Thermal Base Layers

A thermal base layer typically consists of a top and trousers. As anyone who’s climbed a mountain or experienced extreme conditions will testify, thermal base layers can make a huge difference. As people look at more adventurous activities to entertain themselves, the popularity of this item of clothing has markedly increased.

How do they work?

Thermal base layers are often made from a combination of nylon and Lycra. They are tight fitting garments that hug the skin, and by doing so encourage the movement of moisture away from the body enabling you to dry out quickly if you become sweaty or are caught in an unexpected shower. Due to their body hugging nature, they also have the ability to keep you warm by holding a thin layer of air between the body and the base layer.

Do I need one?

During any physical activity, the body starts to perspire.  This is the body saying it wants to cool down but the environment surrounding it can dictate otherwise. A thermal base layer is essential if you are to keep warm, dry and comfortable in the most demanding environments, particularly if you’re putting your body under physical strain.

Before deciding what other clothing you will wear on an expedition, it is always good to start with a thermal base layer. After that, depending on the temperature and humidity that day, you can decide what else you need to wear on top. It’s advisable to wear lots of thin layers rather than a couple of very thick items. This will allow you better control over your bodies temperature as you will be able to better adjust your clothing dependant on how warm or cold you are.

People who participate in the following activities tend to require a thermal base layer:

Skiing & Snowboarding

Hiking

Sailing

Skydiving

All of these activities can experience vastly differing environments so the demand on clothing has never been so great.

What to look for when buying a thermal base layer?

As previously mentioned, a good thermal base layer will be made up of nylon and Lycra. Some models will have thumb loops to prevent them from riding up the arm and cooling the wrist area.  This can be really beneficial if you plan on visiting an area with very low temperatures.

Some base layers now come with hoodies. I would only recommend purchasing one of these if you plan on going to a very cold area, otherwise the hood will get in the way and be a nuisance. A hat should always be worn in lower temperatures so a hood would be redundant.

If you are unsure of sizing, it’s always wise to get a size too small rather than a size too large. When too large, thermal base layers don’t transport moisture away from the skin or retain heat so they are virtually useless and a waste of money.

Will I need any other equipment?

Yes. A base layer is part of a collection of clothes that should be worn together to ensure the correct temperature for the body is achieved. It can be broken down into three groups:

Inner Layer

Mid Layer

Shell Layer

The mid layer provides extra insulation but should fit more loosely than the inner layer as this allows for a better transfer of moisture between the two layers. This layer is traditionally made of wool or fleece although in recent years man made substitutes such as synthetic fibrefill such as polyester have been used.

The shell lay is the outermost piece of clothing and its primary propose is to protect the other layers from rain and wind. It should be slightly porous so it lets moisture through to the outside however there is always a trade off between breathability of the fabric and its water/wind resistance.

Conclusion

Hopefully this article has provided you with a good level of understanding of thermal base layers which will hold you in good stead should you come to purchase them. Due their popularity more and more manufactures have begun producing base layers which has cause the price to fall. There has never been a better time to purchase a thermal base layer so don’t delay any longer!