Friday, 19 November 2010

A Guide to Choosing a Sleeping Bag

Here is a guide to buying sleeping bags. 
The main questions to ask; first, what is the lowest temperature that you are likely to experience? Secondly, will you be carrying the bag and in what type of environment will it be used?

Comfort Temperature Ratings
EN 13537 provides a standard and uniform method of measuring the performance of a sleeping bag within the European Union, and allows consumers to compare different sleeping bags from different brands accurately. The testing within EN 13537 also provides a comfort temperature range shown as the T (comfort) and T (limit), to suggest a range of use depending on the individual user.
The T (comfort) is related to a woman and the T (limit) is related to a man. The T (extreme) is to be considered only in very extreme situations. The ratings from the EN13537 test compare the performance of sleeping bags under very controlled standard test conditions, they do not take into account the many various conditions encountered in use such as wind, posture, clothing, ground insulation, humidity or the individual's physical or psychological state (hunger, fatigue etc.). Therefore these temperature ratings should be used as a guideline and adapted to each individual's situation. To avoid confusion and to assist in helping make the right decision Deuter sleeping bags also carry a Comfort Zone recommendation based on experience but as with EN13537, individual circumstances should be considered and advise from the retailer taken.
TIP: As a general rule, if you think you feel the cold more than the average person then go for a bag which has a comfort rating 5ºC colder than the conditions will be. For example, if you expect –10ºC then buy a –15ºC bag.

 Insulation Materials: Down versus Synthetic
Natural down clusters and synthetic wadding are the two main types of air-trapping insulation material used to make sleeping bags.

Down Pros
  • Warmth to weight ratio is far greater than any synthetic.
  • Small pack size.
  • Greater breathability.
  • Will cover wider range of temperatures.
  • Will last years longer if looked after.
 Down Cons
  • More expensive.
  • Useless when wet.
  • Difficult to wash and dry.
  • Shouldn't be stored compressed.
 Synthetic Pros
  • Relatively inexpensive.
  • Dries and cleans easily.
  • Retains up to 70% performance when wet.
  • Can be stored compressed (not for long periods.)
Synthetic Cons
  • Heavier weight.
  • Covers less range of temperature.
  • Shorter life span than down.
  • Larger pack size
Down is the most efficient and long lasting, the sleeping bags are smaller and lighter and feel much softer, however they do lose their insulating qualities when wet, are difficult to clean and more expensive. Down sleeping bags do offer the best warmth to weight ratio, if you need a very warm bag (-15ºC or lower?) then buy down. Fill power and construction also needs to be considered when buying a down bag. Fill weight tells you how much down is in the bag, however the better the down in terms of fill power the less you need to keep warm. Fill power gives a gauge of how efficient the down is at trapping air – e.g. a 30g sample of down with a fill power of 600+ will occupy a minimum of 600 cubic inches. Therefore, the higher the fill power, the better the performance of the bag.
Note: Fill power is calculated in two different ways depending on origin, either by the American or European method. This results in slightly different figures (500 European = approx 550 American). When you see a bags down/feather ratio it means the following: - 90/10 would mean 90% down and 10% feather. You may ask 'why isn't it 100% down', the answer is that the down requires a certain amount of feather so it has something to cling to – like leaves on a branch. Any less than 3% feathers and the down will have no purchase and will just clump together and not loft. Any more than 10-12% feather and there will not be enough down and the performance will be adversely affected. Construction methods affect the down distribution and therefore insulation, methods such as trapezoidal chamber construction offer good down distribution and resistance to shift, but are more expensive. Stitch through and box wall construction is cheaper but can allow cold spots.
 Synthetic Sleeping Bags
Synthetic sleeping bags are less expensive. Synthetic insulation performs better than down when wet but they are bulkier and heavier. Buy synthetic if the bag will be used regularly in damp conditions, be washed fairly frequently or the conditions just don't demand the higher performance of down. The same rules for construction apply to synthetic bags, if stitched through cold spots can form, look for bags with a shingle construction.
Other features to consider:
Hood: test the hood, pull it tight and see whether it feels comfortable and snug.
Shoulder baffle: A shoulder or neck baffle helps to trap warm air inside the bag; these are usually not necessary on summer bags and are more common on bags where a higher performance is required.
Side Zips: Two way zips running the whole length enable you to let your feet cool down and allows you to vent your feet outside the bag in hot weather, check the zip has a guard to ensure it does not snag.
Materials: Nylon or Polyester micro fibre is the standard fabric for both lining and shell as it is breathable, quick drying and durable. Poly cotton or cotton is often used for lining in budget bags but is slow drying and adds weight and bulk.
Proper Storage - When storing your bag it's best to put it in a storage bag or a pillow case as loosely as possible to help the bag maintain its loft. Never use a plastic bag for storage as this will prevent the elimination of any moisture and promote the growth of mildew.
Washing - When it finally comes to the point that you need to wash your sleeping bag, follow these steps:
1. Follow the manufacturer's care label instructions. They know how their product should be cleaned and dried. If any of the points below contradict the label, follow the label instructions.
2. Zip up all zippers (open teeth can snag the shell or lining) and fasteners, then turn the bag inside out so that body oils accumulated on the inside will wash out easily.
3. Always use a front-loading washer, the agitator in a top-loading washer will tear baffles apart or rip the bag itself.
4. For a down-filled bag, use cold water with a gentle detergent like Nikwax Down Wash. For a synthetic fill bag, use cold or warm water with a mild detergent. Whether down or synthetic, wash on the gentle cycle, use as little detergent as possible and no bleach or fabric softener.
5. Run at least one full cycle with no detergent to completely rinse the bag; two if you still detect soap.
6. To remove the bag from the washing machine, gently lift and support the bag from below to prevent water-soaked insulation weight from tearing baffles or ripping stitches.
7. If possible, place in large commercial dryer (home dryers are generally too small to allow sufficient fluffing) on a low heat. Intermittently stop the dryer and be sure that the fill is not clumping to be sure of even drying. Using a tennis ball in the dryer will help fluff the fill.
8. Finally, never dry clean your sleeping bag. The petroleum-based dry cleaning chemicals will damage the bag. With proper care, a quality sleeping bag can last up to 20 years and provide you with many nights of clean, warm, comfortable sleep

No comments: