Down or synthetic ski jacket? PrimaLoft, Thinsulate and goose down explained

Down or synthetic ski jacket: the choice decides how warm you stay on a dry, cold chairlift, and how warm you stay once snow has melted into the fabric. Goose down gives the most warmth for its weight and packs small. Synthetic insulation such as PRIMALOFT, 3M Thinsulate or POWERFILL keeps more of its warmth when it gets damp and asks for less care. This guide explains how each one works, what the names on the label mean, and which suits the way you ski.

Insulation is only half of a jacket. The other half is the shell that keeps snow and wind out. Waterproof ratings and membranes have their own guide: what Gore-Tex is and how waterproof ratings work. Here we stay inside the shell.

How ski jacket insulation keeps you warm

No insulation makes heat. Your body does. Insulation traps still air close to you, and still air is a poor conductor of heat. The more air a filling holds, and the longer it keeps that structure under a shell, a backpack strap and the pressure of a chairlift bar, the warmer the jacket stays.

That is why two things matter more than anything else: loft (how much space the filling holds open) and what happens to that loft when it gets wet. Down and synthetics answer those two questions differently.

Goose down: fill power and the 750 figure

Down is the soft cluster that grows under the feathers of geese and ducks. Each cluster spreads into thousands of fine filaments that hold air. Two numbers describe it:

• Down-to-feather ratio. "90/10" or "90% down" means nine parts down clusters to one part small feathers. More down, more loft for the same weight.
• Fill power. How much space one ounce of down fills, in cubic inches. Higher fill power means each gram traps more air, so a jacket can be warmer for the same weight, or lighter for the same warmth.

Our down pieces state their filling on the product page:

• Cloud Active Short Down Ski Jacket Women: 90% white goose down, 750 fill power, under a water-repellent, wind-resistant shell.
• Cloud Warm Down Ski Overall Women: 90% white goose down and 10% feather, 750 fill power, in a one-piece whose top and bottom detach at the waist. For one-pieces in general, see our women's one-piece ski suit guide.
• The Reversible Waterproof Long and Short Down Jackets: 750 white goose down (90% goose down), with the down fill weight in grams listed on each page.

Where down is strong, and where it is not

• Warmth for weight. Down is the warmest filling per gram. It suits cold, dry days and long, still lift rides.
• Compression. It packs small and springs back. A down jacket rolls into a bag for the drive or the flight.
• Moisture. Wet down clumps and loses loft, and with it most of its warmth. Sweat from the inside counts as much as snow from the outside.
• Care. Down needs gentle washing and thorough drying to fluff up again. Follow the care label.

Synthetic insulation: PRIMALOFT, 3M Thinsulate and POWERFILL

Synthetic insulation is made of fine polyester fibres arranged to trap air the way down clusters do. Fibres do not absorb water the way down does, so a synthetic filling keeps more of its loft when damp and dries faster. It is also more forgiving: it handles hard use and regular washing well. The trade-off is weight and bulk: for the same warmth, a synthetic filling is usually a little heavier and packs less small.

You will see three names on our product pages. Each is 100% polyester.

The PrimaLoft logo on a hang tag tells you the brand of the filling, not how much of it there is. Our product pages name the insulation type; they do not list a fill weight in grams for the synthetic pieces. Compare jackets by type of insulation and by where it sits: some jackets insulate the body and sleeves only, which keeps the cut slimmer and the arms freer.

Down vs synthetic ski jacket: side by side

Hybrid jackets: down where you need warmth, synthetic where you sweat

Some jackets combine both. The Cloud Slim Fit Down Ski Jacket Women pairs 90/10 white goose down with POWERFILL insulation, under a mechanical stretch shell with a 20K waterproof and 20K breathable membrane. The idea behind a hybrid is simple: down for warmth across the core, synthetic fibre where moisture builds up or where the jacket takes pressure.

Which insulation suits the way you ski

• Cold, dry resorts, steady piste skiing, long lifts: down. Most warmth for the least weight.
• Wet snow, coastal or spring conditions: synthetic. It copes better with damp from outside and inside.
• Fast skiing, freeride, hiking for turns: synthetic, or a light insulated jacket plus a mid layer you can remove. High effort means sweat.
• Beginners: synthetic. More falls, more snow on the fabric, and an easier jacket to wash.
• Ski holiday plus town: a short down jacket moves well between slope and village. For the evening, see what to wear for après-ski.

Whichever you choose, layering does the fine-tuning. A thin base layer that moves sweat away from the skin protects the insulation above it, down most of all. Open vents before you overheat on a climb, not after.

Down or synthetic: frequently asked questions

Is down or synthetic warmer for skiing?

For the same weight, down is warmer as long as it stays dry. Synthetic insulation is slightly heavier for the same warmth but keeps more of it when damp, which matters in wet snow or when you sweat.

What does 750 fill power mean?

Fill power measures how much space one ounce of down fills, in cubic inches. At 750, each gram of down traps a lot of air for its weight. Our Cloud Active Short Down Ski Jacket and Cloud Warm Down Ski Overall both list 750 fill power.

Is PrimaLoft better than Thinsulate?

They are different synthetic fillings, both made of polyester. PRIMALOFT is known for softness and warmth when wet; 3M Thinsulate for insulating with little bulk. Compare the whole jacket, not only the filling name.

Does a down ski jacket work in wet snow?

The shell protects the down, but if water or sweat reaches the filling it clumps and loses warmth. In wet conditions a synthetic jacket is the safer choice.

How should I wash an insulated ski jacket?

Follow the care label. Down needs a gentle wash and a thorough dry so the clusters loft again; synthetic fillings are more tolerant. Close all zips and Velcro before washing.

Background on how down and synthetic fillings behave: Burton blog · Outdoor Life. PRIMALOFT is a trademark of PrimaLoft, Inc.; 3M and Thinsulate are trademarks of 3M. Product data: TITTALLON product pages.