UKH

Has anyone got recommendations for super-light sleeping bags for zero Celsius or below?

Mainly optimising for climbing + unplanned bivis...

A few I've found online, from more to less reasonable:

* Decathlon Makalu I, -5C, 560g, £200, ?g / down 800 (https://www.decathlon.co.uk/p/makalu-i-light-sleeping-bag-5-size-m/_/R-p-17...)
* ME Firefly, -3C, 550g, £500, 252g / down 900 (https://www.mountain-equipment.co.uk/products/firefly)
* Rab Mythic 400, -6C, 660g, £560, 400g / down 900 (https://rab.equipment/uk/mythic-400)
* Rab Mythic Ultra 180, 0C, 400g, £590, 180g / down 900 (https://rab.equipment/uk/mythic-ultra-180-sleeping-bag)
* Rab Mythic Ultra 360, -8C, 606g, £740, 360g / down 900 (https://rab.equipment/uk/mythic-ultra-360-sleeping-bag)

AlpKit don't seem to have anything competitive weight-wise.  The closest are:

* AlpKit Ultra 120, 1C, 590g, £210 (https://alpkit.com/products/ultra-120-ultralight-synthetic-sleeping-bag)
* AlpKit PipeDream 400, -6C, 865g, £240 (https://alpkit.com/products/pipedream-400)

The Decathlon Makalu seems like the clear winner, with the only reservations that the down doesn't seem to be treated, and it looks *tight*.  Very few reviews online though; has anyone had experience with it?

Also has something happened to the prices of down recently?  The firefly was £360 in 2019: https://www.ukclimbing.com/gear/camping/sleeping_bags/mountain_equipment_fi...

A real issue is whether those ratings are ones where you'd be toasty warm vs surviving. Are the fill weights comparable?

Maybe!  I'll add to the list... but perhaps there are subtle design issues too - Rab have some kind of tinfoil lining in their bags, ME & Simond don't have collars, and shapes are different.  And is the quality of the down is also important?  E.g. Down 9000 etc.

It's worth noting that you aren't comparing apples with apples for Alpkit, their "Sleep limit" is defined differently to the comfort value quoted for the other, they don't explain this on the page for the sleeping bag you linked, but they do on the Skyehigh page:

https://alpkit.com/products/skyehigh-500?variant=31617477967977

This does make Alpkit look even less favourable but it helps to understand what they are stating.

Worth having a look at Cumulus sleeping bags to add to the mix. They make a good range of high quality, well priced options. 

They also make a pied d'elephant style bag which might be worth considering for unplanned use, the weight saving if you are carrying a down jacket might be worthwhile. They also seem to be receptive to custom options. 

You seem to have noted the fill weight for the Simond while looking at the total weight for all other sleeping bags. So the Makalu is actually the heaviest of these bags at 1070g total weight.

The Simond bag is excellent value for money and very good quality, I've got the old version. As someone else has mentioned it's actually 1160g, it's also warmer than the others and will actually keep you warm rather than just alive. I've used mine all over UK in winter. No idea of actual temperature but definitely below zero.

good fill weights on the ultra range https://www.expeduk.com/products/ultra0

If you sleep hot and/or can wear a down jacket you may get away with this, I use this and it's a bit chilly for 0c

https://ultralightoutdoorgear.co.uk/spark-spi-down-sleeping-bag/

Comfort 5, 342g, £179.99.

Very very light and small packing size! Best bag I've ever had.

If you want more comfort for 0c then

https://ultralightoutdoorgear.co.uk/spark-spii-down-sleeping-bag/

Comfort -2, Weight 506g, £236.99

I'd second the Spark II. I really like it though not used it close to its limit

It's on sale, at the moment - bargain at that price!!

Nobody mentioned PHD yet?

https://www.phdesigns.co.uk/autumn-m-degree-300-down-sleeping-bag-23

I've been using the same old tired joke in UKC sleeping bag reviews for well over a decade now I'm sure, but: Cheap. Light. Warm. Pick two. Philosophers call this an inconsistent triad where only two out three are logically possible - God is omnipotent, God is omnibenevolent, evil exist. Which ever two are true logically excludes the third from being true.

