Layering System Buying Guide
WHAT IS A LAYERING SYSTEM?
A layering system consists of three types of clothing: a base layer, a mid layer, and an outer layer. The system has three main functions: to wick sweat away from the skin, trap body heat, and protect you from the weather. Each part of your clothing serves a different purpose, working with the other layers to keep you warm, dry, and comfortable. An effective layering system lets you adjust and regulate your body temperature when active, resting or when weather conditions change.
What is a base layer?
A base layer is the first item of clothing you wear over your underwear, next to skin.
The foundation of a clothing layering system, the primary function is to wick sweat away from the skin and towards the outer fabrics, helping you to regulate temperature. Moisture conducts heat 25 times faster than air, so if it can't escape the surface of your skin, you become cold very quickly. Available as a top or bottom, base layers should be close fitting to work effectively.
What are base layers made from?
Base layers are usually made from polyester or merino wool due to their moisture-wicking and fast-drying properties. Elastane (Lycra) may be added to the blend to improve stretch and shape retention. Available in different fabric weights, the heavier the fabric, the warmer the base layer. Heavy-weight base layers which prioritise warmth are also known as thermals.
You should avoid wearing cotton as a base layer because it soaks up sweat and is slow to dry. As a result, it can leave you feeling damp, clammy, and cold.
Polyester vs. merino wool – what should I choose?
Both materials give good base layer performance but have different characteristics and benefits:
- Synthetic fibre
- Fast drying
- Easy to care for
- Good value for money
- Natural fibre
- Odour resistant
- Soft against the skin
- Warm even when wet
How to choose a base layer
The base layer you choose will depend on the activity you are doing. Consider where you are heading, how long you are going for, and expected weather conditions.
For example, if hiking in warmer climates, you want a lightweight base layer top that will wick sweat fast. If you are skiing in January, choose a base layer top and bottom made from a thick fabric for extra warmth.
What is a mid layer?
A mid layer is the item of clothing you wear over your base layer and under your outer shell. Available in a variety of materials and styles, the aim of the mid layer is to help regulate temperature. The mid layer traps body heat but is also breathable. This allows sweat to pass through to the outer layers to stop you feeling clammy.
Mid layers can vary greatly, from microfleece hoodies to down-insulated vests. The type you choose will depend on the activity and conditions you'll be experiencing.
What are mid layers made from?
Mid layers are made from materials which can trap heat. This includes fleece, synthetic insulation, and down insulation. Each material has different characteristics and benefits, which can favour particular temperatures or activities.
Fleeces are usually made from synthetic materials like polyester, in varying thicknesses and designs. Thin microfleece garments offer lightweight warmth and quick drying performance. They make an excellent option in mild temperatures or for high-output activities in the cold, such as cross-country skiing. Mid- to heavy-weight fleeces are warmer. They are better suited to hiking and climbing in the colder months or low-output activities like camping. Fleeces are durable, easy to clean, and offer excellent value for money. However, they are often heavier and bulkier than other forms of insulation. This makes them less suitable for weight and space-conscious expeditions.
- Synthetic Insulation
Mid layers containing synthetic insulation are warm and resilient. Usually made from sheets of polyester, the strands of synthetic fibre create a down-like material to trap heat effectively. A key benefit is wet-weather performance. Synthetic insulation can maintain warmth when damp and dries quickly. The material is also robust and easy to care for. Synthetic-insulated mid layers are ideal for moisture-prone activities and environments, such as Scottish winter mountaineering. The easy-clean properties make them the top choice for kids' insulated clothing.
- Down Insulation
Mid layers containing down insulation are best for lower-output activities in cold, dry conditions. The natural filling comes from goose or duck plumage, the soft, fluffy material underneath the feathers. Down insulation is measured in fill power, which reflects how much the down can loft. The higher the fill power, the better the warmth-to-weight ratio will be. Gram for gram, nothing insulates as effectively as down. However, without a water-repellent (hydrophobic) treatment, down is susceptible to moisture - when wet, its insulating capabilities will significantly drop..
What is an outer layer?
An outer layer is the final item of clothing in your layering system. Available as a jacket or trousers, they are worn over everything else. Outer layers include windshells, softshells, and hardshells. The type dictates the level of weather protection on offer.
What are outer layers made from?
Outer layers use a variety of materials, depending on the shell type. Each category offers different benefits, and fabrics within each category will also change.
For more detail about hard shell fabrics, read our full Waterproof Fabrics Buying Guide.
A hardshell offers the most weather protection. The fabric is waterproof and windproof but also breathable. This allows sweat vapour to escape, which stops moisture from building up inside the clothing. Hardshell fabrics have an outer layer (face fabric), a waterproof-breathable membrane, and an inner layer (scrim) that sits against the skin.
The face fabric - usually polyester or nylon - comes in different deniers. The higher the denier, the thicker and more durable the material. The face fabric often has a Durable Water Repellent (DWR) coating to help moisture roll off.
Waterproof membranes are made from expanded polytetrafluoroethylene (ePTFE) or expanded polyethylene (ePE), with or without a polyurethane (PU) coating. The most famous waterproof membrane is GORE-TEX. Others include Pertex Shield, Patagonia's H2No, and The North Face's DryVent.
The scrim can be a fabric backer, loose liner, or a coating. It protects the waterproof membrane from contaminants such as skin oils and dirt. For in-depth information about hardshell fabrics, read our Waterproof Fabrics Buying Guide.
Hardshells give the highest level of weather protection. They are your go-to when rain, sleet, or snow is due. However, there are some downsides compared to a windshell or softshell. Waterproofs are less breathable, so if it is mild and only light drizzle or showers are forecast, you may prefer the comfort of a softshell. The fabric also tends to create a noisier, rustling sound.
A softshell offers medium weather protection. The emphasis is on comfort, breathability, and movement rather than total waterproofness. Commonly made from polyester or nylon blends, softshell fabrics can vary from light and stretchy to durable and abrasion-resistant. Durable Water Repellent (DWR) finishes stop moisture from immediately sinking in, but the materials are not waterproof.
Available in a variety of styles, the type you choose will depend on what activity you are doing. Softshells made for climbing prioritise abrasion resistance to withstand scrapes against the rock. Softshells designed for winter hiking focus on comfort and warmth. They usually have brushed linings that trap heat and wick moisture.
Softshells provide more versatility than hardshells. Extending use beyond wet-weather days, they'll see you through fluctuating temperatures and changing seasons. However, when heavy rain, sleet or snow is forecast, you'll need a hardshell to stay fully protected.
A windshell offers lightweight weather protection. Made from highly wind-resistant or windproof fabrics, they block draughts while remaining light and breathable. Windshells are a favourite of runners, climbers, and hikers looking to move fast and agile outdoors.
As one of the more specialist outer layers, windshells tend to have minimalist feature sets. Low-profile hoods or collars, elasticated cuffs and hems, and fewer pockets help to keep the weight low. The packable designs make them easy to stash in a backpack or running vest.
Windshells are excellent for fast-paced activities and breezy conditions. However, if you need more warmth or protection from your outer layer, a softshell or hardshell will better meet your needs. As with the rest of your clothing layering system, it all comes down to context. Choose your layers to best match the activity and weather conditions you'll be experiencing, and you'll stay dry and comfortable throughout.