Down Jackets vs Synthetic Jackets

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 insulation thicknesses 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 two.

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 cannot 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 a percentage of 85/15, 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.

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.

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.

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.

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 insulators 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.

Most down jackets use a simple ‘stitch-through’ construction. This is where the down is housed in compartments - often referred to as ‘baffles’. However, 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, making these jackets thicker and warmer than stitch-through jackets. Even though 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 during cold weather.