5. Montbell Seamless Down Hugger

Our top pick if you’re looking for something that’s light enough for ultralight hiking and fastpacking

Price: From €359
Weight: 541g
Key attributes: Exceptionally lightweight, totally windproof
Temperature rating: comfort rating: 4C, comfort limit: -1C
Length: 170cm
Fill type: down

Designed for three-season use and weighing just 541g, this sleeping bag should really appeal to those who are after that perfect warmth-to-weight ratio where the right balance is struck between comfort in the day, thanks to a low weight to carry, and comfort during the night. We’ve used this extensively on numerous fastpacking trips and consider it a go-to option if you want something warm but lightweight.

With this model, there are no chambers and there’s no stitching (hence the seamless in the name), with the down instead prevented from moving around too much within the walls of the bag by a unique ‘Spider Baffle System’. This is essentially a web-like layer that traps down feathers, ensuring that the fill is never able to fully migrate from one area of the sleeping bag. It seems to work well.

On top of all that (quite literally), Montbell has used Gore’s Infinium fabric for the shell. This is basically the next gen version of their Windstopper fabric. It’s super lightweight, highly water resistant (but not waterproof), totally windproof and has a lovely bit of stretch to it. It’s top grade stuff that you only really see in the best of sleeping bags out there.

The bag has a fill power of no less than 900. That basically means super high loft and thermal efficiency. The comfort rating is 4℃ and the lower limit is -1℃ and, from our experience, this won’t be warm enough for every single night through early spring and late autumn – not in Britain anyway – but for the milder days in those seasons it’ll be fine. One final thing to bear in mind is that this sleeping bag isn’t great for tall people (length is 170cm) It was fine for our 5 foot 10 tester though.

Full Specifications

Face fabric: Gore-Tex Infinium Windstopper 13d Ballistic Airlight nylon ripstop / lining: 7d Ballistic Airlight nylon / insulation: 900 fill power down / comfort rating 4ºC / limit rating -1ºC / pack size: 28 x 14cm.

Read our full Montbell Seamless Down Hugger review.

Buy the Montbell Seamless Down Huger: £225 at Ultralightoutdoorgear.co.uk

6. Rab Alpine 800

Price: £330
Weight: 1260g
Key attributes: Good warmth-to-weight, lofty fill
Temperature rating: comfort limit: -16C
Length: 215 or 230cm
Fill type: down

During our tests with this sleeping bag we were impressed by the loftiness of its 650 fill power fill and the cosy warmth inside it. We used it on a frosty trip in the Cairngorms and it was a reliably comfortable cocoon.

Rab have used some quality materials and ingredients here, including European down that’s treated with Nikwax, a durable but lightweight Pertex Quantum outer shell fabric that’s made from 100% recycled materials and, finally, YKK zips.

The main two-way zip was handy for regulating the temperature inside the bag and the zipped pocket at the hood was useful for keeping a head torch or your phone close at hand. The only downside to this sleeping bag is its stuff sack which is a little on the basic side with no compression straps to let you really reduce the packed size.

Full Specifications

Available in different sizes and temperature ratings / sleep limit: -16C / Lengths: 85 inches or 90 inch / fill: 800g 650 fill power European duck down / Nikwax hydrophobic treatment / shell: 20D Pertex Quantum / liner: 20D recycled nylon.

Check out our full Rab Alpine Pro 600 review.

Buy the Rab Alpine 800: £330 at Rab.equipment

9. Gruezi Biopod DownWool Ice 185

Price: £369
Weight: 1400g
Key attributes: Innovative technology, effective in damp conditions
Temperature rating: comfort rating: 2C, comfort limit: -4C
Length: 176 to 190cm
Fill type: down and wool

Uniquely blending 70% duck down and 30% wool, the idea behind Gruezi’s fill is that it solves the moisture problem that fully down filled sleeping bags have (while also offering a natural alternative to the fully synthetic options out there).

Even condensation in a tent can drastically reduce the effectiveness of a down sleeping bag when it comes to insulation. The main solution to this in the past few years has been to add a hydrophobic treatment from the likes of Nikwax. This, however, doesn’t permanently solve the problem. It needs to be reapplied and reapplied. Gruezi’s idea is that by adding wool to the down, it not only brings extra warmth but it also helps to draw moisture away from it, like some kind of natural dehumidifier.

Contained within a nylon outer and inner lining with v-shaped baffles, the DownWool mix really does just feel like normal down. There’s certainly none of that itchiness we often associate with wool products and, at 1,400g, the warmth-to-weight ratio of the Biopod DownWool Ice 185 is decent too.

OK, it’s not the lightest sleeping bag out there but it’s still worth considering due to the unique cosiness, warmth and moisture resistance that the wool content provides.

Full Specifications

Face fabric: 100% polyamide / lining: 100% polyamide / insulation: 70% duck down and 30% wool / comfort rating -1ºC / limit rating -8ºC / extreme rating -26ºC / pack size: 23 x 25cm.

Read our full Gruezi Biopod Downwool Ice 185 review.

Buy the Gruezi Biopod Downwool Ice 185: £399 at Alpinetrek.co.uk

10. Nemo Disco Endless Promise 15F

Price: £320
Weight: 1257g
Key attributes: very lofty and snug, excellent eco credentials
Temperature rating: comfort: -3C, limit: -9C
Length: 183cm and 198cm
Fill type: down

This is a luxuriously lofty down sleeping bag that makes for a very comfortable night’s sleep in temperatures as low as -3C.  It also has some excellent eco credentials, because, like the Nemo Forte which is also in this list, it is designed for circularity, with repairability and recyclability all factored into the design thinking and recycled materials already used.

