The latest innovation from renowned UK down specialist PH Designs (PHD) is something the company is calling 'Sleep Systems'. It's a series of recommended mix and match combinations of lightweight down sleeping bags, supplementary bags and down clothing that's reckoned to be not only lighter than just carrying a single sleeping bag, but also more adaptable to conditions and easier and neater to pack and carry.
Of course combining sleeping bags and clothing is nothing new, mountaineers and lightweight backpackers have been doing it for years, but this is the first time a manufacturer has come out with a series of specifically recommended combinations for different scenarios and environments and done the hard statistical legwork for you by telling you exactly how much each set-up weighs.
Think of it as choosing from a menu of different ingredients to make your ideal dish and you won't go far wrong. These include PHD's selection of lightweight conventional sleeping bags, down jackets and trousers, down had-bags and filler bags which sit inside the main bag to add warmth or over-bags that layer over your existing sleeping bag.
Choose By Activity Or Destination
That's nothing new in itself, where it gets clever is the way that PHD's website guides you through the process. You can select either your main activity, Uk Winter Camp maybe, Alps In Summer or 8000m Peaks for example, or choose a destination, Denali perhaps or Kilimanjaro.
Once you've chosen, click on through and the website will show you two possible systems that should keep you comfortable. Say you're off to Kilimanjaro, System 1 matches PHD's Yukon down jacket and Minimus trousers with the Hispar 500 down sleeping bag for a combination that should see you good for -30˚C night-time temperatures, but will also, in clothing form cope with -15˚C during the day.
System 2 matches the warmer (-20˚C) Rondoy down jacket with the same sleeping bag and trousers for a slightly warmer result that might suit you if you want a warmer jacket during the day or simply sleep colder.
And because PHD are nothing if not thorough, they spec the wide version of the sleeping bag to allow enough space for the clothing to loft and insulate efficiently.
How Much Weight Can You Save?
As much as half the weight of your main sleeping bag says PHD giving two examples of actual combinations compared to the more conventional full sleeping bag approach. On Broad Peak in the Himalya for example, mixing a down suit and a Hispar over-bag gives a total weight of 820g - the suit is also worn during the day - compared to 1290g for the ultra-light Hispar 800 down sleeping bag or 1740g for a full-on Diamir 900.
That's quite a saving and it's possible because you're going to be carrying and using the down jacket and suit anyway. Another benefit is that the multiple, smaller and lighter packages are easier to pack away neatly compared to a single, big, fat sleeping bag.
And if you chose carefully, it could leave you with a lighter all-round sleeping bag with more general usability than a classic expedition bag as well as a really nice down jacket...
Build Your Own
What's nice is that you don't have to buy one of PHD's recommended combinations. You could just as easily use the detailed information on the Sleep Systems page to build your own set-up using your existing clothing, or by supplementing it with something new. A down jacket, after all, is a down jacket whether PHD makes it or not - though to be fair, the brand makes some of the best down clothing in the world in deepest, darkest Stalybridge, Manchester.
Scroll down to the bottom of the Sleep Systems page and there's a stash of invaluable technical information - you need, for example, to insulate your legs as well as your torso, so all the PHD systems incorporate insulated legwear and not just down jackets.
On top of that, if you use a standard sleeping bag, a wide version makes sense to allow clothing to loft properly. And if you expect a jacket to earn its keep, it'll need a hood to give full insulation levels.
There's lots more besides that's invaluable both for understanding PHD's own recommendations or helping you to ad lib and create your own personal system. And yes, we suspect that it may work out more expensive to buy several individual PHD items than a single sleeping bag, but who said sleeping systems were fair?
Full details of the PHD Sleep System concept at www.phdesigns.co.uk/what-is-sleep-systems
Main image by Jon Griffiths of Alpine Exposures courtesy of PD Designs.