Confessions: Xero Down Socks Review & Bootie Hack

During the 16/17 ski season I was researching down product design, mostly in order to design/create my own half bag and some other more "simple" products like down booties. Throughout my research on DIY forums I came across one company over and over which DIYers held at very high regard, PHD or Peter Hutchinson Designs. I contacted them about my half bag design and ended up purchasing several of their down products, including the Xero Down Socks.

After using the Xero Down Socks on a couple of overnight camping trips I knew they were warm, really warm but standing on snow wasn't, due to them being socks and not true booties. After trying a couple of different ideas I came up with a simple and cheap hack to get better preformance to my specific needs.

Simple Down Socks

Like much of the PHD product line many of the bells and whistles, which you find in most gear, are removed to save weight. My previous booties had lots of unnessaracy draw strings and heavy face fabric. With the Xero Down Socks you get really warm down socks at an extermely light weight. They have 100% wind-proof/water-resistant outer fabric, a tougher nylon underfoot fabric, elastic ankles and are filled with 900 European Goose down. They were more than half the weight of my previous pair of booties at 170g (mine came in at 180g) and compact down to about the size of 2 cans of Pepsi.

Sock Use Warmth/Durability

Used purely as a sock they are insanely warm, afterall they are described as a "High-altitude expedition sock" by PHD. At -40C in my Xero Half Bag I was probably too warm, you'd need some seriously cold weather to feel cold wearing these to bed. These would make the perfect accessory for any sleep system; tempuraure drops below your sleep bags limit? Throw these on and you're not going to have to worry about frostbite. As far as durability goes, in the context of sock use, I think they should last a life time. The underfoot fabric is more than tough enough to deal with walking on snow and the upper fabric is thick enough to easily deal with many nights of rubbing against the inside of a sleeping bag.

Sock To Bootie Hack

The thing I didn't like about the Xero Down Sock was the fact it was a sock. I know, that sounds stupid but I had purchased them to replace my heavier booties so I had to figure out a way to make them work as such. The main problem with a sock is that the underfoot down packs out while standing on the snow and the bottoms of your feet get cold, whereas a bootie will have some kind of dense foam pad under the foot. I fixed this problem by creating a footbed out of 1cm thick closed-cell foam. My first tests were done by inserting the footbed into the bootie like a shoe footbed, this worked well for warmth but it moved around while I walked creating cold spots. The next step was to cut open the sock, remove most of the underfoot down and insert and seal the footbed in place. This worked well with the process being faster and easier than I had expected.

Step 1) Turn the sock inside out.

Step 2) Place the sock against some foam and trace out the shape of the footbed.

Step 3) Cut the footbed and compare it to the inside-out sock bottom.

Step 4) Cut open the underfoot fabric inside the sock, I found a single cut from one side to the other worked well.

Step 5) Remove most of the down and place it in zip lock bags (I needed 5 in total). Save the down for a future project I hope to write about soon (I'll link it here when it's online).

Step 6) Insert the footbed by putting the longer side in first. The remaining side can be tricky, rolling or folding the foam worked but try not to force it in order to not damage the fabric too much.

Step 7) Cut a piece of tape as wide as the cut and tape the fabric from the inside. I used duct tape for the inside since I was running out of Tenacious Tape.

Step 8) Tape the outside fabric. I used Tenacious Tape for the outside as I have found it to be extermely durabile and I figured that this side would get more direct friction from walking.

Step 9) Turn the sock back right side out and try them out on snow!

Bootie Use Warmth/Durability

Once the foam was in place the socks were trasformed into true booties and worked great as such. My feet were warm while standing around camp for several hours at -20 to -25C and I have used them on test walks down to -40C directly on snow without issue. The bottom fabric has good grip on snow and doesn't seem to allow snow build up to be cleaned off for when I want to go to bed with them on. It will be a while before I find out how my foam/tape job holds up but I figure I can always replace the foam/tape in the future fairly easily regardless.

Better and Lighter

Usually when you alter a product to provide more function it ends up costing you something, in this case I thought it could be weight. To my surprise I ended up loosing a total of 20g, taking my total weight down to 160g. Of course the draw back might end up being long term durability issues due to having to cut the product open and using tape to patch it back. I have meantioned my alteration to PHD and I'm hoping they offer a similar product for those looking for a bootie over a sock but until that happens I'll take the possible durablility disadvantage to fulfil my needs. Obviously they now compress slightly less due to the foam but barely so. After it is all said and done they serve my individual needs better as a bootie.

Warm Happy Feet

Regardless if you are looking for a sock or bootie project the Xero Down Socks are likely the warmest you'll find at their weight. They take up almost no space, weigh very little and you will probably never have cold feet again. On all trips further than a few kms from a road I always take warm mitts and booties because without working hands and feet most of us are useless. At 170g the Xero Down Socks can gladly live in my pack while skiing, climbing and camping in the Canadian Rockies.

For more information about this PHD product please visit