Gear Review: Zpacks 10F Full Zip Sleeping Bag

As an outdoor writer and photographer, I spend a lot of time on the trail. Long days with a fully-laden pack is part of my job so I am constantly looking for products which help me lighten the load, without a reduction in performance. A sleeping bag is one of the heaviest items that a backpacker carries and the differences in weights between products can be large. The very lightest sleeping bags are light because they incorporate the lightest products available and these are pared down to the bare minimum. Very light bags normally use goose down as the fill because it offers the most favourable warmth to weight ratio: obviously, the more fill you include, the heavier the bag. However, the outer materials of sleeping bags vary greatly from manufacturer to manufacturer. To keep weight down they tend to be very thin. And very thin material is often not very durable so that is something that I pay close attention to. The holy grail of sleeping bags is therefore one that is very warm, very light and very durable. And I have to say that Zpacks’ Full Zip Sleeping Bag is as close to perfection as I have seen.

Wild camping in the Mourne Mountains in Northern Ireland

"I would honestly say that this is the gold standard for sleeping bags"

However, before we get into that in detail, let’s go over a few basic facts about sleeping bags. Each bag has a ‘comfort rating’: this is the lowest temperature at which the standard woman should enjoy a comfortable night’s sleep. There is also a ‘lower comfort limit’ which is for men. That may sound simple but it is not. Although all reputable sleeping bag manufacturers use the same independent standard, the bags are not tested in the same place so there is a lack of consistency amongst ratings. Also, the ratings are designed with an average man and woman in mind but every person is different: some people get colder than others. The ratings should therefore be used as a guide only and it is wise to choose a bag with a comfort rating which is a few degrees lower than the night temperatures that you will encounter.
I have used a lot of sleeping bags over the years but have rarely found that the very lightest bags perform well at the lower end of their intended temperature range. Now it is fair to say that, as I am skinny, I tend to ‘sleep cold’ and am therefore pushing my sleep systems to the limit: I rarely find that I can get a comfortable night’s sleep if outside temperatures drop to the bottom of the sleeping bag’s comfort limit. Accordingly, I think that my body provides science with a sensible guinea pig to test bags in the real world.

Over here in Europe, I had been hearing great things about Zpacks’ sleeping bags. Zpacks is a US manufacturer and I was very impressed with their Arcblast 55 backpack last year so I was very keen to get my hands on one of their sleeping bags. I had a trip to Patagonia planned so it would provide the perfect opportunity for me to test a bag rated down to 10F/-12C. Accordingly, I chose Zpacks’ Full Zip 10F which has a good reputation in the US as an ultralight option for multi-day treks. I tested the long version (as I am 6’1”/183cm in height) with the standard width. It weighed 760g without the included dry-bag. Because the bag has no integrated hood, I also used one of Z-packs’ Goose Hoods.

First Impressions
As you unwrap the sleeping bag, it is the rip-stop outer which is immediately striking: it seems very thin and you can even see the down itself through the outer. The drawcord is thin and light, however, the zip seems larger and heavier than that on many other bags. Five minutes after unwrapping the bag, the loft was impressive. I was very confident that it was going to perform well from an insulation point of view but I had my doubts that the outer would survive all the abuse of a long unsupported backpacking trip.

Using Zpacks' excellent Goose Hood

Zpacks Full Zip Sleeping Bag zipped up

Zpacks Full Zip Sleeping Bag unzipped

Fitting
At 183cm tall, I was in the middle between the medium and the long size. I chose the long length and I did not regret this choice. Zpacks’ sizing seems very accurate. Although, it was slightly too long for me, it has no integrated hood so I was able to snuggle down and pull the material up around the side of my head. I hate having my feet wedged against the bottom of a smaller bag. Anybody slightly smaller than me might go for the medium.

