Down vs Synthetic Insulation for Travel
Take down if the trip is cold and dry and pack space is tight; take synthetic if it will be wet, if you cannot dry things reliably, or if the jacket will take abuse.
Down gives more warmth per gram and packs smaller than any synthetic. Its weakness is water: wet down collapses and loses almost all its insulating value, and it takes a long time to dry. Synthetic fill is heavier and bulkier for the same warmth, keeps working when damp, and costs less. For most travel that crosses climates, synthetic is the safer choice and down is the better one only when you know it will stay dry.
How each one actually insulates
Both work the same way: they trap air, and trapped air is what keeps you warm. The difference is the structure doing the trapping.
Down is the fine under-plumage of ducks and geese. Each cluster is three-dimensional and springy, so a small mass creates a large volume of trapped air. That is why down wins decisively on warmth per gram.
Synthetic fill is polyester fibre engineered to mimic that structure, either as continuous filament sheets or as short staple fibres. It cannot match down's loft-to-weight ratio, but the fibres do not collapse when wet, because they absorb almost no water themselves.
| Down | Synthetic | |
|---|---|---|
| Warmth per gram | Best available | Roughly half to two thirds of down |
| Packed size | Smallest | Noticeably bulkier |
| When wet | Collapses, loses most insulation | Retains a useful proportion |
| Drying time | Slow, hours to days | Fast, often overnight |
| Lifespan | Very long if cared for | Loft degrades with compression cycles |
| Cost | High | Low to moderate |
| Care | Specialist wash, careful drying | Tolerant |
Reading fill power, and what it does not tell you
Fill power measures the volume in cubic inches that one ounce of down occupies under a standard load. Higher fill power means loftier down, so less weight is needed for the same warmth.
| Fill power | Quality |
|---|---|
| 550 to 650 | Entry level. Heavier for the warmth delivered |
| 650 to 750 | Good general purpose range for travel |
| 800 and above | Premium. Lightest and most compressible, most expensive |
The number people forget is fill weight: how many grams of down are actually in the garment. A jacket with 800 fill power and 60 g of down is much less warm than one with 650 fill power and 150 g. Fill power describes quality, fill weight describes quantity, and warmth needs both. If a brand publishes only fill power, it is telling you half the story.
Synthetic fills are usually described by weight alone, in g/m2, which is more straightforward. Around 60 g/m2 is a light insulated jacket, 100 g/m2 is a warm one, and above 130 g/m2 is genuinely cold-weather kit.
The water problem, stated fairly
The received wisdom is that down is useless when wet. That is close to true for soaked-through down and unfair to modern garments.
Hydrophobic down, treated with a water-repellent finish at the cluster level, resists wetting longer and dries faster than untreated down. It is a genuine improvement. It is not waterproofing, and thoroughly wet hydrophobic down still collapses.
The practical question is not whether it rains. It is whether you can dry the jacket. On a trip with heated indoor space every night, a damp down jacket recovers. On a trip through humid climates with no reliable drying, or where the jacket lives in a pannier, synthetic removes an entire category of risk.
This is also why the insulated layer should sit under a shell rather than serve as the outer layer in wet weather. A waterproof outer keeps the insulation dry regardless of type, which is the whole argument for separating the two functions in the practical travel wardrobe.
Choosing by trip
| Trip | Choose | Why |
|---|---|---|
| Cold, dry, carry-on only | Down | Pack space is the binding constraint and the risk is low |
| Iceland, coastal Britain, Patagonia | Synthetic | Wind-driven rain and unreliable drying |
| Shoulder season city breaks | Either, lightly filled | The layer is occasional, so the stakes are low |
| Bike commuting | Synthetic | Repeated damp compression is exactly down's weakness |
| Long trip, humid climates | Synthetic, or none | Nothing dries, and the layer may not be needed at all |
| Winter city travel with hotels | Down | Warmth per gram wins and drying is available |
Ask one question: if this jacket gets soaked, can I dry it before I need it again? If yes, down. If no, synthetic.
Looking after both
Neither should be stored compressed. Loft is the insulation, and long periods in a stuff sack permanently reduce it, faster in synthetics than in down. Store both loosely at home and compress only for the journey.
Down needs a down-specific detergent, a gentle cool wash, and a long tumble dry on low with dryer balls to break up clumps, which is one of the few cases where tumble drying is correct. Synthetic tolerates normal washing but dislikes high heat.
Neither should be washed with fabric softener, which coats fibres and reduces loft in synthetics and destroys the water repellency of treated down. The same rule applies to shells, for the same underlying reason, as covered in how to wash a waterproof jacket.
Where VEAR fits
We make the shell layer rather than the insulation, so this choice is yours to make independently of us. The connection worth drawing is that a waterproof shell removes most of down's disadvantage: keep the insulation dry underneath and the wet-collapse problem largely goes away.
The VEAR Jacket is uninsulated by design for exactly this reason. It layers over whatever insulation the trip needs, which is what lets one jacket cover a wide temperature range. Our shell was tested by SGS at a hydrostatic head of at least 20,000 mm under ISO 811:2018, with the full results and their limits on our lab tests page.
The VEAR Winter Jacket combines insulation and shell into one garment, which is the right call for a trip that stays cold and the wrong one for a trip that crosses climates.
Quick glossary
- Fill power: the volume one ounce of down occupies. Describes quality, not quantity.
- Fill weight: the actual mass of down in a garment. Describes quantity.
- Hydrophobic down: down treated to resist wetting. Better, not waterproof.
- Loft: the thickness of trapped air an insulation creates. Loft is warmth.
- Baffle: a sewn or welded chamber that stops insulation migrating within a garment.
- Continuous filament: synthetic fill made from long fibres, more durable than short staple.
Frequently asked questions
Is down warmer than synthetic?
Per gram, yes, by a wide margin, and it packs smaller for the same warmth. That advantage holds only while the down stays dry. Wet down collapses and loses most of its insulating value, whereas synthetic fill retains a useful proportion because the fibres absorb almost no water themselves.
What fill power should I look for in a travel down jacket?
650 to 750 is the practical range for travel, balancing compressibility against cost. Higher fill power is lighter for the same warmth but expensive. Always check fill weight alongside it, since a high fill power jacket with very little down in it is not warm, and many jackets publish only the fill power.
Does hydrophobic down solve the wet problem?
It reduces it rather than solving it. Treated down resists wetting longer and dries faster than untreated down, which matters in damp conditions and light exposure. Thoroughly soaked hydrophobic down still collapses. If you expect sustained rain without reliable drying, synthetic remains the safer choice.
Can I wash a down jacket at home?
Yes, with care. Use a down-specific detergent, wash cool on a gentle cycle, and rinse thoroughly. Then tumble dry on low for a long time with a few dryer balls to break up the clumps as it dries. This is one of the few technical garments where tumble drying is the correct method rather than a mistake.
Should I store insulated jackets compressed?
No. Loft is what provides the insulation, and prolonged compression permanently reduces it, more quickly in synthetic fills than in down. Store insulated jackets loosely on a hanger or in a large breathable bag at home, and compress them only for the duration of a journey.
Keep reading
- Softshell vs hardshell for travel: the layer that goes over the top.
- Packable vs structured travel jackets: the volume trade-off in detail.
- What to pack for Iceland in summer: where synthetic wins outright.
- The practical travel wardrobe: how insulation fits the system.
- All comparison guides and the glossary.