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Buying Guides : Sleeping Bags |
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It is trapped air that provides insulation and the first consideration is to choose between down or synthetic fill.
Down:
This is the most efficient insulation, the lightest weight and packs into a smaller size than a synthetic fill.
When one bag is required to cover a broad range of temperatures (e.g. trekking to different altitudes) down is best. Furthermore, a well-treated bag can last for many years without much drop in performance and certainly justifies the extra price in comparison to the synthetic bag.
The downside (excuse the pun!) – not a great performer when wet! In effect the down in each baffle will clump and a lump of down in the corner of a Pertex bag doesn’t do a lot for insulation – so don’t let it get wet. Whilst a wet synthetic bag isn’t very pleasant either because the fill is in sheet form, as opposed to being loose, it retains an even warmth over the whole area of the bag.
Down generally comes from ducks or geese, with the latter providing a “higher fill power” (see below). Down from the Eider Duck provides the higher quality but since this has to be collected by hand from used nests, it is prohibitively expensive.
In order to measure the loft, a “fill-power” rating has been devised. 30gms of down are put in a cylinder; a lid placed on top and the scale along the cylinder side enables a fill-power rating to be read off. (The more air that is trapped, the higher the lid and the higher the rating). Unfortunately the USA method does not equate to the European standard – the latter uses The Lorch Fill Power Meter – and so beware there is a disparency of approximately 5% between the two.
Although the weight of fill is one method of ascertaining the quality of the bag, it’s also important to note the ratio of the down/feather mix. (E.g. 85/15 means 85% down, 15% small feather, and without hand-picking the highest achievable would be 96/4). The higher the %age down, the better the performance.
Synthetic:
These fibres or filaments are generally hollow and the large surface areas trap air. Quality varies between very simple matting of tubed filaments to more complex structures within the fibres – the latter resulting in higher efficiency, more compressibility and prolongs the life of the bag.
Comparative quality rating is more difficult to assess than for down bags. A lightweight fibre with high loft, a good recovery, weighs little and will fit in a pocket is what everybody is seeking – at £25 we would sell a bundle! However it’s not possible and quality is usually reflected in the price.
Shell and Shape:
No, this is not an exercise routine, it’s an attempt to highlight the importance of materials and the consequences of different shapes and bags.
Shell materials or general use, lightweight nylons, taffeta nylons and Pertex are common throughout the brands. They are lightweight, repel moisture from the outside and allow perspiration to be transported through them from inside to out. Bags for summer use only may have a cotton or poly cotton lining, but when conditions are more demanding viscose nylons that have the textured feel of cotton will be more appreciated as we all now understand the shortcomings of cotton as a performance fabric!
In sub-zero conditions a water repellent outer fabric that prevents frost melting into the insulation is essential, but this comes at the expense of convenience as fabric with an additional coating is then heavier and harder to stuff into it’s stuffsack.
Since bags don’t have taped seams, the only way to provide waterproofness is to use an overbag or bivi bag. Both have taped seams, but differ in features and weight.
The use of a sleeping bag liner will save washing the entire bag and are available in technical (fleece, silk, coolmax) or non-technical (cotton, flannel) fibres. Choose the fabric appropriate to your needs.
Shape – Ensure you have enough length and shoulder width for a comfortable night. Don’t squeeze yourself into a tiny bag to save pack size or weight. Thus no need to select the restricting shape of a mummy bag if you are in a hot climate or under cover in a bunkhouse, hostel or whatever.
A two-way zip allows for ventilation when necessary and connection with another to create a double bag – if lucky! Only consider zip less or restricted zips if weight is absolutely paramount.
Storage and Care:
Always store you sleeping bag outside of its stuff or compression bag when not in use. This is vital if you want to get the most out of your bag. It will loft more and last for longer. The more expensive the sleeping bag you have the more we would recommend you have it professionally cleaned. Good bags have a label inside of where to send your bag for cleaning, alternatively contact us and we’ll tell you the best places or look in the back of Outdoor magazines for advertising.
Camping Mat:
A good mat will always help with the insulation from the cold ground air. Ignore a good sleeping mat at your peril as you will never achieve the claim of the sleeping bag rating without one. Again like most things in life the more you spend the greater the insulation and therefore comfort you will achieve.
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