When the cold weather hits, we all need a warm and reliable jacket to get us through the winter season. And if you’re a fan of the outdoors, choosing the right jacket for you is a very important task. Sure, there are lots of great jackets on the market, but a good quality insulated jacket is a must-have for those who really feel the cold, or spend a lot of time outside.

When choosing winter coats, it’s good to understand the different types of insulation so you can buy something which suits your needs. We’re going to look at the difference between down and synthetic jackets to help make that choice a little easier.

What is an insulated jacket?

Insulated jackets are great for cold temperatures and are filled with an insulating material: down insulation, synthetic insulation or a combination of the 2 (hybrid insulation). They keep your body heat inside the jacket, with varying thickness of insulation to suit your activity and environment. A lightweight insulated jacket is the perfect layering partner, and can be worn under your waterproof jacket for extra protection in cold and wet weather. Or a super warm insulated jacket will stand up against the elements in snowy conditions. Down and synthetic insulation are both great choices if you want to keep warm, but there are a few key differences between the 2.

What is down insulation technology?

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Down jackets are ideal for low-intensity activities in cold weather – fishing or dog-walking for example. If you’re doing anything too physical, you may get too hot in a down jacket. Most serious hikers would probably choose to wear multiple layers of fleece and other materials, which is more versatile and easier to adapt to the conditions. A down jacket is great for keeping warm when you take a break or if the weather cools down, and they'll squash down nicely, taking up little space in your backpack.

Down jackets contain a layer of down and feathers to help keep you warm. Down is the soft and fluffy feathers underneath the normal feathers of ducks and geese. Decathlon and most other major outdoor brands ethically source this down as a product of the food industry to avoid any form of animal cruelty. Down is a great insulator as the loft (fluffiness) of down creates thousands of tiny air pockets which trap warm air and retain heat. Normal feathers are unable to retain loft on their own, which is why down is used too. Look out for the percentage figures on any down product to see how much of the insulation is down and how much is normal feathers. For example, if a down jacket has the percentages 85/15 this indicates the garment contains 85% down, and 15% feathers. Using feathers gives down jackets a fantastic warmth to weight ratio, making the jackets lightweight. Goose down is often regarded as the lightest and warmest, though duck down jackets are often cheaper.

What is down fill power?

Down is sorted, washed and sterilised during the manufacturing process, and it’s at this point that the fill power (a number from around 500 - 900) is determined. This ‘Down fill power’ rating is based on how many cubic inches of space the down takes up (how fluffy it is) and its insulating properties. So generally, the higher the fill power, the better the quality of down used. This means increased insulating capabilities, and because less down is needed to provide the same amount of warmth, jackets with a higher fill power tend to be lighter and more compressible - perfect for stuffing into your backpack!

This is roughly what to expect when it comes to the down fill power rating:

  • 500 fill power – standard quality
  • 600 fill power – good quality
  • 700 fill power – high quality
  • 800 fill power – extremely high quality
  • 900 fill power – best quality (incredibly rare)

Although it’s important to remember that just because a jacket has a higher fill power, it doesn’t mean it’s necessarily warmer. It could simply mean it has more down stuffed into it.

Are down jackets waterproof?

The main disadvantage to down jackets is that they’re not waterproof (unless stated otherwise). Moisture causes the down to clump, which will affect the insulating properties and it will take a long time to dry. So it’s a good idea to take a lightweight waterproof with you to throw on over the top if you’re heading out in the rain. Although, some manufacturers now treat their down with a moisture-repellent-coating, and others use water-repellent fabrics in their jackets, but in the wet British climate, down jackets are best worn as a midlayer, so you might want to opt for a thinner jacket.

What is synthetic insulation technology?

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While down jackets are suited to the dry cold of high alpine environments, synthetic insulation is ideal in cold drizzly weather. Synthetic insulated jackets contain man-made, synthetic insulation made using polyfibres. This is often a popular choice for people who’d rather not use anything derived from animal products. Synthetics replicate the warming and heating effects of down, without the bulk. They’re often more breathable than down jackets, and are generally cheaper to buy. However, synthetic insulation does allow heat to escape at a faster rate compared to a natural down jacket.

