Sierra Designs Cloud 800 | Tested and reviewed

A sleeping bag with no zip or drawstring? James Forrest tests out this wacky bag from Sierra Designs

Sierra Designs Sleeping Bag on a lake district gate

by James Forrest |
Updated on

This sleeping bag is a maverick. It does things differently, adopting an innovative design that’s exceptionally comfortable. There’s no zip, but the bag still opens wide thanks to a curved, wraparound ‘comforter’ – a duvet-like flap that pulls over your upper body. The Sierra Designs Cloud 800 delivers a sensation far more akin to your beloved bed at home than any other sleeping bag.

A big overlap between the comforter and the bag’s edge prevents draughts, while the zipperless design makes getting in and out easy. Such a design will probably polarise opinion, though. Some campers will love the sleeping sensation you get with the Sierra Designs Cloud 800; others may find it way too loose compared to an alpine-style, mummy-shaped sleeping bag. Which camp (pun intended) will you be in?


  • Innovative quilt-like and zipperless design
  • Impressive temperature ratings
  • Many venting options


  • Design won’t suit everyone
  • Risk of cold spots
  • No hood drawcord

Temperature ratings

The Sierra Designs Cloud 800 20° has the following EN/ISO lab test temperature ratings: comfort -3C, comfort limit -10C and extreme -25C. These are impressive stats, considering the low 880g weight of the bag. The £300 price-tag is expensive, but far from extortionate, and represents fair value for money.

While we probably wouldn’t push the limits of this sleeping bag to -3C, for temperatures hovering around the 0C mark it should be warm enough.

If you are looking for better value and don’t need a bag quite as warm as the Sierra Designs Cloud 800 20°, the brand’s Night Cap 20° is a viable alternative. It is effectively the synthetic version of the Cloud 800 20° down bag. It’s £140 cheaper but 490g heavier, and has EN/ISO temperature ratings of -1C comfort and -5C comfort limit.

Insulation, fill power, and fill weight

closeup of the baffles on the sierra designs

The Cloud 800 20° is filled with 800 fill power goose down, housed in chunky box-wall baffles. An 800 fill power rating is a high quality of down (many other bags use a lower grade) and therefore the insulation of the Cloud 800 fluffs up beautifully into a thick, plush ‘loft’ – a little like a cloud. The warmth-to-weight ratio is excellent.

The fill weight of the down is 419g, which is rather mid-range – some other bags have a much higher fill weight. However, due to the high quality of the 800 fill power down, the low fill weight doesn’t affect all-round warmth.

It’s important to also note that this sleeping bag has no down whatsoever on the underside. Instead all of the down is concentrated over the top and sides of the body, which helps to maximise warmth and cut down on the weight. The logic is that any down on the underside, below your body, will get squashed, lose its loft and ultimately be ineffective as insulation. Sierra Designs has, therefore, done away with any down on the underside, replacing it instead with a sleeve to accommodate your sleeping bag. This means that you will need a well-insulated mat with a decent R-Value to guarantee you stay warm.

Sierra Designs Sleeping Bag on a lake district wall

Many sleeping bag manufacturers use ‘zoned’ insulation techniques, with 60-70% of the down placed on the top and 30-40% on the underside, but to go for 100% and 0% is quite an extreme approach. Consequently the style of the Cloud 800 20° is likely to polarise opinion. Some campers may dislike having no insulation below their bodies, or dislike the sensation of sleeping directly on a sleeping mat. But many others may find the Cloud 800’s design enhances all-round comfort.

All of the down used by Sierra Designs adheres to the Responsible Down Standard, meaning it meets important ethical criteria. The type of down – known as DriDown – has also been treated with a molecular level polymer, creating a hydrophobic finish on the individual down plumes. According to Sierra Designs, this means the down stays dry 10 times longer, lofts better and dries 33% faster than untreated down.