This is also a sleeping bag that’s specially designed for side sleepers, with extra room at the knees and at the elbows while narrowing at the feet and lower torso. This gives wiggle room where it’s needed while also ensuring that the overall weight is still light – 1.3kg to be precise.

You can also expect little zipped vents at the torso that can be opened up when you want to dump heat and they’re covered by a very thin layer of fabric that lets warm air escape will keeping out draughts. A two-way zip also gives a venting option down at the base of the sleeping bag.

Full Specifications

Fill Power: 650 / hydrophobic treated / 30D nylon ripstop fabric / traceable responsibly sourced down / Comfort: 27°F | -3°C / Limit: 16°F | -9°C.

Read our full Nemo Disco 15 review.

Buy the Nemo Disco 15: £320 at Ellis-brigham.co.uk

What Makes a Good Three-Season Sleeping Bag?

At the most basic level, the best three-season sleeping bag is one that will give you a good night’s sleep. But, when it comes to outdoor adventure, the reality is that you actually need a sleeping bag that has a bit more to it. If you’re a backpacker, for instance, you’re going to want a sleeping bag that is light and packable, so that it’ll make your life easier in the day as well as in the night. Then there are other considerations, including your budget and your environmental conscience. One of the main questions to start with is whether you want a down filled sleeping bag or a synthetic filled one.

Down Versus Synthetic

We wouldn’t really call the down versus synthetic thing an argument, as some people do. It’s more to do with personal preferences and scenarios.

For its weight, down is the warmest, lightest and most packable option. Its main disadvantage, however, is that if it gets wet, it loses its insulating properties. Synthetic sleeping bags are generally heavier and bulkier but they also tend to be cheaper and they will provide insulation even in wet conditions.

Generally speaking, down tends to be favoured by ultralight hikers and backpackers, while synthetic filled sleeping bags are favoured by those who aren’t too concerned by their pack weight or that want reliable warmth in wet conditions. Still, it’s fair to say that the performance gap between down and synthetic insulation is narrowing, so you can now find down sleeping bags that are treated to withstand wet weather and synthetic filled bags that have impressive warmth-to-weight ratios.

The Different Sleeping Bag Constructions

Sleeping bags come in two primary designs: Rectangular and Mummy, with the latter being by far the most popular design today.

Rectangular sleeping bags offer ample space for movement and versatility, often doubling as quilts or blankets when unzipped. They are more budget-friendly but tend to be heavier and bulkier and their designs usually make them less suitable for cold weather due to potential heat loss. Mummy sleeping bags, on the other hand, prioritise thermal efficiency and weight reduction. They have a snug fit that reduces dead air space, enhancing warmth retention, and they tend to pack down smaller, making them ideal for backpacking and colder conditions. Their downside is that some people, especially those who move about in their sleep, find them restrictive.

Baffle Design

Within sleeping bag designs, the baffle design has a big impact on the overall performance. Sewn-through baffles tend to be seen on lower cost sleeping bags as the design is less technical and, with these types of bags, thermal efficiency doesn’t tend to be great. Often you can find they allow for cold spots along seams due to heat loss, compromising warmth.

Box baffles, alternatively, prevent insulation from shifting, ensuring consistent warmth throughout the bag. This type of baffling is found on all of the leading sleeping bag designs.

Then there’s the orientation of the baffles with the choice between vertical and horizontal. Look online and you’ll find generally inconclusive arguments about the advantages and disadvantages of these different types when weighed against each other. Some say that vertical baffles limit the movement of insulation, ensuring that it stays evenly distributed throughout the bag while horizontal baffles allow the insulation to be shifted within the bag, offering more flexibility to adjust warmth according to personal preference. These days, just about all sleeping bags have horizontal baffles and that should perhaps say enough about which kind is best!

Sleeping Bag Temperature Ratings Explained

To compare the warmth of different bags, look at their temperature ratings. Many sleeping bag brands use a rating – normally by the European Norm (EN) standard or the ISO (International Organisation of Standardisation).

The EN standard is represented by three temperature ratings – comfort, limit, and extreme. The comfort rating is defined as the temperature at which a ‘standard female’ can sleep comfortably. The limit is the temperature at which a ‘standard male’ will be able to sleep without waking. Extreme is the temperature at which a ‘standard female’ can remain for six hours without risk of hypothermia. It’s not a perfect system, as we all differ in shape, size and how much we feel the cold.

The ISO standard focuses on a single rating, the lower limit, indicating the lowest temperature at which an average adult male can have a restful sleep.

A three-season sleeping bag typically has a temperature rating between 10°F to 32°F (-12°C to 0°C). This rating is designed to provide comfort and warmth during spring, summer, and fall, covering a range of moderate to slightly chilly conditions. The figure you need to consider most, we’d say, is the limit rating. Most of the bags featured here have a limit rating of around -5ºC.

Other Things to Consider

Many sleeping bags come in different lengths so it’s worth just checking that you’ve got the right size for you when you buy. Don’t be tempted to go for a longer bag than you need as you’ll have to work harder to warm up the empty space in the bag.

There’s also the ethical side of things. We all have different levels of conscientiousness here but, to put it simply, if you care about your eco footprint, look for high amount of recycled and recyclable content and, if you’re buying a down filled bag, look for RDS down. RDS, or Responsible Down Standard certification guarantees that the that’s down used comes from ducks or geese that have been treated humanely, without unnecessary harm, including force-feeding or live-plucking. The certification also verifies traceability throughout the supply chain, ensuring that the down in the product can be traced back to RDS-certified farms.

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