Generally speaking, the more you wear, the more difficult it is for sweat to evaporate. Heavily insulated jackets are designed to be warm rather than breathable, but if you’re doing something active (like hiking or climbing), most insulated jackets will feel too warm as your body generates heat. If your jacket doesn’t allow your skin to breathe, then you could become hot and sweaty very quickly. This is where a synthetic jacket is more suited.

Are synthetic jackets waterproof?

Synthetic fills are a good choice for cold and damp conditions. Synthetic insulation is much better at handling moisture than down as the fibres have been treated so they are hydrophobic and do not absorb water. That means if they do get wet, they retain most of their insulating properties. They also dry much more quickly compared to natural down jackets, and are a lot easier to clean.

Down Vs Synthetic Insulation

The decision on whether to buy a natural down or synthetic jacket comes down to personal choice. You need to consider where and when you’re most likely to wear your jacket so you can choose the right type of insulation for you. Here are the main pros and cons of each to help make your decision.

Down Insulation Pros:

  • Excellent heat retention
  • Better warmth-to-weight ratio
  • Very durable (with proper care)
  • Lightweight and compact (packable)
  • Wider comfort temperature range (suitable for cold and warm temperatures)

Down Insulation Cons:

  • Loses insulating ability when wet
  • Takes a long time to dry
  • More expensive
  • Not hypoallergenic
  • Requires special cleaning

Synthetic Insulation Pros:

  • Remains warm in wet weather
  • It doesn’t clump like down does
  • Fill doesn’t leak if jacket is damaged
  • It’s a cheaper option
  • Easier to clean and care for
  • Hypoallergenic

Synthetic Insulation Cons:

  • Usually heavier and bulkier than down jackets
  • Offers less warmth for its weight than down
  • May lose heat more quickly
  • Less durable than down

What is hybrid insulation?

If you’re still unsure as to which type of jacket you want to go for, there is a third option. Jackets with hybrid insulation combine both down and synthetic materials in an attempt to harness the benefits of both. They come in a variety of styles, and some feature both types of insulator separately within the jacket to improve range of motion. Hybrid jackets are warm, compact and they can handle moisture in the air, making them a good alternative to down or synthetic jackets. They also tend to be cheaper than down jackets, though more expensive than synthetic jackets.

Does the jacket construction make a difference to performance?

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Most down jackets use a simple ‘stitch-through’ construction. This is where the down is housed in compartments - often referred to as ‘baffles’. Though the stitched areas which separate the compartments create cold spots, since there isn’t any down along the stitch lines. In general, fewer stitch lines (and wider baffles) will be warmer than a jacket with narrower baffles.

Some more expensive down jackets are manufactured using ‘box baffle’ construction. This maximises the loft and warmth of the down fill as each separate baffle has its own section of down. This minimised cold spots, and these jackets tend to be thicker and warmer than stitch-through jackets. Though as they require extra material and they're more complex to make, a box-baffle jacket tends to be more expensive.

A super lightweight insulated jacket will have a thin and light outer shell. This is ideal for reducing weight, but this does mean your jacket will be less durable and may tear if it gets caught on trees and thorns. A thin, lightweight jacket is perfect for dog-walking, golf or stuffing into your back on a cold day, but if you’re looking for a more heavy-duty jacket, then it’s worth looking at one with a slightly heavier and thicker outer shell.

And finally, your jacket should not be too fitted. You should allow for adding layers underneath, but ensure it’s not too loose so cold air doesn’t get in through the arms and hem. And choose something which doesn’t restrict your movement.

So what type of insulated jacket will you go for, down, synthetic or a combination of the 2? Think about where you’ll be wearing it, how much weight you want to carry, what the weather will be like and how much money you want to spend. If warmth, weight and packability are your priorities, then it’s worth spending a bit more and going for a natural down jacket. Or if you want something that’s versatile and does better in the rain, then go with synthetic. Either way, your insulated jacket is sure to keep you nice and warm this winter.