Pack size and weight

Packed down: the sierra designs cloud 20

The Cloud 800 20° clocks in at a weight of 880g in the regular-sized version. This is impressively lightweight for a -3C comfort rating, making this sleeping bag a weight-saving choice for long-distance trekking and wild camping adventures. The only drawback is that – due to the total absence of insulation on the underside of the bag – it will have to be paired with a warm sleeping mat. Mats with a higher R-Value are heavier than ultralight mats, and therefore some of your weight savings will be lost.

The long version of the Cloud 800 20° weighs 940g. The regular sized Cloud 800 20° compresses down to a size of 38cm x 19cm, when packed inside the included stuff sack. This is small and packable, and works well.

For storage at home, a much bigger mesh storage sack (51x31cm) is provided. Using this sack ensures you won’t ruin the insulation’s loft by storing the sleeping bag in a compressed state.

Materials and sustainability

Both the shell and liner of this sleeping bag are made from a 15-denier ripstop nylon. The materials are thin, light and comfy, although they do feel a tad flimsy, so should be treated with care.

Eco credentials are not this sleeping bag’s strong point. None of the materials are recycled.

Size and shape

Sierra Designs Sleeping Bag on a lake district gate

This sleeping bag has a gently-tapered mummy shape. But in-use it does not have that classic tight, restrictive, cocoon-like feel of some mummy-style sleeping bag. Instead it has a rather relaxed mummy cut, with what Sierra Designs calls an “oversized” roomy interior. Some campers will enjoy the extra roominess; others may desire a tighter, cosier fit with less risk of ‘dead space’ cold spots.

The regular Cloud 800 20° is suitable for anyone up to 183cm (6ft) tall. The length is 198cm, the shoulder girth is 152cm, the hip girth is 147cm and the footbox girth is 102cm. The long version is suitable for people up to 198cm (6ft 6”) tall, and the shoulder, hip and knee girths are 157cm, 152cm and 107cm respectively. The length is 213cm.


closeup of the Sierra Designs hood

Innovative features are what really set this sleeping bag apart from its competitors. There are quite a few unique design touches, so let’s run through them.

Firstly there’s no zip on this sleeping bag. Instead the bag opens wide thanks to a curved, wraparound ‘comforter’ – a duvet-like flap that pulls over your upper body. This half-length, quilted flap delivers a sensation far more akin to your beloved bed at home than any other sleeping bag.

A big overlap between the comforter and the bag’s edge helps prevent draughts, and a 3D-sculpted shoulder pocket helps keep the comforter wrapped around you and seal out draughts. The zipperless design makes getting in and out easy. For many this design delivers unrivalled comfort levels and, during our tests, we were thoroughly impressed. The drawback is that such a design might prove draughty for some, with a risk of cold air getting in.

Sierra Designs Cloud 800 hanging over a gate

Another big feature of the Cloud 800 20° is the integrated sleeping mat system. On the underside of the sleeping bag there’s a sleeve into which you can slide your sleeping pad. This ensures excellent bag-to-mat integration, holding the mat neatly in place below your sleeping bag. One potential drawback, however, may present itself to sleepers who tend to roll over or twist around at night. You may end up with the non-insulated base of the sleeping bag on top or over your sides, rather than below your body, thus significantly reducing your warmth.

Ventilation is a strong suit of the 800 20° too. On warmer nights, you can fling open the comforter for an airier, cooler sensation. If so inclined, you can also stick your feet out of the footwell vent.

You also get a well-shaped hood, although it can’t be tightened or adjusted due to the absence of a drawcord.

How we tested

James forest eating in glen coe scotland

The tester for this bag was James Forrest. A prolific name in UK hillwalking, James reviews every type of outdoor kit for LFTO and is a real authority on everything you need for wild camping and packing light for a multi-day walk. He tested this bag for a few camping trips in his natural habitat of the Lake District.


A versatile, warm and extremely comfy sleeping bag with an innovative design – but the quilt-like approach won’t suit everyone.

Don't forget to subscribe to the Live For The Outdoors newsletter to get expert advice and outdoor inspiration delivered to your inbox!

Just so you know, whilst we may receive a commission or other compensation from the links on this website, we never allow this to influence product selections - read why you should trust us