Testing
Unfortunately, the Covid epidemic dragged on and so a week-long winter backpacking adventure in the Mourne Mountains in Northern Ireland had to do instead of the wilds of Patagonia. Fortunately, the weather ‘played ball’ and threw some challenging night time temperatures at me: the bag was tested all the way down to -8°C over a seven night period. I used two different sleeping pads over that period: a Thermarest Neo Xlite and a Thermarest Neo Xtherm. I chose these because in Europe they are probably the most commonly used pads for long-distance backpackers. The Xlite has an R-value (insulation rating) of 4.2 and the Xtherm is 6.9 so the Xtherm is a good bit warmer than the Xlite. I wore the same thin merino baselayers (long arms and legs) in the bag throughout the week.
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Comfort: Over 7 days in temperatures down to -8°C, I found that the bag performed extremely well. Using Zpacks goose hood for my head and the less-insulated Xlite pad, I was warm and comfortable throughout the night until about 5 a.m. when the temperature I recorded was at its lowest (-8°C): at that point I simply slipped another layer on my torso and I was warm again. To be fair, I would not normally use the Xlite pad in such low temperatures. 

​Using Zpacks goose hood and the more-insulated Xtherm pad, I was extremely warm and comfortable all night, even in the early hours of the morning. I have used plenty of sleeping bags that will keep me warm at such low temperatures but never one that is as light as Zpacks’ offering. At only 760g, the level of heat insulation is remarkable: apparently, it has 30% more 900 Fill Power Premium Goose Down than is necessary for maximum loft to account for any future down compression.

Frost and ice on the tent during testing!

Thermarest Neo Air Xlite

Thermrest Neo Air Xtherm

The outer is water-repellent and the down is water-resistant so I found that the bag did not lose heat even when the outer was damp with condensation. This is a very important consideration when cold weather camping because condensation is unavoidable. The draft tube along the zip was effective and I did not feel that much heat escaped from there. I found no ‘dead spots’ in the insulation either: it is obvious that this is a premium product.

I liked the draw cord which was thin but easily strong enough. It is clear that many manufacturers are over-specing drawcords. I also liked the clip at the top of the zip which stops unintentional unzipping.
I was concerned about the lack of an integrated hood but in fact, this has completely changed the way that I look at sleeping bags. The separate goose hood was a revelation for a front/side sleeper like me. You can twist and turn in the sleeping bag without the main body of the bag turning too. This ensures that you stay warm all night. It works so much better than an integrated hood if you do not sleep on your back.

My only slight niggle is the zip which seems overly robust and heavy compared to the zips used by some other manufacturers such as Thermarest. Could there be a potential weight-saving here?

The foot of the Zpacks 10F

The sleeping bag in its waterproof bag

​Durability: Backpacking in the wild puts a lot of pressure on gear. However, over 7 days I noticed no wear at all on the outer and I found it to be very robust. Of course, there will be bags that have tougher outers but not at this weight. Personally, I would rather carry a very light bag and try to take good care of it.

Conclusion
The Zpacks’ Full Zip Sleeping Bag 10F is now my ‘go-to’ bag for backpacking in temperatures below zero. It has easily the best ratio of warmth to weight that I have ever experienced and it is the lightest bag I have ever used that actually keeps me warm at -8°C. I expect that those who sleep warm would easily be able to use it down to 10F/-12°C.

Unlike many other bags, it has both water-resistant outer and down which is an important and much-overlooked characteristic. It also comes with a waterproof Dyneema bag which is extremely tough and light. The outer seems to be sufficiently robust if you take good care of it.

The full zip provides welcome flexibility: if you ever get too warm you can simply stick your feet out the bottom. Bags with ¾ length zips do not allow for that.

At $469, it is not cheap but if you like to travel ultralight then it is a price worth paying. Without hesitation, I would honestly say that this is the gold standard for sleeping bags. And it comes in four different colours: see images below.
​
If I had to find a fault, it would be the zip which seems to be a little over-speced. Could Zpacks not save even more weight by using a lighter zip such as the one on the Thermarest Hyperion? But honestly, that is the only fault I can find with this exceptional sleeping bag

Colour Option: Blue

Colour Option: Green

Colour Option: Orange

Colour Option: Black

​Andrew McCluggage is an outdoor writer and photographer. He is also the CEO of Knife Edge Outdoor Guidebooks. He has written a large number of books for walking and trekking including Tour du Mont Blanc, Trekking the Dolomites AV1, Trekking the Corsica GR20, Trekking the West Highland Way, Trekking the Hadrian’s Wall Path and The Haute Route: Chamonix to Zermatt. Follow Andrew on Facebook and Instagram: @knifeedgeoutdoor

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