Gore has announced a new bivvy bag fabric with greater gas
permeability which, they say, means the bag can be used completely
sealed in extreme weather conditions.
The fabric uses a new, improved Gore-Tex membrane which, says
Gore, not only allows more gas to flow both in and out of the bag,
even when sealed, but also improves insulation. Gas permeability is
crucial with bivvy bags, which use a different grade of Gore-Tex to
shell clothing since without gas permeability, it's erm, impossible
or difficult to breathe.
In tests Gore found that the air inside a bivvy bag made from the
new fabric remained 'up to 19 degrees warmer when the outside air
temperature was minus 20 C'. Water and wind proofing remains
unimpaired, but volunteers were 'more comfortable' even in
'exceptionally heavy rainfall'.
It's an interesting development for the UK where generally wet,
damp conditions mean that most bivvy bags are simply impractical
because they don't breathe sufficiently well to prevent internal
condensation. The new fabric, says Gore's John McDonald, 'Remains
comfortable in even the most extreme conditions'.
New generation Gore bivvy bags will be in the shops early next
year with models available from Terra Nova, Mountain Range and
Equip.
Gore-Tex web
site
