Down
Facts and Performance Sleeping Bags
INSULATION CARE
There is nothing as great as a bone dry down sleeping
bag. Unfortunately there is also nothing as grim as a wet one. Saturated
down loses 90% of its insulation as the delicate structure of the
clusters stick together and collapse. The down absorbs a lot of
water and because it loses most of its thermal performance it must
be dried via an outside heat source like the sun, a tumble dryer
or a body.
In many cases where there is moisture present, a down bag will
lose performance each night it is used, as the down becomes slowly
saturated. The rate at which this happens is dependent on the skill
of the user and the conditions in which it is being used. This water
contamination comes both from without and within the bag and learning
to slow the speed of this performance drop is one of the skills
needed to use a down bag effectively.
Down just doesn't work in high saturated environments and best
suits cold and dry conditions, or the protected sanctuary of a dry
space like a tent, hut or snow hole. Open bivvys in the rain, even
when using a bivvy bag are asking for trouble. When the temperature
drops the down begins to really come into its own. All the nasty
moisture is now frozen and so what would otherwise have wetted out
your bag can be brushed off. Care must be taken to limit any frozen
moisture melting on to the bag (like lying on snow that has fallen
on your mat). This includes bivvy bags with hoar frost coating the
inside due to you breathing into it, warm parts of the bag pressing
against snow. If boiling water within a tent or snow hole, try to
keep your bag packed away so it doesn't become damp, or if that's
not possible then limit the damage by covering the bag with clothes.
The modern water-resistant shells are just that (apart from the
Mountain Hardwear Banshee), as moisture can get through the untaped
seams, but they still provide a very good barrier to secondary contamination
(i.e. not direct rain).
Try not to get into the bag with wet clothes on and don't breathe
into it either as this will increase the amount of moisture in the
bag by several thousand percent. If you must get into a down bag
with frozen clothes on then try and remove any snow off your clothes
and pay close attention to ice on the Velcro on your shell, removing
it with a knife or peg before it can melt in your bag. If you must
dry clothes then lay them on top of the bag, or lay on them, or
just leave them wet and aim to dry them on the move the following
day. The only exception to this rule is socks and gloves which should
be placed flat against the skin (stomach, groin, armpits) under
your base layer to dry. When you get up in the morning stuff the
bag away straight away so the warm moisture within it is pushed
out before it can cool and condense within the down. Make sure your
stuff sack is waterproof and consider buying a dedicated dry bag
to store it in if doing a very wet trip.
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Facts and Performance Sleeping Bags
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