Quilted jackets: down, synthetic, and the warmth-to-bulk trade

A quilted jacket is a grid of pockets with insulation inside, and the decision comes down to what that insulation is. Down and synthetic solve the same problem in opposite ways, and the numbers on the tag, fill power and fill weight, tell you which problem the jacket was built to solve.

Down: loft per ounce

Down is the undercoating of waterfowl: fine, three-dimensional clusters that trap air. Its advantage is loft — the clusters spring back after compression, and the volume of trapped air is what insulates.

Fill power, under the International Down and Feather Bureau’s test regulations, is the volume in cubic inches that one ounce of conditioned down occupies under a set load in a standard cylinder — traditionally reported as cubic inches per ounce. It is a quality measure of the down itself: 600-fill lofts more per ounce than 500-fill, so the same warmth needs less fill and less weight. Our read of the tiers: 550-600 is midgrade, fine for cool-weather city wear; 650-750 is the sweet spot for real winter; 800 and up is expedition territory, where you pay for every ounce of carried weight saved.

Fill weight is the second number, and the one brands print less often: the total amount of down in the jacket. Fill power without fill weight is half a spec — 800-fill down in a thin shell is an autumn jacket, while 600-fill in a heavy baffle system can out-warm it. Construction matters too: box-baffle walls beat plain sewn-through quilting at equal fill, because the down needs room to loft.

Synthetic: bulk for damp

Synthetic insulation is spun polyester filament arranged to trap air, and it is rated in grams rather than fill power — there is no loft-per-ounce scale that maps the same way. The trade is direct: synthetic needs more bulk and weight to reach the warmth of down, but it keeps that bulk when damp. Down clusters collapse when wet and lose their insulating volume until dried; synthetics shake off moisture and keep insulating while wet. Synthetics also dry faster, machine wash more forgivingly, and cost less. Down compresses smaller for the same warmth and lasts decades if stored loose — which is why it remains the backpacker’s answer.

The behavior table

Wet weather, in practice

The wet difference is the one to plan around. A down jacket in drizzle absorbs moisture at the surface and seams long before the down itself is soaked; loft drops, and it takes a long dry to come back. Where the weather sits above freezing and rains, a synthetic quilted jacket is the honest choice — bulkier in the closet, warmer on a wet day. In dry cold, down wins every time.

Storage and revival

Insulation is a volume, and volume is easy to damage. Store quilted jackets loose, hung or laid flat, not compressed in a stuff sack for months at a time; compression slowly presses the loft out of down and synthetic alike. To revive a tired jacket, give it a no-heat tumble with clean dryer balls, which restores much of the volume.

How to choose

Match the fill to the weather, not the photo. Dry, cold, weight-sensitive: down, sized by fill weight first and fill power second. Damp, variable, low-maintenance: synthetic, sized by grams and cut. In both cases the shell matters as much as the fill — great insulation under a shell that cannot block wind is half a solution.