SDUL .75 Down Sweater

The SDUL (super duper ultralight) series sweaters are currently the lightest we can make a down garment. They have the highest warmth to weight ratio and the highest fill weight to materials weight that can be achieved. These are down sweaters in the strictest sense. No zippers, no pockets, no drawcords, no linings, no webbing, just insulation in the form of down in a nylon shell. The SDUL series uses 1000fp down and switches to a 7d shell fabric that weighs .49oz/yd2.

Fill type – 1000fp goose down

Approximate fill weight – 1.55oz (small)

Approximate total weight – 3.6oz (small)

Approximate total weight with cords removed – 3.4oz (small)

The goal with the SDUL down sweater .75 was to make the lightest jacket possible while achieving functional warmth. The chambers are 4″ wide and the calculated loft is .75″. It is surprisingly warm for such a light garment. Alone, I estimate this to go down to freezing while inactive, but it’s probably getting uncomfortable for most people in the 30s (Fahrenheit). It has a cinch at the neck and a cinch at the bottom hem to keep out drafts. Both cinches are removable. One should plan on adding room for loft in the fit. When in doubt, oversize. A snug and fitted puffy is cold. A loose fitting puffy is warmer and usually ends up covering more of your body.

It’s a great garment to pair with the Alpha Direct Hoodie and Wind shell. Those two cover a huge range of active scenarios. Add the SDUL .75 to the mix and you extend the static insulation capabilities quite low. The Alpha inner layer, SDUL .75 mid layer, wind shell outer layer combo can provide solid 4 season warmth.

A puffy is most often used as an inactive layer for stops, at camp, or to help boost a sleep system. They don’t make for very good active layers since your sweat can easily compromise the down fill. This makes a zipper for ventilation a somewhat frivolous feature that can add a significant amount of weight and bulk. Pockets can be nice to have, but they often add a big chunk of weight and bulk and compromise the performance of a jacket by creating cold spots and by pulling insulation flat when there is weight in them. For those wanting pockets to warm hands I recommend adding a few inches to the sleeve to cover your hands. This is lighter than pockets and doesn’t compromise the overall warmth. All non-essential sewn through lines have been eliminated so the down can loft and cold spots are reduced. Simplicity and reduced weight and bulk are not the only benefits of all this. Leaving off many tedious features also reduces my labor and allows me to offer a very affordable jacket at an extremely low weight.

It’s meant to be used with a modular hood or head insulation, but can be built with an integrated hood.

More warmth out of less fill Sewn Through Baffle Construction and Its Effect on Warmth – Timmermade