Light and warm sleeping bags are filled with high quality down and the nylon holding the down in the various tubes has to be built in complex ways which require lots of sewing (box wall instead of sewn through designs) in order to allow the down to insulate properly. Basically it's going to be expensive. 

Obviously you are going to, at times, find things on sale, but otherwise if a bag is about the same weight, size (a sneaky way to save weight it just make bags narrower and shorter) - perfect for some, not good at all for others!) and warmth, they're going to cost about the same.

Almost everyone uses the EN/ISO rating system now which is great as it makes bags comparable in a way they used not to be - you just need to find out where you are on that scale (I'm normally OK down to the comfort limit with long underwear, socks and a hat on, across a number of different bags from different firms that I've tried).

Quality of down does make a difference, but if you are comparing two bags with the same weight of 900 fill power goose down in one, and 650 duck down in the other, the 900 one will be warmer for the weight and a lot more expensive.

There were some firms that didn't use cruelty free down in the past (or at least not independently certified as such), but even that seems to have become the norm now - perhaps if you buy some Chinese brand off Amazon or Aliexpress that might still be an issue but it is hard to know how much to trust any of the rating on bags like that. 

There's discussion of design, down and rating systems in many UKC reviews, here's a couple I wrote in recent years that go into them a bit and are of light down bags like you are considering. That might help you think about what you want and what you can afford.

https://www.ukclimbing.com/gear/camping/sleeping_bags/therm-a-rest_hyperion...

https://www.ukclimbing.com/gear/camping/sleeping_bags/lightwave_firelight_2...

Unless...   there is some bargain sale to be had
In which case sometimes you can stumble across something approaching all three at the same time. But those opportunities don't last long. get them while they last

https://ultralightoutdoorgear.co.uk/spark-spii-down-sleeping-bag/ 28
Comfort -2, Weight 506g, £236.99

Have you considered the French brand 'Valandre' ? Excellent reputation, solid build quality, lasts for years.

The 'Vieux Campeur' is the French outdoor shop, par excellence 🙂 I searched their website for you, for Valandre bags that can cope with sub zero temps.

Link : https://www.auvieuxcampeur.fr/catalogsearch/result/index/marques_filtre/182...

Good luck with your hunt !

Edit - I'd mispelled the name, doh !

Be careful buying into the UK from EU for goods worth £135 or more.

I bought by Amazon (yes shameful I know) something for £209.92 which originated in Italy because I thought Amazon price and shipping was all-in and it wouldn't get complicated. But today I've just had to pay £82.69 for customs/VAT/tax and handling fees to DHL to release the order. I'm not interested in any Brexit moans (I know all about that already), just as a warning that buying goods worth £135 or more from EU websites might not be as plain sailing like it was less than 2 years ago

Have a look atthe Jackson Sports website. It's an excellent retailer based in Northern Ireland but is closing down. There are still some great bargains to be had.

Also worth thinking about how much below zero. Bit of a difference between -1 and -20, for example. (The latter is perfectly possible in the UK.)

I used an Alpkit pipedream 600 for both my winter ML training and assessments, and it kept me very warm in a snowhole and in a bothy. Snow hole would have been between 0 and -1 probably, bothy probably a bit colder.

Agreed, I think I did mention that sometimes you get lucky and find things on sale. Not used that S2S bag but the one I did review years back was great.

No one's mentioned mats, or lack thereof yet, plus other factors. If unplanned bivis then insulation will be less than ideal, but if you're just sitting, then is it long enough, and will you be wearing a down or synth jacket as well? Does it have a more water resistant foot section? All these factors might affect your night's sleep more than the online specs.

Fwiw, I've mostly been a warm sleeper, maybe less so as I get older. I have several bags, but in your range, I have a PHD Minim 400 and a Alpkit Pipedream 600, both XLong. The Minim is barely enough at -5C and the Pipedream barely enough at -10C. Survival? Sure. Comfort? Hmmm...