Down vs Synthetic - A Rab Guide To Insulation

Nothing beats the insulative performance of down and no one knows down insulation like Rab.

An insulated jacket is a key part of your layering system for outdoor adventures. Warm,
breathable, and protective, insulated jackets work with your base, mid, and outer layers
to regulate your temperature.
But with so many options, selecting the right insulation for your adventure can feel like
finding a particular snowflake in a blizzard! Whether you are looking for an everyday winter jacket, or planning a Himalayan adventure, this handy guide will give you all the information you need to pick the right jacket for the job and help you look after it.
Choose the right insulation for you, select down for maximum warmth-to-weight ratio, or synthetic for all-conditions resilience. The right choice can make all the difference between staying comfortable all day and struggling on the mountain.

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What is Down Insulation?

Down is the soft, fluffy layer found beneath the tougher outer feathers of ducks and geese. Its job is to efficiently trap air and keep the birds warm, the same reason it’s so effective in outdoor gear. Made up of fine, lofted clusters, down creates an incredibly light and efficient thermal barrier. The air it traps provides exceptional warmth for the down’s weight, making down-filled jackets and sleeping bags both cosy and extremely packable. Down can be used loose to maximise air trapping potential, or in sheet form (like in the Rab Optical Jacket), which is lower bulk and great for areas like the arms where you need better mobility.

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What is fill power?

Fill power refers to how good the down is at trapping air. The higher the fill power number, the higher amount of air trapped per gram of down. High quality down with a higher fill power can create a warmer jacket for less weight than down with a lower fill power.

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What are down jackets best for?

Offering the highest warmth-to-weight ratio of any type of insulation available on the market, down is the perfect insulator for outdoor activities. Highly compressible and lightweight, it can be easily pulled from your pack for an instant boost of warmth. When down gets wet however, it can lose much of its insulating power, making it most suitable for very cold, dry conditions, or for activities where weight and packability are your priority.

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Pictured: Down insulation. Image courtesy of Rab

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Lightweight Down Jackets

A lightweight down jacket is perfect for stop-start activities like hiking, biking and snowsports, or for stashing in your pack as an emergency layer. They are generally built with breathable, stitch-through micro baffles and have a minimal feature set to keep the weight down.

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Mid-warmth Down Jackets

A midweight down jacket strikes a good balance of warmth, weight and packability, perfect for cold conditions and high mountain pursuits. They are often built with larger baffles and may feature a water-resistant outer fabric and mountain ready features, like adjustable cuffs and a helmet compatible hood for extra protection.

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Ultra-warm Down Jackets

When you’re venturing into extreme environments, only the warmest down jackets will do. Designed for alpinism and mountaineering, these jackets may feature boxwall baffles to allow the down to loft fully, heat reflecting fabrics, and clever designs to eliminate cold spots, offering reliable warmth in the coldest conditions.

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Waterproof Down Jackets

You can pair your down jacket with a waterproof shell, which gives you flexibility with your layers. However, if you know you’ll be in wet and cold conditions, a fully waterproof down jacket could be a great option.

Rab use Grangers Down Defend® to treat all the down used in their products. This bluesign® APPROVED treatment creates hydrophobic down – water resistant down that copes well in damp conditions. Devised in the UK and a world first in hydrophobic down technology, Down Defend® ensures that down stays lofted even when wet.

Although not entirely waterproof, the down has 5% higher fill power and is over 375 times more durable than untreated down, keeping you warmer for longer and enduringwash after wash.

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Image courtesy of Rab

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What is Synthetic Insulation?

Synthetic insulation is an entirely man-made alternative to down that’s designed to mimic the way down works, trapping air in its intwined structure and creating an insulating layer. It’s usually created from polyester to form sheets of wadding or lofted (blown) structures.

You can choose between static insulation, which keeps you warm when you’re standing around belaying or brewing up, and active insulation, which breathes beautifully when you’re on the move. But you can be guaranteed it will be lightweight, durable, warm and fast drying in any of its forms.

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What are Synthetic Insulated jackets best for?

Synthetic insulation is incredibly versatile. It may not quite reach the warmth-to-weight ratios of down, but it’s designed to handle everything the mountains throw at you. It dries in no time, shrugs off damp conditions, and doesn’t lose its warming ability even if it gets wet.

Plus, it’s tough enough to be stuffed in and out of your pack all day without losing loft. Many options are now made from post-consumer recycled materials too so you can stay warm and feel better about your environmental footprint. In short, it’s ideal for unpredictable mountain weather.

