Sierra Designs Cloud 800 20 review: cleverly designed zipless sleeping bag

The Sierra Designs 800 20 is all designed to make nights in the great outdoors more comfortable – no zips required!

Sierra Designs Cloud 800 20 review
(Image credit: Matthew Jones)
T3 Verdict

An unusual and innovative sleeping bag with a unique design, high-quality down fill and excellent ventilation options, the Sierra Designs Cloud 800 20 is likely to polarise opinions.

Reasons to buy
  • +

    Plenty of room for wriggling around in the bag

  • +

    Excellent weight-to-warmth ratio

  • +

    Zipless design prevents zip-related issues

  • +

    Clever foot vent helps dump heat

Reasons to avoid
  • -

    May not suit side sleepers

  • -

    Requires a good sleeping mat

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The Sierra Designs Cloud 800 20F is a three-season 800-fill power-down sleeping bag that is warm enough to deal with temperatures below freezing, with a comfort rating of -3°C (or -6°C for the women’s version). It has an excellent warmth-to-weight ratio that ensures this bag is competitive in both weight and packability for a bag of this class, making it one of the best lightweight sleeping bags out there.

However, the Cloud’s real USP is its unusual zipperless design – which will appeal to anyone who’s ever struggled with a jammed sleeping bag zipper or woken up hot and sweaty in a tent with their bag wrapped around them. It also offers plenty of other features that ensure this bag stands out from the pack, including an integrated sleeve for your sleeping mat or pad, a self-sealing vent, and a quilt-like flap or ‘comforter’ designed to feel just like you’re sleeping under your duvet at home.

Sierra Designs Cloud 800 20 review

Sierra Designs Cloud 800 20 review: price and release date

The Sierra Designs Cloud 800 20 is available to buy right now directly from Sierra Designs with prices from $340/ £300 (approx. AU$ 539) for the regular length version. It is available in both standard and long lengths in men's and women's versions.

Sierra Design has other zipless sleeping bags, some cheaper than the Cloud 800 20. These include the Night Cap 20, a more affordable, responsibly-made version of the Cloud that still packs down to a backpack-friendly size. It's sold for just $200 for the standard version.

Sierra Designs Cloud 800 20 review: specifications

Sierra Designs Cloud 800 20 review

(Image credit: Matthew Jones)
  • Pack size (mm): 380 x 190 
  • Sizes: Men's Reg (183cm)/ Long (198cm), Women's (173cm)
  • Weight: Men's Reg 880g/ Long 940g, Women's 1,030g
  • Fill: 800FP RDS-certified DriDown
  • Fill weight: Men's Reg 419g/ Long 465g, Women's 580g
  • Temp rating: Men's -3°c comfort/ -10°c lower (Women,s -6°c comfort/ -13°c lower) 

Sierra Designs Cloud 800 20 review: design and build quality

Sierra Designs Cloud 800 20 review

(Image credit: Matthew Jones)

Sierra Designs has taken a different approach from most other sleeping bag manufacturers when it comes to their down-filled Cloud series. Rather than adopting the nearly ubiquitous zippered mummy-style cut, these have an unconventional zipperless design. Instead of a full or half-length zip, there’s a half-length quilted flap (or comforter, in American parlance), which has a 3D-sculpted shoulder pocket to help keep it wrapped around you. It makes for an extremely comfortable bag. The rest of the bag is similarly focused on comfort, with a roomy and oversized fit. 

There’s also a clever foot vent to help dump heat if it gets too toasty. This has a stitched flap over the opening to ensure it self-seals, but it is easy to kick your feet out through the hole if you start to overheat. This adds versatility for camping in milder conditions, as does the comforter, which is easy to throw aside – certainly far more practical than trying to unzip most sleeping bags, which inevitably snag at the most inconvenient moment.

When it comes to specs, the bag is filled with 419g of 800-fill power moisture-resistant DriDown. The downfill is zoned, by which we mean it is strategically placed on the top and sides of the bag. Conversely, the underside of the bag has no fill at all. The brand’s rationale is that placing down fill here is of limited value since it is compressed by the user’s own body weight, negating its loft and, therefore, its insulating power.

