) in cold conditions.