Friday 15 October 2021

A Look At Insulated Clothing

A light down jacket worn over an ultralight synthetic jacket at a cold camp in the Cairngorms

From now until sometime next May an insulated jacket will be in my pack on every hill walk. It’ll be thick enough to keep me warm when stationary in freezing stormy weather. I may also be wearing a thinner insulated jacket when walking too. On every camping trip and in the coldest weather on day walks I’ll carry insulated trousers too. Such garments are great for comfort and also good for safety. I’ve written many reviews of insulated garments over the years, You can read some of them, such as this one, on The Great Outdoors website. Here is an edited piece I wrote for the magazine about insulated garments in general.

The basic choice in insulated clothing is between down and synthetic fills. The latter have improved noticeably in recent years but despite this down is still warmer for the weight and more compact when packed. Down is longer lasting too, though the latest synthetics are pretty durable, and also soft and very comfortable, moulding to the body for near instant warmth.

A light synthetic jacket worn on a damp stormy day

The big plus point of synthetics is resistance to moisture. They soak up less water and dry much quicker than standard down. Hydrophobic down, which has a water repellent treatment, is more resistant to moisture but still not as good as synthetics. Nothing is very comfortable when sodden though. In rain down clothing is generally too warm to wear while moving anyway and you probably won’t need it at rest stops – if you do getting it on and then pulling a waterproof over the top can be done quickly (if you plan on doing this make sure your waterproof jacket is big enough). Also, down clothing usually has a DWR treatment that keeps rain out for short periods. Whilst getting down clothing soaked is best avoided a little dampness isn’t a problem. I’ve used down garments for two-week trips in very humid conditions with wet snow or rain most days and they’ve stayed dry and kept me warm as they were never directly exposed to the weather for very long.

New types of synthetic insulation have made it more comparable with down. Some of these new insulation materials are made up of loose fibres rather than matts and can be blown into compartments like down. Garments with these can often be recognised by the typical stitch lines between compartments, making them look just like down ones. Synthetic insulation is made from oil. To reduce the environmental impact of using this some companies have started making insulation from recycled materials.


Down jacket on the summit of Ben Macdui

Down comes from geese and ducks bred for food. Until a decade or so ago there was little concern about the conditions in which these birds were kept or how they were treated. However, investigations by environmental and animal rights organisations showed that some were force-fed for foie gras while others were live-plucked, and many were kept in poor conditions. This resulted in many companies setting standards for down supply.

Garments fall into two categories. Thick, warm ones designed to be worn at rest stops and in camp, but which are too warm for walking except in extreme cold and lighter, thinner ones that can be worn all day in cold weather. The latter are replacements for a thick fleece or softshell. They can be worn on their own – most are windproof and water-resistant – or under a shell. Because synthetic insulation works okay when damp garments can be pulled on over wet waterproofs, so you don’t lose any heat removing the latter.


A lightweight down jacket


Down and synthetic fills both have advantages and disadvantages. Down is lighter and more compact for the warmth and lasts longer if cared for properly. Synthetic insulation performs better when wet and dries more quickly. Each type comes in different forms.

There are now quite a few synthetic fills, many of them companies own (these may be the same under different names). PrimaLoft is the leading brand and there are now several varieties of this fill alone.

Down quality is measure by fill power, which is how much a given amount of down will rise or loft when uncompressed. The higher the fill power the more loft the down has, making high fill power down warmer for the weight.

Some down garments have synthetic insulation at key points for moisture resistance.

Hydrophobic down resists moisture far better than standard down. It’s still wise to avoid getting it wet though.

A light synthetic insulation jacket

Shell Fabrics

Shells are usually made from tightly woven nylon or polyester fabrics as these are windproof, breathable and downproof. They dry fast too and can be quite water-resistant if they have a good DWR treatment. Pertex is the leading brand but there are similar fabrics. They are all usually quite thin and so don’t have the tear or abrasion resistance needed for scrambling or bushwhacking. However, they are mostly quite smooth, so a shell can be worn over them without it binding and restricting movement.

Waterproof/breathable shells are found on some insulated garments. They do make them waterproof but also a little bulkier and more expensive.


Insulated hand warmer pockets are very useful in a warm garment. Jacket pockets that can be accessed while wearing a pack hipbelt are the best if you plan on walking in a garment. Roomy pockets into which you can stuff hats and gloves when you’re not wearing them for short periods are worth having too – ones inside the garment are especially useful for this as hats and gloves will stay warm.


Whilst not essential a warm hood can be very welcome on a stormy day and replaces the need for a separate hat. Adjustable hoods are best as these can be tightened to stop them blowing off in strong winds.


Down jacket, synthetic insulated trousers & bootees at a very cold Caingorms camp


Full-length leg zips are useful on insulated trousers so you can easily pull them on over footwear. However if you carry them for sleeping ones without zips are the most comfortable.

Weight & bulk

Down garments are very light for the warmth provided. The heavier ones are suitable for temperatures well below freezing, the lightest can be carried in summer for cool evenings and combined with other warm garments in sub-zero temperatures. Synthetic insulated garments are generally heavier  and bulkier for similar warmth. The thinnest synthetic insulated garments are equivalent in warmth to heavyweight fleece and can be used as midlayers.


Having the same size label doesn’t mean that garments are actually the same size as each other. Some garments are sized to fit closely so if you want to wear them over a fleece or softshell a size larger than normal is needed. Other garments are sized to fit over several layers and feel baggy worn over just a base layer. Sizing isn’t consistent between companies either. I’m a Large in some garments, a Medium in others.

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