When the going gets gnarly, the gnarly get insulated, but should you be going for down or synthetic fillings and what other features should you be looking at come buying time?
When things get seriously cold and gnarly you can only get so far
with fleece - if you need to go nuclear, you want a proper insulated
jacket, either down or a synthetic equivalent that's going to give
you significantly more warmth per gramme than a fabric insulator.
But with so many options to choose from and with everything having
different pros and cons, how do you choose? Our Buyers' Guide to
insulated clothing willl give you the basic information you need to
separate your Primaloft from your 900+ fill power down...
helps if you understand how insulation works - basically what keeps
you warm isn't the fabric or the filling, but the air which is
trapped inside it and warmed by your body. The more air you can trap,
the warmer the insulating garment will be, everything else being
That's why different grades of down give different levels of
insulation depending on how much space they expand to occupy, which
is why fill-power ratings are important. Synthetics don't trap as
much air, so generally pound for pound aren't as warm as down, but
they have other advantages.
Finally, it's essential that any insulated garment has a windproof
outer shell. Without it, any wind will simply strip away the warm air
trapped inside the insulation and leave you chilling as your body
re-warms the air again and again.
Top tip Damp air transmits heat faster, so an insulated
jacket that's comfortable at -20 in Nepal may feel chilly at -10 in
damp old Scotland.
WHEN TO INSULATE
Unless it's seriously cold, and we mean well below freezing point,
only thin insulated garments will be any use at all for active use.
When you stop moving however,
it's a different matter. You'll cool fast and a big, fat insulated
jacket is ideal for keeping you comfortable in winter conditions. Of
course it's ideal for that snowy walk to the pub too, but we wouldn't
do that, erm, would we?
The logical extension of the layer-up when stopped principle is
the 'belay jacket', a system developed by winter climbers. While
actually climbing and working hard they wear thin, breathable layers.
But at the end of a pitch and on belay, they simply throw on an
over-sized insulated jacket over anything else they're wearing.
Once they move off and are climbing again, the process is
reversed. It works really well and not just for climbers. There's no
reason why walkers and mountain bikers can't do the same.
Top tip most people wear too much when moving, but not
enough when stopped still and cooling down.
Goose and duck down is fantastic stuff with an amazing
warmth to weight ratio and a small pack size, it has one major
disadvantage though. If down gets damp then the surface tension of
the water overcomes the ability of the lighweight fluff to loft up
and the whole thing collapses into a porridgy mess that offers no
insulation at all.
means that while down is great in cold, dry, high mountain
environments like, say, the Alps or the Himalaya, in damper
conditions like the UK, you have to be very careful to keep it dry,
which is sometimes easier said than done.
Down is also fussy to care for, you need to either have it
professionally cleaned or use special cleaning products yourself and
washing tends to degrade its performance slightly every time.
You'll see fill-power figures quoted for down, they are
based on the volume of space that a certain weight of the down will
occupy, so the higher the number, the warmer the down. So 600+ down
is slightly less warm for a given weight than 700+ fill power down,
in which case you can use the same amount of the higher rated down
and get a warmer garment or use less of it for the same warmth.
Generally manufacturers won't quote temperature ratings as so much
depends on other factors, like the humidity, what is worn underneath
the insulation and individual physiology, but full-weight down duvet
jackets are generally too warm for active use unless it's
ridiculously cold, ie well below zero.
Top tip The best down tends to be eastern European goose
Synthetic insulation - the best known is Primaloft, but there are
plenty of alternatives - tends not to be as warm for its weight as
down, but has far more of a knockabout character. It still retains a
reasonable proportion of its insulating abilities when wet and can be
washed using normal detergents without problems.
That makes it a great choice for damp, cold places like, well, the
UK really and is an ideal filling for a British throw-over belay
jacket which may have to cover damp clothing.
The gap between down and synthetics is closing as well with hollow
fibres and soft feel making some synthetics feel almost luxurious
Top tip Primaloft One is the closest synthetic insulation
to down in terms of softness and weight for warmth ratio, but is more
FEATURES - WHAT TO LOOK
Starting with down, ideally you want a windproof outer
fabric with some sort of water-repellant treatment. Waterproof
down tops are really pub coats, you shouldn't be wearing down in
conditions where it's warm enough to rain anyway...
are two basic forms of down construction: box wall -
 - which puts the down in a walled-channel which, in turn,
eliminates cold spots and the simpler 'sewn-through'
construction where the inner and outer materials are simply sewn
together to create a channel - () - creating cold spots where the
Sewn-through is light and simple, but down garments designed for
extreme conditions generally use box-walls because of the increased
warmth and lack of cold spots.
Look for insulated zip baffles on both synthetic and down
jackets to prevent zips becoming cold spots. Handwarmer pockets are
great too and, well, give you somewhere to put your hands when it's
cold. Adjustable cuffs seal the wrist opening and minimise
heat loss there, ditto collars. An insulated hood,
possibly a detachable one, is an ideal way of keeping your head warm
with minimal fuss. You also want a close-fitting hem, again to prevent
heat loss from down below.
A water-resistant outer shell fabric will deal with snow
and contact with damp surfaces, but won't stand up to heavy rain;
then again, you shouldn't be wearing down in heavy rain.
Most of the above principles also hold true for synthetics, though
construction may be different with batts of synthetic fabric being
glued or stitched in place.
Top tip A good feel is the easiest way to distinguish
between box and sewn-through construction; try pulling the inner and
outer stitching apart and you can feel the difference.
of an alternative to fleece than a step-up, lightweight insulated
garments score by packing smaller and offering windproofing in
addition to warmth. The choice between down and synthetics is down to
the same factors as with heavier jackets and, again, synthetics are
arguably more versatile for UK conditions, with lighter, warmer but
more expensive down scoring in cold, dry, high mountain
They don't have the same 'pub snug' appeal as fleece, but are more
effective in performance terms and generally warmer for the weight as
Top tip Buy loose and you can use a lightweight synthetic
garment like a belay parka and simply pull it over the top of
everything else when you grind to a halt.
Help and Advice
This article should have given you some basic
pointers. The good news is that there's a load more advice on
Ask on the gear
forum about general issues or specific
Check the member
reviews section for user experiences of
See OM editorial reviews on the front of the
site for our impressions.
Richard Gear if you have a specific
question you need answering.
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