Down
Facts and Performance Sleeping Bags
HOW TO GET THE MOST FROM YOUR BAG
How warm is a sleeping bag?
In the past climbers used to look at the fill weight of the bag
(the amount of down stuffed into the shell) in order to judge how
warm it would be. They were aware that down bags with less than
500g of down were summer weight and for winter use they would look
for a bag with 900 or more grams of down. The fill power would then
be taken into account, for example a 500g 700-fill bag would give
you a 'warm 500g'. This was in the days when the sleeping bag consumer
was well-educated in what they wanted.
Once the outdoors became mass market, manufacturers had to come
up with ways of demonstrating how warm their bags were to customers
who had only ever slept at room temperature. So, in an effort to
make purchases easier, temperature ratings came into vogue, however,
by simplifying the process they not only introduced manufacturer
interpretation but also steered customers from understanding the
mechanics of how a sleeping bag works.
Since it is the individual's metabolism that heats a sleeping bag,
it remains important for you to fully understand the functions of
fill weight, loft, internal girth, etc. No amount of simplification
will benefit the customer. Only by understanding how a bag works
will a customer make the correct choice. To this day fill weights
are still listed in manufacturers' charts because of how useful
they really are.
Judging a sleeping bag's temperature value by looking only at its
temperature rating is strongly discouraged. Temperature ratings
are nothing more than a rough guide and should only be used as a
starting point. Also, one company's temperature rating has no bearing
or relationship to another company's rating system and some company's
stated rating is literally dangerous.
To give you an idea of usage here's a rough idea of season, temperature
and usage for a well-fed sleeper wearing a thin thermal layer and
sleeping on a well-insulating mat.
200-300g (1+ season/ +5/0°C). High quality down and construction
will allow this weight of bag to be used in mild spring and autumn
conditions if used within a tent by a fit, well-fed and dressed
sleeper. A common marathon weight bag.
350-550g (2+ season/ 0/-5°C). Performing a similar role as
the bag above but with a little more range for not too much more
weight. A good summer weight bag for a cold sleeper. With a well-dressed
and high metabolism sleeper this weight bag can be used into the
winter although don't expect to be fully comfortable. A good summer
Alpine weight bag or three season ultra lightweight backpacking
bag.
600-800g (3+ season -5/-15°C). A good all round sleeping bag,
suitable for four season use within a tent. A fully dressed climber
can use this bag in the open in high mountain conditions comfortably
and this weight of bag is used by most expedition climbers.
900-1,200g (4+ season -15°C to very cold indeed). Expedition
weight and suitable for four season mountain use and a popular weight
for sleepers who don't want to wear clothes in their bag or want
total warmth whatever the weather (1,000g of standard quality fill).
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Facts and Performance Sleeping Bags
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