So, instead, there’s a rear sleeve to accommodate your sleeping mat. This makes it impractical to twist the bag around, so it may not suit side sleepers – though the roomy fit makes it relatively easy to move around inside the bag itself. It does, however, mean that you really need a well-insulated sleeping mat underneath you to guarantee you stay warm. 

Still, it’s a clever weight-saver – despite its luxurious construction and accommodating dimensions, this bag weighs in at under a kilo. The pack size is competitive, too, and all in all, it’s a good value package.

Sierra Designs Cloud 800 20 review: comfort and performance

Sierra Designs Cloud 800 20 review

(Image credit: Matthew Jones)

We paired this bag with one of Sierra Designs’ Granby Insulated Air Mats, which has an R-value of 2.1. This ensured that the bag was plenty warm enough for late spring, summer and early autumn camps. The high-quality 800FP moisture-resistant down lofts well, being housed in chunky box-wall baffles. The quilted flap can also be pulled right up to the chin, ensuring we experience minimal heat loss. 

In colder conditions, when overnight temperatures started to approach freezing, we did start to get cold – but here, the mat was the culprit, not the bag. Upgrading to a warmer mat (in our case, a NEMO Tensor Insulated pad, with an R-value of 4.2) hugely extended the viable temperature range of the Cloud 800 20F. 

This experience simply reiterates the point that it is essential to pair this bag with a decently warm mat. That’s true of most sleeping bags, of course, but the fact that this particular model has zero down filling on the underside makes it absolutely critical. It’s also worth checking that if you already own a sleeping mat, it will fit inside the Cloud’s integrated sleeve.

This will accommodate any mat up to 20 inches wide and 2.5 inches thick (or 51 x 6.4 cm in metric dimensions). You can also get away with using a narrower but thicker mat, provided its overall circumference doesn’t exceed 45.5 inches (approx. 115 cm). The optimum mat would be approx. 50 cm wide, though, as this effectively prevents the mat from sliding around inside the sleeve.

Sierra Designs Cloud 800 20 review: verdict

Sierra Designs Cloud 800 20 review

(Image credit: Matthew Jones)

The Sierra Designs Cloud 800 20 adopts an undeniably innovative design approach. The use of zoned down fill, and the lack of a zipper are both good weight savers, which means that the Cloud can utilise a roomier, more comfort-focused fit without adding excess weight or bulk to the overall package.

We also like the added ventilation options, which add versatility for use across a range of different seasons and temperatures. Some will find it an absolute dream to sleep in. Others might not get on with its unusual design so well, though, and we reckon it’ll prove to be a bit of a Marmite product – you’ll either love it or hate it.

Having said that, the Cloud 800 is well worth a try if you find conventional zippered mummy bags restrictive but don’t want to carry the added weight that usually comes with more generously proportioned sleeping bags. On the other hand, you could save even more weight and bulk by opting for a backpacking quilt – like Sierra’s own Nitro 800 20.

Sierra Designs Cloud 800 20 review: also consider

There are any number of other 800FP down three-season sleeping bags on the market, including various models from highly regarded brands like Rab, Mountain Equipment, Therm-a-rest and Sea to Summit, as featured in T3's best sleeping bag guide. Most, however, are either zippered mummy bags or, in a few cases, zipperless backpacking quilts.

There’s nothing else on the market that uses the ‘zipperless bag’ approach of the Cloud 800 – though Big Agnes’ Sidewinder SL20 is another bag specifically designed with side sleepers in mind.

Similarly, NEMO Equipment’s spoon-shaped Forte, Disco and Riff sleeping bags are also intended to accommodate side sleepers, offering some extra room at the hips, knees and shoulders. All these are worth considering if you find traditional zippered, mummy-style bags restrictive or uncomfortable. 

Matthew Jones

An outdoors writer and editor, Matt Jones has been testing kit in the field for nearly a decade. Having worked for both the Ramblers and the Scouts, he knows one or two things about walking and camping, and loves all things adventure, particularly long-distance backpacking, wild camping and climbing mountains – especially in Wales. He’s based in Snowdonia and last year thru-hiked the Cambrian Way, which runs for 298 miles from Cardiff to Conwy, with a total ascent of 73,700ft (that’s nearly 2½ times the height of Everest). Follow Matt on Insta and Twitter at @mattymountains