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Lightweight Synthetic Jackets

These go-to layers are perfect for all kinds of outdoor adventures, as an outer layer in warmer weather or as a midlayer when the temperature drops. Lightweight and packable, they are often built with highly breathable fabrics, ideal for high output activities like climbing, biking and ski touring, and may feature stretchy side panels for mobility and air flow.

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Ultra-Warm Synthetic Jackets

Need serious warmth in cold conditions? Look for larger baffled synthetic insulated jackets that may feature smart tech like supercharged insulation or heat reflecting fabrics. Ideal for high altitude, winter mountain activities, these jackets are built with a wealth of harness and helmet compatible features.

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Waterproof Synthetic Jackets

Designed to deal with the worst weather, a waterproof synthetic insulated jacket is ideal for throwing on over all your layers, perfect for snowsports. But remember, you can always pair your synthetic jacket with a waterproof hardshell for greater versatility.

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Pictured: Synthetic insulation. Image courtesy of Rab

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What is PrimaLoft®?

Rab use PrimaLoft® insulation in their synthetic jackets, a leading name in high performance insulation. There’s a wide range of different PrimaLoft® technologies, each tailored to suit specific needs, so Rab can match the right type of insulation to each jacket depending on its intended use.

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Active Insulation

PrimaLoft® Active Evolve: With varied fibre thicknesses, it traps air effectively and allows moisture to pass through, ideal for high intensity activities.

PrimaLoft® Gold Active +: Warm, breathable and stretchy, often paired with highly air permeable fabrics for excellent breathability on the move.

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Static Sheet Insulation

PrimaLoft® Gold Insulation with Cross Core™: Infused with ultralight and insulating aerogel for supercharged performance in the coldest conditions.

PrimaLoft® Silver Insulation: Breathable, fast drying and warm, and made from 100% recycled material.

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Loose Fill Insulation

PrimaLoft® Silver: RISE: An impressive warmth-to-weight ratio and highly durable, ideal for damp conditions and general, all-mountain use.

PrimaLoft® ThermoPlume®: Soft, featherweight synthetic insulation that closely mimics down, offering the best warmth-to-weight ratio and still coping in damp conditions.

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Down vs Synthetic Insulation

Broadly speaking, Rab garments and sleeping bags use one of two types of insulation – down or synthetic.

Ultimately, the choice between down and synthetic insulation comes down to your priorities and the conditions you expect to face. Down consistently offers the highest warmth-to-weight ratio and superior compressibility, making it ideal for very cold, dry environments or situations where every gram and centimetre of pack space matters. However, it is less resilient to moisture, requires more careful maintenance, and benefits from being paired with a waterproof layer in wet conditions.

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Image courtesy of Rab

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Synthetic insulation, on the other hand, is more robust, warm when damp, easier to clean, and generally more affordable, making it a reliable choice for wet or variable climates and for those who value low-maintenance gear. Whatever the mountain throws at you and whatever your chosen pursuit, an insulating layer is a key part of your get-up. Taking the time to decide whether a down or synthetic jacket will suit you best, could mean the difference between staying warm andunstoppable, or shivering your way through the day. Choose wisely, and you’ll keep going back for more.

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How to care for your Rab Jacket

Once you’ve got your new jacket, you’ll want to make sure it lasts - we’ve got a few pointers to help you keep it good as new.

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1. Washing Down

Rab® down products can be home cleaned, however this is a difficult and time-consuming job as the drying process can take several hours. If you’re in the UK then you can take advantage of Rab’s new wash service, a no fuss, specialist down wash service that ensures that your Rab® jacket or sleeping bag is clean, fully lofted and ready for your next adventure. If you’re outside the UK, you can find information on caring for your down products in their help centre.

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2. Storing Down

Down should be stored uncompressed and out of direct sunlight in a dry, cool place. If your down product gets damp, air it thoroughly and make sure it is completely dry before putting it back into storage. If the product is still damp after airing, a short cycle in a tumble dryer on a cool setting should help to complete the drying and restore the loft.

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3. Washing and Storing Synthetic

Synthetic items can be cleaned according to the instructions on the item. If your item has a DWR on the shell this will normally need to be reproofed after washing and throughout its life to keep it performing well. It can be stored compressed or loose in a dry environment just like the other items in your wardrobe making it very simple to look after. Synthetic provides a low maintenance insulation piece which will last for years to come through some easy maintenance.

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Now you know what you’re looking for, why not take a look at our full range of Rab insulated jackets?

Shop all Rab Clothing here

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