Down and synthetic jackets can look almost identical on the rail, but they behave very differently once the weather turns. Down is lighter and warmer for its weight, but it costs more and stops insulating well when it gets wet. Synthetic is heavier and often cheaper, and it keeps working when it’s damp.
In wet British winters, that usually makes synthetic the better everyday jacket, and down the better choice for hiking and camping with a waterproof on top. This guide explains down vs synthetic jackets in plain terms, including what fill power means and which I’d choose for different uses. If you already know which type you want, my best insulated jackets for UK weather guide covers the ones I’ve tested.
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The Short Answer
- Choose down if: you want the lightest, warmest jacket for hiking and camping, and you’re happy to wear a waterproof jacket over it when it rains
- Choose synthetic if: you want an everyday insulated jacket to wear on its own through a wet British winter, or you want to spend less
- Neither is waterproof: both rely on a water-resistant shell, so you’ll still need a rain jacket in heavy rain
What Is the Difference Between Down and Synthetic Insulation?
Both types of insulation keep you warm the same way: they trap still air close to your body. The difference is what traps it.
Down is the soft, fluffy layer that sits under the outer feathers of ducks and geese. Each down cluster spreads out into a 3D ball of fine filaments, and those clusters trap a lot of air for very little weight. Most jackets use a mix of down and small feathers, shown as a ratio such as 90/10 (90% down, 10% feather).
Synthetic insulation is made from polyester fibres designed to copy how down traps air. It comes either as sheets of fibre or as loose fibres that behave more like down. You’ll see brand names such as PrimaLoft and Thinsulate, but many jackets, especially cheaper ones, just list “polyester” or “microfibre” fill.
What Does Fill Power Mean?
Fill power measures how much space a set weight of down fills when it lofts. Higher numbers mean more warmth for the weight, and 700 is a good mid-range figure for UK walking. It isn’t the whole story, though: the total weight of down in the jacket matters just as much. My guide on down fill power explains what the numbers mean and how much you need.
As an example, the OEX Kintra I reviewed uses mid-range 700 fill power down, and it kept me comfortable at 0°C with a base layer and fleece underneath.
Down vs Synthetic Jacket: How They Compare
Down vs Synthetic: Which Is Warmer?
Weight for weight, down is warmer. Good quality down traps more air per gram than any synthetic fill, so a down jacket gives you the same warmth for less weight. A synthetic jacket can be just as warm, but it needs more fill to get there, which makes it heavier and bulkier.
Weight and Packed Size
Down wins here too. It compresses much smaller than synthetic fill and springs back when you unpack it, which is why it’s the default for backpacking and anything where pack space matters.
What Happens When They Get Wet?
This is the biggest difference. Down clumps when it gets wet and loses most of its ability to trap air, so a soaked down jacket stops keeping you warm. It also takes a long time to dry. Synthetic fibres hold much less water, keep most of their loft when damp, and dry far faster.
It isn’t only rain. Sweat from a hard uphill walk, condensation in a tent and wet snow can all dampen a down jacket from the inside or out.
Hydrophobic down narrows the gap. It’s down treated with a water-repellent coating, so it resists moisture for longer and dries faster than untreated down. It still won’t match synthetic in prolonged wet weather.
Why it matters in the UK: British winters are more often wet and mild than dry and freezing. On a typical winter day out, you’re more likely to deal with drizzle, damp air and sweat than sub-zero temperatures, and that’s where synthetic insulation has the advantage.
Are Down Jackets Waterproof?
No. Most down jackets have a shell with a DWR (durable water repellent) coating, which makes light rain and snow bead off. In steady rain, water soaks through the seams and fabric, and the down underneath gets wet.
Are Synthetic Jackets Waterproof?
No, not usually. Most synthetic jackets use the same type of water-resistant shell as down jackets. The difference is that the insulation keeps working when water gets through. If you need an insulated and waterproof jacket, look for one with a waterproof membrane, or wear a rain jacket over the top.
Which Is Better as an Everyday Jacket in the UK?
If you’ll wear it as your outer layer, synthetic is usually the better everyday insulated jacket. It copes with drizzle and damp days without losing its warmth, and it’s cheaper to buy.
If you choose down, plan to pair it with a waterproof jacket. A rain jacket over the top keeps the down dry, so you get the warmth and low weight without the main downside. My best waterproof jackets guide covers the ones I’ve tested.
Durability and Care
Looked after well, down lasts longer. It keeps its loft for many years, while synthetic fill slowly loses loft each time it’s compressed, so a synthetic jacket gets a little less warm over time.
Synthetic is easier to look after. You can wash it with a normal non-bio detergent, and it dries quickly. Down needs a down-specific wash and a long, careful tumble dry. I cover both in my how to wash a puffer jacket guide.
Cost
Synthetic jackets are usually cheaper. Down is a more expensive raw material, and higher fill powers push the price up further.
Ethics and Sustainability
Down is an animal product. If that matters to you, look for jackets certified to the Responsible Down Standard (RDS), which bans live-plucking and force-feeding and tracks the down through the supply chain. Many synthetic fills now use recycled polyester, which is the other option if you’d rather avoid animal products altogether.
Down vs Synthetic: Which Would I Choose?
Choosing between a down vs synthetic jacket depends on what you’re doing and what the weather is likely to be. This is what I’d pick for hiking, camping, and everyday wear.
- Day hikes in cold, dry weather: Down. It’s the warmest option for the weight, and it packs small enough to carry in a daypack for stops and summits.
- Wild camping and backpacking: Down, for the weight and pack space. Keep it in a dry bag during the day and wear it in camp.
- Everyday wear and dog walks through a wet winter: Synthetic, worn as your outer layer. It keeps working in drizzle and doesn’t need a rain jacket over it on most days.
- Wet, mild days on the hills: Synthetic. When you’re moving, sweating and getting rained on, it keeps working where down would start to clump.
- Paddle boarding and water sports: Synthetic. Anything near water is likely to get splashed, and synthetic copes with that far better than down.
- On a tight budget: Synthetic. You get more warmth for your money, even if it’s heavier.
How to Layer an Insulated Jacket with a Rain Jacket
In the UK, you’ll often need both. The simplest system is:
- Base layer: a merino or synthetic top that moves sweat away from your skin.
- Mid layer: a fleece, if it’s very cold.
- Insulated jacket: down or synthetic, worn when you stop or when it’s cold enough to wear it on the move.
- Rain jacket: over the top in rain or strong wind.
A down jacket under a rain jacket stays dry and gives you the best of both. The catch is sweat. If you’re working hard uphill, take the insulated jacket off and put it back on when you stop, or the moisture builds up inside it. Fleece vs down for hiking comes down to this too: a fleece breathes better on the move, and a down jacket is warmer when you stop.
Final Thoughts
Down gives you more warmth for less weight and packs smaller, and it lasts for years if you look after it. Synthetic is cheaper, easier to wash and keeps working when it’s damp, which counts for a lot in UK weather.
If you want one jacket to wear on its own through a wet British winter, synthetic is the safer choice. If you want the lightest, warmest option for hiking and camping, choose down and pair it with a waterproof jacket.
Related Guides & Reviews
The resources below cover the basics, common questions, and related kit to help you get more out of your time outdoors.
- Best Waterproof Jackets for Hiking in the UK
- Best Waterproof Hiking Boots UK
- Berghaus Maitland GORE-TEX Overtrousers Review
Steve Cleverdon
Adventure-driven outdoor gear reviewer and paddleboarder, Steve has spent 20 years exploring rivers, coastlines, and trails across Britain and abroad, sharing what he’s learned along the way. Learn more about Steve or get in touch.
